Dissertations / Theses on the topic 'Proton transfer reactions'
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Redondo, Marey Carmen-Maria. "Femtodynamics of double proton transfer reactions." Thesis, University College London (University of London), 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.398981.
Full textLinares-Samaniego, Sandra I. "Excited state proton transfer in microheterogeneous conditions." Diss., Georgia Institute of Technology, 1997. http://hdl.handle.net/1853/27263.
Full textPapageorgiou, Alexia. "Influence of proton transfer kinetics and natural convection on Proton-Coupled Electron Transfer (PCET) reactions." Doctoral thesis, Universite Libre de Bruxelles, 2021. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/318308.
Full textDoctorat en Sciences
info:eu-repo/semantics/nonPublished
Cooper, Ian Blake. "Photosynthetic water oxidation and proton-coupled electron transfer." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/26707.
Full textCommittee Chair: Bridgette Barry; Committee Member: El-Sayed, Mostafa; Committee Member: Fahrni, Christoph; Committee Member: Kröger, Nils; Committee Member: McCarty, Nael. Part of the SMARTech Electronic Thesis and Dissertation Collection.
Fernandez, M. T. N. "Thermodynamics of proton transfer reactions in the gas phase." Thesis, University of Warwick, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.378296.
Full textJenson, David L. Jenson. "Proton-coupled electron transfer and tyrosine D of phototsystem II." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/29667.
Full textCommittee Chair: Bridgette Barry; Committee Member: Ingeborg Schmidt-Krey; Committee Member: Jake Soper; Committee Member: Nils Kroger; Committee Member: Wendy Kelly. Part of the SMARTech Electronic Thesis and Dissertation Collection.
Maza, William Antonio. "Reaction Enthalpy and Volume Profiles for Excited State Reactions Involving Electron Transfer and Proton-Coupled Electron Transfer." Scholar Commons, 2013. http://scholarcommons.usf.edu/etd/4539.
Full textMurphy, Christine Fecenko Thorp H. Holden. "Coupled electron proton transfer reactions in biological redox active substrates." Chapel Hill, N.C. : University of North Carolina at Chapel Hill, 2009. http://dc.lib.unc.edu/u?/etd,2895.
Full textTitle from electronic title page (viewed Jun. 23, 2010). "... in partial fulfillment of the requirements for the degree of Doctor of Philosophy in the Department of Chemistry." Discipline: Chemistry; Department/School: Chemistry.
Marks, David Roland Azoulai. "Femtosecond studies of excited-state proton transfer reactions in solutions." [S.l. : Amsterdam : s.n.] ; Universiteit van Amsterdam [Host], 2000. http://dare.uva.nl/document/82013.
Full textMeng, Kejie. "MECHANISTIC STUDIES OF PROTON-COUPLED ELECTRON TRANSFER REACTIONS INVOLVING ANTIOXIDANTS." VCU Scholars Compass, 2018. https://scholarscompass.vcu.edu/etd/5498.
Full textSullivan, Erica N. "Photoexcited hydroxyarenes as probes for microenvironments." Diss., Georgia Institute of Technology, 2000. http://hdl.handle.net/1853/27440.
Full textHarvey, Lilia Cuesta. "Excited state proton transfer in ortho substituted naphthols : Part II Mechanistic studies of ortho allyl-naphthol photocyclizations." Diss., Georgia Institute of Technology, 1992. http://hdl.handle.net/1853/30017.
Full textWan, Min. "1,3 proton transfer catalysts supported by Merrifield resin or Jeffamine gel." Scholarly Commons, 1998. https://scholarlycommons.pacific.edu/uop_etds/2344.
Full textBeelen, Eric Stephan Edmond van. "Proton transfer and ligand exchange induced reactions in the gas phase." [S.l. : Amsterdam : s.n.] ; Universiteit van Amsterdam [Host], 2005. http://dare.uva.nl/document/18421.
Full textPatel, Jagvi Ramesh. "Kinetics and mechanism of hydrolysis and proton transfer reactions in solution." Thesis, King's College London (University of London), 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.271412.
