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  • 51.
    Adamovic, Nadja
    et al.
    TU Wien, ISAS, Vienna, Austria..
    Asinari, Pietro
    Politecn Torino, Dept Energy, Turin, Italy..
    Goldbeck, Gerhard
    Goldbeck Consulting Ltd, St Johns Innovat Ctr, Cambridge, England..
    Hashibon, Adham
    Fraunhofer Inst Mech Mat IWM, Freiburg, Germany..
    Hermansson, Kersti
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Strukturkemi.
    Hristova-Bogaerds, Denka
    DPI, Eindhoven, Netherlands..
    Koopmans, Rudolf
    Koopmans Consulting GmbH, Zurich, Switzerland..
    Verbrugge, Tom
    Dow Benelux BV, Hoek, Netherlands..
    Wimmer, Erich
    Mat Design, Le Mans, France..
    European Materials Modelling Council2017Ingår i: Proceedings Of The 4Th World Congress On Integrated Computational Materials Engineering (Icme 2017) / [ed] Mason, P Fisher, CR Glamm, R Manuel, MV Schmitz, GJ Singh, AK Strachan, A, Springer Publishing Company, 2017, s. 79-92Konferensbidrag (Refereegranskat)
    Abstract [en]

    The aim of the European Materials Modelling Council (EMMC) is to establish current and forward looking complementary activities necessary to bring the field of materials modelling closer to the demands of manufacturers (both small and large enterprises) in Europe. The ultimate goal is that materials modelling and simulation will become an integral part of product life cycle management in European industry, thereby making a strong contribution to enhance innovation and competitiveness on a global level. Based on intensive efforts in the past two years within the EMMC, which included numerous consultation and networking actions with representatives of all stakeholders including Modellers, Software Owners, Translators and Manufacturers in Europe, the EMMC identified and proposed a set of underpinning and enabling actions to increase the industrial exploitation of materials modelling in Europe. EMMC will pursue the following overarching objectives in order to bridge the gap between academic innovation and industrial application: enhance the interaction and collaboration between all stakeholders engaged in different types of materials modelling, including modellers, software owners, translators and manufacturers, facilitate integrated materials modelling in Europe building on strong and coherent foundations, coordinate and support actors and mechanisms that enable rapid transfer of materials modelling from academic innovation to the end users and potential beneficiaries in industry, achieve greater awareness and uptake of materials modelling in industry, in particular SMEs, elaborate Roadmaps that (i) identify major obstacles to widening the use of materials modelling and (ii) elaborate strategies to overcome them.

  • 52. Adamska-Venkatesh, Agnieszka
    et al.
    Mirmohades, Mohammad
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Sommer, Constanze
    Reijerse, Edward
    Lubitz, Wolfgang
    Lomoth, Reiner
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Hammarström, Leif
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Following [FeFe] Hydrogenase Active Site Intermediates by Flash Photolysis/Mid-IR ProbingManuskript (preprint) (Övrigt vetenskapligt)
  • 53.
    Afifi, Hala
    et al.
    King’s College London, Institute of Pharmaceutical Science, U.K..
    Karlsson, Göran
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för fysikalisk och analytisk kemi, Fysikalisk kemi.
    Heenan, Richard K
    ISIS-CCLRC, Rutherford Appleton Laboratory, U.K..
    Dreiss, Cécile A
    King’s College London, Institute of Pharmaceutical Science, U.K..
    Solubilization of Oils or Addition of Monoglycerides Drives the Formation of Wormlike Micelles with an Elliptical Cross-Section in Cholesterol-Based Surfactants: A Study by Rheology, SANS, and Cryo-TEM2011Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 27, nr 12, s. 7480-7492Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We report the formation of wormlike micelles (WLM) in poly(oxyethylene) cholesteryl ether (ChEO(10)) aqueous solutions by the addition of lipophilic monoglycerides at room temperature (monolaurin (ML), monocaprin (MC), and monocaprylin (MCL)) bearing 12-, 10-, and 8-carbon alkyl chains, respectively. A combination of rheology, small-angle neutron scattering (SANS), and cryo-TEM was used to study their viscoelastic properties and structure. With the successive addition of cosurfactant, a significant increase in viscosity and a clear solidlike behavior is obtained, suggesting the formation of a viscoelastic network of wormlike micelles. Only for MCL is typical Maxwellian behavior obtained. The onset of micellar growth, as detected by the occurrence of solidlike behavior and a significant increase in viscosity, is obtained for 0.30 (1 wt %), 0.34 (1 wt %), and 0.60 (1.5 wt %) cosurfactant/ChEO(10) molar ratios with ML, MC, and MCL, respectively. With ML and MC, extremely long relaxation times (exceeding 20 s) compared to those of MCL are obtained, and zero-shear viscosity values are more than 1 order of magnitude higher than with MCL. These results show that cosurfactants with longer alkyl chain lengths (ML and MC) induce the formation of longer wormlike micelles and do so at lower concentrations. SANS measurements on dilute solutions confirm that the viscoelastic behavior correlates with an increase in contour length and reveals an elliptical cross-section with an axial ratio of around 2. Cryo-TEM images provide visual evidence of the wormlike micelles and confirm the elliptical shape of the cross-section. The addition of small amounts of aliphatic oils (ethyl butyrate, EB, and ethyl caprylate, EC) and cyclic oils (peppermint, PP, and tea tree, TT, oils) to ChEO(10) solutions induces wormlike micelle formation at a lower cosurfactant concentration or even in its absence (for PP, TT, and EC) because of their probable localization in the palisade layer. The viscosity peak and height of the plateau modulus occur at increasing monoglyceride concentration following the order PP ≈ TT > EC > EB > no oil.

  • 54.
    Afifi, Hala
    et al.
    Institute of Pharmaceutical Science, King’s College London, UK.
    Karlsson, Göran
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - BMC, Analytisk kemi.
    Heenan, Richard K.
    ISIS-CCLRC, Rutherford Appleton Laboratory, Chilton, UK.
    Dreiss, Cécile A.
    Institute of Pharmaceutical Science, King’s College London, UK.
    Structural transitions in cholesterol-based wormlike micelles induced by encapsulating alkyl ester oils with varying architecture2012Ingår i: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 378, nr 1, s. 125-134Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The effect of encapsulating oils on the phase behaviour and the microstructure of wormlike micelles formed by polyoxyethylene cholesteryl ether (ChEO10) and triethylene glycol monododecyl ether co-surfactant (C12EO3) was investigated using rheology, Cryo-TEM and small-angle neutron scattering measurements. Six alkyl ester oils bearing small, systematic variations in their molecular structure were encapsulated: ethyl butyrate (EB24), ethyl caproate (ECO26), ethyl caprylate (EC28), methyl enanthate (ME17), methyl caprylate (MC18) and butyl butyrate (BB44), where the subscripts refer to the length of the alkyl chain and fatty acid chain, respectively, on either sides of the ester link. The addition of alkyl ester oils to ChEO10/C12EO3 solutions promotes the longitudinal growth of the surfactant aggregates into wormlike micelles possessing an elliptical cross-section, with rminor 31 Â± 2 Ã… and rmajor varying from 45 to 70 Ã…. At fixed alkyl chain length, oils with longer fatty acid chains were found to be more efficient in inducing wormlike micelle formation or their elongation, following the order: EC28 > ECO26 > EB24. Instead, at fixed fatty acid chain length, increasing the alkyl chain has a negative effect on the longitudinal micellar growth (MC18 > EC28 and EB24 > BB44). At high co-surfactant concentrations and in the presence of EB24, an unusual phase of ring-like micelles was detected. Overall, the orientation of the oil molecules within the micelles enables them to act as co-surfactants with a small head-group, decreasing the average cross-section area and promoting longitudinal growth of the micelles into worms.

  • 55.
    Agalo, Faith
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - BMC, Analytisk kemi. Uppsala universitet, Medicinska och farmaceutiska vetenskapsområdet, Farmaceutiska fakulteten, Institutionen för läkemedelskemi, Avdelningen för organisk farmaceutisk kemi.
    Synthesis of Insulin-Regulated Aminopeptidase (IRAP) inhibitors2015Självständigt arbete på avancerad nivå (yrkesexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    The need for alternative cognitive enhancers has risen due to the fact that clinical trial results of the drugs currently approved for treating these disorders have not been satisfactory.

    IRAP has become a possible drug target for treating cognitive impairment brought about by Alzheimer’s disease, head trauma or cerebral ischemia, among others. This came after the revelation that Angiotensin IV enhances memory and learning. Angiotensin IV, the endogenous ligand of IRAP has been structurally modified with the aim of producing potent IRAP inhibitors. However, the peptidic nature of these inhibitors restricts their use; they are not likely to cross the blood brain barrier.

