Dissertations / Theses: 'Biology - Electron Transfer'

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Lee, Lester Y. C. "Transmembrane electron transfer in artificial bilayers /." Full text open access at:, 1985. http://content.ohsu.edu/u?/etd,86.

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Danyal, Karamatullah. "Electron Transfer and Substrate Reduction in Nitrogenase." DigitalCommons@USU, 2014. https://digitalcommons.usu.edu/etd/2181.

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Population growth over the past ~50 years accompanied by the changes in dietary habits due to economic growth have markedly increased the demand for fixed nitrogen. Aided by biological nitrogen fixation, the Haber-Bosch process has been able to fulfill these demands. However, due to its high temperature and pressure requirements, Haber-Bosch is an expensive process. Every year, approximately 2% of the total energy expenditure by man is used to manufacture fixed nitrogen. Biological systems, on the other hand, produce ammonia at ambient temperature and pressure with much higher efficiency than the Haber-Bosch process. Research in the field of biological nitrogen fixation could prove valuable in understanding the mechanism of the enzyme responsible, nitrogenase. This could eventually allow researchers to mimic the enzyme and fix nitrogen at standard temperature and pressure, which would lead to greater availability of fixed nitrogen and a better standard of living for mankind. As part of this research, nitrogenase of Azotobacter vinelandii was studied to understand the order of events in reduction of substrates and the conformational changes in the enzyme responsible for its ability to reduce said substrates at room temperature and pressure. This knowledge was used to study variant forms of nitrogenase that could be activated using controlled external reductants. This freedom from the biological reductant of nitrogenase opens the door for further research into the understanding and development of enzyme mimics that can reduce substrates at room temperature and pressure.

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Chen, Dawei. "The Methylotrophic Bacterium W3A1 Electron Transfer Flavoprotein: Cloning, Expression, and Cofactor Binding Properties /." The Ohio State University, 1996. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487931993468247.

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Batchelor-McAuley, Christopher. "Multi-electron transfer to and from organic molecules." Thesis, University of Oxford, 2012. http://ora.ox.ac.uk/objects/uuid:14f0d2d6-da21-4041-9a5a-e0186fb36239.

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Herein, the influence of protonation and adsorption upon the redox and electrocatalysis of quinone species - specifically anthraquinone derivatives – is investigated. Through the comparison of the measured rate constants of one-electron reductions of a family of quinones in acetonitrile at both graphite and gold electrodes, it was confirmed that the redox potential indirectly influences the rate of electron transfer in a manner consistent with the potential-dependence of the density of states. In aqueous media, the voltammetric response of both anthraquione-2-sulfonate (AQMS) and anthraquinone-2,6-disulfonate (AQDS) was measured over the full aqueous pH range. A model is provided which is able to describe not just the variation in the formal potential but also the peak height as a function of pH. Importantly, this model predicts that the formal potential for the first (Ef1) and second (Ef2) electron transfers are comparable in magnitude (E^θ _f2−E^_θf1 equals -15mV for AQMS and -36mV for AQDS). This quantitative model is then further extended to consider the situation in which the system is not fully buffered, giving insight into the change of pH at the electrode surface during experimentation. Adsorption to graphitic electrodes can impart a strong influence on the measured voltammetric response. It is demonstrated that through the pre-exposure of a newly prepared graphitic electrode to organic solvents, these adsorption processes can be predominantly blocked. Moreover, it is shown that the electroactivity of the electrode is not significantly altered. This thesis also highlights two cases in which adsorption of the electroactive species may be used to positive effect. First, the surface adsorption of anthraquinone-2-monosulfonate is studied on a graphite electrode, where it is demonstrated that the heterogeneity of the electrode surface may be probed through studying the electrochemical response of the adsorbed species. From this work it is concluded that the rate of electron transfer at the graphitic basal plane is 2-3 orders of magnitude lower than that observed on the edge plane sites. Second, the co-adsorption of DNA and anthraquinone-2-monosulfonate is used as an indirect method to measure the solution phase concentration of DNA (LOD = 8.8μM). The reduced form of anthraquinone is also known to readily reduce oxygen. Through the use of a boron-doped diamond electrode it was possible to directly study the anthraquinone mediated reduction mechanism. Significantly, the voltammetric response indicates the reduction of the oxygen via the semi-quinone intermediate (kf = 4.8 × 10⁹ mol⁻¹ dm³ s⁻¹) is over two orders of magnitude faster than the reaction involving the di-reduced form (kf = 1 × 10⁷ mol⁻¹ dm³ s⁻¹). More importantly, this work provides voltammetric evidence for the existence of the semi-quinone species. This work is subsequently extended through the investigation of the poorly soluble anthraquinone derivative quinizarin. Not only is it possible to detect voltammetrically this biologically relevant species to concentrations as low as 5nM (100ppt), but the methodology also allows the electrochemistry of the quinizarin species to be probed, something which was not previously possible.

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Feng, Yucheng. "Role of electrostatic interactions in regulating redox potentials and electron transfer of flavodoxin from Desulfovibrio Vulgaris (Hildenborough)/." The Ohio State University, 1998. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487953204280307.

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Roberts, Lezah Wilette. "Effect of Netropsin on One-electron Oxidation of DNA." Diss., Georgia Institute of Technology, 2005. http://hdl.handle.net/1853/7228.

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One electron oxidation of DNA has been studied extensively over the years. When a charge is injected into a DNA duplex, it migrates through the DNA until it reaches a trap. Upon further reactions, damage occurs in this area and strand cleavage can occur. Many works have been performed to see what can affect this damage to DNA. Netropsin is a minor groove binder that can bind to tracts of four to five A:T base pairs. It has been used in the studies within to determine if it can protect DNA against oxidative damage, caused by one-electron oxidation, when it is bound within the minor groove of the DNA. By using a naphthacenedione derivative as a photosensitizer, several DNA duplexes containing netropsin binding sites as well as those without binding sites, were irradiated at 420 nm, analyzed, and visualized to determine its effect on oxidative damage. It has been determined netropsin creates a quenching sphere of an average of 5.8 * 108 Šwhether bound to the DNA or not. Herein we will show netropsin protects DNA against oxidative damage whether it is free in solutions or bound within the minor groove of a DNA duplex.

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Wallrapp, Frank. "Mixed quantum and classical simulation techniques for mapping electron transfer in proteins." Doctoral thesis, Universitat Pompeu Fabra, 2011. http://hdl.handle.net/10803/22685.