Full textAdekola, Aderemi S. "Proton-transfer study of unbound ¹⁹Ne states via ²H(¹⁸F,[alpha]¹⁵O)n REACTION." Ohio : Ohio University, 2009. http://www.ohiolink.edu/etd/view.cgi?ohiou1230079038.
Full textLiu, Ping. "Composite proton exchange membranes for fuel cells." Diss., Connect to online resource - MSU authorized users, 2006.
Find full textÄdelroth, Pia. "Mechanisms and pathways for proton transfer in cytochrome-c oxidase." Göteborg : Göteborg University, 1998. http://catalog.hathitrust.org/api/volumes/oclc/68945135.html.
Full textChoi, Pyoungho. "Investigation of thermodynamic and transport properties of proton-exchange membranes in fuel cell applications." Link to electronic thesis, 2004. http://www.wpi.edu/Pubs/ETD/Available/etd-0430104-094215/.
Full textXu, Shujuan. "EPR studies of electron and proton transfer in cytochrome c oxidase." Diss., Connect to online resource - MSU authorized users, 2008.
Find full textTitle from PDF t.p. (viewed on July 2, 2009) Includes bibliographical references. Also issued in print.
Wyngaardt, Shaun Metzler. "Relativistic plane wave description of spin transfer observables for proton knockout reactions." Thesis, Stellenbosch : Stellenbosch University, 2001. http://hdl.handle.net/10019.1/52429.
Full textENGLISH ABSTRACT: In this dissertation we set out to develop the first relativistic model for calculating complete sets of (p, 2p) spin transfer observables. In addition to this a new technique has been developed which allows us to evaluate the transition amplitude, which is used to calculate the scattering observables for the reaction directly. The influence of various modiuin-modificd parameters ()1I the scattered wave functions anr] NN interact ion lH-IVC' })('('11 invest igatcd DlIC t,C) (I,llIlJigllitic's surrounding the nNN coupling we have included both pseudosoalar and pseudovector coupling into the nucleon-nucleon interaction model. Furthermore we have included two different kinematic prescriptions to obtain the effective NN laboratory kinetic energy and center of mass scattering angle, which are used to obtain the NN scattering amplitudes. The aim of this study is to investigate the effects of the various model parameters on complete sets of scattering observables. Our investigation has shown that although the analyzing power is not very sensitive to nuclear medium effects, and the various other spin transfer observables such as Dnn should provide valuable insight. Further refinements of the model would be to include nuclear distortions as well as the IA2 model of the NN interaction.
AFRIKAANSE OPSOMMING: In hierdie tesis ontwikkel ons die eerste relatiwistiese model vir die berekening van 'n volledige stel (p, 2p) spin waarneembares. Verder word 'n nuwe tegniek ingevoer wat ons toelaat om die oorgangsamplitude, wat gebruik word in berekening van die verstrooings waarneembares vir die reaksie, direk te evalueer. Die invloed van verskeie medium-gemodifiseerde parameters op die verstrooide golffunksies en die NN wisselwerking word bestudeer. As gevolg van onsekerhede betreffende die лNN koppeling word beide die pseudoskalaar en pseudovektor koppeling in die nukleon-nukleon interaksie model ingesluit. Ons sluit ook twee verskillende kinematiese preskripsies in om die effektiewe NN laboratorium kinetiese energie en die massa middelpunt verstrooiings hoek, wat gebruik word vir die berekening van die NN verstrooiings amplitude, te bereken. Die doel van hierdie studie is om die effek van verskeie model parameters op 'n volledige stel spin waarneembares te ondersoek. Die studie toon dat alhoewel die analiseervermoë nie baie sensitief is vir medium effekte nie, die ander spin waarneembares soos byvoorbeeld Dnn waardevolle insig lewer. Daar word voorgestel dat die model verfyn word deur kerndistorsies as ook die meer algemele IA2 model vir die NN interaksie in te sluit.
Keough, James M. "Redox active tyrosines in photosystem II: role in proton coupled electron transfer reactions." Diss., Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/47738.
Full textHodgkiss, Justin M. (Justin Mark) 1978. "Mechanistic studies of photo-induced proton-coupled electron transfer and oxygen atom transfer reactions in model systems." Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/38539.
Full textThis electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Vita.
Includes bibliographical references.
