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  • 1.
    Agervald, Åsa
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Molekylär biomimetik. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för fotokemi och molekylärvetenskap, Mikrobiell kemi.
    Camsund, Daniel
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Molekylär biomimetik.
    Stensjö, Karin
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Molekylär biomimetik.
    Lindblad, Peter
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Molekylär biomimetik.
    CRISPR in the extended hyp-operon of the cyanobacterium Nostoc sp. strain PCC 7120, characteristics and putative function(s)2012Ingår i: International journal of hydrogen energy, ISSN 0360-3199, E-ISSN 1879-3487, Vol. 37, nr 10, s. 8828-8833Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The presence of small RNAs (sRNA) and their functions in transcriptional regulation has lately turned into a hot topic. Since cyanobacteria often face changes in the surrounding environment, they need to have a well working system for stress response. Quick adaption is necessary, and an RNA-based regulatory system is thus useful. One example of these sRNAs is CRISPRs. In this work we report the existence of a CRISPR within the hyp-operon (hyp genes encode proteins responsible for the maturation of hydrogenases) of the filamentous cyanobacterium Nostoc sp. strain PCC 7120. We present data concerning its characteristics and putative function(s) and raise the question concerning the importance of this CRISPR array and other CRISPR systems in general. In addition, we discuss the use of the CRISPR system as a potential bacterial genetic defence mechanism to achieve robust, cyanobacterial cultures in large scale, commercial production units.

  • 2.
    Ahmadova, Nigar
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Molekylär biomimetik.
    Studies of the two redox active tyrosines in Photosystem II2017Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Photosystem II is a unique enzyme which catalyzes light induced water oxidation. This process is driven by highly oxidizing ensemble of four Chl molecules, PD1, PD2, ChlD1 and ChlD2 called, P680. Excitation of one of the Chls in P680 leads to the primary charge separation, P680+Pheo-. Pheo- transfers electrons sequentially to the primary quinone acceptor QA and the secondary quinone acceptor QB. P680+ in turn extracts electrons from Mn4CaO5 cluster, a site for the water oxidation. There are two redox active tyrosines, TyrZ and TyrD, found in PSII. They are symmetrically located on the D1 and D2 central proteins. Only TyrZ acts as intermediate electron carrier between P680 and Mn4CaO5 cluster, while TyrD does not participate in the linear electron flow and stays oxidized under light conditions. Both tyrosines are involved in PCET.

    The reduced TyrD undergoes biphasic oxidation with the fast (msec-sec time range) and the slow (tens of seconds time range) kinetic phases. We assign these phases to two populations of PSII centers with proximal or distal water positions. We also suggest that the TyrD oxidation and stability is regulated by the new small lumenal protein subunit, PsbTn. The possible involvement of PsbTn protein in the proton translocation mechanism from TyrD is suggested.

    To assess the possible localization of primary cation in P680 the formation of the triplet state of P680 and the oxidation of TyrZ and TyrD were followed under visible and far-red light. We proposed that far-red light induces the cation formation on ChlD1.

    Transmembrane interaction between QB and TyrZ has been studied. The different oxidation yield of TyrZ, measured as a S1 split EPR signal was correlated to the conformational change of protein induced by the QB presence at the QB-site. The change is transferred via H-bonds to the corresponding His-residues via helix D of the D1 protein.

    Delarbeten
    1. The protonation state around Tyr(D)/Tyr((D)) over dot in photosystem II is reflected in its biphasic oxidation kinetics
    Öppna denna publikation i ny flik eller fönster >>The protonation state around Tyr(D)/Tyr((D)) over dot in photosystem II is reflected in its biphasic oxidation kinetics
    Visa övriga...
    2017 (Engelska)Ingår i: Biochimica et Biophysica Acta - Bioenergetics, ISSN 0005-2728, E-ISSN 1879-2650, Vol. 1858, nr 2, s. 147-155Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    The tyrosine residue D2-Tyr160 (Tyr(D)) in photosystem II (PSII) can be oxidized through charge equilibrium with the oxygen evolving complex in PSII. The kinetics of the electron transfer from Tyr(D) has been followed using time resolved EPR spectroscopy after triggering the oxidation of pre-reduced Tyr(D) by a short laser flash. After its oxidation Tyro is observed as a neutral radical (Tyr((D)) over dot) indicating that the oxidation is coupled to a deprotonation event. The redox state of Tyro was reported to be determined by the two water positions identified in the crystal structure of PSII [Saito et al. (2013) Proc. Natl. Acad. Sci. USA 110, 7690]. To assess the mechanism of the proton coupled electron transfer of Tyr(D) the oxidation kinetics has been followed in the presence of deuterated buffers, thereby resolving the kinetic isotope effect (KIE) of Tyro oxidation at different H/D concentrations. Two kinetic phases of Tyro oxidation - the fast phase (msec-sec time range) and the slow phase (tens of seconds time range) were resolved as was previously reported [Vass and Styring (1991) Biochemistry 30, 830]. In the presence of deuterated buffers the kinetics was significantly slower compared to normal buffers. Furthermore, although the kinetics were faster at both high pH and pD values the observed KIE was found to be similar (similar to 2.4) over the whole pL range investigated. We assign the fast and slow oxidation phases to two populations of PSII centers with different water positions, proximal and distal respectively, and discuss possible deprotonation events in the vicinity of Tyro.

    Nyckelord
    Photosystem II, Tyrosine D, Electron transfer, Proton transfer, Deuterium isotope effect
    Nationell ämneskategori
    Biokemi och molekylärbiologi Biofysik
    Identifikatorer
    urn:nbn:se:uu:diva-316938 (URN)10.1016/j.bbabio.2016.11.002 (DOI)000392776400007 ()27823941 (PubMedID)
    Forskningsfinansiär
    Vetenskapsrådet, 621-2013-5937Energimyndigheten, 11674-5Knut och Alice Wallenbergs Stiftelse, KAW 2011.0067
    Tillgänglig från: 2017-03-09 Skapad: 2017-03-09 Senast uppdaterad: 2017-04-30
    2. Tyrosine D oxidation and redox equilibrium in Photosystem II
    Öppna denna publikation i ny flik eller fönster >>Tyrosine D oxidation and redox equilibrium in Photosystem II
    2017 (Engelska)Ingår i: Biochimica et Biophysica Acta - Bioenergetics, ISSN 0005-2728, E-ISSN 1879-2650, Vol. 1858, nr 6, s. 407-417Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    Tyrosine ID (Tyr(D)) is an auxiliary redox active tyrosine residue in photosystem II (PSII). The mechanism of Tyr(D) oxidation was investigated by EPR spectroscopy, flash-induced fluorescence decay and thermoluminescence measurements in PSII enriched membranes from spinach. PSII membranes were chemically treated with 3 mM ascorbate and 1 mM diaminodurene and subsequent washing, leading to the complete reduction of Tyr(D). Tyr(D) oxidation kinetics and competing recombination reactions were measured after a single saturating flash in the absence and presence of DCMU (inhibitor of the Q(B)-site) in the pH range of 4.7-8.5. Two kinetic phases of Tyro oxidation were observed by the time resolved EPR spectroscopy the fast phase (msec-sec time range) and the pH dependent slow phase (tens of seconds time range). In the presence of DCMU, Tyr(D) oxidation kinetics was monophasic in the entire pH range, i.e. only the fast kinetics was observed. The results obtained from the fluorescence and thermoluminescence analysis show that when forward electron transport is blocked in the presence of DCMU, the S(2)Q((S) over bar) recombination outcompetes the slow phase of Tyr(D) oxidation by the S-2 state. Modelling of the whole complex of these electron transfer events associated with Tyr(D) oxidation fitted very well with our experimental data. Based on these data, structural information and theoretical considerations we confirm our assignment of the fast and slow oxidation kinetics to two populations of PSII centers with different water positions (proximal and distal) in the Tyr(D) vicinity.

    Nyckelord
    Photosystem II, Electron transfer, Tyrosine D
    Nationell ämneskategori
    Naturvetenskap
    Forskningsämne
    Biokemi
    Identifikatorer
    urn:nbn:se:uu:diva-320913 (URN)10.1016/j.bbabio.2017.02.011 (DOI)000402349000001 ()28235460 (PubMedID)
    Forskningsfinansiär
    Vetenskapsrådet, 621-2013-5937Energimyndigheten, 11674-5Knut och Alice Wallenbergs Stiftelse, 2011.0067
    Tillgänglig från: 2017-04-27 Skapad: 2017-04-27 Senast uppdaterad: 2017-07-06Bibliografiskt granskad
    3. The triplet state of the primary donor, P680, in Photosystem II is not formed by far-red light at 5 K ; Implications for the localization of the primary radical pair.
    Öppna denna publikation i ny flik eller fönster >>The triplet state of the primary donor, P680, in Photosystem II is not formed by far-red light at 5 K ; Implications for the localization of the primary radical pair.
    Visa övriga...
    (Engelska)Manuskript (preprint) (Övrigt vetenskapligt)
    Nyckelord
    Photosystem II, P680, primary charge separation
    Nationell ämneskategori
    Naturvetenskap
    Identifikatorer
    urn:nbn:se:uu:diva-321127 (URN)
    Tillgänglig från: 2017-04-30 Skapad: 2017-04-30 Senast uppdaterad: 2017-05-04
    4. Formation of tyrosine radicals in photosystem II under far-red illumination
    Öppna denna publikation i ny flik eller fönster >>Formation of tyrosine radicals in photosystem II under far-red illumination
    2018 (Engelska)Ingår i: Photosynthesis Research, ISSN 0166-8595, E-ISSN 1573-5079, Vol. 136, nr 1, s. 93-106Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    Photosystem II (PS II) contains two redox-active tyrosine residues on the donor side at symmetrical positions to the primary donor, P680. TyrZ, part of the water-oxidizing complex, is a preferential fast electron donor while TyrD is a slow auxiliary donor to P680 +. We used PS II membranes from spinach which were depleted of the water oxidation complex (Mn-depleted PS II) to study electron donation from both tyrosines by time-resolved EPR spectroscopy under visible and far-red continuous light and laser flash illumination. Our results show that under both illumination regimes, oxidation of TyrD occurs via equilibrium with TyrZ at pH 4.7 and 6.3. At pH 8.5 direct TyrD oxidation by P680 + occurs in the majority of the PS II centers. Under continuous far-red light illumination these reactions were less effective but still possible. Different photochemical steps were considered to explain the far-red light-induced electron donation from tyrosines and localization of the primary electron hole (P680 +) on the ChlD1 in Mn-depleted PS II after the far-red light-induced charge separation at room temperature is suggested.

    Nyckelord
    Photosystem II, Tyrosine Z and D, electron transfer
    Nationell ämneskategori
    Biokemi och molekylärbiologi
    Forskningsämne
    Kemi med inriktning mot biofysik
    Identifikatorer
    urn:nbn:se:uu:diva-320914 (URN)10.1007/s11120-017-0442-3 (DOI)000427394300007 ()28924898 (PubMedID)
    Forskningsfinansiär
    Vetenskapsrådet
    Tillgänglig från: 2017-04-27 Skapad: 2017-04-27 Senast uppdaterad: 2018-05-16Bibliografiskt granskad
    5. Role of the PsbTn, a small luminal protein in Photosystem II, in the redox reactions of Tyrosine D
    Öppna denna publikation i ny flik eller fönster >>Role of the PsbTn, a small luminal protein in Photosystem II, in the redox reactions of Tyrosine D
    (Engelska)Manuskript (preprint) (Övrigt vetenskapligt)
    Nyckelord
    Photosystem II, PsbTn, TyrD
    Nationell ämneskategori
    Naturvetenskap
    Identifikatorer
    urn:nbn:se:uu:diva-321125 (URN)
    Tillgänglig från: 2017-04-30 Skapad: 2017-04-30 Senast uppdaterad: 2017-05-04
    6. The Donor-Acceptor side interactions in Photosystem II
    Öppna denna publikation i ny flik eller fönster >>The Donor-Acceptor side interactions in Photosystem II
    (Engelska)Manuskript (preprint) (Övrigt vetenskapligt)
    Nyckelord
    Photosystem II, QA, QB, TyrZ, quinones
    Nationell ämneskategori
    Naturvetenskap
    Forskningsämne
    Biokemi
    Identifikatorer
    urn:nbn:se:uu:diva-321124 (URN)
    Tillgänglig från: 2017-04-30 Skapad: 2017-04-30 Senast uppdaterad: 2017-05-04
  • 3.
    Ahmadova, Nigar
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Molekylär biomimetik.
    Ho, Felix
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Molekylär biomimetik.
    Styring, Stenbjörn
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Molekylär biomimetik.
    Mamedov, Fikret
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Molekylär biomimetik.
    Tyrosine D oxidation and redox equilibrium in Photosystem II2017Ingår i: Biochimica et Biophysica Acta - Bioenergetics, ISSN 0005-2728, E-ISSN 1879-2650, Vol. 1858, nr 6, s. 407-417Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Tyrosine ID (Tyr(D)) is an auxiliary redox active tyrosine residue in photosystem II (PSII). The mechanism of Tyr(D) oxidation was investigated by EPR spectroscopy, flash-induced fluorescence decay and thermoluminescence measurements in PSII enriched membranes from spinach. PSII membranes were chemically treated with 3 mM ascorbate and 1 mM diaminodurene and subsequent washing, leading to the complete reduction of Tyr(D). Tyr(D) oxidation kinetics and competing recombination reactions were measured after a single saturating flash in the absence and presence of DCMU (inhibitor of the Q(B)-site) in the pH range of 4.7-8.5. Two kinetic phases of Tyro oxidation were observed by the time resolved EPR spectroscopy the fast phase (msec-sec time range) and the pH dependent slow phase (tens of seconds time range). In the presence of DCMU, Tyr(D) oxidation kinetics was monophasic in the entire pH range, i.e. only the fast kinetics was observed. The results obtained from the fluorescence and thermoluminescence analysis show that when forward electron transport is blocked in the presence of DCMU, the S(2)Q((S) over bar) recombination outcompetes the slow phase of Tyr(D) oxidation by the S-2 state. Modelling of the whole complex of these electron transfer events associated with Tyr(D) oxidation fitted very well with our experimental data. Based on these data, structural information and theoretical considerations we confirm our assignment of the fast and slow oxidation kinetics to two populations of PSII centers with different water positions (proximal and distal) in the Tyr(D) vicinity.