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El objetivo de esta tesis se centra en el estudio de la transferencia de electrones (ET), una de las reacciones más simples y cruciales en bioquímica. Para dichos procesos, obtener información directa de los factores que lo promueves, asi como del camino de transferencia electronica, no es una tarea trivial. Dicha información a un nivel de conocimiento detallado atómico y electrónico, sin embargo, es muy valiosa en términos de una mejor comprensión del ciclo enzimático, que podría conducir, por ejemplo, a un diseño más eficaz de inhibidores. El objetivo principal de esta tesis es el desarrollo de una metodología para el estudio cuantitativo de la ET en los sistemas biológicos. En este sentido, hemos desarrollado un nuevo método para obtener el camino de transferencia electrónico, llamado QM/MM e-‐ Pathway, que se puede aplicar en sistemas complejos con ET de largo alcance. El método se basa en una búsqueda sucesiva de residuos importantes para la ET, utilizando la modificación de la región quantica en métodos mixtos QM/MM, y siguiendo la evolución de la densidad de espín dentro de la zona de transferencia. Hemos demostrado la utilidad y la aplicabilidad del algoritmo en el complejo P450cam/Pdx, identificando el papel clave de la Arg112 (en P450cam) y del Asp48 (en Pdx), ambos conocidos en la literatura. Además de obtener caminos de ET, hemos cuantificado su importancia en términos del acoplamiento electrónico entre el dador y aceptor para los diferentes caminos. En este sentido, se realizaron dos estudios de la influencia del solvente y de la temperatura en el acoplamiento electrónico para sistemas modelo oligopéptidos. Ambos estudios revelaron que los valores del acoplamiento electrónico fluctúan fuertemente a lo largo de las trayectorias de dinámica molecular obtenidas, y el mecanismo de transferencia de electrones se ve ampliamente afectado por el espacio conformacional del sistema. La combinación del QM/MM e-‐pathway y de los cálculos de acoplamiento electronico fueron utilizados finalmente para investigar la ET en el complejo CCP/Cytc. Nuestros hallazgos indican el papel fundamental del Trp191 en localizar un estadio intermedio para la transferencia electronica, así como el camino ET principal que incluye Ala194, Ala193, Gly192 y Trp191. Ambos hallazgos fueron confirmados a través de la literatura. Los resultados obtenidos para el muestro de manios de ET, junto con su evaluación a través de cálculos de acoplamiento electrónico, sugieren un enfoque sencillo y prometedor para investigar ET de largo alcance en proteínas. The focus of this PhD thesis lies on electron transfer (ET) processes, belonging to the simplest but most crucial reactions in biochemistry. Getting direct information of the forces driving the process and the actual electron pathway is not a trivial task. Such atomic and electronic detailed information, however, is very valuable in terms of a better understanding of the enzymatic cycle, which might lead, for example, to more efficient protein inhibitor design. The main objective of this thesis was the development of a methodology for the quantitative study of ET in biological systems. In this regard, we developed a novel approach to map long-‐range electron transfer pathways, called QM/MM e-‐Pathway. The method is based on a successive search for important ET residues in terms of modifying the QM region following the evolution of the spin density of the electron (hole) within a given transfer region. We proved the usefulness and applicability of the algorithm on the P450cam/Pdx complex, indicating the key role of Arg112 of P450cam and Asp48 of Pdx for its ET pathway, both being known to be important from the literature. Besides only identifying the ET pathways, we further quantified their importance in terms of electronic coupling of donor and acceptor incorporating the particular pathway residues. Within this regard, we performed two systematic evaluations of the underlying reasons for the influence of solvent and temperature onto electronic coupling in oligopeptide model systems. Both studies revealed that electronic coupling values strongly fluctuate throughout the molecular dynamics trajectories obtained, and the mechanism of electron transfer is affected by the conformational space the system is able to occupy. Combining both ET mapping and electronic coupling calculations, we finally investigated the electron transfer in the CcP/Cytc complex. Our findings indicate the key role of Trp191 being the bridge-‐localized state of the ET as well as the main pathway consisting of Ala194, Ala193, Gly192 and Trp191 between CcP and Cytc. Both findings were confirmed through the literature. Moreover, our calculations on several snapshots state a nongated ET mechanism in this protein complex. The methodology developed along this thesis, mapping ET pathways together with their evaluation through electronic coupling calculations, suggests a straightforward and promising approach to investigate long-‐range ET in proteins.

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Abhijit, Saha. "Chemical Biology Approaches for the Molecular Recognition of DNA Double Helix." 京都大学 (Kyoto University), 2015. http://hdl.handle.net/2433/199116.

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Xiong, Ling. "Modification of the protein matrix around active- and inactive pheophytins by site-directed mutagenesis; affects on energy and electron transfer processes in photosystem II /." The Ohio State University, 2002. http://rave.ohiolink.edu/etdc/view?acc_num=osu1486549482671579.

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10

Ghosh, Avik Kumar. "Charge migration and one-electron oxidation at adenine and thymidine containing DNA strands and role of guanine N1 imino proton in long range charge migration through DNA." Diss., Available online, Georgia Institute of Technology, 2007, 2007. http://etd.gatech.edu/theses/available/etd-05132007-000502/.

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Thesis (Ph. D.)--Chemistry and Biochemistry, Georgia Institute of Technology, 2008. Wartell, Roger, Committee Member ; Bunz, Uwe, Committee Member ; Doyle, Donald, Committee Member ; Fahrni, Christoph, Committee Member ; Schuster, Gary, Committee Chair.

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Mecker, Christoph J. Chemistry Faculty of Science UNSW. "The synthesis of advanced " special pair " models for the photosynthetic reaction centre." Awarded by:University of New South Wales. School of Chemistry, 2000. http://handle.unsw.edu.au/1959.4/17835.

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Multi-step photoinduced electron transfer takes place over a large distance in the photosynthetic reaction centres (PRCs). Electron donor in this life-spending event is the photo-excited 'special pair', a unit of two electronically coupled porphyrinoid chromophores. Bacteriopheophytin and two quinone molecules function as electron acceptors and contribute to the charge separation with almost unit quantum efficiency. The natural photosynthetic reaction centre is the most sophisticated molecular electronic device to date and interest is high in increasing our understanding of the basic quantum mechanical principles behind efficient electron transfer and ultimately copying Nature and construct similar efficient devices. Two main approaches towards a better understanding of the mechanisms involved have been taken. The more biological disciplines isolate, cultivate and alternate reaction centres whereas synthetic chemists prefer to construct well-defined models that mimic certain aspects of the reaction centres. Such a synthetic approach is described in the 'Synthesis of Advanced 'Special Pair' Models for the Photosynthetic Reaction Centre'. The aspect to be mimicked is the 'special pair'. One or two porphyrins in a well-defined spatial disposition (kinked or non-kinked in respect to each other) were to act as electron donor in rigid bichromophoric and trichromophoric systems. A tetracyanonaphthoquinodimethane (TCNQ) unit was employed as the electron acceptor in the series of dyads synthesised. The TCNQ acceptor was replaced by a naphthoquinone (NQ) primary acceptor covalently linked to a TCNQ secondary electron acceptor in the series of triads. Rigid norbornylogous bridges held the chromophores in place and Diels-Alder methodology as well as condensation reactions were applied to link donor, bridge and acceptor components. Despite larger interchromophoric separation than in the natural 'special pair', the two porphyrin chromophores of the series of 'special pair' dyads show some interaction and thereby prove the success of our approach towards 'special pair' mimics. Strong fluorescence quenching in the porphyrin-TCNQ dyads indicates the sought after electron transfer process. A number of synthetic problems experienced and overcome in the synthesis of the series of triads led to discovery of a one-step 'bis-ketonisation' from an olefin under Sharpless bis-hydroxylation conditions with N-methylmorpholine-N-oxide. High pressure was applied to circumvent a lack of reactivity in the condensation reaction used to attach the porphyrin moieties (one or two) to the donor backbone. For the linkage of donor, bridge and acceptor component, a procedure was developed and successfully applied to give the giant mono-porphyrin-NQ-TCNQ trichromophore. In a similar manner 'special pair' trichromophoric systems should be available as part of future work.

