Дисертації з теми "Reaction centre"
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1
Watson, Ashley James. "Stability and interactions of the purple bacterial reaction centre." Thesis, University of Bristol, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.424644.
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2
Ashby, M. K. "Reaction centre and light harvesting genes of Rhodobacter sphaeroides." Thesis, Imperial College London, 1988. http://hdl.handle.net/10044/1/46944.
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3
He, Weizhong. "Spectroscopic properties of the isolated photosystem II reaction centre." Thesis, Imperial College London, 1991. http://hdl.handle.net/10044/1/46812.
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Wakeham, Marion Charlotte. "Inactive branch electron transfer in the purple bacterial reaction centre." Thesis, University of Bristol, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.400271.
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Rolfe, Stephen Alexander. "Electron transport in cyanobacterial photosystem II." Thesis, University of Cambridge, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.258430.
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Alizadeh, Sedigheh. "Characterisation of the photosystem two reaction centre complex from Chlamydomonas reinhardtii." Thesis, Imperial College London, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.294966.
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Bohles, Felix. "Protein-cofactor interactions in the photosynthetic reaction centre of Rhodobacter sphaeroides." Thesis, Queen Mary, University of London, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.509673.
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Newell, William Robert. "Organisation of the photosystem two reaction centre as revealed by spectroscopy." Thesis, Imperial College London, 1989. http://hdl.handle.net/10044/1/47587.
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Ashraf, Khuram Umar. "Studies of the green sulphur bacterial reaction centre from Chlorobaculum tepidum." Thesis, University of Glasgow, 2014. http://theses.gla.ac.uk/6379/.
Повний текст джерелаАнотація:
Photosynthetic organisms harvest sunlight through antenna light-harvesting complexes. Light absorbed by chromophores is transferred down an energy gradient to a reaction centre (RC) where photoinduced electron transfer occurs. A charge-separated state is generated that preserves some of the original light energy as electrochemical potential. By studying these RCs allows for us to deduce how they function through the elucidation of their structure, which ultimately allows for artificial mimics to be made. Chlorobaculum tepidum (C. tepidum) is a green sulphur photosynthetic bacterium that contains a type I RC. Light energy is transferred to the RC from chlorosomes via a soluble Fenna-Mathews-Olson (FMO) protein. Although the structure of FMO has been solved on its own, little is known about the molecular organization of the reaction centre complex. This thesis looks at two of the RC sub-units (PscB and PscD) that are water-soluble. To understand the contribution that these proteins make to RC function, they have been made in E. coli using an in-house expression vector. Using a 3C protease - iLOV - biotin acceptor domain - His10 (CLBH) tag, both PscB and PscD can be readily purified on a milligram-scale in four simple steps (Ni2+-affinity, subtractive IMAC (immobilized metal affinity chromatography) after cleavage with 3C protease, gel-filtration). PscD and PscB have been labelled with 15N and 13C for structural analysis by NMR, so far PscD has shown to partially disordered implying that a potential binding partner may be required. PscB has shown to be well structured and is in the process of having its structure elucidated. The binding PscD with FMO and ferredoxin from Arabadopsis thaliana has also been assessed by isothermal calorimetry to help identify the function of this protein. Here it is also observed that when the RC is coupled to plasmons a near 5 fold increase is observed in fluorescence enhancement as compared to RC by itself. Plasmonic metallic nanoparticles are able to drastically alter the emission of vicinal fluorophores. Metallic nanoparticles can influence the fluorescence emission of nearby molecules by enhancing the absorbance of the molecule, and by modifying the radiative decay rate of that molecule. And this is what is observed. This can further be increased when coupling the RC to the Plasmon by placing a silicon dioxide (SiO2) spacer in-between the RC and nanoparticle. This is the highest flouresence enhancement observed to date. As yet, no green sulphur bacterial RC has had its structure determined. Here, purification protocols have been developed that allow milligram quantities of a complex between the RC and FMO to be prepared. As well as identifying the best suitable detergents for solubilising and purifying the RC, two different populations of the RC have been discovered that can be separated by sucrose density gradients. Vapor diffusion, lipidic-cubic phase (LCP), bicelle, and co-crystallisation trials have been performed with pure RC-FMO. Thus far, promising crystals have been obtained when the RC has been co-crystallised with ferredoxin to 60 Å. These promising crystals are the first of its type, as this is the first type 1 RC crystal obtained.
