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  • 1.
    Abrashev, Miroslav V.
    et al.
    Univ Sofia St Kliment Ohridski, Fac Phys, Sofia 1164, Bulgaria.
    Chernev, Petko
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics. Free Univ Berlin, Fachbereich Phys, Arnimallee 14, D-14195 Berlin, Germany.
    Kubella, Paul
    Free Univ Berlin, Fachbereich Phys, Arnimallee 14, D-14195 Berlin, Germany.
    Mohammadi, Mohammad Reza
    Free Univ Berlin, Fachbereich Phys, Arnimallee 14, D-14195 Berlin, Germany;Univ Sistan & Baluchestan, Dept Phys, Zahedan 9816745845, Iran.
    Pasquini, Chiara
    Free Univ Berlin, Fachbereich Phys, Arnimallee 14, D-14195 Berlin, Germany.
    Dau, Holger
    Free Univ Berlin, Fachbereich Phys, Arnimallee 14, D-14195 Berlin, Germany.
    Zaharieva, Ivelina
    Free Univ Berlin, Fachbereich Phys, Arnimallee 14, D-14195 Berlin, Germany.
    Origin of the heat-induced improvement of catalytic activity and stability of MnOx electrocatalysts for water oxidation2019In: Journal of Materials Chemistry A, ISSN 2050-7488, Vol. 7, no 28, p. 17022-17036Article in journal (Refereed)
    Abstract [en]

    Catalysis of the oxygen evolution reaction (OER) by earth-abundant materials in the near-neutral pH regime is of great interest as it is the key reaction for non-fossil fuel production. To address the pertinent stability problems and insufficiently understood structure-activity relations, we investigate the influence of moderate annealing (100-300 degrees C for 20 min) for two types of electrodeposited Mn oxide films with contrasting properties. Upon annealing, the originally inactive and structurally well-ordered Oxide 1 of birnessite type became as OER active as the non-heated Oxide 2, which has a highly disordered atomic structure. Oxide 2 also improved its activity upon heating, but more important is the stability improvement: the operation time increased by about two orders of magnitude (in 0.1 M KPi at pH 7). Aiming at atomistic understanding, electrochemical methods including quantitative analysis of impedance spectra, X-ray spectroscopy (XANES and EXAFS), and adapted optical spectroscopies (infrared, UV-vis and Raman) identified structure-reactivity relations. Oxide structures featuring both di-mu-oxo bridged Mn ions and (close to) linear mono-mu-oxo Mn3+-O-Mn4+ connectivity seem to be a prerequisite for OER activity. The latter motif likely stabilizes Mn3+ ions at higher potentials and promotes electron/hole hopping, a feature related to electrical conductivity and reflected in the strongly accelerated rates of Mn oxidation and O-2 formation. Poor charge mobility, which may result from a low level of Mn3+ ions at high potentials, likely promotes inactivation after prolonged operation. Oxide structures related to the perovskite-like zeta-Mn2O3 were formed after the heating of Oxide 2 and could favour stabilization of Mn ions in oxidation states lower than +4. This rare phase was previously found only at high pressure (20 GPa) and temperature (1200 degrees C) and this is the first report where it was stable under ambient conditions.

  • 2.
    Agervald, Åsa
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Microbial Chemistry.
    Camsund, Daniel
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Stensjö, Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Lindblad, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    CRISPR in the extended hyp-operon of the cyanobacterium Nostoc sp. strain PCC 7120, characteristics and putative function(s)2012In: International journal of hydrogen energy, ISSN 0360-3199, E-ISSN 1879-3487, Vol. 37, no 10, p. 8828-8833Article in journal (Refereed)
    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.

  • 3.
    Ahmadova, Nigar
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Studies of the two redox active tyrosines in Photosystem II2017Doctoral thesis, comprehensive summary (Other academic)
    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.

    List of papers
    1. The protonation state around Tyr(D)/Tyr((D)) over dot in photosystem II is reflected in its biphasic oxidation kinetics
    Open this publication in new window or tab >>The protonation state around Tyr(D)/Tyr((D)) over dot in photosystem II is reflected in its biphasic oxidation kinetics
    Show others...
    2017 (English)In: Biochimica et Biophysica Acta - Bioenergetics, ISSN 0005-2728, E-ISSN 1879-2650, Vol. 1858, no 2, p. 147-155Article in journal (Refereed) 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.