    Other strategies for generating IRAP inhibitors have been through structure-based design and receptor based virtual screening. These drug-like molecules have exhibited positive results in animal studies.

    IRAP inhibitors have been identified via a HTS of 10500 low-molecular weight compounds to give the hit based on a spirooxindole dihydroquinazolinone scaffold, with an IC50 value of 1.5 µM. In this project, some analogues to this hit compound have successfully been synthesized using a known method, whereas others have been synthesized after additional method development.

    The application of the developed method was found to be limited, because poor yield was obtained when a compound with an electron withdrawing substituent on the aniline was synthesized. As a result of this, modification of this method may be required or new methods may have to be developed to synthesize these types of analogues.

    Inhibition capability of 5 new spirooxindole dihydroquinazolinones was tested through a biochemical assay. Compound 6e emerged as the most potent inhibitor in the series, with an IC50 value of 0.2 µM. This compound will now serve as a lead compound and should be used as a starting point for future optimization in order to generate more potent IRAP inhibitors.

     

  • 56.
    Agback, M
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för kvantkemi. Kemiska sektionen, Institutionen för fysikalisk och analytisk kemi, Kvantkemi. Kvantkemi.
    Lunell, S
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för kvantkemi. Kemiska sektionen, Institutionen för fysikalisk och analytisk kemi, Kvantkemi.
    Hussenius, A
    Kemiska institutionen. Kemiska sektionen, Institutionen för fysikalisk och analytisk kemi, Kvantkemi.
    Matsson, O
    Kemiska institutionen. Kemiska sektionen, Institutionen för fysikalisk och analytisk kemi, Kvantkemi.
    Theoretical studies of proton transfer reactions in 1-methylindene1998Ingår i: ACTA CHEMICA SCANDINAVICA, ISSN 0904-213X, Vol. 52, nr 5, s. 541-548Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The base-catalysed 1,3-proton transfer reactions in 1-methylindene have been studied theoretically in polar (water) and unpolar (cyclohexane) solvents, respectively, for two different choices of bases, namely ammonia and trimethylamine (TMA), using the SM

  • 57.
    Agervald, Åsa
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för fotokemi och molekylärvetenskap, Mikrobiell Kemi.
    Maturation and Regulation of Cyanobacterial Hydrogenases2009Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Accelerated global warming plus an increasing need for energy is an equation not easily solved, thus new forms of sustainable energy production are urgently requested. In this context hydrogen production based on a cyanobacterial system offers an environmentally friendly alternative for energy capture and conversion. Cyanobacteria can produce hydrogen gas from sun light and water through the combination of photosystems and hydrogenases, and are suitable to cultivate in large scale.

    In the present thesis the maturation process of [NiFe]-hydrogenases is investigated with special focus on transcription of the accessory genes encoding proteins needed for assembly of the large and possibly also for the small hydrogenase subunit. The cyanobacteria used are two N2-fixing, filamentous, heterocystous strains; Nostoc sp. strain PCC 7120 and Nostoc punctiforme PCC 73102.

    For a biotechnological exploration of hydrogen production tools for regulatory purposes are important. The transcription factor CalA (cyanobacterial AbrB like) (Alr0946 in the genome) in Nostoc sp. strain PCC 7120 was found to be involved in hydrogen metabolism by regulating the transcription of the maturation protein HypC. Further the bidirectional hydrogenase activity was down-regulated in the presence of elevated levels of CalA, a result important to take into account when optimizing cyanobacteria for hydrogen production.

    CalA regulates at least 25 proteins in Nostoc sp. strain PCC 7120 and one of the down-regulated proteins was superoxide dismutase, FeSOD. The characterization of FeSOD shows that it has a specific and important function in the oxidative stress tolerance of Nostoc sp. stain PCC 7120. Since CalA is involved in regulation of both the hydrogen metabolism as well as stress responses these findings indicate that Alr0946 is an important transcription factor in Nostoc sp. strain PCC 7120 active on a global level in the cell.

    This thesis adds more knowledge concerning maturation and regulation of cyanobacterial hydrogenases which might be useful for future large scale hydrogen.

    Delarbeten
    1. The CyAbrB transcription factor Alr0946 regulates the iron superoxide dismutase in Nostoc sp. strain PCC 7120
    Öppna denna publikation i ny flik eller fönster >>The CyAbrB transcription factor Alr0946 regulates the iron superoxide dismutase in Nostoc sp. strain PCC 7120
    (Engelska)Manuskript (preprint) (Övrigt vetenskapligt)
    Abstract [en]

    In the present investigation we analyse the results of induced over-production of the CyAbrB transcription factor Alr0946 in the cyanobacterium Nostoc sp. PCC 7120 with special focus on its effects on FeSOD. With gel based quantitative proteomics the induced over-expression of Alr0946 was shown to influence the abundance of at least 25 proteins. One of the proteins with a significant lower abundance was FeSOD, one of two types of superoxide dismutases in Nostoc sp. PCC 7120. The change in protein abundance was also followed by lower transcript as well as activity levels. Purified Alr0946 from Nostoc sp. PCC 7120 was shown to interact with the promoter region of alr2938, encoding FeSOD, indicating a transcriptional regulation of FeSOD by Alr0946. The Alr0946 over-expression strain showed a bleaching phenotype with lower growth rate and truncated filaments already two days after induction of over-expression. The phenotype was even more pronounced when illumination was increased from 35 to 125 μmol m-2s-1. This is in line with an increased need of FeSOD during a stronger oxidative stress. The results indicate that Alr0946 is involved in regulation of stress responses and that FeSOD has a specific and important function in the oxidative stress tolerance of the multicellular cyanobacterium Nostoc sp. PCC 7120.

    Nyckelord
    Nostoc sp. PCC 7120, FeSOD, Alr0946, transcription factor, CyAbrB
    Nationell ämneskategori
    Naturvetenskap
    Identifikatorer
    urn:nbn:se:uu:diva-110862 (URN)
    Tillgänglig från: 2009-11-27 Skapad: 2009-11-27 Senast uppdaterad: 2016-04-21
    2. Transcription of the extended hyp-operon in Nostoc sp. strain PCC 7120
    Öppna denna publikation i ny flik eller fönster >>Transcription of the extended hyp-operon in Nostoc sp. strain PCC 7120
    2008 (Engelska)Ingår i: BMC Microbiology, ISSN 1471-2180, E-ISSN 1471-2180, Vol. 8, s. 69-Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    Background: The maturation of hydrogenases into active enzymes is a complex process and e. g. a correctly assembled active site requires the involvement of at least seven proteins, encoded by hypABCDEF and a hydrogenase specific protease, encoded either by hupW or hoxW. The N2fixing cyanobacterium Nostoc sp. strain PCC 7120 may contain both an uptake and a bidirectional hydrogenase. The present study addresses the presence and expression of hypgenes in Nostoc sp. strain PCC 7120. Results: RTPCRs demonstrated that the six hypgenes together with one ORF may be transcribed as a single operon. Transcriptional start points (TSPs) were identified 280 bp upstream from hypF and 445 bp upstream of hypC, respectively, demonstrating the existence of several transcripts. In addition, five upstream ORFs located in between hupSL, encoding the small and large subunits of the uptake hydrogenase, and the hypoperon, and two downstream ORFs from the hypgenes were shown to be part of the same transcript unit. A third TSP was identified 45 bp upstream of asr0689, the first of five ORFs in this operon. The ORFs are annotated as encoding unknown proteins, with the exception of alr0692 which is identified as a NifUlike protein. Orthologues of the four ORFs asr0689alr0692, with a highly conserved genomic arrangement positioned between hupSL, and the hyp genes are found in several other N2fixing cyanobacteria, but are absent in non N2fixing cyanobacteria with only the bidirectional hydrogenase. Short conserved sequences were found in six intergenic regions of the extended hypoperon, appearing between 11 and 79 times in the genome. Conclusion: This study demonstrated that five ORFs upstream of the hypgene cluster are cotranscribed with the hypgenes, and identified three TSPs in the extended hypgene cluster in Nostoc sp. strain PCC 7120. This may indicate a function related to the assembly of a functional uptake hydrogenase, hypothetically in the assembly of the small subunit of the enzyme.