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Wallin, Elizabeth. "The germinal centre reaction and follicular T cells in alloantibody formation." Thesis, University of Oxford, 2016. https://ora.ox.ac.uk/objects/uuid:e4ecdd13-7c1e-4d4e-8491-8a22857cdb86.
Повний текст джерелаАнотація:
Kidney transplantation is the optimal treatment for end-stage renal failure, however graft lifespan remains limited, and a major cause of graft loss is chronic, low-grade antibody-mediated damage. Understanding more about how these antibodies are produced, and how immunosuppression affects cells producing them, may allow both prediction of those at risk, and a mechanism for preventing or minimising antibody production, therefore improving graft lifespan. In particular, interest has grown in CD4 T cells known as circulating T follicular helper (cTfh) and T follicular regulatory (cTfr) cells, which appear to correlate with antibody production in vaccination, autoimmunity and potentially transplantation, however little is known about how immunosuppression alters these cells and their function. This study aimed to establish whether cTfh and cTfr cells could be used to predict the risk of de novo donor-specific antibody (DSA) formation in 61 kidney and simultaneous pancreas kidney (SPK) transplant recipients. Results suggested that high cTfh cells and low cTfr associated with de novo DSA formation, and the ratio of the two cells may be useful for identifying at-risk patients. Different immunosuppression regimens were associated with different levels of risk for de novo DSA formation, with basiliximab induction combined with azathioprine maintenance therapy having the lowest risk, despite being considered a less intensive regimen. In vitro experiments suggest this may be due to a differential effect of azathioprine on cTfh and B cells compared to mycophenolate mofetil, an alternative maintenance agent. Combining the in vitro and clinical data suggests that azathioprine may reduce the risk of de novo DSA formation after transplantation compared to other agents because of its effects on B cells, cTfh and cTfr. This is an exciting development that warrants further investigation.
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Hingorani, Kastoori. "Photo-oxidation of tyrosine in a bio-engineered bacterioferritin 'reaction centre'." Phd thesis, Canberra, ACT : The Australian National University, 2012. http://hdl.handle.net/1885/11774.
Повний текст джерелаАнотація:
The photosynthetic reaction centre (RC) is central to conversion of solar energy into chemical energy. In this thesis, in order to introduce the redox-active cofactors similar to that of the Photosystem II RC, a non-photosynthetic protein scaffold was used as an in vitro model. The protein tasked for this purpose was the heme containing bacterioferritin (BFR) protein found in E. coli. The BFR protein naturally expresses as a homodimer based on a 4-helix bundle monomer. Desirable properties included: (i) a promiscuos di-nuclear metal binding site which provides ligands for class II metals such as Mn (ii) a hydrophobic pocket at the dimer interface which can bind a photosensitive porphyrin, in this case a chlorin (Ce6), and (iii) presence of tyrosine residues proximal to the bound cofactors, which can be utilised as efficient electron-tunnelling intermediates.
The work in this thesis extends earlier work in the group by refining and improving the BFR system. Several mutants were made and an improved protein expression system was developed. For these samples experiments demonstrated ligation of weakly coupled equivalent Mn2II,II at the di-nuclear binding site of apo-BFR, and binding of the photo-active pigment ZnCe6 in hydrophobic pocket of the protein. Light-induced electron transfer from proximal tyrosine residue(s) to the photo-oxidised ZnCe6+, in the modified BFR reconsitituted with both ZnCe6 and MnII is presented.
Three site-specific tyrosine mutants (Y25F, Y58F and Y45F) were made to localise the redox-active tyrosine in this engineered system. The results indicate that: (i) presence of bound MnII is necessary to observe tyrosine oxidation in all BFR variants, (ii) Y45 (within van Der Waals network of ZnCe6) is singly the most important tyrosine as the immediate electron donor to the oxidised ZnCe6+, and (iii) Y25 and Y58 are both redox-active in this system, but appear to be interchangebale.
A high-resolution (~1.5 Ã…) crystal structure of the three tyrosine mutants was obtained and these structures showed there to be no mutation-induced effects on the overall 3-D structure of the protein. Minimal effects observed in the Y45F mutant are reported. The molecular design of a "second generation" of the BFR series is also presented where the symmetry of the BFR homodimer is broken to generate a BFR heterodimer to contain genetically distinct electron donor and acceptor subunits. The BFR heterodimer was made by introducing a small (20 aa) peptide linker between the two subunits. The ultimate goal will be to demonstrate light-induced directional electron flow in the BFR heterodimer.