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Mahato, Joyanto. "Comparative study of three Fe (III)-ion reducing bacteria gives insights into bioelectricity generation in the MFC technique." Thesis, Högskolan i Skövde, Institutionen för biovetenskap, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:his:diva-18598.

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Microbial fuel cell (MFC) technology is a renewable energy source that employs microorganisms as biocatalysts to degrade substrates into electrons and protons, and then transfer the electrons to the anode electrode. Electron transfer rates by microorganisms depend on many factors as well as on their diverse electron transfer mechanisms. The present study compared cytochromes, flavoproteins, electron transfer complexes, redoxins and other extracellular membrane proteins that have direct involvement in electron transfer mechanisms in Escherichia coli str. K-12 MG1655, Rhodopseudomonas pulastris DX-1 and Shewanella oneidensis MR-1. Escherichia coli str. The results showed that K-12 MG1655 had a more diverse range of extracellular proteins for electron transfer mechanisms compared to Rhodopseudomonas pulastris DX-1 and Shewanella oneidensis MR-1. Escherichia coli str. K-12 MG1655 expressed more flavoproteins, redoxin and electron transfer complex related proteins that had direct involvement in electron transfer mechanisms compared to two other bacterial species indicating that it may be able to transfer more electrons when employed in MFC technique. Escherichia coli str. K-12 MG1655 expressed 16 cytochromes, 9 flavoproteins, 6 redoxins, 6 electron transport complexes, 1 hypothetical and 1 oxidoreductase proteins. On the other hand, Rhodopseudomonas pulastris DX-1 and Shewanella oneidensis MR-1 expressed 26 and 35 cytochromes proteins. But these two bacterial species expressed less flavoproteins and redoxin related proteins and they didn’t express any electron transport complexes or hypothetical and oxidoreductase related proteins for electron transfer. STRING and SMART results suggested that the identified proteins transferred electrons either by connecting with other types of identified proteins in the constructed gene network or independently by taking part in oxidation-reduction reaction, metal ion reduction reaction or by their FMN binding activities.

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Gonska, Nathalie. "Proton pathways in energy conversion : K-pathway analogs in O2- and NO-reductases." Doctoral thesis, Stockholms universitet, Institutionen för biokemi och biofysik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-147267.

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Oxygen and nitric oxide reductases are enzymes found in aerobic and anaerobic respiration, respectively. Both enzyme groups belong to the superfamily of Heme-Copper Oxidases, which is further divided into several subgroups: oxygen-reducing enzymes into A-, B- and C-type and nitric oxide reductases into qNORs and cNORs. Oxygen reducing enzymes use the energy released from oxygen reduction to take up electrons and protons from different sides of the membrane. Additionally, protons are pumped. These processes produce a membrane potential, which is used by the ATP-synthase to produce ATP, the universal energy currency of the cell. Nitric oxide reductases are not known to conserve the energy from nitric oxide reduction, although the reaction is highly exergonic. Here, the detailed mechanism of a B-type oxidase is studied with special interest in an element involved in proton pumping (proton loading site, PLS). The study supports the hypothesis that the PLS is protonated in one and deprotonated in the consecutive step of the oxidative catalytic cycle, and that a proton is pumped during the final oxidation phase. It further strengthens the previous suggestion that the PLS is a cluster instead of a single residue or heme propionate. Additionally, it is proposed that the residue Asp372, which is in vicinity of the heme a3 propionates previously suggested as PLS, is part of this cluster. In another study, we show that the Glu15II at the entry of the proton pathway in the B-type oxidase is the only crucial residue for proton uptake, while Tyr248 is or is close to the internal proton donor responsible for coupling proton pumping to oxygen reduction. The thesis also includes studies on the mechanism and electrogenicity of qNOR. We show that there is a difference in the proton-uptake reaction between qNOR and the non-electrogenic homolog cNOR, hinting at a different reaction mechanism. Further, studies on a qNOR from a different host showed that qNOR is indeed electrogenic. This surprising result opens up new discussions on the evolution of oxygen and nitric oxide reductases, and about how energy conservation can be achieved. At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 4: Manuscript.

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Gnandt, David [Verfasser], Thorsten [Akademischer Betreuer] Koslowski, and Oliver [Akademischer Betreuer] Einsle. "A multi-scale approach to electron transfer in protein complexes." Freiburg : Universität, 2020. http://d-nb.info/1226656978/34.

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Belsare, Ketaki Deepak [Verfasser]. "Directed evolution of P450cin for mediated electron transfer / Ketaki Deepak Belsare." Aachen : Hochschulbibliothek der Rheinisch-Westfälischen Technischen Hochschule Aachen, 2014. http://d-nb.info/1065848250/34.

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Ley, Claudia [Verfasser]. "Screening tools for artificial electron transfer to P450 BM3 / Claudia Ley." Bremen : IRC-Library, Information Resource Center der Jacobs University Bremen, 2013. http://d-nb.info/1035267829/34.

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Riehm, Jan Leo [Verfasser], and Michael [Akademischer Betreuer] Hutter. "Molecular simulations on electron transfer proteins / Jan Leo Riehm ; Betreuer: Michael Hutter." Saarbrücken : Saarländische Universitäts- und Landesbibliothek, 2018. http://d-nb.info/1169132537/34.

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Lin, Tzong-Yuan. "Electron transfer between the reductase and ferredoxin component of toluene dioxygenase." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät I, 2012. http://dx.doi.org/10.18452/16584.