    Nationell ämneskategori
    Kemi
    Identifikatorer
    urn:nbn:se:uu:diva-110173 (URN)10.1186/1471-2180-8-69 (DOI)000256297500001 ()
    Tillgänglig från: 2009-11-05 Skapad: 2009-11-05 Senast uppdaterad: 2017-12-12
    3. CalA, a cyanobacterial AbrB protein, interacts with the upstream region of hypC and acts as a repressor of its transcription in the cyanobacterium Nostoc sp. strain PCC 7120
    Öppna denna publikation i ny flik eller fönster >>CalA, a cyanobacterial AbrB protein, interacts with the upstream region of hypC and acts as a repressor of its transcription in the cyanobacterium Nostoc sp. strain PCC 7120
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    2010 (Engelska)Ingår i: Applied and Environmental Microbiology, ISSN 0099-2240, E-ISSN 1098-5336, Vol. 76, nr 3, s. 880-890Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    The filamentous, heterocystous, nitrogen-fixing cyanobacterium Nostoc sp. strain PCC 7120 may contain, depending on growth condition, up to two hydrogenases directly involved in hydrogen metabolism. HypC is one out of at least seven auxiliary gene products required for synthesis of a functional hydrogenase, specifically involved in the maturation of the large subunit. In this study we present a protein, Alr0946, belonging to the transcription regulator family AbrB, which in protein-DNA assays was found to interact with the upstream region of hypC. Transcriptional investigations showed that alr0946 is co-transcribed with the downstream gene alr0947, which encodes a putative protease from the abortive infection superfamily, Abi. Alr0946 was shown to interact specifically not only with the upstream region of hypC but also with its own upstream region, acting as a repressor on both. The bidirectional hydrogenase activity was significant down-regulated when Alr0946 was over-expressed demonstrating a correlation to the transcription factor, either direct or indirect. In silico studies showed that homologues to both Alr0946 and Alr0947 are highly conserved proteins within cyanobacteria with a very similar physical organisation of the corresponding structural genes. Possible functions of the co-transcribed downstream protein Alr0947 are presented. In addition, we present a 3D model of the CyAbrB domain of Alr0946 and putative DNA-binding mechanisms are discussed.

    Nyckelord
    Nostoc sp. strain PCC 7120, hypC, Alr0946, CyAbrB, hydrogen metabolism
    Nationell ämneskategori
    Biologiska vetenskaper
    Identifikatorer
    urn:nbn:se:uu:diva-110863 (URN)10.1128/AEM.02521-09 (DOI)000274017400030 ()
    Tillgänglig från: 2009-11-27 Skapad: 2009-11-27 Senast uppdaterad: 2017-12-12
    4. Isolation and characterization of thylakoid membranes from the filamentous cyanobacterium Nostoc punctiforme
    Öppna denna publikation i ny flik eller fönster >>Isolation and characterization of thylakoid membranes from the filamentous cyanobacterium Nostoc punctiforme
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    2007 (Engelska)Ingår i: Physiologia Plantarum: An International Journal for Plant Biology, ISSN 0031-9317, E-ISSN 1399-3054, Vol. 131, nr 4, s. 622-634Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    Nostoc punctiforme strain Pasteur Culture Collection (PCC) 73102, a sequenced filamentous cyanobacterium capable of nitrogen fixation, is used as a model organism for characterization of bioenergetic processes during nitrogen fixation in Nostoc. A protocol for isolating thylakoid membranes was developed to examine the biochem. and biophys. aspects of photosynthetic electron transfer. Thylakoids were isolated from filaments of N. punctiforme by pneumatic pressure-drop lysis. The activity of photosynthetic enzymes in the isolated thylakoids was analyzed by measuring oxygen evolution activity, fluorescence spectroscopy and ESR spectroscopy. Electron transfer was found functional in both PSII and PSI. Electron transfer measurements in PSII, using diphenylcarbazide as electron donor and 2,6-dichlorophenolindophenol as electron acceptor, showed that 80% of the PSII centers were active in water oxidn. in the final membrane prepn. Anal. of the membrane protein complexes was made by 2D gel electrophoresis, and identification of representative proteins was made by mass spectrometry. The ATP synthase, several oligomers of PSI, PSII and the NAD(P)H dehydrogenase (NDH)-1L and NDH-1M complexes, were all found in the gels. Some differences were noted compared with previous results from Synechocystis sp. PCC 6803. Two oligomers of PSII were found, monomeric and dimeric forms, but no CP43-less complexes. Both dimeric and monomeric forms of Cyt b6/f could be obsd. In all, 28 different proteins were identified, of which 25 are transmembrane proteins or membrane associated ones.

    Nyckelord
    Nostoc punctiforme, isolation, membranes, thylakoids, proteomics, photosystem II, photosystem I
    Nationell ämneskategori
    Kemi Biologiska vetenskaper
    Forskningsämne
    Biokemi
    Identifikatorer
    urn:nbn:se:uu:diva-12478 (URN)10.1111/j.1399-3054.2007.00982.x (DOI)000250763500010 ()18251853 (PubMedID)
    Tillgänglig från: 2012-05-08 Skapad: 2007-12-27 Senast uppdaterad: 2017-12-11Bibliografiskt granskad
    5. Transcript analysis of the extended hyp-operons in the cyanobacteria Nostoc sp. strain PCC 7120 and Nostoc punctiforme ATCC 29133
    Öppna denna publikation i ny flik eller fönster >>Transcript analysis of the extended hyp-operons in the cyanobacteria Nostoc sp. strain PCC 7120 and Nostoc punctiforme ATCC 29133
    Visa övriga...
    2011 (Engelska)Ingår i: BMC Research Notes, ISSN 1756-0500, E-ISSN 1756-0500, Vol. 4, nr 186Artikel i tidskrift (Övrigt vetenskapligt) Published
    Abstract [en]

    The ability of cyanobacteria to capture solar energy, via oxygenic photosynthesis, and convert that energy to molecular hydrogen (H2) has made them an interesting group of organisms with potential as future energy producers. There are three types of enzymes directly involved in the cyanobacterial hydrogen metabolism; nitrogenases that produce H2 as a by-product when fixating atmospheric nitrogen, uptake hydrogenases that catalyze the oxidation of H2,thereby preventing energy losses from the cells, and bidirectional hydrogenases that has the capacity to both oxidize and reduce H2. Hydrogenases are complex metalloenzymes, and the insertion of ligands and correct folding of the proteins require assistance of accessory proteins, the Hyp proteins. Cyanobacterial hydrogenases are NiFe-type hydrogenases and consist of a large and a small subunit. Today, the maturation process of the large subunit has been uncovered to a large extent in cyanobacteria, mostly by analogy assumptions from studies done in other bacteria such as Escherichia coli but also from mutational analyses in cyanobacteria, while the maturation process of the small subunit is still unknown. Recently a set of genes, putatively involved in the maturation process of the small subunit, was discovered in Nostoc sp. PCC 7120 and Nostoc punctiforme ATCC 29133. These five ORFs, encoding unknown proteins, are located in between the uptake hydrogenase structural genes and the hyp-genes were shown to be transcribed together with the hyp-genes in Nostoc PCC 7120. The ORFs upstream the hyp-genes can be found in the same genomic arrangement in other filamentous, nitrogen fixing cyanobacterial strains but are interestingly missing in strains incapable of nitrogen fixation. In this study we have further investigated the function of the ORFs upstream the hyp-genes by studying their transcription pattern after nitrogen depletion in the filamentous, nitrogen fixing strains Nostoc PCC 7120 and N. punctiforme. The transcription pattern were compared to the transcription pattern of hupS and hoxY, encoding the uptake and bidirectional hydrogenase small subunits, nifD, encoding a nitrogenase subunit and hypC and hypF, encoding the maturation process accessory proteins HypC and HypF. All the five ORFs upstream the hyp-genes, in both organisms, were upregulated after nitrogen step down in accordance with the transcription pattern for hupS, nifD, hypC and hypF which support the theory that these genes might be involved in the maturation of the small subunit.