    Keywords
    Photosystem II, Tyrosine D, Electron transfer, Proton transfer, Deuterium isotope effect
    National Category
    Biochemistry and Molecular Biology Biophysics
    Identifiers
    urn:nbn:se:uu:diva-316938 (URN)10.1016/j.bbabio.2016.11.002 (DOI)000392776400007 ()27823941 (PubMedID)
    Funder
    Swedish Research Council, 621-2013-5937Swedish Energy Agency, 11674-5Knut and Alice Wallenberg Foundation, KAW 2011.0067
    Available from: 2017-03-09 Created: 2017-03-09 Last updated: 2017-04-30
    2. Tyrosine D oxidation and redox equilibrium in Photosystem II
    Open this publication in new window or tab >>Tyrosine D oxidation and redox equilibrium in Photosystem II
    2017 (English)In: Biochimica et Biophysica Acta - Bioenergetics, ISSN 0005-2728, E-ISSN 1879-2650, Vol. 1858, no 6, p. 407-417Article in journal (Refereed) 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.

    Keywords
    Photosystem II, Electron transfer, Tyrosine D
    National Category
    Natural Sciences
    Research subject
    Biochemistry
    Identifiers
    urn:nbn:se:uu:diva-320913 (URN)10.1016/j.bbabio.2017.02.011 (DOI)000402349000001 ()28235460 (PubMedID)
    Funder
    Swedish Research Council, 621-2013-5937Swedish Energy Agency, 11674-5Knut and Alice Wallenberg Foundation, 2011.0067
    Available from: 2017-04-27 Created: 2017-04-27 Last updated: 2017-07-06Bibliographically approved
    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.
    Open this publication in new window or tab >>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.
    Show others...
    (English)Manuscript (preprint) (Other academic)
    Keywords
    Photosystem II, P680, primary charge separation
    National Category
    Natural Sciences
    Identifiers
    urn:nbn:se:uu:diva-321127 (URN)
    Available from: 2017-04-30 Created: 2017-04-30 Last updated: 2017-05-04
    4. Formation of tyrosine radicals in photosystem II under far-red illumination
    Open this publication in new window or tab >>Formation of tyrosine radicals in photosystem II under far-red illumination
    2018 (English)In: Photosynthesis Research, ISSN 0166-8595, E-ISSN 1573-5079, Vol. 136, no 1, p. 93-106Article in journal (Refereed) 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.

    Keywords
    Photosystem II, Tyrosine Z and D, electron transfer
    National Category
    Biochemistry and Molecular Biology
    Research subject
    Chemistry with specialization in Biophysics
    Identifiers
    urn:nbn:se:uu:diva-320914 (URN)10.1007/s11120-017-0442-3 (DOI)000427394300007 ()28924898 (PubMedID)
    Funder
    Swedish Research Council
    Available from: 2017-04-27 Created: 2017-04-27 Last updated: 2018-05-16Bibliographically approved
    5. Role of the PsbTn, a small luminal protein in Photosystem II, in the redox reactions of Tyrosine D
    Open this publication in new window or tab >>Role of the PsbTn, a small luminal protein in Photosystem II, in the redox reactions of Tyrosine D
    (English)Manuscript (preprint) (Other academic)
    Keywords
    Photosystem II, PsbTn, TyrD
    National Category
    Natural Sciences
    Identifiers
    urn:nbn:se:uu:diva-321125 (URN)
    Available from: 2017-04-30 Created: 2017-04-30 Last updated: 2017-05-04
    6. The Donor-Acceptor side interactions in Photosystem II
    Open this publication in new window or tab >>The Donor-Acceptor side interactions in Photosystem II
    (English)Manuscript (preprint) (Other academic)
    Keywords
    Photosystem II, QA, QB, TyrZ, quinones
    National Category
    Natural Sciences
    Research subject
    Biochemistry
    Identifiers
    urn:nbn:se:uu:diva-321124 (URN)
    Available from: 2017-04-30 Created: 2017-04-30 Last updated: 2017-05-04
  • 4.
    Ahmadova, Nigar
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Ho, Felix
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Styring, Stenbjörn
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Mamedov, Fikret
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Tyrosine D oxidation and redox equilibrium in Photosystem II2017In: Biochimica et Biophysica Acta - Bioenergetics, ISSN 0005-2728, E-ISSN 1879-2650, Vol. 1858, no 6, p. 407-417Article in journal (Refereed)
    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.