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Die Toluol-Dioxygenase von Pseudomonas putida F1 ist eine Rieske-Dioxygenase und besteht aus Reduktase-, Ferredoxin- und Oxygenase-Komponente. Sie katalysiert den ersten Schritt im aeroben Abbau von Toluol. Ein effizienter Elektronentransfer zur terminalen Oxygenase-Komponente - an der die Sauerstoffaktivierung und Umwandlung von Toluol zum cis-Toluol-Dihydrodiol stattfindet - setzt eine reibungslose Interaktion aller Komponenten voraus. Die Ergebnisse der Stopped-flow-Messungen in der reduktiven Halbreaktion zeigen, dass NADH die Reduktase mittels Hydridtransfer reduziert, wodurch ein stabiler Ladungstransfer-Komplex zwischen NAD+ und FADH- entsteht. In der oxidativen Halbreaktion wird dieser dann durch einen Elektronenakzeptor über das blaue Semichinon zum Chinon oxidiert. Dabei zeigt sich, dass der Ladungstransfer-Komplex die Reaktion der Reduktase mit Sauerstoff unterdrückt. Eine Erklärung hierfür liefert die Kristallstruktur des Ladungstransfer-Komplexes. Die Reaktion mit Sauerstoff wird dadurch unterdrückt, dass das NAD+ koplanar mit dem Isoalloxazinring ist und den reaktiven N5-C4a Teil des FADs schützt und zudem den Isoalloxazinring in eine planare, weniger sauerstoffempfindliche Konformation zwängt. Durch die Bildung des Reduktase-Ferredoxin-Komplexes wird ein effizienter Elektronentransfer folgendermaßen ermöglicht: a) das Ferredoxin bindet an die Reduktase aufgrund elektrostatischer Anziehung entgegengesetzter Oberflächenladungen beider Proteine, b) die hydrophobe Region, die die beiden Redoxzentren umgibt, fungiert als Ein- und Ausgang für Elektronen und c) die geringe Entfernung von 11.7 Å zwischen beiden Kofaktoren erlaubt einen schnellen Elektronentransfer. Die Ergebnisse dieser Arbeit zeigen, dass der Elektronentransfer zwischen Reduktase und Ferredoxin durch die Bildung eines stabilen Ladungstransfer- und Reduktase- Ferredoxin-Komplexes beeinflusst wird und dadurch das Problem einer ungewollten Reaktion mit Sauerstoff umgangen wird. The toluene dioxygenase from Pseudomonas putida F1 is a three-component Rieske non-heme iron dioxygenase comprising of a reductase, ferredoxin and an oxygenase component. It catalyzes the initial step in the aerobic degradation of toluene to cis-toluene dihydrodiol. A smooth interaction between all three components needs to be ensured to efficiently transfer the electrons derived from NADH oxidation to the terminal oxygenase component where molecular oxygen is activated and used for the hydroxylation of toluene. The results of the kinetic studies of the reductive half reaction of reductase reveal that NADH reduces the reductase, resulting in the formation of a stable charge transfer complex between NAD+ and FADH-. Oxidation of the charge transfer complex by an electron acceptor proceeds via the neutral semiquinone to the quinone state of FAD. It is shown that the charge transfer complex suppresses the reaction of the reductase with dioxygen. An explanation for this change in reactivity can be deduced from the structure of the charge transfer complex. Its slower reaction with dioxygen results from NAD+ lying coplanar with the FAD shielding its reactive N5-C4a locus and the forced planarity of the isoalloxazine ring. The formation of the reductase-ferredoxin complex allows efficient electron transfer from reductase to ferredoxin because a) the oppositely charged interacting surfaces of both proteins facilitate the pre-orientation of the ferredoxin on the reductase, b) a hydrophobic region surrounding the two redox centers in the complex acts as an exit/entrance port for electrons and c) the short edge-to-edge distance between both cofactors of 11.7 Å guarantees a fast electron transfer. The results demonstrate that the electron transfer between reductase and ferredoxin is governed by the formation of a stable charge transfer and of a reductase-ferredoxin complex with which the problem of an unwanted side reaction with dioxygen is obviated.

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Karyagina, Irina [Verfasser]. "Study of protein-cofactor interaction and electron transfer properties in modified photosystem I complexes by multifrequency time resolved electron paramagnetic resonance / Irina Karyagina." Berlin : Freie Universität Berlin, 2009. http://d-nb.info/1023401878/34.

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Paulino, Karina Heloisa [UNESP]. "Poços quânticos e transferência de elétrons." Universidade Estadual Paulista (UNESP), 2009. http://hdl.handle.net/11449/87523.

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Made available in DSpace on 2014-06-11T19:22:54Z (GMT). No. of bitstreams: 0 Previous issue date: 2009-12-17Bitstream added on 2014-06-13T18:08:49Z : No. of bitstreams: 1 paulino_kh_me_sjrp.pdf: 434360 bytes, checksum: a8e2b302456d5e127779718e98e3d011 (MD5) Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Neste trabalho foram resolvidos, através de Equação de Schrödinger independente do tempo, os potenciais biestáveis do Poço Duplo Quadrado Unidimensional Simétrico (PDQUS) e do Poço Duplo Assimétrico (PDQUA), concentrando neste último grande parte do estudo. Como todo PDQUS é ressonante por definição, é possível então estimar o tempo de tunelamento através da Fórmula de Rabi. O mesmo não acontece com PDQUA, pois nem todo poço duplo assimétrico é ressonante. Foi necessário então, encontrar barreiras de potencial e distância entre os poços que permitiram a ressonância, pois a probabilidade de tunelamento é muito maior que aquelas dos casos onde não há ressonância. Além do tempo de tunelamento, o tempo de transição eletrônica também é estimado, com o objetivo de propor um modelo de transferência eletrônica (TE). Uma possível aplicação para tal modelo está relacionada a sistemas biológicos ocorrendo por tunelamento e por transição, utilizando o PDQUA. Com base na TE em bactérias fotossintéticas, pôde-se obter informações estruturais, como: as distâncias e energias envolvidas no processo, que foram essenciais para os exemplos numéricos tratados nesse trabalho. In this work were resolved, by Schrödinger equation independent of time, the bistable potential of the One Dimensional Symmetric Double Square Well (PDQUS) and Asymmetric Double Well (PDQUA), concentrating largely in the latter study. As all PDQUS is resonant by definition, it is possible then estimate the time of tunneling through the Rabi formula. This not happens with PDQUA, because not all asymmetric double well is resonant. It was necessary then, to find potential barriers and distance between wells that allowed the resonance because the tunneling probability is much higher than those cases where there is no resonance. Besides the time of tunneling, the electronic transition time is also estimated, with the objective of proposing a model of electron transfer (TE). One possible application for such a model is related to biological systems occuring by tunneling and transition, using the PDQUA. Based on the TE in photosynthetic bacteria, could be obtained structural information, such as distances and energies involved in the process, which were essential for the numerical examples treated in this work.

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Berndhäuser, Andreas [Verfasser]. "EPR distance measurements using triaryl methyl radicals and EPR investigation of electron transfer processes in organic radicals / Andreas Berndhäuser." Bonn : Universitäts- und Landesbibliothek Bonn, 2018. http://d-nb.info/1160594244/34.

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Schach, Denise [Verfasser]. "Direct electron transfer to cytochrome c oxidase investigated by electrochemistry and time-resolved surface-enhanced infrared absorption spectroscopy / Denise Schach." Mainz : Universitätsbibliothek Mainz, 2011. http://d-nb.info/102008264X/34.

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Müller, Hubert [Verfasser], Tillmann [Akademischer Betreuer] [Gutachter] Lüders, and Rainer [Gutachter] Meckenstock. "Long-distance electron transfer by cable bacteria in aquifer sediments / Hubert Müller ; Gutachter: Rainer Meckenstock, Tillmann Lüders ; Betreuer: Tillmann Lüders." München : Universitätsbibliothek der TU München, 2017. http://d-nb.info/1130323196/34.

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Schmitz, Simone Verfasser], Miriam [Akademischer Betreuer] Agler-Rosenbaum, and Lars Mathias [Akademischer Betreuer] [Blank. "Mediated electron transfer in defined microbial co-cultures for bioelectrochemical system application / Simone Schmitz ; Miriam Agler-Rosenbaum, Lars Mathias Blank." Aachen : Universitätsbibliothek der RWTH Aachen, 2018. http://d-nb.info/1190360837/34.

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Schmitz, Simone [Verfasser], Miriam Akademischer Betreuer] Agler-Rosenbaum, and Lars Mathias [Akademischer Betreuer] [Blank. "Mediated electron transfer in defined microbial co-cultures for bioelectrochemical system application / Simone Schmitz ; Miriam Agler-Rosenbaum, Lars Mathias Blank." Aachen : Universitätsbibliothek der RWTH Aachen, 2018. http://d-nb.info/1190360837/34.