12
Jun, Daniel Young. "Recombinant expression and band-gap engineering of the bacterial photosynthetic reaction centre." Thesis, University of British Columbia, 2017. http://hdl.handle.net/2429/61292.
Повний текст джерелаАнотація:
The Rhodobacter sphaeroides photosynthetic reaction centre (RC) is a pigment-protein complex that efficiently captures and converts photon energy into a charge-separated state. Given the conversion efficiency and the high electric potential of the electron, the major focus of my project was to deliver/extract electrons to/from various cofactors along the charge-separation pathway in the RC, including the special pair of bacteriochlorophylls (P), the bacteriopheophytin (HA), the primary quinone (QA), and the secondary quinone (QB). An over-expression system was created to produce RCs, using the R. sphaeroides RCx strain, pIND4 plasmid, a modified culture medium, and changes to growth conditions. These changes resulted in a 35-fold increase in protein levels compared to the previous system. To extract electrons from the quinone region of the RC, this region was made more accessible to the solvent by deleting portions of the H subunit cytoplasmic globular domain. The results indicated that the truncated RC mutants assembled stably and thereby reduced the electron transfer distance between the quinone and an external electron acceptor. Photochronoamperometry measurements on mutant RCs designed to test the feasibility of delivering electrons from an electrode to P showed photocurrent generation and direction that were consistent with the binding of the RC P-side to the electrode surface. Similar experiments on the feasibility of extracting electrons from HA, QA and QB, for delivery to highly ordered pyrolytic graphite (HOPG) or gold electrodes, also showed photocurrent generation and direction consistent with the binding of the RC HA-side or Q-side to the electrode surface. Finally, the thermal stability of complexes was studied by in vivo addition of light harvesting complex 1 (LH1) from the thermophile Thermochromatium tepidum to the RC. A hybrid core complex consisting of an R. sphaeroides RC surrounded by T. tepidum TLH1 conferred greater tolerance to thermal energies, compared to the analogous R. sphaeroides RC-LH1 core complex, at temperatures up to 70 °C. The combination of these results show that, in principle, the RC can be modified to extract electrons at different energy levels, or band gaps, with possible applications in heat-stabile biohybrid solar cell technologies.Science, Faculty of
Microbiology and Immunology, Department of
Graduate
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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.
Повний текст джерелаАнотація:
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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Ridge, Justin Paul. "The role of the protein during energy transduction in the bacterial reaction centre." Thesis, University of Sheffield, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.301469.
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Fenning, Trevor. "The expression in E. coli of a cyanobacterial gene encoding a photosystem II reaction centre protein." Thesis, University of Nottingham, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.335196.
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Gibbs, Sheila. "Ground reaction forces and control of centre of mass motion during gait : implications for intervention in cerebral palsy." Thesis, University of Dundee, 2014. https://discovery.dundee.ac.uk/en/studentTheses/f8110ed3-fa10-4580-959f-7ac0486e8d7a.