  • 4.
    Ahmadova, Nigar
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Molekylär biomimetik.
    Mamedov, Fikret
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Molekylär biomimetik.
    Formation of tyrosine radicals in photosystem II under far-red illumination2018Ingår i: Photosynthesis Research, ISSN 0166-8595, E-ISSN 1573-5079, Vol. 136, nr 1, s. 93-106Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Photosystem II (PS II) contains two redox-active tyrosine residues on the donor side at symmetrical positions to the primary donor, P680. TyrZ, part of the water-oxidizing complex, is a preferential fast electron donor while TyrD is a slow auxiliary donor to P680 +. We used PS II membranes from spinach which were depleted of the water oxidation complex (Mn-depleted PS II) to study electron donation from both tyrosines by time-resolved EPR spectroscopy under visible and far-red continuous light and laser flash illumination. Our results show that under both illumination regimes, oxidation of TyrD occurs via equilibrium with TyrZ at pH 4.7 and 6.3. At pH 8.5 direct TyrD oxidation by P680 + occurs in the majority of the PS II centers. Under continuous far-red light illumination these reactions were less effective but still possible. Different photochemical steps were considered to explain the far-red light-induced electron donation from tyrosines and localization of the primary electron hole (P680 +) on the ChlD1 in Mn-depleted PS II after the far-red light-induced charge separation at room temperature is suggested.

  • 5.
    Akkarasamiyo, Sunisa
    et al.
    Stockholm Univ, Dept Organ Chem, S-10691 Stockholm, Sweden..
    Sawadjoon, Supaporn
    Stockholm Univ, Dept Organ Chem, S-10691 Stockholm, Sweden..
    Orthaber, Andreas
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Molekylär biomimetik.
    Samec, Joseph S. M.
    Stockholm Univ, Dept Organ Chem, S-10691 Stockholm, Sweden..
    Tsuji-Trost Reaction of Non-Derivatized Allylic Alcohols2018Ingår i: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 24, nr 14, s. 3488-3498Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Palladium-catalyzed allylic substitution of non-derivatized enantioenriched allylic alcohols with a variety of uncharged N-, S-, C- and O-centered nucleophiles using a bidentate BiPhePhos ligand is described. A remarkable effect of the counter ion (X) of the XPd[kappa(2)-BiPhePhos][kappa(3)-C3H5] was observed. When ClPd[kappa(2)-BiPhePhos][eta(3)-C3H5] (complexI) was used as catalyst, non-reproducible results were obtained. Study of the complex by X-ray crystallography, (PNMR)-P-31 spectroscopy, and ESI-MS showed that a decomposition occurred where one of the phosphite ligands was oxidized to the corresponding phosphate, generating ClPd[kappa(1)-BiPhePhosphite-phosphate][eta(3)-C3H5] species (complexII). When the chloride was exchanged to the weaker coordinating OTf- counter ion the more stable Pd[kappa(2)-BiPhePhos][eta(3)-C3H5](+)+[OTf] (-) (complexIII) was formed. ComplexIII performed better and gave higher enantiospecificities in the substitution reactions. ComplexIII was evaluated in Tsuji-Trost reactions of stereogenic non-derivatized allylic alcohols. The desired products were obtained in good to excellent yields (71-98%) and enantiospecificities (73-99%) for both inter- and intramolecular substitution reactions with only water generated as a by-product. The methodology was applied to key steps in total synthesis of (S)-cuspareine and (+)-lentiginosine. A reaction mechanism involving a palladium hydride as a key intermediate in the activation of the hydroxyl group is proposed in the overall transformation.

  • 6.
    Andersson Schönn, Mikael
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Molekylär biomimetik.
    Promoter regulation: designing cells for biotechnological applications2016Självständigt arbete på avancerad nivå (yrkesexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    The filamentous cyanobacteria Nostoc punctiforme ATCC 29133 is a model species fordevelopment of sustainable production methods of numerous compounds. One of its uniquefeatures is the anaerobic environment of the strains nitrogen fixing heterocyst cells. To be ableto properly utilize this environment, more knowledge regarding what regulates cell specificexpression is required. In this study, three motifs of the NsiR I promoter of Anabaena sp.PCC 7120 was studied in this system utilizing YFP-fluorescence as a reporter to determinetheir impact on spatial expression pattern. Investigations were performed on immobilizedcells with the use of confocal microscopy and results point towards sigma factor regulation.

  • 7.
    Antila, Liisa J.
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Ghamgosar, Pedram
    Maji, Somnath
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Molekylär biomimetik.
    Tian, Haining
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Ott, Sascha
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Molekylär biomimetik.
    Hammarström, Leif
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Dynamics and Photochemical H-2 Evolution of Dye-NiO Photocathodes with a Biomimetic FeFe-Catalyst2016Ingår i: ACS ENERGY LETTERS, ISSN 2380-8195, Vol. 1, nr 6, s. 1106-1111Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Mesoporous NiO films were cosensitized with a coumarin 343 dye and a proton reduction catalyst of the [Fe-2(CO)(6)(bdt)] (bdt = benzene-1,2-dithiolate) family. Femtosecond ultraviolet visible transient absorption experiments directly demonstrated subpicosecond hole injection into NiO from excited dyes followed by rapid (t(50%) similar to 6 ps) reduction of the catalyst on the surface with similar to 70% yield. The reduced catalyst was long-lived (2 mu s to 20 ms), which may allow protonation and a second reduction step of the catalyst to occur. A photo electrochemical device based on this photocathode produced H-2 with a Faradaic efficiency of similar to 50%. Fourier transform infrared spectroscopy and gas chromatography experiments demonstrated that the observed device deterioration with time was mainly due to catalyst degradation and desorption from the NiO surface. The insights gained from these mechanistic studies, regarding development of dye-catalyst cosensitized photocathodes, are discussed.

  • 8.
    Arkhypchuk, Anna
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Molekylär biomimetik.
    Novel Approaches to Phosphorus-containing Heterocycles and Cumulenes2013Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Fast development in all areas of life and science over the last 50 years demands versatile, energy efficient and cheap materials with specific but easily tuneable properties which can be used for example in organic light emitting diodes (OLEDs), thin-film transistors, photovoltaic cells, etc. This thesis is devoted to the development of novel synthetic approaches to molecules with potential applications in the field of molecular electronics.  The acquisition of a detailed mechanistic understanding of the newly developed reactions is central to the work presented in this thesis.

    The first chapter is dedicated to the development of a new procedure for the preparation of phospha-Wittig-Horner (pWH) reagents, i.e. a reagents that has been known to convert carbonyl compounds into compounds with P=C double bonds. Each step of the synthetic sequence, i.e. preparation of the starting P,P-dichlorophosphines, their phosphorylation using the Michaelis-Arbuzov protocol, coordination to the metal centre and final hydrolysis, are presented in detail. A possible route to uncoordinated pWH reagents is also discussed.

    The second chapter focuses on the reactivity of the pWH reagents with acetone under different reaction conditions. The results show how changes in the ratio of starting material vs. base as well as reaction time or structure of the pWH reagent can influence the reaction outcome and the stability of the obtained products. The possibility to prepare unusual phosphaalkenes with unsaturated P-substituents is presented.

    The third chapter of the thesis is dedicated to the reactivity of pWH reagents towards symmetric and asymmetric ketones which contain one or two acetylene units. The proposed mechanisms of the reactions are studied by means of in situ FTIR spectroscopy as well as theoretical calculations. Physical-chemical properties of oxaphospholes, cumulenes and bisphospholes are presented.

    The last chapter is dedicated to reactivity studies of pWH reagents towards ketenes, and the exploration of a reliable route to 1-phosphaallenes. Detailed mechanistic studies of the pWH reaction that are based on the isolation and crystallographic characterization of unique reaction intermediates are presented. The reactivity of phosphaallenes towards nucleophiles such as water and methanol are examined.

    In summary, this thesis presents synthetic routes to novel phosphorus-containing molecules, together with detailed studies of the reaction mechanisms of the observed transformations.

    Delarbeten
    1. Revisiting the Phospha-Wittig - Horner Reaction
    Öppna denna publikation i ny flik eller fönster >>Revisiting the Phospha-Wittig - Horner Reaction
    2012 (Engelska)Ingår i: Organometallics, ISSN 0276-7333, E-ISSN 1520-6041, Vol. 31, nr 3, s. 1118-1126Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    P,P-Dichlorophosphines 2a-c (RPCl2, R = Ph (a), t-Bu (b), 2,4,6-Me3Ph (c)) and P,P-dibromophosphines 4d,e (RPBr2, R = (i-Pr)(3)SiC C (d) and H2C=CH (e)) react with triethylphosphite under Michaelis-Arbuzov conditions to give phosphinodiphosphonates 3a-e in quantitative yields. After complexation to W(CO)(5) and treatment with CH3ONa, phospha-Wittig-Horner reagents 9a,b are obtained on a multigram scale in good overall yield. Phospha-Wittig-Horner reagents with unsaturated, substituents at P-III (10d,e) can be prepared in analogous procedures; however, their prevail in an unusual ylide form that allows conjugation between the lone pair and the acetylene and vinyl pi-systems, respectively. Phosphinophosphonate 9a has been characterized by X-ray crystallography and is shown to react smoothly with acetone within minutes. The resulting W(CO)(5)-coordinated phosphaalkene is shown to dimerize to a 1,2-diphosphitane or to undergo a 1,3-proton shift depending on the reaction conditions. In addition, a one-pot synthetic sequence starting from W(CO)(5)-coordinated phosphinodiphosphonates 5d,e has been developed to engage compounds with vinyl and acetylene substituents in phospha-Wittig-Horner reactions.

    Nationell ämneskategori
    Kemi
    Identifikatorer
    urn:nbn:se:uu:diva-170346 (URN)10.1021/om201158k (DOI)000300116100046 ()
    Tillgänglig från: 2012-03-12 Skapad: 2012-03-12 Senast uppdaterad: 2017-12-07Bibliografiskt granskad
    2. Cascade Reactions Forming Highly Substituted, Conjugated Phospholes and 1,2-Oxaphospholes
    Öppna denna publikation i ny flik eller fönster >>Cascade Reactions Forming Highly Substituted, Conjugated Phospholes and 1,2-Oxaphospholes
    2012 (Engelska)Ingår i: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773, Vol. 51, nr 31, s. 7776-7780Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    The reaction of a phospha-Wittig–Horner reagent with diacetylenic ketones (see scheme) results in a cascade of reactions that can lead to both an oxaphosphole-terminated cumulene system and an alkene-bridged bis-phosphole. The reaction outcome is determined by the nature of the acetylene termini, with phenyl groups stabilizing a carbene intermediate that dimerizes to give the bis-phosphole product.