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Paulino, Karina Heloisa. "Poços quânticos e transferência de elétrons /." São José do Rio Preto : [s.n.], 2009. http://hdl.handle.net/11449/87523.

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Resumo: Neste trabalho foram resolvidos, através de Equação de Schrödinger independente do tempo, os potenciais biestáveis do Poço Duplo Quadrado Unidimensional Simétrico (PDQUS) e do Poço Duplo Assimétrico (PDQUA), concentrando neste último grande parte do estudo. Como todo PDQUS é ressonante por definição, é possível então estimar o tempo de tunelamento através da Fórmula de Rabi. O mesmo não acontece com PDQUA, pois nem todo poço duplo assimétrico é ressonante. Foi necessário então, encontrar barreiras de potencial e distância entre os poços que permitiram a ressonância, pois a probabilidade de tunelamento é muito maior que aquelas dos casos onde não há ressonância. Além do tempo de tunelamento, o tempo de transição eletrônica também é estimado, com o objetivo de propor um modelo de transferência eletrônica (TE). Uma possível aplicação para tal modelo está relacionada a sistemas biológicos ocorrendo por tunelamento e por transição, utilizando o PDQUA. Com base na TE em bactérias fotossintéticas, pôde-se obter informações estruturais, como: as distâncias e energias envolvidas no processo, que foram essenciais para os exemplos numéricos tratados nesse trabalho. Abstract: In this work were resolved, by Schrödinger equation independent of time, the bistable potential of the One Dimensional Symmetric Double Square Well (PDQUS) and Asymmetric Double Well (PDQUA), concentrating largely in the latter study. As all PDQUS is resonant by definition, it is possible then estimate the time of tunneling through the Rabi formula. This not happens with PDQUA, because not all asymmetric double well is resonant. It was necessary then, to find potential barriers and distance between wells that allowed the resonance because the tunneling probability is much higher than those cases where there is no resonance. Besides the time of tunneling, the electronic transition time is also estimated, with the objective of proposing a model of electron transfer (TE). One possible application for such a model is related to biological systems occuring by tunneling and transition, using the PDQUA. Based on the TE in photosynthetic bacteria, could be obtained structural information, such as distances and energies involved in the process, which were essential for the numerical examples treated in this work. Orientador: Elso Drigo Filho Coorientador: Regina Maria Ricotta Banca: Antônio Vidiella Barranco Banca: Jorge Chaine Mestre

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Lin, Tzong-Yuan [Verfasser], Holger [Akademischer Betreuer] Dobbek, Wolfgang [Akademischer Betreuer] Lockau, and Silke [Akademischer Betreuer] Leimkühler. "Electron transfer between the reductase and ferredoxin component of toluene dioxygenase / Tzong-Yuan Lin. Gutachter: Holger Dobbek ; Wolfgang Lockau ; Silke Leimkühler." Berlin : Humboldt Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät I, 2012. http://d-nb.info/1026475228/34.

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Zhang, Shaojian [Verfasser]. "Electron Transfer at Iron Mineral Surface in the Presence of aqueous Sulfide and Dissolved Organic Matter under Anoxic Condition / Shaojian Zhang." Tübingen : Universitätsbibliothek Tübingen, 2021. http://d-nb.info/1227924445/34.

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Palma, Delgado Veronica [Verfasser], and J. [Akademischer Betreuer] Gescher. "Improvement of the electron transfer in S. oneidensis and production of glucose-based platform chemicals / Veronica Palma Delgado ; Betreuer: J. Gescher." Karlsruhe : KIT-Bibliothek, 2020. http://d-nb.info/1207393045/34.

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Koop, Julie L. "A new strain of Wolbachia in the harlequin beetle riding pseudoscorpion male killing, reproductive compensation and horizontal gene transfer /." abstract, 2008. http://0-gateway.proquest.com.innopac.library.unr.edu/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:1460764.

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Dobrev, Plamen [Verfasser], Helmut [Akademischer Betreuer] Grubmüller, Marcus [Akademischer Betreuer] Müller, and Claudia [Akademischer Betreuer] Steinem. "Protonation patterns in reduced and oxidized form of electron transfer proteins / Plamen Dobrev. Gutachter: Helmut Grubmüller ; Marcus Müller ; Claudia Steinem. Betreuer: Helmut Grubmüller." Göttingen : Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2012. http://d-nb.info/1042345694/34.

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Zhiguo, Yu Verfasser], and Klaus-Holger [Akademischer Betreuer] [Knorr. "Electron Transfer Processes between Hydrogen Sulfide and Humic Substances - Implications for Anaerobic Sulfur Cycling in Freshwater Ecosystems / Yu Zhiguo. Betreuer: Klaus-Holger Knorr." Bayreuth : Universität Bayreuth, 2015. http://d-nb.info/1074461894/34.

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Schulze, Andrea [Verfasser], Hannes [Gutachter] Neuweiler, Markus [Gutachter] Sauer, and Thomas [Gutachter] Müller. "Investigating the mechanism of the Hsp90 molecular chaperone using photoinduced electron transfer fluorescence quenching / Andrea Schulze ; Gutachter: Hannes Neuweiler, Markus Sauer, Thomas Müller." Würzburg : Universität Würzburg, 2020. http://d-nb.info/1211328163/34.

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34

Luo, Yusen [Verfasser], Benjamin [Gutachter] Dietzek, Oliver S. [Gutachter] Wenger, and Inke [Gutachter] Siewert. "Photoinduced electron transfer dynamics in Ruthenium(II) Bis(terpyridine) based molecular dyads and triads / Yusen Luo ; Gutachter: Benjamin Dietzek, Oliver S. Wenger, Inke Siewert." Jena : Friedrich-Schiller-Universität Jena, 2019. http://d-nb.info/1206605286/34.

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Paula, Luciana Claudia de. "Dinâmica de modelos minimalistas de solvente em reações de transferência de elétrons : aplicação à experimentos de única molécula /." São José do Rio Preto : [s.n.], 2006. http://hdl.handle.net/11449/100469.

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Orientador: Vitor Barbanti Pereira Leite Banca: Fernando Luis Barroso da Silva Banca: Luis Carlos Gomide de Freitas Banca: Paulo César de Andrade Banca: Elso Drigo Filho Resumo: Neste trabalho é investigada a influência de ambientes complexos na dinâmica de reações de transferência de elétrons. O principal objetivo é demonstrar a ocorrência de fenômenos de intermitência em processos de transferência de elétrons. Entender como estes fenômenos são governados pela ação do solvente e caracterizar a dependência da temperatura, também são parte do propósito deste trabalho. O ambiente polar, no qual ocorre a reação, é tratado de modo simples, seguindo o modelo de Onuchic-Wolynes, e é representado por uma única camada de dipolos em torno da cavidade de carga. O método utilizado para realizar este estudo é através de simulação computacional de Monte Carlo. A dinâmica de solvente é estudada observando-se as razões entre os momentos dos tempos de primeira passagem (first passage time) dos eventos de transferência de elétrons, definido como Rn. Primeiramente é feita uma análise do modelo teórico em que o sistema é caracterizado analiticamente através de parâmetros termodinâmicos. Posteriormente os resultados computacionais são analisados e mostram concordância com a teoria. O sistema apresenta três regiões de temperatura, nas quais, o comportamento cinético da reação se alterna em exponencial, não exponencial e novamente exponencial. Abstract: In this work, we have investigated the influence of complex environments on electron transfer reaction dynamics. The main objective in this work is to show the occurrence of intermittence phenomenon on electron transfer reactions. The understanding on how these phenomenons are governed by solvent and the temperature dependence characterization, are also addressed. The polar environment, in which the reaction takes place, is treated in a simple way, following the Onuchic-Wolynes model, and it is represented by a single shell of dipoles around a charge cavity. This study is performed using Monte Carlo simulation method. The solvent dynamic is studied by the observation of the ratios of the first passage time of electron transfer events, defined as Rn. Firstly, it is performed the analysis of the theoretical model in which the system is characterized, analytically, by thermodynamics parameters. Next the computational results are analyzed and it shows agreement with the theory. The system exhibits three temperature regimes, in which, the kinetic behavior of the reaction is changed from exponential, to nonexponential and again to exponential. Doutor