Повний текст джерелаАнотація:
A question which has arisen clinically is the inability to generate adequate vertical force during the second half of the stance phase in cerebral palsy gait. Neither the mechanism nor the consequences of this inability are understood. It implies that the centre of mass (CoM) is inadequately supported with the potential for collapse of the limb in single support. Normal walking is achieved by the sophisticated control of the neuromuscular and skeletal systems with the purpose of advancing the body with minimum energy expenditure. These control systems are affected by damage to the brain in children with cerebral palsy and result in a multitude of problems which affect their gait making it difficult to determine cause and effect. This study aimed to improve the understanding of the ground reaction forces and motion of the CoM. Objectives The principle objectives were to analyse the supporting forces of the CoM during gait in normal adults, children, and children with diplegic cerebral palsy, by examining the inter-relationships of the vertical and horizontal components of the ground reaction force with the vertical component of motion and temporal parameters of the CoM. Design The study of adults and children’s data was both prospective and retrospective. The study of cerebral palsy data was retrospective. A new software programme was developed to extract specific gait parameters from both normal and cerebral palsy gait patterns. A novel approach to analyse the interaction of motion and force data in normal walking was subsequently developed. Background In normal gait, the vertical component of the ground reaction force forms a double hump where both humps are equal in magnitude and greater than body weight. It is widely accepted that the first hump (FZ1) is associated with deceleration of the downward motion of the CoM as the foot “impacts” the ground and the second hump (FZ2) is the action of “push off” as the body is propelled upwards and forwards. Walking requires force contributions from both legs but traditionally computed three-dimensional (3D) gait analysis packages presents the force data with both legs superimposed, rather than sequentially in time. This gives the impression that there is no period of overlap of the forces and thus ignores the critically important period where the CoM is transferred from one leg to the other during double support. By changing the presentation to view it sequentially in time, plus superimposing the CoM kinematics onto the same scale allowed their interactions to be observed and objectively measured. Methods The kinematic and kinetic data of 53 normal adults, 33 normal children, and 57 diplegic cerebral palsy children were acquired for the study. A new gait cycle, based on CoM motion, was defined to allow analysis of the forces in relation to CoM motion. Software was developed to extract specified parameters from the gait data. Impulse calculations over specific periods (based on the vertical motion of the CoM) allowed analysis of the vertical force contribution of each leg to the vertical support of the CoM. Results The results showed that inadequate generation of vertical force in children with diplegic cerebral palsy was widespread. In approximately 40% of such children there was a reduced ability to generate an adequate FZ2, which resulted in a reduced ability to control of the descent velocity of the CoM. The mean reduction in descent velocity in cerebral palsy was only 54% compared to 86% in adults. Integration of the vertical force and motion of the CoM showed that FZ2 was associated with controlling the descent velocity of the CoM. This reverses the traditionally accepted concept of “impact” and is contrary to the belief that FZ2 is associated with ‘push off’. Conclusions and Relevance This study emphasises the importance of the role of the supporting leg in the second half of stance. Failure to generate an adequate FZ2, which is currently ignored in clinical practice, should be given priority in patient management. This new knowledge has significant implications from a clinical perspective, not only in diplegic cerebral palsy, but in pathologies such as amputees, spina-bifida, and other neuro-muscular conditions.
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Zander, Linda. "The germinal centre reaction : genetic and proteomic analysis of factors important for survival and growth of B lymphocytes /." Göteborg : Dept. of Microbiology and Immunology, Sahlgrenska Academy, Göteborg University, 2008. http://hdl.handle.net/2077/9505.
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Hawkes, C. M. "A study of the reaction esup(+)esup(-)-musup(+)musup(-)(gamma) at centre of mass energies up to 46.78GeV." Thesis, University of Oxford, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.355754.
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Bunner-Pilotelle, Anne. "Lipid-protein and protein-protein interactions in the mechanisms of photosynthetic reaction centre and the Na+, K+-ATPase." Paris 11, 2008. http://www.theses.fr/2008PA112163.
Повний текст джерелаАнотація:
Les interactions lipides -protéines et protéines- protéines jouent un rôle important dans le fonctionnement et la régulatiol1 des protéines de membranes. Cette thèse se concentre sur deux différentes protéines de membrane, les centres réactionne (RC) de bactéries pourpres et l'enzyme Na, K-ATPase. L'influence des lipides et du cholestérol sur le cinetique des RC a été étudié en reconstituant les protéines dans des liposomes contenant du cholestérol ou ses dérivés chimiques connus pour changer la valeur du potentiel dipolaire. Les expériences faites sur l'enzyme Na, K-ATPase ont pour but de mieux comprendre le rôle de l'interaction oligomère dans le fonctionnement de la protéine. Les résultats ont montres que le cholestérol et ses dérivés modulent la cinetique de transfert d'électron. Leurs effets semblent être liés à leur impact sur le potentiel dipolaire. Nous avons interprété ces donnés comme une augmentation de la barrière énergétique pour les protons devant entrer dans la protéine. Des donnés sur la constante de dissociation de l'ATP pour l'enzyme Na, K-ATPase avec des techniques. De cinetique et des techniques de calorimétrie donnent des valeurs différentes. Basé sur des résultats obtenus par ITC calorimétrie et stopped-flow cette thèse propose une explication de ces différence en se proposant d'étudier l'effet du magnésium sur la constante de dissociation de l'ATP. Les résultats ont montrés que le complexe ATP-magnésium se liait à l'enzyme sans aucune intervention de l'enzymeReported Iiterature values of the dissociation constant, Kd, of ATP with the E1 conformation of the Na+. K++ATPase based on equilibrium titrations and kinetic methods disagree. Using isothermal titration calorimetry ((TC) and simulations of the expected equilibrium behaviour for different binding models, this thesis presents an eX~lanation for this apparent discrepancy based on protein-protein interactions. Because of the importanCE of Mg + in ATP hydrolysis, kinetic studies of Mg2+ binding to the protein were also carried out. These studies showed that ATP alone is responsible for Mg2+ complexation, with no significant contribution from the enzyme environ ment
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Bizabani, Christine. "The diversity of root fungi associated with Erica species occurring in the Albany Centre of Endemism." Thesis, Rhodes University, 2015. http://hdl.handle.net/10962/d1018575.