    Nyckelord
    acetylenes, conjugation, cumulenes, phospha-Wittig, reaction mechanisms
    Nationell ämneskategori
    Kemi
    Identifikatorer
    urn:nbn:se:uu:diva-182042 (URN)10.1002/anie.201202153 (DOI)000306757900029 ()
    Tillgänglig från: 2012-10-05 Skapad: 2012-10-02 Senast uppdaterad: 2017-12-07Bibliografiskt granskad
    3. Phosphorus Heterocylces from Phosphinophosphonates and α,β-Unsaturated Ketones
    Öppna denna publikation i ny flik eller fönster >>Phosphorus Heterocylces from Phosphinophosphonates and α,β-Unsaturated Ketones
    Visa övriga...
    (Engelska)Manuskript (preprint) (Övrigt vetenskapligt)
    Nationell ämneskategori
    Organisk kemi Oorganisk kemi
    Identifikatorer
    urn:nbn:se:uu:diva-198753 (URN)
    Tillgänglig från: 2013-04-25 Skapad: 2013-04-24 Senast uppdaterad: 2013-08-30
    4. Mechanism of the Phospha-Wittig-Horner Reaction
    Öppna denna publikation i ny flik eller fönster >>Mechanism of the Phospha-Wittig-Horner Reaction
    2013 (Engelska)Ingår i: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773, Vol. 52, nr 25, s. 6484-6487Artikel i tidskrift (Refereegranskat) Published
    Nyckelord
    ketenes; phosphaallenes; phospha-Wittig-Horner reaction; reaction mechanisms
    Nationell ämneskategori
    Organisk kemi Oorganisk kemi
    Identifikatorer
    urn:nbn:se:uu:diva-198754 (URN)10.1002/anie.201301469 (DOI)000320378800024 ()
    Tillgänglig från: 2013-04-25 Skapad: 2013-04-24 Senast uppdaterad: 2017-12-06Bibliografiskt granskad
  • 9.
    Arkhypchuk, Anna I.
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Molekylär biomimetik.
    D'Imperio, Nicolas
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Molekylär biomimetik.
    Ott, Sascha
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Molekylär biomimetik.
    One-Pot Intermolecular Reductive Cross-Coupling of Deactivated Aldehydes to Unsymmetrically 1,2-Disubstituted Alkenes2018Ingår i: Organic Letters, ISSN 1523-7060, E-ISSN 1523-7052, Vol. 20, nr 17, s. 5086-5089Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The phospha-Peterson reaction between a lithiated secondary phosphane, MesP(Li)TMS, and an aldehyde affords Mes-phosphaalkenes which, upon methanol addition and P-oxidation, react with a second carbonyl compound site specifically to produce unsymmetric alkenes. The E/Z selectivity of the one-pot cross coupling is largely determined by the electronic nature of the aryl substituent of the first aldehyde, with electron-donating groups giving rise to increased amounts of Z-alkenes.

  • 10.
    Arkhypchuk, Anna I.
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Molekylär biomimetik.
    D'Imperio, Nicolas
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Molekylär biomimetik.
    Ott, Sascha
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Molekylär biomimetik.
    Triarylalkenes from the site-selective reductive cross-coupling of benzophenones and aldehydes2019Ingår i: Chemical Communications, ISSN 1359-7345, E-ISSN 1364-548X, Vol. 55, nr 43, s. 6030-6033Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    PhP(Li)TMS converts benzophenones to phosphaalkenes which upon activation under oxidizing, basic conditions react with aromatic aldehydes under the formation of triarylalkenes. The one-pot reaction omits transition metals, proceeds at room temperature and precludes the formation of any homo-coupling products. Systematic substrate variations reveal reactivity patterns that are useful for the identification of ketone/aldehyde combinations that can be coupled in yields up to 80%.

  • 11.
    Arkhypchuk, Anna I.
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - BMC, Fysikalisk-organisk kemi.
    Mijangos, Edgar
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Molekylär biomimetik.
    Lomoth, Reiner
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Ott, Sascha
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Molekylär biomimetik.
    Redox Switching in Ethenyl- Bridged Bisphospholes2014Ingår i: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 20, nr 49, s. 16083-16087Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A 2e(-)/2H(+) redox platform has been implemented in the ethenyl-bridged bisphosphol-3-ol 1 to afford the first phospholes that feature chemically reversible oxidations. Oxidation of the title compounds to the corresponding bisphosphol-3-one 2 leads to a change in conjugation topology and a concomitant hypsochromic shift of the lowest-energy absorption maximum by 100nm. Electrochemical oxidation proceeds without any detectable intermediates, whereas the deprotonated form of 1 can be observed in an aprotic medium during the reduction of 2. This dianionic intermediate 3 is characterized by end absorptions that are bathochromically shifted by circa 200nm compared to those of 2.

  • 12.
    Arkhypchuk, Anna I.
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Molekylär biomimetik.
    Orthaber, Andreas
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Molekylär biomimetik.
    Borbas, K. Eszter
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - BMC. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Molekylär biomimetik.
    Synthesis and Characterization of Ferrocenyl Chlorins, 1,1'-Ferrocene-Linked Chlorin Dimers, and their BODIPY Analogues2017Ingår i: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 56, nr 5, s. 3044-3054Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We present the synthesis and characterization of meso-ferrocenyl-substituted hydroporphyrins (chlorins) and 1,1' -linked chlorin dimers. The dipyrromethane chlorin precursors were also transformed into Fc-substituted BODIPYs and 1,1'-ferrocenyl-linked BODIPY dimers. The chlorin dimers were studied by 1D and 2D NMR experiments and DFT calculations, which showed that their solution structures were dependent on the central metal. Monomeric and dimeric Ni(II) chlorins had similar H-1 NMR spectra. Monomeric and dimeric free base, Zn(II), and Pd(II) chlorins, on the other hand, showed significantly more different spectra. The eclipsed conformer of the free base chlorin dimer was calculated to be energetically more favored than the open form. The chlorin and BODIPY fluorescence emissions were quenched in the Fcsubstituted compounds; these could be recovered by oxidation of the Fe(II) center. Cyclic voltammetry showed up to five oxidation waves for the free base chlorin dimer, which suggests that the macrocycles were not behaving independently of each other.

  • 13.
    Arkhypchuk, Anna I.
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Molekylär biomimetik.
    Orthaber, Andreas
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Molekylär biomimetik.
    Kovacs, Daniel
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Molekylär biomimetik.
    Borbas, K. Eszter
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Molekylär biomimetik.
    Isolation and Characterization of a Monoprotonated Hydroporphyrin2018Ingår i: European Journal of Organic Chemistry, ISSN 1434-193X, E-ISSN 1099-0690, nr 48, s. 7051-7056Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A simple protocol for the controlled preparation of mono- and diprotonated hydroporphyrins (chlorins) is presented. The chlorins carried 10-aryl groups with electron-neutral (phenyl), electron-donating (p-OMe-C6H4) or electron-withdrawing (pentafluorophenyl) substituents. The protonation reactions were readily followed by UV/Vis absorption spectroscopy, enabling the determination of the first (4.8-5.3) and second pK(a)'s (1.7-0.5). Both mono- and diprotonated species were fully characterized by H-1 NMR spectroscopy, which, in combination with theoretical studies, showed that these macrocycles were significantly distorted in solution. A 10-phenyl-substituted monoprotonated chlorin was characterized by X-ray crystallography. This is the first structurally characterized hydroporphyrin monocation, and the first crystal structure of a sterically unencumbered singly protonated tetrapyrrole. The photostabilities of the mono- and diprotonated 10-phenylchlorins were measured upon irradiation into their Soret bands; protonation yielded increased photostabilities.

  • 14.
    Arkhypchuk, Anna I.
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Molekylär biomimetik.
    Orthaber, Andreas
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Molekylär biomimetik.
    Mihali, Viorica Alina
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Strukturkemi.
    Ehlers, Andreas
    Lammertsma, Koop
    Ott, Sascha
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Molekylär biomimetik.
    Oxaphospholes and Bisphospholes from Phosphinophosphonates and alpha,beta-Unsaturated Ketones2013Ingår i: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 19, nr 41, s. 13692-13704Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The reaction of a {W(CO)(5)}-stabilized phosphinophosphonate 1, (CO)(5)WPH(Ph)P(O)(OEt)(2), with ethynyl- (2a-f) and diethynylketones (7-11, 18, and 19) in the presence of lithium diisopropylamide (LDA) is examined. Lithiated 1 undergoes nucleophilic attack in the Michael position of the acetylenic ketones, as long as this position is not sterically encumbered by bulky (iPr)(3)Si substituents. Reaction of all other monoacetylenic ketones with lithiated 1 results in the formation of 2,5-dihydro-1,2-oxaphospholes 3 and 4. When diacetylenic ketones are employed in the reaction, two very different product types can be isolated. If at least one (Me)(3)Si or (Et)(3)Si acetylene terminus is present, as in 7, 8, and 19, an anionic oxaphosphole intermediate can react further with a second equivalent of ketone to give cumulene-decorated oxaphospholes 14, 15, 24, and 25. Diacetylenic ketones 10 and 11, with two aromatic acetylene substituents, react with lithitated 1 to form exclusively ethenyl-bridged bisphospholes 16 and 17. Mechanisms that rationalize the formation of all heterocycles are presented and are supported by DFT calculations. Computational studies suggest that thermodynamic, as well as kinetic, considerations dictate the observed reactivity. The calculated reaction pathways reveal a number of almost isoenergetic intermediates that follow after ring opening of the initially formed oxadiphosphetane. Bisphosphole formation through a carbene intermediate G is greatly favored in the presence of phenyl substituents, whereas the formation of cumulene-decorated oxaphospholes is more exothermic for the trimethylsilyl-containing substrates. The pathway to the latter compounds contains a 1,3-shift of the group that stems from the acetylene terminus of the ketone substrates. For silyl substituents, the 1,3-shift proceeds along a smooth potential energy surface through a transition state that is characterized by a pentacoordinated silicon center. In contrast, a high-lying transition state TS(E-F)(R=Ph) of 37kcalmol(-1) is found when the substituent is a phenyl group, thus explaining the experimental observation that aryl-terminated diethynylketones 10 and 11 exclusively form bisphospholes 16 and 17.

  • 15.
    Arkhypchuk, Anna I.
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Molekylär biomimetik.
    Orthaber, Andreas
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Molekylär biomimetik.
    Ott, Sascha
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Molekylär biomimetik.
    Tuning the Optical Properties of 1,1'-Biphospholes by Chemical Alterations of the P-P Bridge2014Ingår i: European Journal of Inorganic Chemistry, ISSN 1434-1948, E-ISSN 1099-1948, Vol. 2014, nr 10, s. 1760-1766Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    2,5-Di(1-naphthyl)-1-phenylphosphole (2) was prepared from phenylphosphine and dinaphthylbutadiyne in 70% yield, and oxidized to its oxide 3. Treatment of 2 with a solution of potassium naphthalide results in selective formation of phospholide anion 4, which can be oxidized with iodine to afford biphosphole 5. The crystal structure of 5 exhibits an unusual s-trans conformation across the P-P bridge that is most stabilized by - stacking of the naphthyl substituents. Biphosphole 5 can be oxidized to its mono-oxidized 6 and dioxide 7. Generally, all phosphole oxidations lead to decreased pyramidalization of the P centres and, consequently, to significantly redshifted lowest-energy absorption maxima. Mono-oxidized biphosphole 6, which consists of an ordinary phosphole and an electron-deficient oxidized phosphole, features a unique low-energy optical transition (shoulder at 430 nm), which is tentatively assigned to a charge-transfer transition. The UV/Vis spectrum of dioxide 7 lacks this transition. At the same time, the emission maximum of 7 is bathochromically shifted by 80 nm relative to that of 5.

  • 16.
    Arkhypchuk, Anna I.
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Molekylär biomimetik.
    Santoni, Marie-Pierre
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Molekylär biomimetik.
    Ott, Sascha
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Molekylär biomimetik.
    Cascade Reactions Forming Highly Substituted, Conjugated Phospholes and 1,2-Oxaphospholes2012Ingår i: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773, Vol. 51, nr 31, s. 7776-7780Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The reaction of a phospha-Wittig–Horner reagent with diacetylenic ketones (see scheme) results in a cascade of reactions that can lead to both an oxaphosphole-terminated cumulene system and an alkene-bridged bis-phosphole. The reaction outcome is determined by the nature of the acetylene termini, with phenyl groups stabilizing a carbene intermediate that dimerizes to give the bis-phosphole product.