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Nganou, Assonkeng Albert Collins [Verfasser], and Hans Joachim [Akademischer Betreuer] Eichler. "On the role of pigment-pigment and pigment-protein interaction in regulating excitation energy and electron transfer in photosynthesis / Albert Collins Nganou Assonkeng. Betreuer: Hans Joachim Eichler." Berlin : Universitätsbibliothek der Technischen Universität Berlin, 2012. http://d-nb.info/1019852917/34.

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37

Paul, Rajsekhar [Verfasser], Josef [Akademischer Betreuer] Wachtveitl, and C. Roy D. [Akademischer Betreuer] Lancaster. "From static difference to time-resolved spectroscopy of coupled electron and proton transfer in the quinol: fumarate reductase of Wolinella succinogenes / Rajsekhar Paul. Gutachter: Josef Wachtveitl ; C. Roy D. Lancaster." Frankfurt am Main : Univ.-Bibliothek Frankfurt am Main, 2011. http://d-nb.info/1044195150/34.

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38

Paula, Luciana Claudia de [UNESP]. "Dinâmica de modelos minimalistas de solvente em reações de transferência de elétrons: aplicação à experimentos de única molécula." Universidade Estadual Paulista (UNESP), 2006. http://hdl.handle.net/11449/100469.

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Made available in DSpace on 2014-06-11T19:30:54Z (GMT). No. of bitstreams: 0 Previous issue date: 2006-03-31Bitstream added on 2014-06-13T18:41:07Z : No. of bitstreams: 1 paula_lc_dr_sjrp.pdf: 2712667 bytes, checksum: 532220ccc7e56ac66281c7460f0834da (MD5) Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Neste trabalho é investigada a influência de ambientes complexos na dinâmica de reações de transferência de elétrons. O principal objetivo é demonstrar a ocorrência de fenômenos de intermitência em processos de transferência de elétrons. Entender como estes fenômenos são governados pela ação do solvente e caracterizar a dependência da temperatura, também são parte do propósito deste trabalho. O ambiente polar, no qual ocorre a reação, é tratado de modo simples, seguindo o modelo de Onuchic-Wolynes, e é representado por uma única camada de dipolos em torno da cavidade de carga. O método utilizado para realizar este estudo é através de simulação computacional de Monte Carlo. A dinâmica de solvente é estudada observando-se as razões entre os momentos dos tempos de primeira passagem (first passage time) dos eventos de transferência de elétrons, definido como Rn. Primeiramente é feita uma análise do modelo teórico em que o sistema é caracterizado analiticamente através de parâmetros termodinâmicos. Posteriormente os resultados computacionais são analisados e mostram concordância com a teoria. O sistema apresenta três regiões de temperatura, nas quais, o comportamento cinético da reação se alterna em exponencial, não exponencial e novamente exponencial. In this work, we have investigated the influence of complex environments on electron transfer reaction dynamics. The main objective in this work is to show the occurrence of intermittence phenomenon on electron transfer reactions. The understanding on how these phenomenons are governed by solvent and the temperature dependence characterization, are also addressed. The polar environment, in which the reaction takes place, is treated in a simple way, following the Onuchic-Wolynes model, and it is represented by a single shell of dipoles around a charge cavity. This study is performed using Monte Carlo simulation method. The solvent dynamic is studied by the observation of the ratios of the first passage time of electron transfer events, defined as Rn. Firstly, it is performed the analysis of the theoretical model in which the system is characterized, analytically, by thermodynamics parameters. Next the computational results are analyzed and it shows agreement with the theory. The system exhibits three temperature regimes, in which, the kinetic behavior of the reaction is changed from exponential, to nonexponential and again to exponential.

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Jager-Vottero, Pascale. "Caractérisation de transporteurs d'électrons dans l'enveloppe des chloroplastes d'épinard (Spinacia oleracea L)." Université Joseph Fourier (Grenoble), 1995. http://www.theses.fr/1995GRE10022.

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Au cours de notre travail, nous avons mis en evidence et caracterise d'un point de vue structural differentes classes de transporteurs d'electrons presentes dans l'enveloppe des chloroplastes d'epinard. Nous avons demontre la presence de fmn et de fad libres dans ce systeme membranaire, le fad constituant l'espece flavinique majoritaire de la membrane interne et de la membrane externe de l'enveloppe. Les quinones (plastoquinone-9, phylloquinone, -tocoquinone et -tocopherol) etaient les seuls transporteurs d'electrons potentiels dont la presence dans l'enveloppe etait connue au debut de nos travaux. Nous avons etudie leur comportement redox dans l'enveloppe par une technique spectroscopique: la resonance paramagnetique electronique (rpe). Nous avons ainsi mis en evidence la presence d'une semiquinone dont le signal est centre a g = 2. 003. Afin d'estimer la nature de la stabilisation de cette semiquinone, nous avons traite l'enveloppe par le pentane, solvant apolaire permettant d'extraire selectivement les quinones en solution dans les membranes. A la suite de ce traitement, le signal centre a g = 2. 003 demeure visible sur le spectre rpe revelant ainsi une forte stabilisation de cette semiquinone par une proteine ou un complexe proteique de l'enveloppe. L'oxydation chimique de l'enveloppe realisee par addition de nitrate d'ammonium et de cerium (+2. 5 volt enh) provoque une augmentation de l'amplitude du signal centre a g = 2. 003 et egalement l'apparition d'un signal centre a g = 1. 975. Ce comportement spectral est caracteristique d'un couplage spin-spin entre deux especes paramagnetiques tres proches l'une de l'autre. Comme le signal centre a g = 2. 003 est le seul signal amplifie au cours de cette oxydation, le couplage spin-spin materialise par la presence conjointe des signaux centres a g = 2. 003 et a g = 1. 975 doit etre attribue a la formation d'une nouvelle classe de semiquinones fortement stabilisee sur un site localise a proximite de celui des semiquinones observees sur les spectres rpe en absence de tout traitement oxydant. Ce comportement spectral revele l'heterogeneite de la population des semiquinones de l'enveloppe et demontre qu'il est impossible de proceder a une oxydation complete des semiquinones et des quinols de l'enveloppe. Lorsque l'enveloppe est placee dans des conditions fortement reductrices, obtenues par photoreduction en presence d'oxalate et de 5-deazaflavine, le signal centre a g = 2. 003 disparait completement. Ce resultat implique que la semiquinone peut etre reduite sous la forme quinol et ne peut donc osciller dans l'enveloppe qu'entre sa forme semireduite et bireduite. La spectroscopie rpe de l'enveloppe soit photoreduite soit reduite par le dithionite de sodium, nous a egalement permis de decouvrir l'existence de deux centres fer-soufre paramagnetiques a l'etat reduit: un centre fer-soufre x de type inconnu et un centre fer-soufre 4fe-4s#1#+ dont les signaux transverses sont respectivement centres a g = 2. 057 et 1. 921. Une separation des membranes de l'enveloppe a permis de demontrer la localisation exclusive des centres fer-soufre et des semiquinones dans la membrane interne. Les centres fer-soufre x et 4fe-4s#1#+ ainsi que la semiquinone peuvent etre reduits par le nadph. La reduction de l'enveloppe par le nadh provoque l'apparition d'un nouveau signal rpe centre a g = 1. 935 et caracteristique d'un centre 2fe-2s#1#+. L'oxydation des quinols de l'enveloppe en semiquinones est obtenu apres un enrichissement de l'enveloppe en oxygene moleculaire. L'ensemble de ces resultats permet d'envisager l'existence probable d'une chaine de transfert d'electrons dans l'enveloppe des chloroplastes et d'en proposer un premier et hypothetique modele