Повний текст джерелаАнотація:
South Africa has the highest species diversity of ericaceous plants belonging to the Erica genus. There are over 850 identified species in the Cape Floral Region. The Albany Centre of Endemism (ACOE) is located within this region and is a hotspot of diversity consisting of various plant genera. The success of Erica plants is ubiquitously attributed to mycorrhizal relationships they engage in with a diverse group of fungi. This symbiosis is known as the ericoid mycorrhizal (ERM) association. The overall aim of this study was to establish the diversity of root fungi associated with Erica plants using morphological, molecular and 454 pyrosequencing techniques. Six Erica species were identified using leaf and flower morphology according to taxonomic keys. The identified plants were Erica cerinthoides, Erica demissa, Erica chamissonis, Erica glumiflora, Erica caffra and Erica nemorosa. Roots from sampled plants were stained and examined microscopically to determine their mycorrhizal status. Ericoid mycorrhizal associations together with dark septate endophyte (DSE) structures and hyphae that did not form any specific structure were observed in all the roots. In addition arbuscular mycorrhizal (AM) structures in the form of vesicles were detected in E. glumiflora and E. cerinthoides. In order to identify the culturable fungi associated with the respective hosts, sterilised roots were placed on various culture media for cultivation. Thereafter isolated fungi were morphologically classified into 67 morphotypes. These were mostly sterile and darkly pigmented. Non-sporulating mycelia of variable colouration such as white, cream-yellowish, beige, green and brown were also observed. Further identification was carried out using molecular techniques. DNA was extracted separately from pure cultures and amplified using ITS1 and ITS4 primers in a polymerase chain reaction (PCR). Thereafter sequencing and Basic Local Alignment Search Tool (BLAST) were used to identify the isolates to generic level. The fungi were taxonomically classified into 54 operational taxonomic units and 94 percent were Ascomycetes and Helotiales was the dominant order. Unclassified Helotiales with affinities to fungi currently identified as Epacrid root fungus was common in all hosts. Other isolates that were identified included Oidiodendron, Meliniomyces, Phialocephala, Cadophora, Lachnum, Leohumicola Cryptosporiopsis, Chaetomium, Acremonium and Epicoccum species. Basidiomycetes were represented by two OTUs belonging to the genus Mycena. Four OTUs comprised fungi that had no significant alignments in the reference databases. Direct root DNA extraction together with 454 pyrosequencing was used to detect the diversity of culturable and unculturable fungi associated with the identified hosts. The ITS2 region was targeted for sequencing. Although Ascomycetes remained the dominant phyla, Basidiomycetes were also detected in all host plants. Glomeromycota was present in E. caffra and E. cerinthoides. Helotiales was dominant in all Erica plants with the exception of E. cerinthoides and E. chamissonis which were dominated by the order Chaetothyriales. The OTUs identified to genus level included Epacris pulchella root fungus, Oidiodendron cf. maius, Acremonium implicatum, Leohumicola, Lachnum, Capronia and Mycena species. Culture-based techniques and pyrosequencing detected similar fungal composition comprising Ascomycetes, while, pyrosequencing was able to detect Glomeromycetes and Basidiomycetes.
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Juodžbalienė, Vilma. "Paauglių pusiausvyros, paprastosios ir psichomotorinės reakcijos priklausomybė nuo regos lygio." Doctoral thesis, Lithuanian Academic Libraries Network (LABT), 2006. http://vddb.library.lt/obj/LT-eLABa-0001:E.02~2005~D_20060118_182900-43929.
Повний текст джерелаАнотація:
Optimal interaction between vision and other somatosensory systems guaranties the control of human body segment stability and change in position. The lack of visual information causes changes in equilibrium, regulation of body segment position and in response to surrounding stimuli.