    Ort, förlag, år, upplaga, sidor
    London: BioMed Central, 2011
    Nyckelord
    Nostoc sp.strain PCC 7120, Nostoc punctiforme ATCC29133, hyp, hydrogenase maturation
    Nationell ämneskategori
    Biokemi och molekylärbiologi
    Identifikatorer
    urn:nbn:se:uu:diva-110865 (URN)10.1186/1756-0500-4-186 (DOI)
    Tillgänglig från: 2009-11-27 Skapad: 2009-11-27 Senast uppdaterad: 2017-12-12
  • 58.
    Agervald, Åsa
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för fotokemi och molekylärvetenskap, Mikrobiell kemi.
    Baebprasert, Wipawee
    Program of Biotechnology, Faculty of Science, Chulalongkorn University, Bangkok, Thailand.
    Lindblad, Peter
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för fotokemi och molekylärvetenskap, Mikrobiell kemi.
    Stensjö, Karin
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för fotokemi och molekylärvetenskap, Mikrobiell kemi.
    The CyAbrB transcription factor Alr0946 regulates the iron superoxide dismutase in Nostoc sp. strain PCC 7120Manuskript (preprint) (Övrigt vetenskapligt)
    Abstract [en]

    In the present investigation we analyse the results of induced over-production of the CyAbrB transcription factor Alr0946 in the cyanobacterium Nostoc sp. PCC 7120 with special focus on its effects on FeSOD. With gel based quantitative proteomics the induced over-expression of Alr0946 was shown to influence the abundance of at least 25 proteins. One of the proteins with a significant lower abundance was FeSOD, one of two types of superoxide dismutases in Nostoc sp. PCC 7120. The change in protein abundance was also followed by lower transcript as well as activity levels. Purified Alr0946 from Nostoc sp. PCC 7120 was shown to interact with the promoter region of alr2938, encoding FeSOD, indicating a transcriptional regulation of FeSOD by Alr0946. The Alr0946 over-expression strain showed a bleaching phenotype with lower growth rate and truncated filaments already two days after induction of over-expression. The phenotype was even more pronounced when illumination was increased from 35 to 125 μmol m-2s-1. This is in line with an increased need of FeSOD during a stronger oxidative stress. The results indicate that Alr0946 is involved in regulation of stress responses and that FeSOD has a specific and important function in the oxidative stress tolerance of the multicellular cyanobacterium Nostoc sp. PCC 7120.

  • 59.
    Agervald, Åsa
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för fotokemi och molekylärvetenskap, Mikrobiell kemi.
    Baebprasert, Wipawee
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för fotokemi och molekylärvetenskap, Mikrobiell kemi.
    Zhang, Xiaohui
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för fotokemi och molekylärvetenskap, Mikrobiell kemi.
    Incharoensakdi, Aran
    Lindblad, Peter
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för fotokemi och molekylärvetenskap, Mikrobiell kemi.
    Stensjö, Karin
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för fotokemi och molekylärvetenskap, Mikrobiell kemi.
    The CyAbrB transcription factor CalA regulates the iron superoxide dismutase in Nostoc sp. strain PCC 71202010Ingår i: Environmental Microbiology, ISSN 1462-2912, E-ISSN 1462-2920, Vol. 12, nr 10, s. 2826-2837Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    P>In the present investigation the results of induced over-production of the CyAbrB transcription factor CalA (Cyanobacterial AbrB-like, annotated as Alr0946) in the cyanobacterium Nostoc sp. PCC 7120 were analysed. The CalA overexpression strain showed a bleaching phenotype with lower growth rate and truncated filaments 2 days after induction of overexpression. The phenotype was even more pronounced when illumination was increased from 35 to 125 mu mol m-2 s-1. Using gel-based quantitative proteomics, the induced overexpression of CalA was shown to downregulate the abundance of FeSOD, one of two types of superoxide dismutases in Nostoc sp. PCC 7120. The change in protein abundance was also accompanied by lower transcript as well as activity levels. Purified recombinant CalA from Nostoc sp. PCC 7120 was shown to interact with the promoter region of alr2938, encoding FeSOD, indicating a transcriptional regulation of FeSOD by CalA. The bleaching phenotype is in line with a decreased tolerance against oxidative stress and indicates that CalA is involved in regulation of cellular responses in which FeSOD has an important and specific function in the filamentous cyanobacterium Nostoc sp. PCC 7120.

  • 60.
    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.

  • 61.
    Agervald, Åsa
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för fotokemi och molekylärvetenskap.
    Stensjö, Karin
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för fotokemi och molekylärvetenskap.
    Holmqvist, Marie
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för fotokemi och molekylärvetenskap.
    Lindblad, Peter
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för fotokemi och molekylärvetenskap.
    Transcription of the extended hyp-operon in Nostoc sp. strain PCC 71202008Ingår i: BMC Microbiology, ISSN 1471-2180, E-ISSN 1471-2180, Vol. 8, s. 69-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Background: The maturation of hydrogenases into active enzymes is a complex process and e. g. a correctly assembled active site requires the involvement of at least seven proteins, encoded by hypABCDEF and a hydrogenase specific protease, encoded either by hupW or hoxW. The N2fixing cyanobacterium Nostoc sp. strain PCC 7120 may contain both an uptake and a bidirectional hydrogenase. The present study addresses the presence and expression of hypgenes in Nostoc sp. strain PCC 7120. Results: RTPCRs demonstrated that the six hypgenes together with one ORF may be transcribed as a single operon. Transcriptional start points (TSPs) were identified 280 bp upstream from hypF and 445 bp upstream of hypC, respectively, demonstrating the existence of several transcripts. In addition, five upstream ORFs located in between hupSL, encoding the small and large subunits of the uptake hydrogenase, and the hypoperon, and two downstream ORFs from the hypgenes were shown to be part of the same transcript unit. A third TSP was identified 45 bp upstream of asr0689, the first of five ORFs in this operon. The ORFs are annotated as encoding unknown proteins, with the exception of alr0692 which is identified as a NifUlike protein. Orthologues of the four ORFs asr0689alr0692, with a highly conserved genomic arrangement positioned between hupSL, and the hyp genes are found in several other N2fixing cyanobacteria, but are absent in non N2fixing cyanobacteria with only the bidirectional hydrogenase. Short conserved sequences were found in six intergenic regions of the extended hypoperon, appearing between 11 and 79 times in the genome. Conclusion: This study demonstrated that five ORFs upstream of the hypgene cluster are cotranscribed with the hypgenes, and identified three TSPs in the extended hypgene cluster in Nostoc sp. strain PCC 7120. This may indicate a function related to the assembly of a functional uptake hydrogenase, hypothetically in the assembly of the small subunit of the enzyme.

  • 62.
    Agervald, Åsa
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för fotokemi och molekylärvetenskap, Mikrobiell kemi.
    Zhang, Xiaohui
    Department of Biological Sciences, Purdue University.
    Stensjö, Karin
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för fotokemi och molekylärvetenskap, Mikrobiell kemi.
    Devine, Ellenor
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för fotokemi och molekylärvetenskap, Mikrobiell kemi.
    Lindblad, Peter
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för fotokemi och molekylärvetenskap, Mikrobiell kemi.
    CalA, a cyanobacterial AbrB protein, interacts with the upstream region of hypC and acts as a repressor of its transcription in the cyanobacterium Nostoc sp. strain PCC 71202010Ingår i: Applied and Environmental Microbiology, ISSN 0099-2240, E-ISSN 1098-5336, Vol. 76, nr 3, s. 880-890Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The filamentous, heterocystous, nitrogen-fixing cyanobacterium Nostoc sp. strain PCC 7120 may contain, depending on growth condition, up to two hydrogenases directly involved in hydrogen metabolism. HypC is one out of at least seven auxiliary gene products required for synthesis of a functional hydrogenase, specifically involved in the maturation of the large subunit. In this study we present a protein, Alr0946, belonging to the transcription regulator family AbrB, which in protein-DNA assays was found to interact with the upstream region of hypC. Transcriptional investigations showed that alr0946 is co-transcribed with the downstream gene alr0947, which encodes a putative protease from the abortive infection superfamily, Abi. Alr0946 was shown to interact specifically not only with the upstream region of hypC but also with its own upstream region, acting as a repressor on both. The bidirectional hydrogenase activity was significant down-regulated when Alr0946 was over-expressed demonstrating a correlation to the transcription factor, either direct or indirect. In silico studies showed that homologues to both Alr0946 and Alr0947 are highly conserved proteins within cyanobacteria with a very similar physical organisation of the corresponding structural genes. Possible functions of the co-transcribed downstream protein Alr0947 are presented. In addition, we present a 3D model of the CyAbrB domain of Alr0946 and putative DNA-binding mechanisms are discussed.