  • 5.
    Ahmadova, Nigar
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Mamedov, Fikret
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Formation of tyrosine radicals in photosystem II under far-red illumination2018In: Photosynthesis Research, ISSN 0166-8595, E-ISSN 1573-5079, Vol. 136, no 1, p. 93-106Article in journal (Refereed)
    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.

  • 6.
    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 University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Samec, Joseph S. M.
    Stockholm Univ, Dept Organ Chem, S-10691 Stockholm, Sweden..
    Tsuji-Trost Reaction of Non-Derivatized Allylic Alcohols2018In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 24, no 14, p. 3488-3498Article in journal (Refereed)
    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.

  • 7.
    Andersson Schönn, Mikael
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Promoter regulation: designing cells for biotechnological applications2016Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    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.

  • 8.
    Antila, Liisa J.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Ghamgosar, Pedram
    Maji, Somnath
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Tian, Haining
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Ott, Sascha
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Hammarström, Leif
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Dynamics and Photochemical H-2 Evolution of Dye-NiO Photocathodes with a Biomimetic FeFe-Catalyst2016In: ACS ENERGY LETTERS, ISSN 2380-8195, Vol. 1, no 6, p. 1106-1111Article in journal (Refereed)
    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.

  • 9.
    Arkhypchuk, Anna
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Novel Approaches to Phosphorus-containing Heterocycles and Cumulenes2013Doctoral thesis, comprehensive summary (Other academic)
    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.

    List of papers
    1. Revisiting the Phospha-Wittig - Horner Reaction
    Open this publication in new window or tab >>Revisiting the Phospha-Wittig - Horner Reaction
    2012 (English)In: Organometallics, ISSN 0276-7333, E-ISSN 1520-6041, Vol. 31, no 3, p. 1118-1126Article in journal (Refereed) 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.

    National Category
    Chemical Sciences
    Identifiers
    urn:nbn:se:uu:diva-170346 (URN)10.1021/om201158k (DOI)000300116100046 ()
    Available from: 2012-03-12 Created: 2012-03-12 Last updated: 2017-12-07Bibliographically approved
    2. Cascade Reactions Forming Highly Substituted, Conjugated Phospholes and 1,2-Oxaphospholes
    Open this publication in new window or tab >>Cascade Reactions Forming Highly Substituted, Conjugated Phospholes and 1,2-Oxaphospholes
    2012 (English)In: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773, Vol. 51, no 31, p. 7776-7780Article in journal (Refereed) 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.

    Keywords
    acetylenes, conjugation, cumulenes, phospha-Wittig, reaction mechanisms
    National Category
    Chemical Sciences
    Identifiers
    urn:nbn:se:uu:diva-182042 (URN)10.1002/anie.201202153 (DOI)000306757900029 ()
    Available from: 2012-10-05 Created: 2012-10-02 Last updated: 2017-12-07Bibliographically approved
    3. Phosphorus Heterocylces from Phosphinophosphonates and α,β-Unsaturated Ketones
    Open this publication in new window or tab >>Phosphorus Heterocylces from Phosphinophosphonates and α,β-Unsaturated Ketones
    Show others...
    (English)Manuscript (preprint) (Other academic)
    National Category
    Organic Chemistry Inorganic Chemistry
    Identifiers
    urn:nbn:se:uu:diva-198753 (URN)
    Available from: 2013-04-25 Created: 2013-04-24 Last updated: 2013-08-30
    4. Mechanism of the Phospha-Wittig-Horner Reaction
    Open this publication in new window or tab >>Mechanism of the Phospha-Wittig-Horner Reaction
    2013 (English)In: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773, Vol. 52, no 25, p. 6484-6487Article in journal (Refereed) Published
    Keywords
    ketenes; phosphaallenes; phospha-Wittig-Horner reaction; reaction mechanisms
    National Category
    Organic Chemistry Inorganic Chemistry
    Identifiers
    urn:nbn:se:uu:diva-198754 (URN)10.1002/anie.201301469 (DOI)000320378800024 ()
    Available from: 2013-04-25 Created: 2013-04-24 Last updated: 2017-12-06Bibliographically approved
  • 10.
    Arkhypchuk, Anna I.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    D'Imperio, Nicolas
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Ott, Sascha
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    One-Pot Intermolecular Reductive Cross-Coupling of Deactivated Aldehydes to Unsymmetrically 1,2-Disubstituted Alkenes2018In: Organic Letters, ISSN 1523-7060, E-ISSN 1523-7052, Vol. 20, no 17, p. 5086-5089Article in journal (Refereed)
    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.