The objective of the study: to carry out the research on the influence of the degree of visual impairment on equilibrium and simple and psychomotor reactions, and to establish the possible manifestation of compensatory reactions of vestibular and proprioception sensory systems when vision disorders are being faced.
To investigate the influence of the degree of visual impairment on equilibrium and simple and psychomotor reactions, the sighted subjects, legally blind and totally blind subjects voluntarily participated in the study. A static posturography (or stabilography) method has been used for the equilibrium testing. A force plate and computerized equipment for analysis of the signals was applied for posturography. Centre of pressure coordinates have been started to be registered since the moment when the subject in bare feet stands on the force plate in the position required. Posturogram registration in every position of standing lasted 60 s.
To investigate a simple reaction, we have employed an electromyoreflexometer, which consists of the equipment emitting light or sound signals, a response device and a unit for the data registration. The testing has been conducted during two parts when a... [to full text]
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Farrington, Benjamin Joseph. "A tale of two spins : electron spin centre assemblies with N@C60 for use in QIP." Thesis, University of Oxford, 2014. http://ora.ox.ac.uk/objects/uuid:7f280123-41af-4d96-bf34-04094aaba1dd.
Повний текст джерелаАнотація:
Quantum information processing (QIP) has the potential to reduce the complexity of many classically ‘hard’ computational problems. To implement quantum information algorithms, a suitable physical quantum computer architecture must be identified. One approach is to store quantum information in the electron spins of an array of paramagnetic N@C60 endohedral fullerene molecules, using the electron-electron dipolar interaction to permit the formation of the entangled quantum states needed to implement QIP. This thesis explores two different chemical methods to create two-spin centre arrays that contain N@C60. The first method uses a double 2,3 dipolar cycloaddition reaction to a dibenzaldehyde-terminated oligo-p-phenylene polyethynylene (OPE) unit , to create an (S3/2, S3/2) N@C60-N@C60 dimer with a fixed spin centre separation of 2.7 nm. The second approach is via a self-assembly scheme in which a Lewis base functionalised N@C60 molecule coordinates to an antiferromagnetic metallic ring magnet to form a (S3/2, S3/2) two-spin centre N@C60-Cr7Ni system with an inter-spin separation of 1.4 nm. In both systems, a significant perturbation of the electron spin transition energies is observed using CW ESR, this perturbation is shown to be well accounted for by the inclusion of an electron-electron dipolar coupling term in the electron spin Hamiltonians. To create entanglement in an ensemble of two-spin centre molecules, the dipolar coupling interaction must lie within a narrow distribution. To achieve this not only the separation but also the orientation of the inter-spin axis with respect to the applied magnetic field must be controlled for which a method of macroscopic alignment is required. The potential of using a uniaxially drawn liquid crystal elastomer to exert uniaxial order on fullerene dimers is tested, finding that the degree of alignment is insufficient, possibly a result of the propensity for the fullerene molecules to phase separate from the elastomer. This phase separation is shown to restrict N@C60 phase coherence lifetime to 1.4 µs at 40 K due to instantaneous spin diffusion. The electron spin environment of both N@C60 and an N@C60-C60 dimer in a polymer matrix is examined using polystyrene as the host matrix. By deuteration of the polystyrene matrix, a maximum phase coherence lifetimes of 48 µs and 21 µs are measured for the N@C60 and N@C60-C60 dimer, respectively. The concept of reading out the electron spin state of N@C60 molecules by coupling it to a spin system that can be probed using optically detected magnetic resonance (ODMR) such as an NV- centre has been previously suggested. To this end, the photostability of N@C60 under 637 nm laser illumination has been examined in solution. The effect of the presence of an atmospheric concentration of oxygen is striking, affording a 57-fold retardation in the photodecomposition of N@C60 compared to a degassed solution. When ambient oxygen is present, the average number of excitations that are required to cause decomposition is ≈60000. Finally, for future UV photophysics experiments involving N@C60, the best solvent to use was found to be decalin, finding that it significantly slowed decomposition of N@C60 in both ambient and degassed solutions. The conclusions of this work make a significant contribution to the field of QIP with N@C60, showing that there is a bright future for N@C60.
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Dahlenborg, Katarina. "Celluar and molecular aspects of the germinal center reaction." Lund : Lund University, 1998. http://catalog.hathitrust.org/api/volumes/oclc/68945013.html.