Time-resolved optical spectroscopy has been employed for mechanistic studies in model systems designed to undergo photo-induced proton-coupled electron transfer (PCET) and oxygen atom transfer (OAT) reactions, both of which are important to energy conversion chemistry (Chapter I). The effect of coupling proton transfer (PT) to electron transfer (ET) depends on their spatial configuration, thus model PCET systems must control both. Noncovalent amidinium-carboxylate PT interfaces are used assemble an electron D/A pairs (D = donor, A = acceptor), establishing uni-directional ET and PT coordinates. A highly conjugated porphyrin-amidinium derivative bears optical signatures that report on the structure of PT interfaces formed upon association with carboxylate acceptors (Chapter II). PT is supported within the interface and the mediating proton's position is sensitive to the peripheral electronic structure. Transient absorption (TA) spectroscopy is applied to a related porphyrin D---[H+]---A assembly, where ---[H+]--- = amidinecarboxylic acid (Chapter III). Specific probe wavelengths are targeted in order to amplify the optical signatures of PCET over those of competing quenching mechanisms.
(cont.) The observed PCET rates are strongly attenuated compared with comparable covalentlybridged analogues, indicating that the PT interface reduces electronic coupling. Temperature-isotope dependence of the PCET rates reveals an unusual inverse isotope effect at low temperature, which is interpreted in a model of vibrationally-assisted PCET (chapter IV). Hangman porphyrin dyads have been developed to study bi-directional PCET in relation to oxygen activation. ET and PT coordinates are orthogonalized at fixed distances about a FeIII-OH center (Chapters V and VI). TA spectroscopy and electronic structure calculations reveal that the structural reorganization attendant to metal-centered PCET imposes a severe kinetic cost and alternative quenching pathways prevail. Finally, TA spectroscopy has been used to elucidate the mechanism of photocatalytic OAT for bridged diiron [mu]-oxo bisporphyrins (Chapter VII). The [mu]-oxo bond is photo-cleaved to generate a terminal iron(IV) oxo, which undergoes OAT to nucleophilic substrates. OAT rates are maximized when the bridge actively splays the porphyrin subunits apart to present the oxo before reclamping can occur.
by Justin M. Hodgkiss.
Ph.D.
McCoskey, Jacob K. "Sample dehumidification to enhance formaldehyde detection by a proton transfer reaction mass spectrometer." Pullman, Wash. : Washington State University, 2009. http://www.dissertations.wsu.edu/Thesis/Summer2009/J_McCoskey_072109.pdf.
Full textTitle from PDF title page (viewed on Aug. 7, 2009). "Department of Civil and Environmental Engineering." Includes bibliographical references (p. 73-76).
Salvitti, Michael Anthony. "N-methyl-6-hydroxyquinolinium : an investigation into the spectroscopy and applications of excited-state proton transfer /." Thesis, Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/24665.
Full textTian, Feng. "Theoretical Studies on Electrode Reactions in Proton Exchange Membrane Fuel Cells." Case Western Reserve University School of Graduate Studies / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=case1291339549.
Full textRaeker, Tim [Verfasser]. "Full-Dimensional Photodynamics Simulations: From Photoisomerizations to Excited-State Proton Transfer Reactions / Tim Raeker." Kiel : Universitätsbibliothek Kiel, 2018. http://d-nb.info/1161729526/34.
Full textZhang, Jingxin. "Investigation of CO tolerance in proton exchange membrane fuel cells." Link to electronic thesis, 2004. http://www.wpi.edu/Pubs/ETD/Available/etd-0708104-193007/.
Full textParada, Giovanny A. "Synthesis of Biomimetic Systems for Proton and Electron Transfer Reactions in the Ground and Excited State." Doctoral thesis, Uppsala universitet, Institutionen för kemi - Ångström, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-251471.
Full textLiu, Yang, and 刘洋. "Free energy simulations of important biochemical processes." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2013. http://hdl.handle.net/10722/196036.
Full textpublished_or_final_version
Chemistry
Doctoral
Doctor of Philosophy
Graige, Michael Scott. "Revealing the mechanisms and energetics of electron and proton transfer reactions in photosynthetic reaction centers from Rb. sphaeroides using molecular probes /." Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 1998. http://wwwlib.umi.com/cr/ucsd/fullcit?p9908502.