  • 63.
    Aggeryd, Ingrid
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Kemiska institutionen.
    Bestämning av Substitutionsgraden hos Natrium-karboxymetylcellulosa, CMC: En tillämpning av den utvidgade Henderson-Hasselbalchs ekvation och simplex-optimering för bestämning av ekvivalensvolymer vid potentiometrisk titrering1984Licentiatavhandling, monografi (Övrigt vetenskapligt)
  • 64.
    Agmo Hernández, Víctor
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - BMC, Analytisk kemi.
    Eriksson, Emma K.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - BMC, Analytisk kemi.
    Edwards, Katarina
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - BMC, Analytisk kemi.
    Ubiquinone-10 alters mechanical properties and increases stability of phospholipid membranes2015Ingår i: Biochimica et Biophysica Acta - Biomembranes, ISSN 0005-2736, E-ISSN 1879-2642, Vol. 1848, nr 10, s. 2233-2243Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Abstract Ubiquinone-10 is mostly known for its role as an electron and proton carrier in aerobic cellular respiration and its function as a powerful antioxidant. Accumulating evidence suggest, however, that this well studied membrane component could have several other important functions in living cells. The current study reports on a previously undocumented ability of ubiquinone-10 to modulate the mechanical strength and permeability of lipid membranes. Investigations of DPH fluorescence anisotropy, spontaneous and surfactant induced leakage of carboxyfluorescein, and interactions with hydrophobic and hydrophilic surfaces were used to probe the effects caused by inclusion of ubiquinone-10 in the membrane of phospholipid liposomes. The results show that ubiquinone in concentrations as low as 2 mol.% increases the lipid packing order and condenses the membrane. The altered physicochemical properties result in a slower rate of release of hydrophilic components, and render the membrane more resistant towards rupture. As judged from comparative experiments using the polyisoprenoid alcohol solanesol, the quinone moiety is essential for the membrane stabilizing effects to occur. Our findings imply that the influence of ubiquinone-10 on the permeability and mechanical properties of phospholipid membranes is similar to that of cholesterol. The reported data indicate, however, that the molecular mechanisms are different in the two cases.

  • 65.
    Agmo Hernandez, Victor
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för fysikalisk och analytisk kemi, Fysikalisk kemi.
    Hermes, Michael
    Milchev, Alexander
    Scholz, Fritz
    The overall adhesion-spreading process of liposomes on a mercury electrode is controlled by a mixed diffusion and reaction kinetics mechanism2009Ingår i: Journal of Solid State Electrochemistry, ISSN 1432-8488, E-ISSN 1433-0768, Vol. 13, nr 4, s. 639-649Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Using high-resolution chronoamperometric measurements, with sampling each 1.333 micro s, the initial step of the adhesion-spreading of liposomes on a mercury electrode was studied. These measurements allow getting a deeper insight into the first interaction of the liposomes with the mercury electrode, and they show that the overall adhesion-spreading process at different potentials is partially controlled by a fast but weak interaction equilibrium resulting in a mixed diffusion- and reaction-kinetics-controlled mechanism of the overall reaction.

  • 66.
    Agmo Hernández, Víctor
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för fysikalisk och analytisk kemi, Fysikalisk kemi.
    Karlsson, Göran
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för fysikalisk och analytisk kemi, Fysikalisk kemi.
    Edwards, Katarina
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för fysikalisk och analytisk kemi, Fysikalisk kemi.
    Intrinsic Heterogeneity in Liposome Suspensions Caused by the Dynamic Spontaneous Formation of Hydrophobic Active Sites in Lipid Membranes2011Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 27, nr 8, s. 4873-4883Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The spontaneous, dynamic formation of hydrophobic active sites in lipid bilayer membranes is studied and characterized. It is shown that the rates of formation and consumption of these active sites control at least two important properties of liposomes: their affinity for hydrophobic surfaces and the rate by which they spontaneously release encapsulated molecules. The adhesion and spreading of liposomes onto hydrophobic polystyrene nanoparticles and the spontaneous leakage of an encapsulated fluorescent dye were monitored for different liposome compositions employing Cryo-TEM, DLS, and fluorescence measurements. It was observed that an apparently homogeneous, monodisperse liposome suspension behaves as if composed by two different populations: a fast leaking population that presents affinity for the hydrophobic substrate employed, and a slow leaking population that does not attach immediately to it. The results reported here suggest that the proportion of liposomes in each population changes over time until a dynamic equilibrium is reached. It is shown that this phenomenom can lead to irreproducibility in, for example, spontaneous leakage experiments, as extruded liposomes leak much faster just after preparation than 24 h afterward. Our findings account for discrepancies in several experimental results reported in the literature. To our knowledge, this is the first systematic study addressing the issue of an existing intrinsic heterogeneity of liposome suspensions.

  • 67.
    Agmo Hernández, Víctor
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - BMC, Analytisk kemi.
    Lendeckel, Uwe
    Institut für Medizinische Biochemie und Molekularbiologie, Universitätsmedizin Greifswald, Germany.
    Scholz, Fritz
    Institut für Biochemie, Universität Greifswald, Germany.
    Electrochemistry of Adhesion and Spreading of Lipid Vesicles on Electrodes2013Ingår i: Applications of Electrochemistry in Medicine / [ed] Schlesinger, Mordechay, Springer US , 2013, Vol. 56, s. 189-247Kapitel i bok, del av antologi (Övrigt vetenskapligt)
    Abstract [en]

    Biological membranes have developed to separate different compartments of organisms and cells. There is a large number of rather different functions which membranes have to fulfil: (1) they control the material and energy fluxes of metabolic processes, (2) they provide a wrapping protecting the compartments from chemical and physical attacks of the environment, (3) they provide interfaces at which specific biochemical machineries can operate (e.g., membrane bound enzymes), (4) they are equipped for signal transduction, (5) they possess the necessary stability and flexibility to allow cell division, and endo- and exocytosis as well as migration, (6) they present anchoring structures that enable cell-to-cell and cell-to-matrix physical interactions and intercellular communication. These are certainly not all functions of membranes as new functionalities are continuously reported. Since the biological membranes separate essentially aqueous solutions, such separating borders—if they should possess a reasonable stability and also flexibility combined with selective permeability—have to be built up of hydrophobic molecules exposing to both sides a similar interface. It was one of the most crucial and most lucky circumstances for the development and existence of life that certain amphiphilic molecules are able to assemble in bilayer structures (membranes), which—on one side—possess a rather high physical and chemical stability, and—on the other side—are able to incorporate foreign molecules for modifying both the physical properties as well as the permeability of the membranes for defined chemical species. The importance of the chemical function of membranes and all its constituents, e.g., ion channels, pore peptides, transport peptides, etc., is generally accepted. The fluid-mosaic model proposed by Singer and Nicolson [1] is still the basis to understand the biological, chemical, and physical properties of biological membranes. The importance of the purely mechanical properties of membranes came much later into the focus of research. The reasons are probably the dominance of biochemical thinking and biochemical models among biologists and medical researchers, as well as a certain lack of appropriate methods to probe mechanical properties of membranes. The last decades have changed that situation due to the development of techniques like the Atomic Force Microscopy, Fluorescence Microscopy, Micropipette Aspiration, Raman Microspectroscopy, advanced Calorimetry, etc. This chapter is aimed at elucidating how the properties of membranes can be investigated by studying the interaction of vesicles with a very hydrophobic surface, i.e., with the surface of a mercury electrode. This interaction is unique as it results in a complete disintegration of the bilayer membrane of the vesicles and the formation of an island of adsorbed lipid molecules, i.e., a monolayer island. This process can be followed by current-time measurements (chronoamperometry), which allow studying the complete disintegration process in all its details: the different steps of that disintegration can be resolved on the time scale and the activation parameters can be determined. Most interestingly, the kinetics of vesicle disintegration on mercury share important features with the process of vesicle fusion and, thus, sheds light also on mechanisms of endocytosis and exocytosis. Most importantly, not only artificial vesicles (liposomes) can be studied with this approach, but also reconstituted plasma membrane vesicles and even intact mitochondria. Hence, one can expect that the method may provide in future studies also information on the membrane properties of various other vesicles, including exosomes, and may allow investigating various aspects of drug action in relation to membrane properties (transmembrane transport, tissue targeting, bioavailability, etc.), and also the impact of pathophysiological conditions (e.g., oxidative modification) on membrane properties, on a hitherto not or only hardly accessible level.

  • 68.
    Agmo Hernandez, Victor
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för fysikalisk och analytisk kemi.
    Milchev, Alexander
    Scholz, Fritz
    Study of the temporal distribution of the adhesion-spreading events of liposomes on a mercury electrode2009Ingår i: Journal of Solid State Electrochemistry, ISSN 1432-8488, E-ISSN 1433-0768, Vol. 13, nr 7, s. 1111-1114Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The formal analysis of the mechanism of adhesion spreading of liposomes at mercury electrodes shares several characteristics with the mechanism of metal nucleation at electrodes. It is shown that the description of the temporal distribution of the adhesion-spreading events is similar to that of the temporal distribution of metal clusters. Both processes are stochastic in nature and can be described by the Poisson distribution. Using this approach, a previously proposed model for the overall adhesion-spreading mechanism, considering the formation of active sites on the liposome and the actual attachment of the liposomes to the mercury surface, is validated.