  • 11.
    Arkhypchuk, Anna I.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    D'Imperio, Nicolas
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Ott, Sascha
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Triarylalkenes from the site-selective reductive cross-coupling of benzophenones and aldehydes2019In: Chemical Communications, ISSN 1359-7345, E-ISSN 1364-548X, Vol. 55, no 43, p. 6030-6033Article in journal (Refereed)
    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%.

  • 12.
    Arkhypchuk, Anna I.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Physical Organic Chemistry.
    Mijangos, Edgar
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Lomoth, Reiner
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Ott, Sascha
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Redox Switching in Ethenyl- Bridged Bisphospholes2014In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 20, no 49, p. 16083-16087Article in journal (Refereed)
    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.

  • 13.
    Arkhypchuk, Anna I.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Orthaber, Andreas
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Borbas, K. Eszter
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Synthesis and Characterization of Ferrocenyl Chlorins, 1,1'-Ferrocene-Linked Chlorin Dimers, and their BODIPY Analogues2017In: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 56, no 5, p. 3044-3054Article in journal (Refereed)
    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.

  • 14.
    Arkhypchuk, Anna I.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Orthaber, Andreas
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Kovacs, Daniel
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Borbas, K. Eszter
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Isolation and Characterization of a Monoprotonated Hydroporphyrin2018In: European Journal of Organic Chemistry, ISSN 1434-193X, E-ISSN 1099-0690, no 48, p. 7051-7056Article in journal (Refereed)
    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.

  • 15.
    Arkhypchuk, Anna I.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Orthaber, Andreas
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Mihali, Viorica Alina
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Ehlers, Andreas
    Lammertsma, Koop
    Ott, Sascha
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Oxaphospholes and Bisphospholes from Phosphinophosphonates and alpha,beta-Unsaturated Ketones2013In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 19, no 41, p. 13692-13704Article in journal (Refereed)
    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.

  • 16.
    Arkhypchuk, Anna I.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Orthaber, Andreas
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Ott, Sascha
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Tuning the Optical Properties of 1,1'-Biphospholes by Chemical Alterations of the P-P Bridge2014In: European Journal of Inorganic Chemistry, ISSN 1434-1948, E-ISSN 1099-1948, Vol. 2014, no 10, p. 1760-1766Article in journal (Refereed)
    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.

  • 17.
    Arkhypchuk, Anna I.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Santoni, Marie-Pierre
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Ott, Sascha
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Cascade Reactions Forming Highly Substituted, Conjugated Phospholes and 1,2-Oxaphospholes2012In: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773, Vol. 51, no 31, p. 7776-7780Article in journal (Refereed)
    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.

  • 18.
    Arkhypchuk, Anna I.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Santoni, Marie-Pierre
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Ott, Sascha
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Revisiting the Phospha-Wittig - Horner Reaction2012In: Organometallics, ISSN 0276-7333, E-ISSN 1520-6041, Vol. 31, no 3, p. 1118-1126Article in journal (Refereed)
    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.

  • 19.
    Arkhypchuk, Anna I.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Svyaschenko, Yurii V.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Ott, Sascha
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Versatile Approach to 3-Phosphahexatrienes Bearing Low Coordinated Phosphorus2015In: Phosphorus Sulfur and Silicon and the Related Elements, ISSN 1042-6507, E-ISSN 1563-5325, Vol. 190, no 5-6, p. 638-646Article in journal (Refereed)
    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.

  • 20.
    Arkhypchuk, Anna
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Mihali, Viorica Alina
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström.
    Orthaber, Andreas
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Ehlers, Andreas
    VU University Amsterdam.
    Lammertsma, Koop
    VU University Amsterdam.
    Ott, Sascha
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Phosphorus Heterocylces from Phosphinophosphonates and α,β-Unsaturated KetonesManuscript (preprint) (Other academic)
  • 21.
    Arkhypchuk, Anna
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Svyaschenko, Yurii
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Orthaber, Andreas
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Ott, Sascha
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Mechanism of the Phospha-Wittig-Horner Reaction2013In: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773, Vol. 52, no 25, p. 6484-6487Article in journal (Refereed)
  • 22.
    Artero, Vincent
    et al.
    Univ Grenoble Alpes, CNRS, CEA, Lab Chem & Biol Met, F-38000 Grenoble, France..
    Berggren, Gustav
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    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 Hydrogenases2015In: Accounts of Chemical Research, ISSN 0001-4842, E-ISSN 1520-4898, Vol. 48, no 8, p. 2380-2387Article, review/survey (Refereed)
    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.