  • 17.
    Arkhypchuk, Anna I.
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Molekylär biomimetik.
    Santoni, Marie-Pierre
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Molekylär biomimetik.
    Ott, Sascha
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Molekylär biomimetik.
    Revisiting the Phospha-Wittig - Horner Reaction2012Ingår i: Organometallics, ISSN 0276-7333, E-ISSN 1520-6041, Vol. 31, nr 3, s. 1118-1126Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    P,P-Dichlorophosphines 2a-c (RPCl2, R = Ph (a), t-Bu (b), 2,4,6-Me3Ph (c)) and P,P-dibromophosphines 4d,e (RPBr2, R = (i-Pr)(3)SiC C (d) and H2C=CH (e)) react with triethylphosphite under Michaelis-Arbuzov conditions to give phosphinodiphosphonates 3a-e in quantitative yields. After complexation to W(CO)(5) and treatment with CH3ONa, phospha-Wittig-Horner reagents 9a,b are obtained on a multigram scale in good overall yield. Phospha-Wittig-Horner reagents with unsaturated, substituents at P-III (10d,e) can be prepared in analogous procedures; however, their prevail in an unusual ylide form that allows conjugation between the lone pair and the acetylene and vinyl pi-systems, respectively. Phosphinophosphonate 9a has been characterized by X-ray crystallography and is shown to react smoothly with acetone within minutes. The resulting W(CO)(5)-coordinated phosphaalkene is shown to dimerize to a 1,2-diphosphitane or to undergo a 1,3-proton shift depending on the reaction conditions. In addition, a one-pot synthetic sequence starting from W(CO)(5)-coordinated phosphinodiphosphonates 5d,e has been developed to engage compounds with vinyl and acetylene substituents in phospha-Wittig-Horner reactions.

  • 18.
    Arkhypchuk, Anna I.
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Molekylär biomimetik.
    Svyaschenko, Yurii V.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Molekylär biomimetik.
    Ott, Sascha
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Molekylär biomimetik.
    Versatile Approach to 3-Phosphahexatrienes Bearing Low Coordinated Phosphorus2015Ingår i: Phosphorus Sulfur and Silicon and the Related Elements, ISSN 1042-6507, E-ISSN 1563-5325, Vol. 190, nr 5-6, s. 638-646Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    lambda(3)-phosphahexatrienes were prepared from ethoxyvinyl phosphinophosphonates using the phospha-Wittig-Horner reaction. The title compounds can be easily prepared in three steps starting from dichlorophosphines with good overall yields. Although these were found to be thermally unstable, these can be trapped, for instance, with methanol. The resulting methoxyphosphines are isolated in high yields in case of aldehyde starting materials with more bulky substituents.

  • 19.
    Arkhypchuk, Anna
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Molekylär biomimetik.
    Mihali, Viorica Alina
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström.
    Orthaber, Andreas
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Molekylär biomimetik.
    Ehlers, Andreas
    VU University Amsterdam.
    Lammertsma, Koop
    VU University Amsterdam.
    Ott, Sascha
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Molekylär biomimetik.
    Phosphorus Heterocylces from Phosphinophosphonates and α,β-Unsaturated KetonesManuskript (preprint) (Övrigt vetenskapligt)
  • 20.
    Arkhypchuk, Anna
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Molekylär biomimetik.
    Svyaschenko, Yurii
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Molekylär biomimetik.
    Orthaber, Andreas
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Molekylär biomimetik.
    Ott, Sascha
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Molekylär biomimetik.
    Mechanism of the Phospha-Wittig-Horner Reaction2013Ingår i: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773, Vol. 52, nr 25, s. 6484-6487Artikel i tidskrift (Refereegranskat)
  • 21.
    Artero, Vincent
    et al.
    Univ Grenoble Alpes, CNRS, CEA, Lab Chem & Biol Met, F-38000 Grenoble, France..
    Berggren, Gustav
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Molekylär biomimetik.
    Atta, Mohamed
    Univ Grenoble Alpes, CNRS, CEA, Lab Chem & Biol Met, F-38000 Grenoble, France..
    Caserta, Giorgio
    Univ Paris 06, CNRS, Coll France, Lab Chim Proc Biol, F-75005 Paris, France..
    Roy, Souvik
    Univ Grenoble Alpes, CNRS, CEA, Lab Chem & Biol Met, F-38000 Grenoble, France..
    Pecqueur, Ludovic
    Univ Paris 06, CNRS, Coll France, Lab Chim Proc Biol, F-75005 Paris, France..
    Fontecave, Marc
    Univ Grenoble Alpes, CNRS, CEA, Lab Chem & Biol Met, F-38000 Grenoble, France.;Univ Paris 06, CNRS, Coll France, Lab Chim Proc Biol, F-75005 Paris, France..
    From Enzyme Maturation to Synthetic Chemistry: The Case of Hydrogenases2015Ingår i: Accounts of Chemical Research, ISSN 0001-4842, E-ISSN 1520-4898, Vol. 48, nr 8, s. 2380-2387Artikel, forskningsöversikt (Refereegranskat)
    Abstract [en]

    CONSPECTUS: Water splitting into oxygen and hydrogen is one of the most attractive strategies for storing solar energy and electricity. Because the processes at work are multielectronic, there is a crucial need for efficient and stable catalysts, which in addition have to be cheap for future industrial developments (electrolyzers, photoelectrochemicals, and fuel cells). Specifically for the water/hydrogen interconversion, Nature is an exquisite source of inspiration since this chemistry contributes to the bioenergetic metabolism of a number of living organisms via the activity of fascinating metalloenzymes, the hydrogenases. In this Account, we first briefly describe the structure of the unique dinuclear organometallic active sites of the two classes of hydrogenases as well as the complex protein machineries involved in their biosynthesis, their so-called maturation processes. This knowledge allows for the development of a fruitful bioinspired chemistry approach, which has already led to a number of interesting and original catalysts mimicking the natural active sites. More specifically, we describe our own attempts to prepare artificial hydrogenases. This can be achieved via the standard bioinspired approach using the combination of a synthetic bioinspired catalyst and a polypeptide scaffold. Such hybrid complexes provide the opportunity to optimize the system by manipulating both the catalyst through chemical synthesis and the protein component through mutagenesis. We also raise the possibility to reach such artificial systems via an original strategy based on mimicking the enzyme maturation pathways. This is illustrated in this Account by two examples developed in our laboratory. First, we show how the preparation of a lysozyme-{Mn-I(CO)(3)} hybrid and its clean reaction with a nickel complex led us to generate a new class of binuclear Ni-Mn H-2-evolving catalysts mimicking the active site of [NiFe]-hydrogenases. Then we describe how we were able to rationally design and prepare a hybrid system, displaying remarkable structural similarities to an [FeFe]-hydrogenase, and we show here for the first time that it is catalytically active for proton reduction. This system is based on the combination of HydF, a protein involved in the maturation of [FeFe]-hydrogenase (HydA), and a close mimic of the active site of this class of enzymes. Moreover, the synthetic [Fe-2(adt)(CO)(4)(CN)(2)](2-) (adt(2-) = aza-propanedithiol) mimic, alone or within a HydF hybrid system, was shown to be able to maturate and activate a form of HydA itself lacking its diiron active site. We discuss the exciting perspectives this "synthetic maturation" opens regarding the "invention" of novel hydrogenases by the chemists.

  • 22.
    Aster, Alexander
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström. Univ Geneva, Dept Phys Chem, 30 Quai Ernest Ansermet, CH-1211 Geneva, Switzerland.
    Wang, Shihuai
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Mirmohades, Mohammad
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Esmieu, Charlène
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Molekylär biomimetik. CNRS, LCC, 205 Route Narbonne,BP 44099, F-31077 Toulouse 4, France.
    Berggren, Gustav
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Molekylär biomimetik.
    Hammarström, Leif
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström.
    Lomoth, Reiner
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström.
    Metal vs. ligand protonation and the alleged proton-shuttling role of the azadithiolate ligand in catalytic H-2 formation with FeFe hydrogenase model complexes2019Ingår i: Chemical Science, ISSN 2041-6520, E-ISSN 2041-6539, Vol. 10, nr 21, s. 5582-5588Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Electron and proton transfer reactions of diiron complexes [Fe(2)adt(CO)(6)] (1) and [Fe(2)adt(CO)(4)(PMe3)(2)] (4), with the biomimetic azadithiolate (adt) bridging ligand, have been investigated by real-time IR- and UV-vis-spectroscopic observation to elucidate the role of the adt-N as a potential proton shuttle in catalytic H-2 formation. Protonation of the one-electron reduced complex, 1(-), occurs on the adt-N yielding 1H and the same species is obtained by one-electron reduction of 1H(+). The preference for ligand vs. metal protonation in the Fe-2(i,0) state is presumably kinetic but no evidence for tautomerization of 1H to the hydride 1Hy was observed. This shows that the adt ligand does not work as a proton relay in the formation of hydride intermediates in the reduced catalyst. A hydride intermediate 1HHy(+) is formed only by protonation of 1H with stronger acid. Adt protonation results in reduction of the catalyst at much less negative potential, but subsequent protonation of the metal centers is not slowed down, as would be expected according to the decrease in basicity. Thus, the adtH(+) complex retains a high turnover frequency at the lowered overpotential. Instead of proton shuttling, we propose that this gain in catalytic performance compared to the propyldithiolate analogue might be rationalized in terms of lower reorganization energy for hydride formation with bulk acid upon adt protonation.

  • 23.
    Ayub, Rabia
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Molekylär biomimetik.
    El Bakouri, Ouissam
    Univ Girona, IQCC, C Maria Aurelia Capmany 6, Girona 17003, Catalonia, Spain..
    Jorner, Kjell
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Molekylär biomimetik.
    Sola, Miguel
    Univ Girona, IQCC, C Maria Aurelia Capmany 6, Girona 17003, Catalonia, Spain..
    Ottosson, Henrik
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Molekylär biomimetik.
    Can Baird's and Clar's Rules Combined Explain Triplet State Energies of Polycyclic Conjugated Hydrocarbons with Fused 4n pi- and (4n+2)pi-Rings?2017Ingår i: Journal of Organic Chemistry, ISSN 0022-3263, E-ISSN 1520-6904, Vol. 82, nr 12, s. 6327-6340Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Compounds that can be labeled as "aromatic chameleons" are pi-conjugated compounds that are able to adjust their pi-electron distributions so as to comply with the different rules of aromaticity in different electronic states. We used quantum chemical calculations to explore how the fusion of benzene rings onto aromatic chameleonic units represented by biphenylene, dibenbzocyclooctatetraene, and dibenzo[a,e]pentalene modifies the first triplet excited states (T-1) of the compounds. Decreases in T-1 energies are observed when going from isomers with linear connectivity of the fused benzene rings to those with cis- or transbent connectivities. The T-1 energies decreased down to those of the parent (isolated) 4n pi-electron units. Simultaneously, we observe an increased influence of triplet State aromaticity of the central 4n ring as given by Baird's rule and evidenced by geometric, magnetic, and electron density based aromaticity indices (HOMA, NICS-XY, ACID, and FLU). Because of an influence of,triplet state aromaticity in the central 4n pi-electron units,, the most stabilized, compounds, retain the triplet excitation in Baird pi-quartets or octets, enabling the outer benzene rings to adapt closed-shell singlet Clar pi-sextet character. Interestingly, the T-1 energies go down as the total number of aromatic cycles within a molecule in the T-1 state increases.

  • 24.
    Ayub, Rabia
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Molekylär biomimetik. uppsala university.
    El Bakouri, Ouissam
    Univ Girona, IQCC, C Maria Aurelia Capmany 6, Girona 17003, Catalonia, Spain.
    Jorner, Kjell
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Molekylär biomimetik. uppsala university.
    Sola, Miquel
    Univ Girona, IQCC, C Maria Aurelia Capmany 6, Girona 17003, Catalonia, Spain.
    Ottosson, Henrik
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Molekylär biomimetik. uppsala university.
    Can Baird’s and Clar’s Rules Combined Explain Triplet State Energies of Polycyclic Conjugated Hydrocarbons with Fused 4nπ- and (4n + 2)π-Rings?2017Ingår i: Journal of Organic Chemistry, ISSN 0022-3263, E-ISSN 1520-6904, Vol. 82, nr 12, s. 6327-6340Artikel i tidskrift (Refereegranskat)
  • 25.
    Ayub, Rabia
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Molekylär biomimetik. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - BMC.
    Jorner, Kjell
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - BMC. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Molekylär biomimetik.
    Ottosson, Henrik
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - BMC. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Molekylär biomimetik.
    The Silacyclobutene Ring: An Indicator of Triplet State Baird-Aromaticity2017Ingår i: Inorganics, ISSN 2304-6740, Vol. 5, nr 4, artikel-id 91Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Baird's rule tells that the electron counts for aromaticity and antiaromaticity in the first pi pi* triplet and singlet excited states (T-1 and S-1) are opposite to those in the ground state (S-0). Our hypothesis is that a silacyclobutene (SCB) ring fused with a [4n]annulene will remain closed in the T-1 state so as to retain T-1 aromaticity of the annulene while it will ring-open when fused to a [4n + 2]annulene in order to alleviate T-1 antiaromaticity. This feature should allow the SCB ring to function as an indicator for triplet state aromaticity. Quantum chemical calculations of energy and (anti)aromaticity changes along the reaction paths in the T-1 state support our hypothesis. The SCB ring should indicate T-1 aromaticity of [4n]annulenes by being photoinert except when fused to cyclobutadiene, where it ring-opens due to ring-strain relief.