  • 69.
    Agmo Hernández, Víctor
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - BMC, Analytisk kemi.
    Reijmar, Karin
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - BMC, Analytisk kemi.
    Edwards, Katarina
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - BMC, Analytisk kemi.
    Label-Free Characterization of Peptide-Lipid Interactions Using Immobilized Lipodisks2013Ingår i: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 85, nr 15, s. 7377-7384Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Lipodisks, planar lipid bilayer structures stabilized by PEG-ylated lipids, were in the present study covalently bound and immobilized onto sensors for quartz crystal microbalance with dissipation monitoring (QCM-D) studies. It is shown that the modified sensors can be used to characterize the interaction of lipodisks with α-helical amphiphilic peptides with an accuracy similar to that obtained with well established fluorimetric approximations. The method presented has the great advantage that it can be used with peptides in their native form even if no fluorescent residues are present. The potential of the method is illustrated by determining the parameters describing the association of melittin, mastoparan X, and mastoparan with immobilized lipodisks. Both thermodynamic and kinetic analyses are possible. The presented method constitutes a useful tool for fundamental studies of peptide–membrane interactions and can also be applied to optimize the design of lipodisks, for example, for sustained release of antimicrobial peptides in therapeutic applications.

  • 70.
    Agmo Hernández, Víctor
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - BMC, Analytisk kemi.
    Samuelsson, Jörgen
    Department of Engineering and Chemical Sciences, Karlstad University, SE-651 88 Karlstad, Sweden.
    Forssén, Patrik
    Department of Engineering and Chemical Sciences, Karlstad University, SE-651 88 Karlstad, Sweden.
    Fornstedt, Torgny
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - BMC, Analytisk kemi. Department of Engineering and Chemical Sciences, Karlstad University, SE-651 88 Karlstad, Sweden.
    Enhanced interpretation of adsorption data generated by liquid chromatography and by modern biosensors2013Ingår i: Journal of Chromatography A, ISSN 0021-9673, E-ISSN 1873-3778, Vol. 1317, nr SI, s. 22-31Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this study we demonstrate the importance of proper data processing in adsorption isotherm estimations. This was done by investigating and reprocessing data from five cases on two closely related platforms: liquid chromatography (LC) and biosensors. The previously acquired adsorption data were reevaluated and reprocessed using a three-step numerical procedure: (i) preprocessing of adsorption data, (ii) adsorption data analysis and (iii) final rival model fit. For each case, we will discuss what we really measure and what additional information can be obtained by numerical processing of the data. These cases clearly demonstrate that numerical processing of LC and biosensor data can be used to gain deeper understanding of molecular interactions with adsorption media. This is important because adsorption data, especially from biosensors, is often processed using old and simplified methods.

  • 71.
    Agmo Hernández, Víctor
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - BMC, Analytisk kemi.
    The theory of metal electronucleation applied to the study of fundamental properties of liposomes2013Ingår i: Journal of Solid State Electrochemistry, ISSN 1432-8488, E-ISSN 1433-0768, Vol. 17, nr 2 (SI), s. 299-305Artikel, forskningsöversikt (Refereegranskat)
    Abstract [en]

    This short review describes how the theory of electrochemical metal nucleation considering non-stationary effects due to the activation of latent nucleation sites has been successfully translated and applied to describe phenomena observed on lipid membranes. This rather unexpected connection is merely formal, but has resulted in a completely new approach in liposome research. It has been proposed that hydrophobic active sites spontaneously and constantly appear and disappear on lipid membranes. These sites control the affinity of liposomes for hydrophobic surfaces and determine the permeability of the lipid membrane to small hydrophilic molecules. Thus, the kinetic models for liposome adhesion on hydrophobic substrates and for the spontaneous leakage of liposomal content are identical to that of non-stationary nucleation mentioned above. Therefore, the broad scope of the available work on metal nucleation has facilitated the interpretation of the data obtained in liposome research. Future applications of the nucleation model in the realm of liposomes are also discussed.

  • 72.
    Agrios, Alexander G.
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för fysikalisk och analytisk kemi, Fysikalisk kemi.
    Hagfeldt, Anders
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för fysikalisk och analytisk kemi, Fysikalisk kemi.
    Low-temperature TiO2 Films for Dye-sensitized Solar Cells: Factors Affecting Energy Conversion Efficiency2008Ingår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 112, nr 27, s. 10021-10026Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Semiconductor films prepd. by electrostatic layer-by-layer deposition can be used to fabricate dye-sensitized solar cells after low-temp. treatment (150 DegC). However, the resulting photocurrent is much less than when the film is sintered at 500 DegC. The difference in short-circuit current is a factor of 2.2 with the Ru-based dye N719 and is 3.5 with the org. dye D5. The photocurrent at a given wavelength is proportional to the light-harvesting efficiency, charge injection effciency, and charge collection efficiency. Sintered films take up more than 60% more of either dye than unsintered films and therefore absorb more photons. Electron injection is hindered in unsintered films due to a conduction band edge potential 100 mV more neg. than in a sintered electrode. Addnl. injection effects could be due to adsorption of the dye to polymer rather than to TiO2 in unsintered films, although our measurements were inconclusive on this point. Kinetic studies show electron transport times (ttr) an order of magnitude faster then electron lifetimes (te) in both sintered and unsintered electrodes. Furthermore, a Li+ insertion expt. shows that both films have good elec. connectivity between TiO2 nanoparticles. Unsintered films thus exhibit efficient charge transport despite the presence of polymer and the lack of heat treatment to induce necking.

  • 73.
    Aguirre Castillo, José
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Oorganisk kemi.
    Optimisation of the bottom stirring praxis in a LD-LBE converter: Investigations and tests on phosphorous removal, nitrogen as stirring gas, and slopping2015Självständigt arbete på avancerad nivå (yrkesexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    En järnmalmsbaserad stålproduktion börjar med att järnmalm matas i en masugn tillsammans med koks, kalk och tillsatsämnen. Ut kommer råjärn med höga kol och svavelhalter. Råjärnet transporteras till stålverket i så kallade torpedvagnar. I vissa stålverk, t.ex. SSAB Special Steels i Oxelösund, renas råjärnet från svavel i torpedvagnen. I andra stålverk svavelrenar man i separata skänkar. Svavelreningen sker med bland annat kalciumkarbid som binder till svavlet.

    Det svavelfattiga råjärnet måste sedan renas från kol för att bli stål. Det görs i en LD-konvertern (Linz Donawitz). LD-konvertern laddas med flytande råjärn som har en kolhalt på 4,5 procent och som är runt 1350 grader varmt. Råjärnet kyls genom att cirka 20 procent skrot tillsätts. En syrgaslans sänks sedan in i konvertern ovanför smältan och reningen startar.  Syrgaslansen blåser syrgas i ultraljudsfart vilket oxiderar en del av järnet, så väl som kol, kisel, mangan, fosfor and andra föroreningsämnen i råjärnet. Kol försvinner ur konvertern i form av kolmonoxidgas. Andra oxiderade föroreningar och järnoxid bildar tillsammans en så kallad slagg som flyter ovanpå smältan. Det tillsätts även så kallade slaggbildare som förbättrar upptaget av föroreningar i slaggen. Processen varar i cirka 17 minuter och är mycket beroende av slaggen som bildas. Kol försvinner ur konvertern i form av kolmonoxidgas. Under processens gång rör man om smältan med hjälp av gaser som spolas genom botten av konvertern. Omröringen jämnar ut smältans sammansättning och temperatur. När man inte länge behöver avlägsna kol stoppas processen. Stålets temperatur är då cirka 1700 grader och kolhalten ligger nära 0,05 procent.

    Stålet överförs sedan till en skänk för att skilja det ur slaggen. Stålet förädlas vidare i olika processer där sammansättningen justeras så att det möter kundens krav. Sedan gjuts stålet i strängar för transport till valsverk eller kunder.

    Denna studie behandlar bottenomrörningen under LD-processen i SSAB Special Steels's stålverk i Oxelösund. Omrörningen sker genom åtta porösa stenar i botten av konvertern som blåser med argon eller kväve. Gasflödet genom stenarna justeras genom ett ventilsystem. Under blåsningen rör man om med hjälp av förinställda program. Omrörningens primära funktion är att avlasta syrgaslansen. I fallen där ingen bottenomrörning finns måste syrgaslansen blåsa ”hårdare” på stålet för att avlägsna kol. Avlastningen som bottenomrörningen bidrar med gör att processen även kallas för LD-LBE, där LBE står för Lans Bubbling Equilibrium.