  • 23.
    Aster, Alexander
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström. Univ Geneva, Dept Phys Chem, 30 Quai Ernest Ansermet, CH-1211 Geneva, Switzerland.
    Wang, Shihuai
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Mirmohades, Mohammad
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Esmieu, Charlène
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics. CNRS, LCC, 205 Route Narbonne,BP 44099, F-31077 Toulouse 4, France.
    Berggren, Gustav
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Hammarström, Leif
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström.
    Lomoth, Reiner
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström.
    Metal vs. ligand protonation and the alleged proton-shuttling role of the azadithiolate ligand in catalytic H-2 formation with FeFe hydrogenase model complexes2019In: Chemical Science, ISSN 2041-6520, E-ISSN 2041-6539, Vol. 10, no 21, p. 5582-5588Article in journal (Refereed)
    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.

  • 24.
    Ayub, Rabia
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    El Bakouri, Ouissam
    Univ Girona, IQCC, C Maria Aurelia Capmany 6, Girona 17003, Catalonia, Spain..
    Jorner, Kjell
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Sola, Miguel
    Univ Girona, IQCC, C Maria Aurelia Capmany 6, Girona 17003, Catalonia, Spain..
    Ottosson, Henrik
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    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?2017In: Journal of Organic Chemistry, ISSN 0022-3263, E-ISSN 1520-6904, Vol. 82, no 12, p. 6327-6340Article in journal (Refereed)
    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.

  • 25.
    Ayub, Rabia
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics. uppsala university.
    El Bakouri, Ouissam
    Univ Girona, IQCC, C Maria Aurelia Capmany 6, Girona 17003, Catalonia, Spain.
    Jorner, Kjell
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics. uppsala university.
    Sola, Miquel
    Univ Girona, IQCC, C Maria Aurelia Capmany 6, Girona 17003, Catalonia, Spain.
    Ottosson, Henrik
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics. 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?2017In: Journal of Organic Chemistry, ISSN 0022-3263, E-ISSN 1520-6904, Vol. 82, no 12, p. 6327-6340Article in journal (Refereed)
  • 26.
    Ayub, Rabia
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC.
    Jorner, Kjell
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Ottosson, Henrik
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    The Silacyclobutene Ring: An Indicator of Triplet State Baird-Aromaticity2017In: Inorganics, ISSN 2304-6740, Vol. 5, no 4, article id 91Article in journal (Refereed)
    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.

  • 27.
    Ayub, Rabia
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Papadakis, Raffaello
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Jorner, Kjell
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics. uppsala university.
    Zietz, Burkhard
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Ottosson, Henrik
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics. uppsala university.
    Cyclopropyl Group: An Excited-State Aromaticity Indicator?2017In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 23, no 55, p. 13684-13695Article in journal (Refereed)
    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.

  • 28.
    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 University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    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 15041c2018In: Marine Biotechnology, ISSN 1436-2228, E-ISSN 1436-2236, Vol. 20, no 2, p. 109-117Article in journal (Refereed)
    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.

  • 29.
    Bedin, Michele
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Agarwala, Hemlata
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Ott, Sascha
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Thapper, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Heterometallic Mn/Fe complexes versus homometallic Mn/Mn and Fe/Fe complexes as models for the dimetal carboxylate cofactors.2017In: Journal of Biological Inorganic Chemistry, ISSN 0949-8257, E-ISSN 1432-1327, Vol. 22, no Supplement: 1, p. S38-S38Article in journal (Other academic)
  • 30. Berg, Andreas
    et al.
    Lindblad, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Svensson, Bo Håkan
    Cyanobacteria as a source of hydrogen for methane formation2014In: World Journal of Microbiology & Biotechnology, ISSN 0959-3993, E-ISSN 1573-0972, Vol. 30, no 2, p. 539-545Article in journal (Refereed)
    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.

  • 31.
    Berggren, Gustav
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Anderlund, Magnus F.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Styring, Stenbjörn
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Thapper, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    FTIR Study of Manganese Dimers with Carboxylate Donors As Model Complexes for the Water Oxidation Complex in Photosystem II2012In: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 51, no 4, p. 2332-2337Article in journal (Refereed)
    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.

  • 32.
    Berggren, Gustav
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Lundin, Daniel
    Sjöberg, Britt-Marie
    Homo- and Heterometallic Dinuclear Manganese Proteins: Active Site Assembly2017In: <