  • 26.
    Ayub, Rabia
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - BMC. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Molekylär biomimetik.
    Papadakis, Raffaello
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - BMC. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Molekylär biomimetik.
    Jorner, Kjell
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - BMC. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Molekylär biomimetik. uppsala university.
    Zietz, Burkhard
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Ottosson, Henrik
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - BMC. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Molekylär biomimetik. uppsala university.
    Cyclopropyl Group: An Excited-State Aromaticity Indicator?2017Ingår i: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 23, nr 55, s. 13684-13695Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The cyclopropyl (cPr) group, which is a well-known probe for detecting radical character at atoms to which it is connected, is tested as an indicator for aromaticity in the first * triplet and singlet excited states (T-1 and S-1). Baird's rule says that the -electron counts for aromaticity and antiaromaticity in the T-1 and S-1 states are opposite to Huckel's rule in the ground state (S-0). Our hypothesis is that the cPr group, as a result of Baird's rule, will remain closed when attached to an excited-state aromatic ring, enabling it to be used as an indicator to distinguish excited-state aromatic rings from excited-state antiaromatic and nonaromatic rings. Quantum chemical calculations and photoreactivity experiments support our hypothesis; calculated aromaticity indices reveal that openings of cPr substituents on [4n]annulenes ruin the excited-state aromaticity in energetically unfavorable processes. Yet, polycyclic compounds influenced by excited-state aromaticity (e.g., biphenylene), as well as 4n-electron heterocycles with two or more heteroatoms represent limitations.

  • 27.
    Badary, Amr
    et al.
    Tokyo Univ Agr & Technol, Grad Sch Engn, Dept Biotechnol & Life Sci, 2-24-16 Naka Cho, Koganei, Tokyo 1848588, Japan.;JST, CREST, 2-24-16 Naka Cho, Koganei, Tokyo 1848588, Japan..
    Takamatsu, Shouhei
    Tokyo Univ Agr & Technol, Grad Sch Engn, Dept Biotechnol & Life Sci, 2-24-16 Naka Cho, Koganei, Tokyo 1848588, Japan.;JST, CREST, 2-24-16 Naka Cho, Koganei, Tokyo 1848588, Japan..
    Nakajima, Mitsuharu
    JST, CREST, 2-24-16 Naka Cho, Koganei, Tokyo 1848588, Japan.;Tokyo Univ Agr & Technol, Inst Global Innovat Res, 3-8-1 Harumi Cho, Fuchu, Tokyo 1838538, Japan..
    Ferri, Stefano
    JST, CREST, 2-24-16 Naka Cho, Koganei, Tokyo 1848588, Japan.;Shizuoka Univ, Dept Appl Chem & Biochem Engn, Naka Ku, 3-5-1 Johoku, Hamamatsu, Shizuoka 4328561, Japan..
    Lindblad, Peter
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Molekylär biomimetik.
    Sode, Koji
    Tokyo Univ Agr & Technol, Grad Sch Engn, Dept Biotechnol & Life Sci, 2-24-16 Naka Cho, Koganei, Tokyo 1848588, Japan.;JST, CREST, 2-24-16 Naka Cho, Koganei, Tokyo 1848588, Japan.;Tokyo Univ Agr & Technol, Inst Global Innovat Res, 3-8-1 Harumi Cho, Fuchu, Tokyo 1838538, Japan..
    Glycogen Production in Marine Cyanobacterial Strain Synechococcus sp NKBG 15041c2018Ingår i: Marine Biotechnology, ISSN 1436-2228, E-ISSN 1436-2236, Vol. 20, nr 2, s. 109-117Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    An important feature offered by marine cyanobacterial strains over freshwater strains is the capacity to grow in seawater, replacing the need for often-limited freshwater. However, there are only limited numbers of marine cyanobacteria that are available for genetic manipulation and bioprocess applications. The marine unicellular cyanobacteria Synechococcus sp. strain NKBG 15041c (NKBG15041c) has been extensively studied. Recombinant DNA technologies are available for this strain, and its genomic information has been elucidated. However, an investigation of carbohydrate production, such as glycogen production, would provide information for inevitable biofuel-related compound production, but it has not been conducted. In this study, glycogen production by marine cyanobacterium NKBG15041c was investigated under different cultivation conditions. NKBG15041c yielded up to 399 mu g/ml/OD730 when cells were cultivated for 168 h in nitrogen-depleted medium (marine BG11(Delta N)) after medium replacement (336 h after inoculation). Cultivation under nitrogen-limited conditions also yielded an accumulation of glycogen in NKBG15041c cells (1 mM NaNO3, 301 mu g/ml/OD730; 3 mM NaNO3, 393 mu g/ml/OD730; and 5 mM NaNO3, 328 mu g/ml/OD730) under ambient conditions. Transcriptional analyses were carried out for 13 putative genes responsible for glycogen synthesis and catabolism that were predicted based on homology analyses with Synechocystis sp. PCC 6803 (PCC6803) and Synechococcus sp. PCC7002 (PCC7002). The transcriptional analyses revealed that glycogen production in NKBG15041c under nitrogen-depleted conditions can be explained by the contribution of both increased carbon flux towards glycogen synthesis, similar to PCC6803 and PCC7002, and increased transcriptional levels of genes responsible for glycogen synthesis, which is different from the conventionally reported phenomenon, resulting in a relatively high amount of glycogen under ambient conditions compared to PCC6803 and PCC7002.

  • 28.
    Bedin, Michele
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Molekylär biomimetik.
    Agarwala, Hemlata
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Molekylär biomimetik.
    Ott, Sascha
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Molekylär biomimetik.
    Thapper, Anders
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Molekylär biomimetik.
    Heterometallic Mn/Fe complexes versus homometallic Mn/Mn and Fe/Fe complexes as models for the dimetal carboxylate cofactors.2017Ingår i: Journal of Biological Inorganic Chemistry, ISSN 0949-8257, E-ISSN 1432-1327, Vol. 22, nr Supplement: 1, s. S38-S38Artikel i tidskrift (Övrigt vetenskapligt)
  • 29. Berg, Andreas
    et al.
    Lindblad, Peter
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Molekylär biomimetik.
    Svensson, Bo Håkan
    Cyanobacteria as a source of hydrogen for methane formation2014Ingår i: World Journal of Microbiology & Biotechnology, ISSN 0959-3993, E-ISSN 1573-0972, Vol. 30, nr 2, s. 539-545Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In a study during the 1970s co-variation of nitrogenase activity and methane formation associated with Sphagnum riparium was observed. This was suggested as evidence for a possible mechanism of hydrogen transfer from cyanobacteria to methanogens. We show experimentally that such a pathway is feasible. In a series of laboratory experiments, using a hydrogenase deficient strain of the heterocystous cyanobacterium Nostoc punctiforme and the hydrogenotrophic methanogen Methanospirillum hungateii in co-cultures, increasing light intensities resulted in elevated nitrogenase activity and methane production. The increase in methane production can be directly deduced from the nitrogenase activity of the N. punctiforme based on hydrogen balance calculations. These experimental results clearly suggest the possible existence of a novel photosynthetically regulated pathway for methane formation.

  • 30.
    Berggren, Gustav
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Molekylär biomimetik.
    Anderlund, Magnus F.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Molekylär biomimetik.
    Styring, Stenbjörn
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Molekylär biomimetik.
    Thapper, Anders
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Molekylär biomimetik.
    FTIR Study of Manganese Dimers with Carboxylate Donors As Model Complexes for the Water Oxidation Complex in Photosystem II2012Ingår i: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 51, nr 4, s. 2332-2337Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The carboxylate stretching frequencies of two high-valent, di-mu-oxido bridged, manganese dimers has been studied with IR spectroscopy in three different oxidation states. Both complexes contain one monodentate carboxylate donor to each Mn ion, in one complex, the carboxylate is coordinated perpendicular to the Mn-(mu-O)(2)-Mn plane, and in the other complex, the carboxylate is coordinated in the Mn-(mu-O)(2)-Mn plane. For both complexes, the difference between the asymmetric and the symmetric carboxylate stretching frequen-cies decrease for both the Mn-2(IV,IV) to Mn-2(III,IV) transition and the Mn-2(III,IV) to Mn-2(III,III) transition, with only minor differences observed between the two arrangements of the carboxylate ligand versus the Mn-(mu-O)(2)-Mn plane. The IR spectra also show that both carboxylate ligands are affected for each one electron reduction, i.e., the stretching frequency of the carboxylate coordinated to the Mn ion that is not reduced also shifts. These results are discussed in relation to FTIR studies of changes in carboxylate stretching frequencies in a one electron oxidation step of the water oxidation complex in Photosystem II.

  • 31.
    Berggren, Gustav
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Molekylär biomimetik.
    Lundin, Daniel
    Sjöberg, Britt-Marie
    Homo- and Heterometallic Dinuclear Manganese Proteins: Active Site Assembly2017Ingår i: Metalloprotein Active Site Assembly, John Wiley & Sons, 2017, s. 215-233Kapitel i bok, del av antologi (Refereegranskat)
  • 32. Bergman, Birgitta
    et al.
    Sandh, Gustaf
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Molekylär biomimetik.
    Lin, Senjie
    Larsson, John
    Carpenter, Edward J
    Trichodesmium: a widespread marine cyanobacterium with unusual nitrogen fixation properties2013Ingår i: FEMS Microbiology Reviews, ISSN 0168-6445, E-ISSN 1574-6976, Vol. 37, nr 3, s. 286-302Artikel, forskningsöversikt (Refereegranskat)
    Abstract [en]

    The last several decades have witnessed dramatic advances in unfolding the diversity and commonality of oceanic diazotrophs and their N(2) -fixing potential. More recently substantial progress in diazotrophic cell biology has provided a wealth of information on processes and mechanisms involved. The substantial contribution by the diazotrophic cyanobacterial genus Trichodesmium to the nitrogen influx of the global marine ecosystem is by now undisputable and of paramount ecological importance, while the underlying cellular and molecular regulatory physiology has only recently started to unfold. Here we explore and summarize current knowledge, related to optimization of its diazotrophic capacity, from genomics to ecophysiological processes, via eg. cellular differentiation (diazocytes) and temporal regulations, and suggest cellular research avenues that now ought to be explored. © 2012 Federation of European Microbiological Societies. Published by Blackwell Publishing Ltd. All rights reserved.

  • 33.
    Bergman, Nina
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - BMC, Analytisk kemi.
    Thapper, Anders
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Molekylär biomimetik.
    Styring, Stenbjorn
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Molekylär biomimetik.
    Bergquist, Jonas
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - BMC, Analytisk kemi.
    Shevchenko, Denys
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - BMC, Analytisk kemi.
    Quantitative determination of the Ru(bpy)(3)(2+) cation in photochemical reactions by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry2014Ingår i: Analytical Methods, ISSN 1759-9660, E-ISSN 1759-9679, Vol. 6, nr 21, s. 8513-8518Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The coordination compound of Ru(II) with three 2,2'-bipyridine ligands possesses a potent photosensitization capacity for electron- and energy-transfer processes. In combination with salts of peroxydisulfate acid as sacrificial electron acceptors, Ru(bpy)(3)(2+) is widely used for photocatalytic oxidative transformations in organic synthesis and water splitting. The drawback of this system is that bipyridine degrades under the resulting strongly oxidative conditions, the concentration of Ru(bpy)(3)(2+) diminishes, and the photocatalytic reaction eventually stops. A commonly employed assay for the determination of Ru(bpy)(3)(2+), UV-Vis spectroscopy, has low selectivity and does not distinguish between the intact complex and its decayed forms. Here, we report a matrix assisted laser desorption/ionisation mass spectrometric method for the quantitative analysis of Ru(bpy)(3)(2+) in photochemical reaction mixtures. The developed method was successfully used for the determination of intact Ru(bpy)(3)(2+) during the course of the water photooxidation reaction. The significant difference between the results of MALDI MS and UV-Vis analyses was observed.