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40

Bottin, Hervé. "Etude du transfert d'electron dans le photosysteme 1 des vegetaux superieurs par spectroscopie d'absorption par eclairs." Paris 6, 1987. http://www.theses.fr/1987PA066147.

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41

Escriou, Mechin Virginie. "Purification de deux cytochromes des granulocytes neutrophiles de lapin : caractérisation et role du cytochrome b558 dans la production des ions superoxyde de la NADPH oxydase : identification et caractérisation d'un nouveau cytochrome b." Université Joseph Fourier (Grenoble), 1994. http://www.theses.fr/1994GRE10077.

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Quand ils phagocytent des micro-organismes, les neutrophiles actives produisent des quantites importantes d'ions superoxyde, grace a un complexe enzymatique appele nadph oxydase. Le transfert d'un electron, depuis le nadph, jusqu'a l'oxygene moleculaire serait assure par un cytochrome b, le cytochrome b#5#5#8, qui serait un flavocytochrome. Dans le but d'etudier les differents transporteurs d'electrons (heme, fad) qui contribuent a l'activite de production d'ions superoxyde, le cytochrome b#5#5#8 des granulocytes neutrophiles de lapin a ete purifie. Teste en systeme acellulaire, en presence de cytosol, le cytochrome b#5#5#8 purifie par ce protocole est le seul compose membranaire necessaire a la reconstitution d'une activite de production d'ions superoxyde. Des ions superoxyde etant obtenus sans qu'il soit necessaire d'ajouter de la flavine, la presence de flavine endogene sur le cytochrome a ete envisagee. Pourtant, le dosage de fad effectue dans les differentes fractions chromatographiques de la derniere etape de purification du cytochrome b#5#5#8, fait ressortir un pic d'elution du fad decale par rapport au pic d'elution de l'heme. Ces resultats conduisent donc a s'interroger sur le concept de flavocytochrome et sur la validite du systeme acellulaire, pour tester l'activite de production d'ions superoxyde. Au cours de la purification du cytochrome b#5#5#8, une autre hemoproteine (p-30) a ete mise en evidence, purifiee et partiellement caracterisee. Cette hemoproteine presente le meme spectre d'absorption que le cytochrome b#5#5#8. Pourtant, plusieurs de ses caracteristiques, comme le potentiel d'oxydoreduction et la sequence proteique partielle, ont permis de montrer qu'il s'agit d'un nouveau cytochrome b, n'ayant aucune identite de sequence avec le cytochrome b#5#5#8 des phagocytes ou d'autres cytochromes connus. La fonction physiologique de cette hemoproteine dans les neutrophiles n'est pas encore connue. Elle possede pourtant une localisation subcellulaire voisine de celle du cytochrome b#5#5#8, c'est-a-dire a la fois dans la membrane plasmique et dans la fraction granulaire. Apres activation de la cellule, une partie du cytochrome p-30 est transferee dans la membrane plasmique

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42

Hennig, Sandra Elisabeth. "Insights into the ATP-dependent reductive activation of the Corrinoid/Iron-Sulfur Protein of Carboxydothermus hydrogenoformans." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät I, 2014. http://dx.doi.org/10.18452/16984.

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Die Verknüpfung einer exergonischen mit einer endergonischen Reaktion zur Ermöglichung der letzteren ist eine in biologischen Systemen weit verbreitete Strategie. Energetisch benachteiligte Elektronenübertragungsreaktionen im Rahmen der reduktiven Aktivierung von Nitrogenasen, Radikal-abhängigen β,α-Dehydratasen, der zu diesen verwandten Benzoyl-CoA-Reduktasen und diversen Cobalamin-abhängigen Methyltransferasen sind gekoppelt an die Hydrolyse von ATP. Der Methylgruppentransfer des reduktiven Acetyl-CoA-Weges von Carboxydothermus hydrogenoformans erfordert den Co(I)-Zustand des Corrinoid/Eisen-Schwefel Proteins (CoFeSP). Um diese superreduzierte Form nach einer oxidativen Inaktivierung zu regenerieren ist ein „Reparaturmechanismus“ erforderlich. Ein offenes Leseraster (orf7), welches möglicherweise für eine reduktive Aktivase von Corrinoid Enzymen (RACE) kodiert, wurde in dem Gencluster der am reduktiven Acetyl-CoA-Weg beteiligten Proteine entdeckt. Im Rahmen dieser Arbeit wurde dieses potenzielle RACE Protein biochemisch und strukturell charakterisiert und die ATP-abhängige reduktive Aktivierung von CoFeSP untersucht. Auf Grundlage der in dieser Arbeit gewonnenen Ergebnisse wurde ein Mechanismus für die ATP-abhängige Aktivierung entworfen. Dieser gibt Einblicke wie die durch ATP-Hydrolyse bereitgestellte Energie einen energetisch ungünstigen Elektronentransfer ermöglichen kann. Hierzu kombiniert RACo das Ausgleichen von Bindungsenergien mit Modulationen am Elektronenakzeptor. Eine vergleichbare Strategie wurde bisher in keinem anderen ATP-abhängigen Elektronenübertragungssystem wie dem von Nitrogenasen, Radikal-abhängigen β,α-Dehydratasen oder Benzoyl-CoA-Reduktasen beobachtet und könnte ein für RACE Proteine allgemein gültige Eigenschaft darstellen. The principle of coupling an exergonic to an endergonic reaction to enable the latter is a widespread strategy in biological systems. Unfavoured electron transfer reactions in the reductive activation of nitrogenases, radical-dependent β,α-dehydratases and the related benzoyl- CoA reductases, as well as different cobalamin-dependent methyltransferases are coupled to the hydrolysis of ATP. The reductive acetyl-CoA pathway of Carboxydothermus hydrogenoformans relies on the superreduced Co(I)-state of the corrinoid/iron-sulfur protein (CoFeSP) that requires a “repair mechanism” in case of incidental oxidation. An open reading frame (orf7) coding for a putative reductive activase of corrinoid enzymes (RACE) was discovered in the gene cluster of proteins involved in the reductive acetyl-CoA pathway. In this work, this putative RACE protein was biochemically and structurally characterised and the ATP-dependent reductive activation of CoFeSP was investigated. Based on the results of this study, a mechanism for the ATP-dependent reactivation of CoFeSP was deduced providing insights into how the energy provided by ATP could trigger this unfavourable electron transfer. The reductive activator of CoFeSP combines balance of binding energies and modulations of the electron acceptor to promote the uphill electron transfer to CoFeSP. A comparable strategy has not been observed in other ATP-dependent electron transfer systems like nitrogenases, radical-dependent β,α-dehydratases and benzoyl- CoA reductases and could be a universal feature of RACE proteins.