Full textSoper, Jake D. "Reactions at nitrogenous ligands on oxidizing group 8 metal centers /." Thesis, Connect to this title online; UW restricted, 2003. http://hdl.handle.net/1773/8589.
Full textWiley, Jack Scott. "C-H bond activation in iridium complexes /." Thesis, Connect to this title online; UW restricted, 1999. http://hdl.handle.net/1773/8510.
Full textOrtiz, Sánchez Juan Manuel. "Excited state intramolecular proton transfer reactions coupled with non adiabatic processes: electronic structure and quantum dynamical approaches." Doctoral thesis, Universitat Autònoma de Barcelona, 2009. http://hdl.handle.net/10803/3311.
Full textLes tècniques més modernes de cinètica química disponibles avui dia, permeten la monitorització dels processos ESIPT fins l'escala de temps del femtosegond. Tot i això, els resultats experimentals acostumen a ser difícils d'interpretar, especialment quan es veuen involucrats processos competitius. Aquests processos addicionals suposen un desafiament extra en l'estudi d'aquestes reaccions. En aquest sentit, la química teòrica i computacional representa una molt versàtil eina de treball, donat l'absolut control que els investigadors poden imposar a sistemes modelitzats aïllats.
Els sistemes moleculars recollits en la present tesi representen exemples directes dels diferents ordres de complexitat que l'estudi teòric (des del punt de vista del càlcul electrònic i dinàmic) del processos ESIPT poden representar: des de la comprensió del aspectes fonamentals del procés, fins a la necessitat d'adoptar estratègies teòriques eficients per tractar la presència de processos no adiabàtics.
Hydrogen Bonds are of universal importance in chemistry and biochemistry. The properties of hydrogen bonds in the electronic ground state have been investigated since long ago. Nevertheless, much less is known about the chemical reactions involving hydrogen bonds in excited electronic states. One of the most interesting reactions are the excited state intramolecular proton transfer (ESIPT) processes, as they play a crucial role in a plethora of photochemical reactions of chemical and biochemical relevance.
The most modern kinetic experimental techniques available today, allow the monitoring of ESIPT processes up to the order of the femtosecond. However, the experimental results are usually difficult to analyze, specially when competitive processes are involved. Those additional processes suppose an extra challenge in the study of this topic. In this sense, theoretical and computational chemistry represents a powerful tool of interpretation, given the absolute control that researchers can impose on modelized isolated systems.
The molecular systems collected in the present thesis represent direct examples of the different orders of complexity that the theoretical study (both from the electronic and dynamical points of view) of ESIPT can represent: from the comprehension of the essentials of the process, to the need of adoption of efficient theoretical strategies to treat the presence of non adiabatic processes.
Svahn, Emelie. "Molecular machinery of a membrane-bound proton pump : Studies of charge transfer reactions in cytochrome c oxidase." Doctoral thesis, Stockholms universitet, Institutionen för biokemi och biofysik, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-108335.
Full textGeibel, Kerstin [Verfasser]. "Search for Proton Emission in Ni-54 and Multi-Nucleon Transfer Reactions in the Actinide Region / Kerstin Geibel." München : Verlag Dr. Hut, 2012. http://d-nb.info/102878466X/34.
Full textMcQueen, Rachel, and n/a. "Axillary odour in apparel textiles." University of Otago. Department of Clothing and Textile Sciences, 2007. http://adt.otago.ac.nz./public/adt-NZDU20070307.120703.
Full textWang, Xiaohua. "Characterization of Mesoscopic Fluid-like Films with the Novel Shear-force/Acoustic Microscopy." PDXScholar, 2010. https://pdxscholar.library.pdx.edu/open_access_etds/736.
Full textLepp, Håkan. "Experimental studies of proton translocation reactions in biological systems : Electrogenic events in heme-copper oxidases." Doctoral thesis, Stockholm University, Department of Biochemistry and Biophysics, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-8147.