  • 34.
    Bhaya, Devaki
    et al.
    Carnegie Inst Sci, Stanford, CA 94305 USA..
    Lindblad, Peter
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Molekylär biomimetik.
    Emerging technologies illuminate facets of photosynthesis in cyanobacteria2015Ingår i: Photosynthesis Research, ISSN 0166-8595, E-ISSN 1573-5079, Vol. 126, nr 1, s. 1-2Artikel i tidskrift (Övrigt vetenskapligt)
  • 35.
    Bhunia, Asamanjoy
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Molekylär biomimetik. Natl Inst Technol Puducherry, Dept Chem, Karaikal 609609, India.
    Johnson, Ben A.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Molekylär biomimetik.
    Czapla-Masztafiak, Joanna
    Polish Acad Sci, Inst Nucl Phys, PL-31342 Krakow, Poland.
    Sá, Jacinto
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi. Polish Acad Sci, Inst Phys Chem, Ul Kasprzaka 44-52, PL-01224 Warsaw, Poland.
    Ott, Sascha
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Molekylär biomimetik.
    Formal water oxidation turnover frequencies from MIL-101(Cr) anchored Ru(bda) depend on oxidant concentration2018Ingår i: Chemical Communications, ISSN 1359-7345, E-ISSN 1364-548X, Vol. 54, s. 7770-7773Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The molecular water oxidation catalyst [Ru(bda)(L)(2)] has been incorporated into pyridine-decorated MIL-101(Cr) metal-organic frameworks. The resulting MIL-101@Ru materials exhibit turnover frequencies (TOFs) up to ten times higher compared to the homogenous reference. An unusual dependence of the formal TOFs on oxidant concentration is observed that ultimately arises from differing amounts of catalysts in the MOF crystals being active.

  • 36.
    Blikstad, Cecilia
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Molekylär biomimetik.
    Ivarsson, Ylva
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - BMC, Biokemi.
    High-throughput methods for identification of protein-protein interactions involving short linear motifs2015Ingår i: Cell Communication and Signaling, ISSN 1478-811X, E-ISSN 1478-811X, Vol. 13, artikel-id 38Artikel, forskningsöversikt (Refereegranskat)
    Abstract [en]

    Interactions between modular domains and short linear motifs (3-10 amino acids peptide stretches) are crucial for cell signaling. The motifs typically reside in the disordered regions of the proteome and the interactions are often transient, allowing for rapid changes in response to changing stimuli. The properties that make domain-motif interactions suitable for cell signaling also make them difficult to capture experimentally and they are therefore largely underrepresented in the known protein-protein interaction networks. Most of the knowledge on domain-motif interactions is derived from low-throughput studies, although there exist dedicated high-throughput methods for the identification of domain-motif interactions. The methods include arrays of peptides or proteins, display of peptides on phage or yeast, and yeast-two-hybrid experiments. We here provide a survey of scalable methods for domain-motif interaction profiling. These methods have frequently been applied to a limited number of ubiquitous domain families. It is now time to apply them to a broader set of peptide binding proteins, to provide a comprehensive picture of the linear motifs in the human proteome and to link them to their potential binding partners. Despite the plethora of methods, it is still a challenge for most approaches to identify interactions that rely on post-translational modification or context dependent or conditional interactions, suggesting directions for further method development.

  • 37.
    Blunder, Martina
    et al.
    Uppsala universitet, Medicinska och farmaceutiska vetenskapsområdet, Medicinska fakulteten, Institutionen för neurovetenskap, Funktionell farmakologi. Graz Univ, Dept Pharmacognosy, Inst Pharmaceut Sci, Univ Pl 4, A-8010 Graz, Austria.
    Orthaber, Andreas
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Molekylär biomimetik. Graz Univ, Dept Pharmaceut Chem, Inst Pharmaceut Sci, Univ Pl 1, A-8010 Graz, Austria.
    Bauer, Rudolf
    Graz Univ, Dept Pharmacognosy, Inst Pharmaceut Sci, Univ Pl 4, A-8010 Graz, Austria.
    Bucar, Franz
    Graz Univ, Dept Pharmacognosy, Inst Pharmaceut Sci, Univ Pl 4, A-8010 Graz, Austria.
    Kunert, Olaf
    Graz Univ, Dept Pharmaceut Chem, Inst Pharmaceut Sci, Univ Pl 1, A-8010 Graz, Austria.
    Efficient identification of flavones, flavanones and their glycosides in routine analysis via off-line combination of sensitive NMR and HPLC experiments2017Ingår i: Food Chemistry, ISSN 0308-8146, E-ISSN 1873-7072, Vol. 218, s. 600-609Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We present a standardized, straightforward and efficient approach applicable in routine analysis of flavonoids combining sensitive NMR and HPLC experiments. The determination of the relative configuration of sugar moieties usually requires the acquisition of 13C NMR shift values. We use a combination of HPLC and sensitive NMR experiments (1D-proton, 2D-HSQC) for the unique identification of known flavones, flavanones, flavonols and their glycosides. Owing to their broad range of polarity, we developed HPLC and UHPLC methods (H2O/MeOH/MeCN/HCOOH) which we applied and validated by analyzing 46 common flavones and flavanones and exemplified for four plant extracts. A searchable data base is provided with full data comprising complete proton and carbon resonance assignments, expansions of HSQC-spectra, HPLC parameters (retention time, relative retention factor), UV/Vis and mass spectral data of all compounds, which enables a rapid identification and routine analysis of flavones and flavanones from plant extracts and other products in nutrition and food chemistry.

  • 38. Borgström, Magnus
    et al.
    Shaikh, Nizamuddin
    Johansson, Olof
    Anderlund, Magnus F
    Styring, Stenbjörn
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Molekylär biomimetik.
    Åkermark, Björn
    Magnuson, Ann
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Molekylär biomimetik.
    Hammarström, Leif
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Light-Induced Manganese Oxidation and Long-Lived Charge Separation in a Mn2II,II─RuII─Acceptor Triad.2005Ingår i: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 127, s. 17504-17515Artikel i tidskrift (Refereegranskat)
  • 39.
    Bornhof, Anna-Bea
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Molekylär biomimetik.
    Xiong, Ruisheng
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Molekylär biomimetik.
    Borbas, K. Eszter
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Molekylär biomimetik.
    Rational Synthesis of 2-Bromoporphyrins and 2,12-Dibromoporphyrins2017Ingår i: Journal of Organic Chemistry, ISSN 0022-3263, E-ISSN 1520-6904, Vol. 82, nr 23, s. 12908-12913Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Bromoporphyrins were prepared by the metal-mediated self-condensation of brominated 1-formyldipyrromethanes. Depending on the conditions, Mg(II)-2,12-dibromoporphyrin and Mg(II)-2-bromoporphyrin could be obtained in up to 11% and 17% isolated yield, respectively. Zn(II) was also a viable templating metal. The positions of the bromine substituents were confirmed by 2D-NMR spectroscopic analysis and the X-ray crystal structure of a derivative. Suzuki and Sonogashira reactions of the bromoporphyrins yielded 2-substituted or 2,12-disubstituted porphyrins with red-shifted absorption and emission spectra. This method provides access to the minimalist core of beta-mono- and beta,beta'-disubstituted porphyrins from readily available starting materials.

  • 40. Bourrez, Marc
    et al.
    Steinmetz, Romain
    Ott, Sascha
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Molekylär biomimetik.
    Gloaguen, Frederic
    Hammarström, Leif
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Concerted proton-coupled electron transfer from a metal-hydride complex2015Ingår i: Nature Chemistry, ISSN 1755-4330, E-ISSN 1755-4349, Vol. 7, nr 2, s. 140-145Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Metal hydrides are key intermediates in the catalytic reduction of protons and CO2 as well as in the oxidation of H-2. In these reactions, electrons and protons are transferred to or from separate acceptors or donors in bidirectional proton-coupled electron transfer (PCET) steps. The mechanistic interpretation of PCET reactions of metal hydrides has focused on the stepwise transfer of electrons and protons. A concerted transfer may, however, occur with a lower reaction barrier and therefore proceed at higher catalytic rates. Here we investigate the feasibility of such a reaction by studying the oxidation-deprotonation reactions of a tungsten hydride complex. The rate dependence on the driving force for both electron transfer and proton transfer-employing different combinations of oxidants and bases-was used to establish experimentally the concerted, bidirectional PCET of a metal-hydride species. Consideration of the findings presented here in future catalyst designs may lead to more-efficient catalysts.

  • 41.
    Brown, Allison
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Antila, Liisa
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Mirmohades, Mohammad
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Pullen, Sonja
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Molekylär biomimetik.
    Ott, Sascha
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Molekylär biomimetik.
    Hammarström, Leif
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Ultrafast Electron Transfer between Dye and Catalyst on a Mesoporous NiO Surface2016Ingår i: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 26, s. 8060-8063Artikel i tidskrift (Övrigt vetenskapligt)
    Abstract [en]

    The combination of molecular dyes and catalysts with semiconductors into dye-sensitized solar fuel devices (DSSFDs) requires control of efficient interfacial and surface charge transfer between the components. The present study reports on the light-induced electron transfer processes of p-type NiO films cosensitized with coumarin C343 and a bioinspired proton reduction catalyst, [FeFe](mcbdt)(CO)(6) (mcbdt = 3-carboxybenzene-1,2-dithiolate). By transient optical spectroscopy we find that ultrafast interfacial electron transfer (tau approximate to 200 fs) from NiO to the excited C343 ("hole injection") is followed by rapid (t(1/2) approximate to 10 ps) and efficient surface electron transfer from C343 to the coadsorbed [FeFe] (mcbdt)(CO)(6). The reduced catalyst has a clear spectroscopic signature that persists for several tens of microseconds, before charge recombination with NiO holes occurs. The demonstration of rapid surface electron transfer from dye to catalyst on NiO, and the relatively long lifetime of the resulting charge separated state, suggests the possibility to use these systems for photocathodes on. DSSFDs.

  • 42.
    Bunrit, Anon
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - BMC.
    Dahlstrand, Christian
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - BMC.
    Olsson, Sandra K.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - BMC.
    Srifa, Pemikar
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - BMC.
    Huang, Genping
    Orthaber, Andreas
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Molekylär biomimetik.
    Sjöberg, Per J. R.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - BMC, Analytisk kemi.
    Biswas, Srijit
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - BMC.
    Himo, Fahmi
    Samec, Joseph S. M.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - BMC.
    Bronsted Acid-Catalyzed Intramolecular Nucleophilic Substitution of the Hydroxyl Group in Stereogenic Alcohols with Chirality Transfer2015Ingår i: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 137, nr 14, s. 4646-4649Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The hydroxyl group of enantioenriched benzyl, propargyl, allyl, and alkyl alcohols has been intramolecularly displaced by uncharged O-, N-, and S-centered nucleophiles to yield enantioenriched tetrahydrofuran, pyrrolidine, and tetrahydrothiophene derivatives with phosphinic acid catalysis. The five-membered heterocyclic products are generated in good to excellent yields, with high degree of chirality transfer, and water as the only side-product. Racemization experiments show that phosphinic acid does not promote S(N)1 reactivity. Density functional theory calculations corroborate a reaction pathway where the phosphinic acid operates as a bifunctional catalyst in the intramolecular substitution reaction. In this mechanism, the acidic proton of the phosphinic acid protonates the hydroxyl group, enhancing the leaving group ability. Simultaneously, the oxo group of phosphinic acid operates as a base abstracting the nucleophilic proton and thus enhancing the nucleophilicity. This reaction will open up new atom efficient techniques that enable alcohols to be used as nucleofuges in substitution reactions in the future.