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Pous, Rodríguez Narcís. "Bioremediation of nitrate-polluted groundwater using bioelectrochemical systems." Doctoral thesis, Universitat de Girona, 2015. http://hdl.handle.net/10803/302539.

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The presence of nitrates (NO3-) in groundwater is a worldwide concern. The high energy demand and environmental impact of available technologies requires investigating new technologies. This thesis was focused on investigating the usage of bioelectrochemical systems (BES) for treating nitrate-polluted groundwater. BES uses microorganisms able to catalyze oxidation/reduction processes by delivering/obtaining electrons from an electrode. In this thesis, microorganisms able to use the electrode as an electron donor (biocathode) to reduce nitrates into dinitrogen gas (inert) were investigated. As a result, a process could be patented, in which BES are able to treat nitrates at high denitrification rates (up to 700 gN•m-3NCC•d-1), with a competitive energy demand (0.68•10-2 – 1.27•10-2 kWh•gN-1treated), without sludge generation nor chemical dosing. Moreover, the microorganisms were electrochemically characterized, and the key subcommunities of the process were elucidated. In summary, bioelectrochemical systems have the potential for becoming a competitive alternative for the treatment of nitrate-polluted groundwater La presència de nitrats (NO3-) en aigües subterrànies és una preocupació global. L’alt cost energètic i ambiental de les tecnologies actuals requereixen la investigació de noves estratègies. Aquesta tesi ha investigat la utilització de sistemes bioelectroquímics (BES) pel tractament d’aigües subterrànies contaminades per nitrats. Les BES es basen en microorganismes capaços de realitzar oxidacions/reduccions tot alliberant/captant electrons d’un elèctrode. Aquesta tesi ha investigat l’ús de bactèries capaçes d’utilitzar l’elèctrode com a donador d’electrons (biocàtode) per reduir el nitrat a dinitrogen gas (compost inert). Com a resultat, s’ha patentat un procés que permet desnitrificar a altes velocitats (700 gN•m-3NCC•d-1), a un cost energètic competitiu (0.68•10-2 – 1.27•10-2 kWh•gN-1tractat), sense generar fangs ni addicionar substàncies químiques. També s’ha caracteritzat electroquímicament els microorganismes i s’ha elucidat les subcomunitats microbianes responsables de la desnitrificació. En definitiva, aquesta tesi demostra que els sistemes bioelectroquímics poden esdevenir una alternativa competitiva pel tractament d’aigües subterrànies contaminades per nitrats

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Gong, Xing. "Structural and functional studies of electron transfer complexes." 2005. http://digital.library.okstate.edu/etd/umi-okstate-1590.pdf.

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"Temperature and Polarizability Effects on Electron Transfer in Biology and Artificial Photosynthesis." Doctoral diss., 2019. http://hdl.handle.net/2286/R.I.54801.

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abstract: This study aims to address the deficiencies of the Marcus model of electron transfer (ET) and then provide modifications to the model. A confirmation of the inverted energy gap law, which is the cleanest verification so far, is presented for donor-acceptor complexes. In addition to the macroscopic properties of the solvent, the physical properties of the solvent are incorporated in the model via the microscopic solvation model. For the molecules studied in this dissertation, the rate constant first increases with cooling, in contrast to the prediction of the Arrhenius law, and then decreases at lower temperatures. Additionally, the polarizability of solute, which was not considered in the original Marcus theory, is included by the Q-model of ET. Through accounting for the polarizability of the reactants, the Q-model offers an important design principle for achieving high performance solar energy conversion materials. By means of the analytical Q-model of ET, it is shown that including molecular polarizability of C60 affects the reorganization energy and the activation barrier of ET reaction. The theory and Electrochemistry of Ferredoxin and Cytochrome c are also investigated. By providing a new formulation for reaction reorganization energy, a long-standing disconnect between the results of atomistic simulations and cyclic voltametery experiments is resolved. The significant role of polarizability of enzymes in reducing the activation energy of ET is discussed. The binding/unbinding of waters to the active site of Ferredoxin leads to non-Gaussian statistics of energy gap and result in a smaller activation energy of ET. Furthermore, the dielectric constant of water at the interface of neutral and charged C60 is studied. The dielectric constant is found to be in the range of 10 to 22 which is remarkably smaller compared to bulk water( 80). Moreover, the interfacial structural crossover and hydration thermodynamic of charged C60 in water is studied. Increasing the charge of the C60 molecule result in a dramatic structural transition in the hydration shell, which lead to increase in the population of dangling O-H bonds at the interface. Dissertation/Thesis Doctoral Dissertation Chemistry 2019

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Zhu, Jian. "Structure-function studies of electron transfer complexes in bovine heart mitochondria." 2004. http://digital.library.okstate.edu/etd/umi-okstate-1206.pdf.

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Mecker, Christoph J. "The synthesis of advanced "special pair" models for the photosynthetic reaction centre /." 2000. http://www.library.unsw.edu.au/~thesis/adt-NUN/public/adt-NUN20011128.150754/index.html.

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Lin, Chun-yu, and 林俊佑. "(1) C-H Oxidation with Hypervalent Iodine (III) at Benzylic Position without Undergoing SET(Single Electron Transfer)(2) Chemistry and Biology of Triazole-pyrrole: Click Chemistry and DNA Interaction." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/46433024034307236604.

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Abstract:

博士 國立中山大學 化學系研究所 101 There are two parts in this dissertation. Part I : benzylic C-H oxidation of methyl aromatic compounds is a useful reaction. We found that the reactive intermediate was generated by PIDA/TFA/AcOH (6:4:2) system then the reaction of methyl aromatic with the reactive intermediate could undergo benzylic C-H oxidation and studied on the mechanism via the intermediate. We anticipated this reaction without undergoing SET process. The benzylic C-H oxidation of p-methoxy toluene was effective in para electron-donating groups. Part II : we have synthesized a series of triazole-tripyrrole compound and studied on the binding affinity for duplex DNA by CT-DNA melting temperature analysis, ethidium bromide displacement assay for CT-DNA and DNase I footpring studies on HexA and HexB.

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Dubé, Charles-David. "Transfert interespèces d’électrons par conduction directe via la matrice protéinique exocellulaire dans un biofilm anaérobie granulaire." Thèse, 2018. http://hdl.handle.net/1866/21852.

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Baier, Claudia [Verfasser]. "Electron transfer phenomena in interfacial bioelectrochemistry / Claudia Baier." 2010. http://d-nb.info/1009896415/34.

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Dissertations / Theses on the topic 'Biology - Electron Transfer'

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