    Bottenomrörningen tros ha en positiv effekt på stålets rening från fosfor. Sedan tidigare vet man att temperatur och slaggsammansättning är de största faktorerna som påverkar fosforreningen. Fosfor tas lättare upp i slaggen vid låga temperaturen samt i slagg med högre kalkhalter. Olika omrörningsprogram testades och en bättre fosforrening nåddes. Bottenomrörningen visade sig ha positiva effekter som är teoretisk kopplade till kalksmältning. Två möjliga förklaringsmekanismer hittades.

    Studien undersökte även användningen av kväve som omrörningsgas istället för argon, då kväve är ekonomisk fördelaktig gentemot argon. Kväve finns inlöst i råjärnet som sätts in i konvertern. Kvävgasen försvinner ur stålet under och med hjälp av kolreningen. Det visade sig vara säkert att använda kväve från start fram till halva syrgasblåset på kvävekänsliga stålsorter, var efter man sedan byte till argon. Kväve som används sent under blåset visade ge högre kvävehalter.

    Urkok är en kraftig volymökning av slaggen som sker när bildad gas från reningen av smältan fångas i slaggen och får slaggen att ”koka över”. Urkok resulterar i ekonomiska förluster då slaggen som lämnar konvertern vid urkok är rik på järn. Bottenomrörningens eventuella påverkan på urkok studerades. Det visade sig att urkok inte kan undvikas genom att enbart optimera bottenomrörningen.

  • 74.
    Ahlberg, Patrik
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets elektronik.
    Johansson, Fredrik
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi.
    Zhang, Zhibin
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets elektronik.
    Jansson, Ulf
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Oorganisk kemi.
    Zhang, Shi-Li
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets elektronik.
    Lindblad, Andreas
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi.
    Nyberg, Tomas
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets elektronik.
    Defect formation in graphene during low-energy ion bombardment2016Ingår i: APL Materials, ISSN 2166-532X, Vol. 4, nr 4, artikel-id 046104Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This letter reports on a systematic investigation of sputter induced damage in graphene caused by low energy Ar+ ion bombardment. The integral numbers of ions per area (dose) as well as their energies are varied in the range of a few eV's up to 200 eV. The defects in the graphene are correlated to the dose/energy and different mechanisms for the defect formation are presented. The energetic bombardment associated with the conventional sputter deposition process is typically in the investigated energy range. However, during sputter deposition on graphene, the energetic particle bombardment potentially disrupts the crystallinity and consequently deteriorates its properties. One purpose with the present study is therefore to demonstrate the limits and possibilities with sputter deposition of thin films on graphene and to identify energy levels necessary to obtain defect free graphene during the sputter deposition process. Another purpose is to disclose the fundamental mechanisms responsible for defect formation in graphene for the studied energy range.

  • 75.
    Ahlberg, Patrik
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets elektronik.
    Nyberg, Tomas
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets elektronik.
    Zhang, Shi-Li
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets elektronik.
    Zhang, Zhi-Bin
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets elektronik.
    Jansson, Ulf
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Oorganisk kemi.
    Toward synthesis of oxide films on graphene with sputtering based processes2016Ingår i: Journal of Vacuum Science & Technology B, ISSN 1071-1023, E-ISSN 1520-8567, Vol. 34, nr 4, artikel-id 040605Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The impact of energetic particles associated with a sputter deposition process may introduce damage to single layer graphene films, making it challenging to apply this method when processing graphene. The challenge is even greater when oxygen is incorporated into the sputtering process as graphene can be readily oxidized. This work demonstrates a method of synthesizing ZnSn oxide on graphene without introducing an appreciable amount of defects into the underlying graphene. Moreover, the method is general and applicable to other oxides. The formation of ZnSn oxide is realized by sputter deposition of ZnSn followed by a postoxidation step. In order to prevent the underlying graphene from damage during the initial sputter deposition process, the substrate temperature is kept close to room temperature, and the processing pressure is kept high enough to effectively suppress energetic bombardment. Further, in the subsequent postannealing step, it is important not to exceed temperatures resulting in oxidation of the graphene. The authors conclude that postoxidation of ZnSn is satisfactorily performed at 300 degrees C in pure oxygen at reduced pressure. This process results in an oxidized ZnSn film while retaining the initial quality of the graphene film.

  • 76.
    Ahlgren, Joakim
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för fysikalisk och analytisk kemi, Analytisk kemi.
    Organic Phosphorus Compounds in Aquatic Sediments: Analysis, Abundance and Effects2006Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Phosphorus (P) is often the limiting nutrient in lacustrine and brackish eco-systems, and enhanced input of P into an aquatic system might therefore negatively impact the environment. Because modern waste water manage-ment have reduced external P input to surface waters, internal P loading from the sediment has become one of the main P sources to aquatic ecosys-tems, in which relatively unknown organic P compounds seem to be more active in P recycling than previously thought.

    This thesis focus is on improving analysis methods for organic P com-pounds in lacustrine and brackish sediments, as well as determining which of these compounds might be degraded, mobilized and subsequently recycled to the water column and on what temporal scale this occur. In both lacustrine and brackish environments, the most labile P compound was pyrophosphate, followed by different phosphate diesters. Phosphate monoesters were the least labile organic P compounds and degraded the slowest with sediment depth. In regulated lakes, it was shown that pyrophosphate and polyphos-phate compound groups were most related to lake trophic status, thus indi-cating their involvement in P cycling. This thesis also indicates faster P turn-over in sediment from the brackish environment compared to sediment from the lacustrine environment.

    A comparison of organic P extraction procedures showed that pre-extraction with EDTA, and NaOH as main extractant, was most efficient for total P extraction. Using buffered sodium dithionite (BD) as a pre-extractant and NaOH as main extractant was most efficient for extracting the presuma-bly most labile organic P compound groups, pyrophosphate and polyphos-phate. Furthermore, it was determined that organic P compounds associated with humic substances were more recalcitrant than other P compounds, that the BD step used in traditional P fractionation might extract phosphate monoesters, and that NMR is a statistically valid method for quantification of organic P compounds in sediment extracts.

    Delarbeten
    1. Depth attenuation of biogenic phosphorus compounds in lake sediment measured by 31P NMR
    Öppna denna publikation i ny flik eller fönster >>Depth attenuation of biogenic phosphorus compounds in lake sediment measured by 31P NMR
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    2005 (Engelska)Ingår i: Environmental Science and Technology, ISSN 0013-936, Vol. 39, nr 3, s. 867-872Artikel i tidskrift (Refereegranskat) Published
    Nationell ämneskategori
    Naturvetenskap
    Identifikatorer
    urn:nbn:se:uu:diva-94212 (URN)
    Tillgänglig från: 2006-03-31 Skapad: 2006-03-31 Senast uppdaterad: 2017-11-30Bibliografiskt granskad
    2. Characterization of phosphorus in sequential extracts from lake sediments using P-31 nuclear magnetic resonance spectroscopy
    Öppna denna publikation i ny flik eller fönster >>Characterization of phosphorus in sequential extracts from lake sediments using P-31 nuclear magnetic resonance spectroscopy
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    2006 (Engelska)Ingår i: Canadian Journal of Fisheries and Aquatic Sciences, ISSN 0706-652X, E-ISSN 1205-7533, Vol. 63, nr 8, s. 1686-1699Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    Phosphorus (P) compounds in three different lake surface sediments were extracted by sequential P extraction and identified by P-31 nuclear magnetic resonance (P-31 NMR) spectroscopy. The extraction procedure primarily discriminates between inorganic P-binding sites but most extraction steps also contained P not reacting (nrP) with the molybdenum complex during P analyses. In all three lakes, the nrP dominated in the NaOH extracts. Nonreactive P from the dystrophic lake was dominated by potentially recalcitrant P groups such as orthophosphate monoesters, while the nrP in the two more productive lakes also contained polyphosphates, pyrophosphate, and organic P groups such as P lipids and DNA-P that may be important in remineralization and recycling to the water column. In addition, polyphosphates showed substantial dynamics in settling seston. The Humic-P pools (P associated with humic acids) showed strong signals of orthophosphate monoesters in all three lakes, which supported the assumption that P-containing humic compounds are indeed recovered in this fraction, although other organic P forms are also present. Thus, in addition to expanding the understanding of which organic P forms that are present in lake sediments, the P-31 NMR technique also demonstrated that the chemical extraction procedure may provide some quantification of recalcitrant versus labile organic P forms.