  • 43.
    Calard, Francois
    et al.
    Ecole Natl Super Chim Montpellier, Inst Charles Gerhardt , Architectures Mol & Mat Nanostruct, Montpellier, France..
    Wani, Ishtiaq Hassan
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Tillämpad materialvetenskap.
    Hayat, Aqib
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Tillämpad materialvetenskap.
    Jarrosson, Thibaut
    Ecole Natl Super Chim Montpellier, Inst Charles Gerhardt Montpellier, Architectures Mol & Mat Nanostruct, Montpellier, France..
    Lere-Porte, Jean-Pierre
    Ecole Natl Super Chim Montpellier, Inst Charles Gerhardt Montpellier, Architectures Mol & Mat Nanostruct, Montpellier, France..
    Jafri, S. Hassan M.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Tillämpad materialvetenskap. Mirpur Univ Sci & Technol, Dept Elect Engn, Azad Kashmir, Pakistan..
    Serein-Spirau, Francoise
    Ecole Natl Super Chim Montpellier, Inst Charles Gerhardt Montpellier, Architectures Mol & Mat Nanostruct, UMR CNRS 5253, Montpellier, France..
    Leifer, Klaus
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Tillämpad materialvetenskap.
    Orthaber, Andreas
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Molekylär biomimetik.
    Designing sterically demanding thiolate coated AuNPs for electrical characterization of BPDT in a NP-molecule-nanoelectrode platform2017Ingår i: MOLECULAR SYSTEMS DESIGN & ENGINEERING, ISSN 2058-9689, Vol. 2, nr 2, s. 133-139Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Molecular electronics with single or few molecules requires a stable metal-molecule nanojunction platform. Herein, we report the design and synthesis of gold nanoparticles coated with sterically demanding thiol ligands that are essential to fabricate a versatile and stable nanoelectrode-molecule-nanoparticle platform suitable for electrical characterization of small organic molecules. By combining.-tetraphenylmethane ether functionalized alkyl thioacetate and alkyl thiols, we prepared highly stable gold nanoparticles in a one-phase reaction providing simple and efficient purification. This robust preparation gives highly pure nanoparticles in very high yields (up to 90%) with long-time shelf stability. The synthesis in this work has superior reproducibility compared to previous synthesis processes that are currently being used for such molecular electronics platforms. Electron microscopy confirms the formation of uniform and small nanoparticles in the range of 5 to 7 nm. These nanoparticles with different ligand surface coverages were placed in a 20 nm nanoelectrode setup using dielectrophoretic forces. This setup was utilized to characterize the conductivity of the molecular wire 4,4'-biphenyldithiol introduced via ligand placeexchange under ambient conditions.

  • 44.
    Camsund, Daniel
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Molekylär biomimetik.
    Engineering Transcriptional Systems for Cyanobacterial Biotechnology2014Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Cyanobacteria are solar-powered cell factories that can be engineered to supply us with renewable fuels and chemicals. To do so robust and well-working biological parts and tools are necessary. Parts for controlling gene expression are of special importance in living systems, and specifically promoters are needed for enabling and simplifying rational design. Synthetic biology is an engineering science that incorporates principles such as decoupling, standardization and modularity to enable the design and construction of more advanced systems from simpler parts and the re-use of parts in new contexts. For these principles to work, cross-talk must be avoided and therefore orthogonal parts and systems are important as they are decoupled by definition. This work concerns the design and development of biological parts and tools that can enable synthetic biology in cyanobacteria. This encompasses parts necessary for the development of other systems, such as vectors and translational elements, but with a focus on transcriptional regulation. First, to enable the development and characterization of promoters in different cyanobacterial chassis, a broad-host-range BioBrick plasmid, pPMQAK1, was constructed and confirmed to function in several cyanobacterial strains. Then, ribosome binding sites, protease degradation tags and constitutive, orthogonal promoters were characterized in the model strain Synechocystis PCC 6803. These tools were then used to design LacI-regulated promoter libraries for studying DNA-looping and the behaviour of LacI-mediated loops in Synechocystis. Ultimately, this lead to the design of completely repressed LacI-regulated promoters that could be used for e.g. cyanobacterial genetic switches, and was used to design a destabilized version of the repressed promoter that could be induced to higher levels. Further, this promoter was used to implement an orthogonal transcriptional system based on T7 RNAP that was shown to drive different levels of T7 promoter transcription depending on regulation. Also, Gal4-repressed promoters for bacteria were engineered and examined in Escherichia coli as an initial step towards transferring them to cyanobacteria. Attempts were also made to implement a light-regulated one-component transcription factor based on Gal4. This work provides a background for engineering transcription and provides suggestions for how to develop the parts further.

    Delarbeten
    1. Design and characterization of molecular tools for a Synthetic Biology approach towards developing cyanobacterial biotechnology
    Öppna denna publikation i ny flik eller fönster >>Design and characterization of molecular tools for a Synthetic Biology approach towards developing cyanobacterial biotechnology
    2010 (Engelska)Ingår i: Nucleic Acids Research, ISSN 0305-1048, E-ISSN 1362-4962, Vol. 38, nr 8, s. 2577-2593Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    Cyanobacteria are suitable for sustainable, solar-powered biotechnological applications. Synthetic biology connects biology with computational design and an engineering perspective, but requires efficient tools and information about the function of biological parts and systems. To enable the development of cyanobacterial Synthetic Biology, several molecular tools were developed and characterized: (i) a broad-host-range BioBrick shuttle vector, pPMQAK1, was constructed and confirmed to replicate in Escherichia coli and three different cyanobacterial strains. (ii) The fluorescent proteins Cerulean, GFPmut3B and EYFP have been demonstrated to work as reporter proteins in cyanobacteria, in spite of the strong background of photosynthetic pigments. (iii) Several promoters, like P-rnpB and variants of P-rbcL, and a version of the promoter P-trc with two operators for enhanced repression, were developed and characterized in Synechocystis sp. strain PCC6803. (iv) It was shown that a system for targeted protein degradation, which is needed to enable dynamic expression studies, is working in Synechocystis sp. strain PCC6803. The pPMQAK1 shuttle vector allows the use of the growing numbers of BioBrick parts in many prokaryotes, and the other tools herein implemented facilitate the development of new parts and systems in cyanobacteria.

    Nationell ämneskategori
    Kemi
    Identifikatorer
    urn:nbn:se:uu:diva-137784 (URN)10.1093/nar/gkq164 (DOI)000277238900008 ()
    Tillgänglig från: 2010-12-15 Skapad: 2010-12-15 Senast uppdaterad: 2017-12-11
    2. Synthetic Biology in Cyanobacteria: Engineering and Analyzing Novel Functions
    Öppna denna publikation i ny flik eller fönster >>Synthetic Biology in Cyanobacteria: Engineering and Analyzing Novel Functions
    Visa övriga...
    2011 (Engelska)Ingår i: Methods in Enzymology, ISSN 0076-6879, E-ISSN 1557-7988, Vol. 497, s. 539-579Artikel, forskningsöversikt (Refereegranskat) Published
    Abstract [en]

    Cyanobacteria are the only prokaryotes capable of using sunlight as their energy, water as an electron donor, and air as a source of carbon and, for some nitrogen-fixing strains, nitrogen. Compared to algae and plants, cyanobacteria are much easier to genetically engineer, and many of the standard biological parts available for Synthetic Biology applications in Escherichia coli can also be used in cyanobacteria. However, characterization of such parts in cyanobacteria reveals differences in performance when compared to E. coli, emphasizing the importance of detailed characterization in the cellular context of a biological chassis. Furthermore, cyanobacteria possess special characteristics (e.g., multiple copies of their chromosomes, high content of photosynthetically active proteins in the thylakoids, the presence of exopolysaccharides and extracellular glycolipids, and the existence of a circadian rhythm) that have to be taken into account when genetically engineering them. With this chapter, the synthetic biologist is given an overview of existing biological parts, tools and protocols for the genetic engineering, and molecular analysis of cyanobacteria for Synthetic Biology applications.

    Nationell ämneskategori
    Naturvetenskap
    Identifikatorer
    urn:nbn:se:uu:diva-155689 (URN)10.1016/B978-0-12-385075-1.00024-X (DOI)000291321200024 ()
    Tillgänglig från: 2011-06-30 Skapad: 2011-06-28 Senast uppdaterad: 2017-12-11
    3. Design and analysis of LacI-repressed promoters and DNA-looping in a cyanobacterium
    Öppna denna publikation i ny flik eller fönster >>Design and analysis of LacI-repressed promoters and DNA-looping in a cyanobacterium
    2014 (Engelska)Ingår i: Journal of Biological Engineering, ISSN 1754-1611, E-ISSN 1754-1611, Vol. 8, nr 4Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    Background

    Cyanobacteria are solar-powered prokaryotes useful for sustainable production of valuable molecules, but orthogonal and regulated promoters are lacking. The Lac repressor (LacI) from Escherichia coli is a well-studied transcription factor that is orthogonal to cyanobacteria and represses transcription by binding a primary lac operator (lacO), blocking RNA-polymerase. Repression can be enhanced through DNA-looping, when a LacI-tetramer binds two spatially separated lacO and loops the DNA. Ptrc is a commonly used LacI-repressed promoter that is inefficiently repressed in the cyanobacterium Synechocystis PCC 6803. Ptrc2O, a version of Ptrc with two lacO, is more efficiently repressed, indicating DNA-looping. To investigate the inefficient repression of Ptrc and cyanobacterial DNA-looping, we designed a Ptrc-derived promoter library consisting of single lacO promoters, including a version of Ptrc with a stronger lacO (Ptrc1O-proximal), and dual lacO promoters with varying inter-lacO distances (the Ptrc2O-library).

    Results

    We first characterized artificial constitutive promoters and used one for engineering a LacI-expressing strain of Synechocystis. Using this strain, we observed that Ptrc1O-proximal is similar to Ptrc in being inefficiently repressed. Further, the Ptrc2O-library displays a periodic repression pattern that remains for both non- and induced conditions and decreases with longer inter-lacO distances, in both E. coli and Synechocystis. Repression of Ptrc2O-library promoters with operators out of phase is less efficient in Synechocystis than in E. coli, whereas repression of promoters with lacO in phase is efficient even under induced conditions in Synechocystis. Two well-repressed Ptrc2O promoters were highly active when tested in absence of LacI in Synechocystis.

    Conclusions

    The artificial constitutive promoters herein characterized can be utilized for expression in cyanobacteria, as demonstrated for LacI. The inefficient repression of Ptrc and Ptrc1O-proximal in Synechocystis, as compared to E. coli, may be due to insufficient LacI expression, or differences in RNAP subunits. DNA-looping works as a transcriptional regulation mechanism similarly as in E. coli. DNA-looping contributes strongly to Ptrc2O-library repression in Synechocystis, even though they contain the weakly-repressed primary lacO of Ptrc1O-proximal and relatively low levels of LacI/cell. Hence, Synechocystis RNAP may be more sensitive to DNA-looping than E. coli RNAP, and/or the chromatin torsion resistance could be lower. Two strong and highly repressed Ptrc2O promoters could be used without induction, or together with an unstable LacI.

    Nationell ämneskategori
    Biokemi och molekylärbiologi
    Identifikatorer
    urn:nbn:se:uu:diva-217339 (URN)10.1186/1754-1611-8-4 (DOI)000335793400001 ()
    Tillgänglig från: 2014-02-03 Skapad: 2014-02-03 Senast uppdaterad: 2017-12-06Bibliografiskt granskad
    4. A LacI-regulated promoter for Synechocystis and its use for implementing a T7 RNA polymerase-based orthogonal transcriptional system
    Öppna denna publikation i ny flik eller fönster >>A LacI-regulated promoter for Synechocystis and its use for implementing a T7 RNA polymerase-based orthogonal transcriptional system
    (Engelska)Manuskript (preprint) (Övrigt vetenskapligt)
    Nationell ämneskategori
    Biokemi och molekylärbiologi
    Identifikatorer
    urn:nbn:se:uu:diva-223598 (URN)
    Tillgänglig från: 2014-04-22 Skapad: 2014-04-22 Senast uppdaterad: 2014-06-30
    5. Genetically engineered light sensors for control of bacterial gene expression
    Öppna denna publikation i ny flik eller fönster >>Genetically engineered light sensors for control of bacterial gene expression
    2011 (Engelska)Ingår i: Biotechnology Journal, ISSN 1860-6768, E-ISSN 1860-7314, Vol. 6, nr 7, s. 826-836Artikel, forskningsöversikt (Refereegranskat) Published
    Abstract [en]

    Light of different wavelengths can serve as a transient, noninvasive means of regulating gene expression for biotechnological purposes. Implementation of advanced gene regulatory circuits will require orthogonal transcriptional systems that can be simultaneously controlled and that can produce several different control states. Fully genetically encoded light sensors take advantage of the favorable characteristics of light, do not need the supplementation of any chemical inducers or co-factors, and have been demonstrated to control gene expression in Escherichia coli. Herein, we review engineered light-sensor systems with potential for in vivo regulation of gene expression in bacteria, and highlight different means of extending the range of available light input and transcriptional output signals. Furthermore, we discuss advances in multiplexing different light sensors for achieving multichromatic control of gene expression and indicate developments that could facilitate the construction of efficient systems for light-regulated, multistate control of gene expression.