Full textTerminal heme-copper oxidases (HCuOs) are transmembrane proteins that catalyze the final step in the respiratory chain - the reduction of O2 to H2O, coupled to energy conservation by generation of an electrochemical proton gradient. The most extensively investigated of the HCuOs are the aa3-type oxidases, to which cytochrome c oxidase (CytcO) belongs, which uses energy released in the O2-reduction for proton pumping. The bacterial nitric oxide reductases (NORs) have been identified as divergent members of the HCuO-superfamily and are involved in the denitrification pathway where they catalyze the reduction of NO to NO2. Although as exergonic as O2-reduction, this reaction is completely non-electrogenic. Among the traditional HCuOs, the cbb3-type oxidases are the closest relatives to the NORs and as such provide a link between the aa3 oxidases and the NORs. The cbb3 oxidases have been shown to pump protons with nearly the same efficiency as the aa3 oxidases, despite low sequence similarity.
This thesis is focused on measurements of membrane potential generating reactions during catalysis in the CytcO and the cbb3 oxidase from Rhodobacter sphaeroides, and the NOR from Paracoccus denitrificans, using a time resolved electrometric technique. The pH dependence of the membrane potential generation in CytcO showed that only one proton is taken up and that no protons are pumped, at high pH. An additional kinetic phase was also detected at high pH that presumably originates to from charge-transfer within the K-pathway. Possible reasons for uncoupling, and the extent of charge-transfer, were studied using structural variants of CytcO. The measurements established that electrons and protons are taken up from the same side of the membrane in NOR. In addition, the directionality for proton uptake in cbb3 oxidase appeared to be dependent on the choice of substrate while proton pumping was indicated to occur only during O2-reduction.
Romanini, Simone. "Beyond simple proton transfer processes: domino reactions between 4-substituted indoles and nitroethene as a new gateway to ergot alkaloids." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2014. http://amslaurea.unibo.it/7325/.
Full textMahmoud, Hatem Ahmed. "Resonance Two Photon Ionization Study of Binary Clusters of Styrene with Polar Molecules." VCU Scholars Compass, 2003. http://scholarscompass.vcu.edu/etd/983.
Full textOffenbacher, Adam R. "Protein structural changes and tyrosyl radical-mediated electron transfer reactions in ribonucleotide reductase and model compounds." Diss., Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/39473.
Full textLi, Zhao. "The Kinetics and Mechanisms of Some Fundamental Organic Reactions of Nitro Compounds." DigitalCommons@USU, 2012. https://digitalcommons.usu.edu/etd/1407.
Full textDilbeck, Preston Lee. "Proton transfer reactions in photosynthetic water oxidation| Second sphere ligands of the manganese cluster modulate the water oxidation mechanism of photosystem ii." Thesis, Oklahoma State University, 2014. http://pqdtopen.proquest.com/#viewpdf?dispub=3614379.
Full textIn the D1-D61N mutant, it was possible to resolve a clear lag phase prior to the appearance of O2, indicating formation of an intermediate before onset of O2 formation. The lag phase and the photochemical miss factor were more sensitive to isotope substitution in the mutant indicating that proton efflux in the mutant proceeds via an alternative pathway. The results are discussed in comparison with earlier results obtained from the substitution of CP43-Arg357 with lysine and in regards to hypotheses concerning the nature of the final steps in photosynthetic water oxidation. These considerations lead to the conclusion that proton expulsion during the initial phase of the S3-S0 transition starts with the deprotonation of primary catalytic base, probably CP43-Arg357, followed by efficient proton egress involving the carboxyl group of D1-D61 in a process that constitutes the lag phase immediately prior to O2 formation chemistry. The asparagine, phenylalanine and threonine substitutions to D1-V185 were able to accumulate significant levels of charge separating PSII. Of the three substitutions the phenylalanine substitution was the most severe with a complete inability to evolve oxygen, despite being able to accumulate Photosystem II and to undergo stable charge separations. The threonine substitution had no apparent effect on oxygen evolution other than a 40% reduction in the steady state rate of O2 production compared to type Synechocystis, which can be attributed to that mutants reduced ability to accumulate PSII. The asparagine substitution produced the most complex phenotype. While still able to evolve oxygen, it does so less efficiently than wild type PSII, with a miss factor 4% higher than wild type Synechocystis. The substitution on D1-Val185 with asparagine also decreased the t1/2 of O2 release from thylakoid membranes from 1.2 ms to 10.0 ms and decreased the t1/2 lag phase prior to the onset of O2 release to 2.8 ms. The combination of a long lag period and a decreased rate of O2 release can also be observed in the D1-D61N mutant strains of Synechocystis and in PSII centers in which chloride has been replaced by iodide.