    Nationell ämneskategori
    Biologiska vetenskaper
    Identifikatorer
    urn:nbn:se:uu:diva-94213 (URN)10.1139/F06-070 (DOI)000239655100003 ()
    Tillgänglig från: 2006-03-31 Skapad: 2006-03-31 Senast uppdaterad: 2017-12-14Bibliografiskt granskad
    3. Degradation of organic phosphorus compounds in anoxic Baltic Sea sediments: A P-31 nuclear magnetic resonance study
    Öppna denna publikation i ny flik eller fönster >>Degradation of organic phosphorus compounds in anoxic Baltic Sea sediments: A P-31 nuclear magnetic resonance study
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    2006 (Engelska)Ingår i: Limnology and Oceanography, ISSN 0024-3590, E-ISSN 1939-5590, Vol. 51, nr 5, s. 2341-2348Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    The composition and abundance of phosphorus extracted by NaOH-ethylenediaminetetraacetic acid from anoxic Northwest Baltic Sea sediment was characterized and quantified using solution P-31 nuclear magnetic resonance. Extracts from sediment depths down to 55 cm, representing 85 yr of deposition, contained 18.5 g m(-2) orthophosphate. Orthophosphate monoesters, teichoic acid P, microbial P lipids, DNA P, and pyrophosphate corresponded to 6.7, 0.3, 1.1, 3.0, and 0.03 g P m(-2), respectively. The degradability of these compound groups was estimated by their decline in concentration with sediment depth. Pyrophosphate had the shortest half-life (3 yr), followed by microbial P lipids with a half-life of 5 yr, DNA P (8 yr), and orthophosphate monoesters (16 yr). No decline in concentration with sediment depth was observed for orthophosphate or teichoic acid P.

    Nationell ämneskategori
    Biologiska vetenskaper
    Identifikatorer
    urn:nbn:se:uu:diva-94214 (URN)000240673800036 ()
    Tillgänglig från: 2006-03-31 Skapad: 2006-03-31 Senast uppdaterad: 2017-12-14Bibliografiskt granskad
    4. Biogenic phosphorus in oligotrophic mountain lake sediments: Differences in composition measured with NMR spectroscopy
    Öppna denna publikation i ny flik eller fönster >>Biogenic phosphorus in oligotrophic mountain lake sediments: Differences in composition measured with NMR spectroscopy
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    2006 (Engelska)Ingår i: Water Research, ISSN 0043-1354, E-ISSN 1879-2448, Vol. 40, nr 20, s. 3705-3712Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    Phosphorus (P) composition in alkaline sediment extracts from three Swedish oligotrophic mountain lakes was investigated using P-31-NMR spectroscopy. Surface sediments from one natural lake and two mature reservoirs, one of which has received nutrient additions over the last 3 years, were compared with respect to biogenic P composition. The results show significant differences in the occurrence of labile and biogenic P species in the sediments of the different systems. The P compound groups that varied most between these three systems were pyrophosphate and polyphosphates, compound groups known to play an important role in sediment P recycling. The content of these compound groups was lowest in the reservoirs and may indicate a coupling between anthropogenic disturbances (i.e., impoundment) to a water system and the availability of labile P species in the sediment. A statistical study was also conducted to determine the accuracy and reliability of using P-31-NMR spectroscopy for quantification of sediment P forms.

    Nyckelord
    phosphorus species, P-31-NMR spectroscopy, reservoirs, oligotrophication, method validation, P-31-NMR accuracy
    Nationell ämneskategori
    Biologiska vetenskaper
    Identifikatorer
    urn:nbn:se:uu:diva-94215 (URN)10.1016/j.watres.2006.09.006 (DOI)000242988600005 ()17070896 (PubMedID)
    Tillgänglig från: 2006-03-31 Skapad: 2006-03-31 Senast uppdaterad: 2017-12-14Bibliografiskt granskad
    5. Degradation rates of organic phosphorus in lake sediment
    Öppna denna publikation i ny flik eller fönster >>Degradation rates of organic phosphorus in lake sediment
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    2007 (Engelska)Ingår i: Biogeochemistry, ISSN 0168-2563, E-ISSN 1573-515X, Vol. 82, nr 1, s. 15-28Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    Phosphorus (P) binding groups were identified in phytoplankton, settling particles, and sediment profiles by 31P NMR spectroscopy from the Swedish mesotrophic Lake Erken. The 31P NMR analysis revealed that polyphosphates and pyrophosphates were abundant in the water column, but rapidly mineralized in the sediment. Orthophosphate monoesters and teichoic acids degraded more slowly than DNA-P, polyphosphates, and P lipids. Humic acids and organic acids from phytoplankton were precipitated from the NaOH extract by acidification and identified by 31P NMR spectroscopy. The precipitated P was significantly more recalcitrant than the P compound groups remaining in solution, but does not constitute a major sink of P as it did not reach a stable concentration with depth, which indicates that it may eventually be degraded. Since P also precipitated from phytoplankton, the origin of humic-P can not be related solely to allochthonous P.

    Nyckelord
    Organic P, 31P NMR, Lake sediment, Degradation rates
    Nationell ämneskategori
    Biologiska vetenskaper Kemi
    Identifikatorer
    urn:nbn:se:uu:diva-97627 (URN)10.1007/s10533-006-9049-z (DOI)000244070900002 ()
    Tillgänglig från: 2008-10-15 Skapad: 2008-10-15 Senast uppdaterad: 2017-12-14Bibliografiskt granskad
    6. Sediment Phosphorus Extractants for Phosphorus-31 Nuclear Magnetic Resonance Analysis: A Quantitative Evaluation
    Öppna denna publikation i ny flik eller fönster >>Sediment Phosphorus Extractants for Phosphorus-31 Nuclear Magnetic Resonance Analysis: A Quantitative Evaluation
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    2007 (Engelska)Ingår i: Journal of Environmental Quality, ISSN 0047-2425, E-ISSN 1537-2537, Vol. 36, nr 3, s. 892-898Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    The influence of pre-extractant, extractant, and post-extractant on total extracted amounts of P and organic P compound groups measured with 31P nuclear magnetic resonance (31P-NMR) in lacustrine sediment was examined. The main extractants investigated were sodium hydroxide (NaOH) and sodium hydroxide ethylenediaminetetraacetic acid (NaOH-EDTA) with bicarbonate buffered dithionite (BD) or EDTA as pre-extractants. Post extractions were conducted using either NaOH or NaOH-EDTA, depending on the main extractant. Results showed that the most efficient combination of extractants for total P yield was NaOH with EDTA as pre-extractant, yielding almost 50% more than the second best procedure. The P compound groups varying the most between the different extraction procedures were polyphosphates and pyrophosphates. NaOH with BD as pre-extractant was the most efficient combination for these compound groups.

    Nationell ämneskategori
    Kemi
    Identifikatorer
    urn:nbn:se:uu:diva-94217 (URN)10.2134/jeq2006.0235 (DOI)000246430500028 ()17485721 (PubMedID)
    Tillgänglig från: 2006-03-31 Skapad: 2006-03-31 Senast uppdaterad: 2017-12-14Bibliografiskt granskad
  • 77.
    Ahlgren, Joakim
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för fysikalisk och analytisk kemi.
    De Brabandere, Heidi
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för fysikalisk och analytisk kemi.
    Reitzel, Kasper
    Rydin, Emil
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och evolution. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och genetik, Limnologi.
    Gogoll, Adolf
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för biokemi och organisk kemi.
    Waldebäck, Monica
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för fysikalisk och analytisk kemi.
    Sediment Phosphorus Extractants for Phosphorus-31 Nuclear Magnetic Resonance Analysis: A Quantitative Evaluation2007Ingår i: Journal of Environmental Quality, ISSN 0047-2425, E-ISSN 1537-2537, Vol. 36, nr 3, s. 892-898Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The influence of pre-extractant, extractant, and post-extractant on total extracted amounts of P and organic P compound groups measured with 31P nuclear magnetic resonance (31P-NMR) in lacustrine sediment was examined. The main extractants investigated were sodium hydroxide (NaOH) and sodium hydroxide ethylenediaminetetraacetic acid (NaOH-EDTA) with bicarbonate buffered dithionite (BD) or EDTA as pre-extractants. Post extractions were conducted using either NaOH or NaOH-EDTA, depending on the main extractant. Results showed that the most efficient combination of extractants for total P yield was NaOH with EDTA as pre-extractant, yielding almost 50% more than the second best procedure. The P compound groups varying the most between the different extraction procedures were polyphosphates and pyrophosphates. NaOH with BD as pre-extractant was the most efficient combination for these compound groups.