    Nyckelord
    Multichromatic, light-regulated promoter, Photoreceptor, Protein engineering, Synthetic biology
    Nationell ämneskategori
    Kemi
    Identifikatorer
    urn:nbn:se:uu:diva-156829 (URN)10.1002/biot.201100091 (DOI)000292738100007 ()
    Tillgänglig från: 2011-08-11 Skapad: 2011-08-09 Senast uppdaterad: 2017-12-08Bibliografiskt granskad
    6. Development of Gal4-regulated transcriptional systems in Escherichia coli
    Öppna denna publikation i ny flik eller fönster >>Development of Gal4-regulated transcriptional systems in Escherichia coli
    (Engelska)Manuskript (preprint) (Övrigt vetenskapligt)
    Nationell ämneskategori
    Biokemi och molekylärbiologi
    Identifikatorer
    urn:nbn:se:uu:diva-223565 (URN)
    Tillgänglig från: 2014-04-22 Skapad: 2014-04-22 Senast uppdaterad: 2014-06-30
  • 45.
    Camsund, Daniel
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Molekylär biomimetik.
    Heidorn, Thorsten
    Bioforsk, Norge.
    Lindblad, Peter
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Molekylär biomimetik.
    Design and analysis of LacI-repressed promoters and DNA-looping in a cyanobacterium2014Ingår i: Journal of Biological Engineering, ISSN 1754-1611, E-ISSN 1754-1611, Vol. 8, nr 4Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Background

    Cyanobacteria are solar-powered prokaryotes useful for sustainable production of valuable molecules, but orthogonal and regulated promoters are lacking. The Lac repressor (LacI) from Escherichia coli is a well-studied transcription factor that is orthogonal to cyanobacteria and represses transcription by binding a primary lac operator (lacO), blocking RNA-polymerase. Repression can be enhanced through DNA-looping, when a LacI-tetramer binds two spatially separated lacO and loops the DNA. Ptrc is a commonly used LacI-repressed promoter that is inefficiently repressed in the cyanobacterium Synechocystis PCC 6803. Ptrc2O, a version of Ptrc with two lacO, is more efficiently repressed, indicating DNA-looping. To investigate the inefficient repression of Ptrc and cyanobacterial DNA-looping, we designed a Ptrc-derived promoter library consisting of single lacO promoters, including a version of Ptrc with a stronger lacO (Ptrc1O-proximal), and dual lacO promoters with varying inter-lacO distances (the Ptrc2O-library).

    Results

    We first characterized artificial constitutive promoters and used one for engineering a LacI-expressing strain of Synechocystis. Using this strain, we observed that Ptrc1O-proximal is similar to Ptrc in being inefficiently repressed. Further, the Ptrc2O-library displays a periodic repression pattern that remains for both non- and induced conditions and decreases with longer inter-lacO distances, in both E. coli and Synechocystis. Repression of Ptrc2O-library promoters with operators out of phase is less efficient in Synechocystis than in E. coli, whereas repression of promoters with lacO in phase is efficient even under induced conditions in Synechocystis. Two well-repressed Ptrc2O promoters were highly active when tested in absence of LacI in Synechocystis.

    Conclusions

    The artificial constitutive promoters herein characterized can be utilized for expression in cyanobacteria, as demonstrated for LacI. The inefficient repression of Ptrc and Ptrc1O-proximal in Synechocystis, as compared to E. coli, may be due to insufficient LacI expression, or differences in RNAP subunits. DNA-looping works as a transcriptional regulation mechanism similarly as in E. coli. DNA-looping contributes strongly to Ptrc2O-library repression in Synechocystis, even though they contain the weakly-repressed primary lacO of Ptrc1O-proximal and relatively low levels of LacI/cell. Hence, Synechocystis RNAP may be more sensitive to DNA-looping than E. coli RNAP, and/or the chromatin torsion resistance could be lower. Two strong and highly repressed Ptrc2O promoters could be used without induction, or together with an unstable LacI.

  • 46.
    Camsund, Daniel
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Molekylär biomimetik.
    Lindblad, Peter
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Molekylär biomimetik.
    A LacI-regulated promoter for Synechocystis and its use for implementing a T7 RNA polymerase-based orthogonal transcriptional systemManuskript (preprint) (Övrigt vetenskapligt)
  • 47.
    Camsund, Daniel
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Molekylär biomimetik.
    Lindblad, Peter
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Molekylär biomimetik.
    A LacI-regulated promoter for Synechocystis and its use for implementing a T7 RNA polymerase-based orthogonal transcriptional systemManuskript (preprint) (Övrigt vetenskapligt)
  • 48.
    Camsund, Daniel
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Molekylär biomimetik.
    Lindblad, Peter
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Molekylär biomimetik.
    Jaramillo, Alfonso
    School of Life Sciences. University of Warwick, Institute of Systems and Synthetic Biology. CNRS FRE3561.
    Development of Gal4-regulated transcriptional systems in Escherichia coli Manuskript (preprint) (Övrigt vetenskapligt)
  • 49.
    Canton, S. E.
    et al.
    Max Planck Inst Biophys Chem, IFG Struct Dynam Biochem Syst, D-37077 Gottingen, Germany.;Deutsch Elektronensynchrotron DESY, Struct Dynam Ultra Short Pulsed Xrays, FS SCS, D-22607 Hamburg, Germany..
    Zhang, X.
    Argonne Natl Lab, Xray Sci Div, Argonne, IL 60439 USA..
    Liu, Y.
    Lund Univ, Ctr Anal & Synth, Dept Chem, S-22100 Lund, Sweden..
    Zhang, J.
    Tianjin Polytech Univ, Sch Environm & Chem Engn, Tianjin 300387, Peoples R China..
    Papai, M.
    Hungarian Acad Sci, Wigner Res Ctr Phys, H-1525 Budapest, Hungary..
    Corani, A.
    Lund Univ, Dept Chem Phys, S-22100 Lund, Sweden..
    Smeigh, Amanda L.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström.
    Smolentsev, G.
    Paul Scherrer Inst, CH-5232 Villigen, Switzerland..
    Attenkofer, K.
    Brookhaven Natl Lab, Photon Sci Directorate, Upton, NY 11973 USA..
    Jennings, G.
    Argonne Natl Lab, Xray Sci Div, Argonne, IL 60439 USA..
    Kurtz, C. A.
    Argonne Natl Lab, Xray Sci Div, Argonne, IL 60439 USA..
    Li, F.
    Dalian Univ Technol, State Key Lab Fine Chem, Dalian 116024, Peoples R China..
    Harlang, T.
    Lund Univ, Dept Chem Phys, S-22100 Lund, Sweden..
    Vithanage, D.
    Lund Univ, Dept Chem Phys, S-22100 Lund, Sweden..
    Chabera, P.
    Lund Univ, Dept Chem Phys, S-22100 Lund, Sweden..
    Bordage, A.
    Univ Paris 11, UMR CNRS 8182, Inst Chim Mol & Mat Orsay, F-91405 Orsay, France..
    Sun, L.
    KTH Royal Inst Technol, Sch Chem Sci & Engn, Dept Chem, S-10044 Stockholm, Sweden..
    Ott, Sascha
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Molekylär biomimetik.
    Warnmark, K.
    Lund Univ, Ctr Anal & Synth, Dept Chem, S-22100 Lund, Sweden..
    Sundstrom, V.
    Lund Univ, Dept Chem Phys, S-22100 Lund, Sweden..
    Watching the dynamics of electrons and atoms at work in solar energy conversion2015Ingår i: Faraday discussions (Online), ISSN 1359-6640, E-ISSN 1364-5498, Vol. 185, s. 51-68Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The photochemical reactions performed by transition metal complexes have been proposed as viable routes towards solar energy conversion and storage into other forms that can be conveniently used in our everyday applications. In order to develop efficient materials, it is necessary to identify, characterize and optimize the elementary steps of the entire process on the atomic scale. To this end, we have studied the photoinduced electronic and structural dynamics in two heterobimetallic ruthenium-cobalt dyads, which belong to the large family of donor-bridge-acceptor systems. Using a combination of ultrafast optical and X-ray absorption spectroscopies, we can clock the light-driven electron transfer processes with element and spin sensitivity. In addition, the changes in local structure around the two metal centers are monitored. These experiments show that the nature of the connecting bridge is decisive for controlling the forward and the backward electron transfer rates, a result supported by quantum chemistry calculations. More generally, this work illustrates how ultrafast optical and X-ray

  • 50.
    Carlsson, Anna-Carin C.
    et al.
    Univ Gothenburg, Dept Chem & Mol Biol, SE-41296 Gothenburg, Sweden.;Colorado State Univ, Dept Biochem & Mol Biol, Ft Collins, CO 80523 USA..
    Mehmeti, Krenare
    Univ Gothenburg, Dept Chem & Mol Biol, SE-41296 Gothenburg, Sweden..
    Uhrbom, Martin
    Univ Gothenburg, Dept Chem & Mol Biol, SE-41296 Gothenburg, Sweden.;AstraZeneca, CVMD iMED, Pepparedsleden 1, S-43183 Molndal, Sweden..
    Karim, Alavi
    Univ Gothenburg, Dept Chem & Mol Biol, SE-41296 Gothenburg, Sweden..
    Bedin, Michele
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Molekylär biomimetik. Univ Gothenburg, Dept Chem & Mol Biol, SE-41296 Gothenburg, Sweden..
    Puttreddy, Rakesh
    Univ Jyvaskyla, Dept Chem, Nanosci Ctr, POB 35, FI-40014 Jyvaskyla, Finland..
    Kleinmaier, Roland
    Univ Gothenburg, Dept Chem & Mol Biol, SE-41296 Gothenburg, Sweden.;Chemtura Organometall GmbH, D-59192 Bergkamen, Germany..
    Neverov, Alexei A.
    Queens Univ, Dept Chem, Kingston, ON K7L 3N6, Canada.;Afton Chem, Richmond, VA 23219 USA..
    Nekoueishahraki, Bijan
    Univ Gothenburg, Dept Chem & Mol Biol, SE-41296 Gothenburg, Sweden..
    Grafenstein, Jurgen
    Univ Gothenburg, Dept Chem & Mol Biol, SE-41296 Gothenburg, Sweden..
    Rissanen, Kari
    Univ Jyvaskyla, Dept Chem, Nanosci Ctr, POB 35, FI-40014 Jyvaskyla, Finland..
    Erdelyi, Mate
    Univ Gothenburg, Dept Chem & Mol Biol, SE-41296 Gothenburg, Sweden.;Swedish NMR Ctr, Medicinaregatan 5, SE-41390 Gothenburg, Sweden..
    Substituent Effects on the [N-I-N](+) Halogen Bond2016Ingår i: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 138, nr 31, s. 9853-9863Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We have investigated the influence of electron density on the three-center [N-I-N](+) halogen bond. A series of [bis(pyri din e) io dine](+) and [1,2-bis ( (pyridin e-2-71 ethynyl)b e nze n e)io dine](+) BF4- complexes substituted with electron withdrawing and donating functionalities in the para-position of their pyridine nitrogen were synthesized and studied by spectroscopic and computational methods. The systematic change of electron density of the pyridine nitrogens upon alteration of the para-substituent (NO2, CF3, H, F, Me, OMe, NMe2) was confirmed by N-15 NMR and by computation of the natural atomic population and the pi electron population of the nitrogen atoms. Formation of the [N-I-N](+) halogen bond resulted in >100 ppm N-15 NMR coordination shifts. Substituent effects on the N-15 NMR chemical shift are governed by the pi population rather than the total electron population at the nitrogens. Isotopic perturbation of equilibrium NMR studies along with computation on the DFT level indicate that all studied systems possess static, symmetric [N-I-N](+) halogen bonds, independent of their electron density. This was further confirmed by single crystal X-ray diffraction data of 4-substituted [bis(pyridine)iodine](+) complexes. An increased electron density of the halogen bond acceptor stabilizes the [N center dot center dot center dot I center dot center dot center dot N](+) bond, whereas electron deficiency reduces the stability of the complexes, as demonstrated by UV-kinetics and computation. In contrast, the N-I bond length is virtually unaffected by changes of the electron density. The understanding of electronic effects on the [N-X-N](+) halogen bond is expected to provide a useful handle for the modulation of the reactivity of [bis(pyridine)halogen](+)-type synthetic reagents.

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