Medina, Ramos Jonnathan. "ACID-BASE CATALYSIS IN PROTON-COUPLED ELECTRON TRANSFER REACTIONS (PCET): THE EFFECTS OF BRÖNSTED BASES ON THE OXIDATION OF GLUTATHIONE AND HYDROQUINONE." VCU Scholars Compass, 2012. http://scholarscompass.vcu.edu/etd/2918.
Full textPolshakov, Dmitrii Arkadyevich. "Ultrafast spectroscopy and dynamics of nitrenes and carbenes." Columbus, Ohio : Ohio State University, 2005. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1130968887.
Full textRini, Matteo. "Femtosecond mid-infrared spectroscopy of elementary photoinduced reactions." Doctoral thesis, [S.l. : s.n.], 2003. http://deposit.ddb.de/cgi-bin/dokserv?idn=970187912.
Full textWalmsley, Ryan Steven. "An investigation into the antidiabetic and catalytic properties of oxovanadium(IV) complexes." Thesis, Rhodes University, 2012. http://hdl.handle.net/10962/d1004978.
Full textBruylants, Gilles. "Etude par calorimétrie à titrage isotherme (ITC) et spectroscopie de résonnance magnétique nucléaire (RMN) des effets de protonation liés à l'interaction entre l'alpha-chymotrypsine et la proflavine / Gilles Bruylants." Doctoral thesis, Universite Libre de Bruxelles, 2005. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/210977.
Full textCette étude s’est essentiellement composée de trois volets. (i) La réalisation d’un modèle du complexe d’interaction afin de confronter des données structurales aux données expérimentales recueillies. (ii) L’étude de l’interaction entre l’α-chymotrypsine et la proflavine par spectroscopie de Résonance Magnétique Nucléaire (RMN) afin de mettre en évidence les résidus ionisables dont les équilibres de protonation/déprotonation sont influencés par la complexation du ligand. (iii) L’étude de la thermodynamique de l’interaction par Calorimétrie à Titrage Isotherme (ITC) et spectroscopie d’absorption en fonction de l’état d’ionisation des résidus identifiés par l’étude RMN.
Le modèle du complexe d’interaction entre l’α-chymotrypsine et la proflavine a été réalisé sur base de la structure cristallographique du complexe entre cet inhibiteur et une protéase apparentée à la chymotrypsine, la thrombine. Il ressort de l’analyse du modèle obtenu que la proflavine est profondément enfouie dans le subsite S1 de l’enzyme et présente une très grande complémentarité de surface avec cette poche hydrophobe. Nous avons également pu constater la présence de plusieurs molécules d’eau immobilisées au sein du complexe, et d’une molécule en particulier faisant office de relais de liens-H.
L’étude de l’interaction entre l’α-chymotrypsine et la proflavine par RMN du 1H a été précédée par une étude de l’effet du degré de maturité de l’enzyme sur les interactions liant les différents résidus composant la triade catalytique (Asp102, His57 et Ser195). Lors de l’activation du précurseur inactif de l’enzyme, le chymotrypsinogène, vers la forme mature, l’α-chymotrypsine, il semble en effet que le lien-H entre le NH&949;2 de l’His57 et le Oγ de la Ser195 soit affaibli, contrairement à celui qui relie le NHδ1 de cette même histidine au Oδ1 de l’Asp102. Nous rapportons pour la première fois l’observation de l’influence de la protonation de l’Asp102 sur les déplacements chimiques des protons NHδ1 et NH&949;2 de l’His57. L’étude de l’interaction entre l’α-chymotrypsine et la proflavine par RMN, nous a permis de mettre en évidence l’effet de la complexation du ligand sur l’état d’ionisation des résidus His57 et Asp102 de la triade catalytique, les pKa de ces résidus dans l’enzyme libre valant respectivement 7 et approximativement 4.
Les paramètres thermodynamiques de l’interaction α-chymotrypsine - proflavine et des différents équilibres de protonation/déprotonation qui y sont liés ont été obtenus par spectroscopie d’absorption et ITC. Cette dernière technique constitue un outil précieux pour l’étude d’interactions moléculaires car il s’agit de la seule technique expérimentale permettant la mesure directe de l’enthalpie d’interaction. Lorsque des équilibres de protonation/déprotonation sont thermodynamiquement liés à l’interaction, il s’agit également de la seule technique permettant la quantification de ces effets. En mesurant la constante d’affinité et l’enthalpie d’interaction observées à différents pH et dans différents tampons, nous avons pu, sur base du modèle obtenu par RMN, déterminer les paramètres thermodynamiques intrinsèques des différents équilibres.
La corrélation entre les données thermodynamiques obtenues par ITC et spectroscopie d’absorption et les données structurales obtenues par RMN et sur base de l’analyse du modèle du complexe d’interaction, nous a permis de rationaliser les facteurs à la base de l’interaction préférentielle de l’inhibiteur avec une des formes de l’enzyme. L’interaction entre l’α-chymotrypsine et la proflavine est la plus favorable lorsqu’à la fois l’His57 et l’Asp102 sont déprotonnés. Cette interaction est caractérisée par un terme enthalpique favorable et un terme entropique légèrement défavorable. Ce dernier terme s’expliquerait en partie par l’immobilisation dans le site d’interaction de plusieurs molécules d’eau. L’affinité entre l’α-chymotrypsine et la proflavine diminue lorsque l’His57 se protonne. La répulsion électrostatique entre les charges positives de la proflavine et de l’His57 est vraisemblablement un des facteurs permettant d’expliquer cette diminution de la constante d’affinité. Nous n’avons pu mettre en évidence d’interaction entre ces deux molécules dès lors que l’Asp102 est protonné, malgré que ce résidu soit situé relativement loin de la proflavine dans le complexe. Il s’agit donc d’un effet indirect, probablement relayé par l’His57. Tant que l’Asp102 est déprotonné, sa charge négative compenserait la charge positive de l’His57 et réduirait la répulsion électrostatique avec la proflavine, ce qui n’est plus le cas lorsque l’aspartate se protonne.
Doctorat en sciences appliquées
info:eu-repo/semantics/nonPublished
Le, Crom Benjamin. "Étude de l'appariement neutron-proton dans les noyaux instables N=Z par réactions de transfert." Thesis, Université Paris-Saclay (ComUE), 2016. http://www.theses.fr/2016SACLS007/document.
Full textA nucleus is described as a set of independent neutrons and protons linked by a mean-field potential. However, in order to have a better description one needs to take in account some residual interactions such as pairing. Neutron-neutron and proton-proton pairings are well-studied but neutron-proton pairing is not well-known. np pairing can be isovector pairing such as nn and pp pairing or isoscalar which is yet unknown. Overbinding of N=Z nuclei could be a manifestation of np pairing.We have studied np pairing through transfer reactions. In this case, the cross-section of np pair transfer is expected to be enhanced in the presence of important np pairing. np pairing is expected to be important in N=Z nuclei with high J orbitals. Since the development of radioactive beam facilities, such beams are only available.The experiment was performed at GANIL with an efficient set-up so as to detect products from the (p,³He) transfer reaction. This reaction is affected by isovector and isoscalar np pairing. We used ⁵⁶Ni and ⁵²Fe beams so as to see the effect of the occupancy of 0f7/2 shell on the np pairing.First, we analysed the data from the ⁵⁶Ni(p,d)⁵⁵Ni reaction and we compared the results with the literature to validate analysis procedure.After analysing data from the ⁵⁶Ni(p,3He)⁵⁴Co reaction and extracting the population of the various states of ⁵⁴Co, we obtained information about the relative intensity between isoscalar and isovector np pairing in ⁵⁶Ni showing the predominance of isovector np pairing in this nucleus .Moreover, in the framework of developing a new charged particle detector, R&D on the discrimination of light nuclei using pulse shape analysis was performed and is presented