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HUBERT, JEAN-GASPARD. "Rmn de proteines 4fe-4s : proprietes structurales et transfert electronique intramoleculaire." Université Joseph Fourier (Grenoble), 1996. http://www.theses.fr/1996GRE10175.
Повний текст джерелаАнотація:
Les proprietes de deplacement chimique et de relaxation des spins nucleaires, surtout quand elles sont influencees par le paramagnetisme de centres polymetalliques, apportent de nouvelles informations sur la structure atomique, electronique et magnetiques des proteines 4fe-4s et sur la vitesse d'echange electronique entre clusters
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Meziane, Driss. "Etude de la polymérisation des alcynes amorcée par un dérivé alkylidène du tungstène." Paris 13, 1986. http://www.theses.fr/1986PA132002.
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26
Bartoli, Alexandra. "Approche unifiée aux squelettes polycycliques de molécules isolées du genre Schisandra via une nouvelle réaction domino." Thesis, Aix-Marseille 3, 2011. http://www.theses.fr/2011AIX30023.
Повний текст джерелаАнотація:
Le système spirocyclique [6.4] est un motif récurrent dans un certain nombre de produits naturels tels que les Lancifodilactones, les Micrandilactones ou les Rubriflordilactones. Ces structures polycycliques représentent un défi synthétique pour les chimistes organiciens puisqu’elles présentent au moins neuf centres stéréogènes dont plusieurs sont quaternaires. L’objectif principal de ce travail était de développer de nouvelles réactions métallo-catalysées, et de les utiliser comme étape clé afin d’obtenir rapidement et efficacement le squelette polycyclique de ces composés. La première partie de ces travaux a été consacrée au développement d’une nouvelle réaction domino pallado-catalysée donnant accès, selon les conditions employées, à différents cœurs polycycliques de nortriterpénoïdes issus d’une même famille, de manière totalement diastéréosélective. Cette séquence domino de trois réactions en un seul pot permet donc la synthèse unifiée de différents squelettes de produits naturels isolés du genre Schisandra, en une seule étape. Une approche au squelette tétracyclique ABCD de la Lancifodilactone F appliquant cette méthodologie pour la construction du motif spirolactone a été envisagée. Un cycle D hautement fonctionnalisé a ainsi été synthétisé de manière diastéréosélective via un réarrangement d’Ireland-Claisen et une réaction de métathèse cyclisante. Une réaction de cyclopropanation intramoléculaire et la réaction domino devraient permettre d’obtenir, par la suite, le squelette complet de la Lancifodilactone F. Dans une deuxième partie, deux approches aux coeurs CDEF et ACDE de la Rubriflordilactone A ont été développées autour d’une même réaction clé, c’est-à-dire une cycloaddition [2+2+2] d’un composé triynique permettant d’accéder en une seul étape au squelette tricyclique CDE. Le motif tétracyclique ACDE devrait être rapidement accessible après quelques aménagements de la voie de synthèse initialeThe spiro [6.4] ring system is a recurring structural motif in numerous natural products such as Lancifodilactones, Micrandilactones and Rubriflordilactones. These polycyclic structures represent a synthetic challenge for organic chemists. Indeed, these molecules present at least nine stereogenic centers including several quaternary ones. The main goal of this work was to develop new metal-catalyzed reactions as key steps to obtain quickly and efficiently the polycyclic core of those natural products. The first part of these studies was dedicated to the development of a new palladium-catalyzed domino reaction leading to, depending on the conditions used, different polycyclic cores of nortriterpenoids coming from the same family, in a totally diastereoselective manner. This domino sequence of three reactions allowed the collective synthesis of various skeletons of natural products isolated from the Schisandra genus, in one pot. An approach to the tetracyclic core of Lancifodilactone F applying this methodology for the construction of the spirolactone moiety was then envisaged. A highly functionalized cycle D was synthetized in a diastereoselctive way via an Ireland-Claisen rearrangement and a ring closing metathesis reaction. Afterwards, an intramolecular cyclopropanation followed by the domino reaction should allow an access to the ABCD skeleton of Lancifodilactone F. In the last part, two approaches to the CDEF and ACDE cores of Rubriflordilactone A were developed around the same key reaction: a [2+2+2] cycloaddition of an acyclic triynic compound. The tricyclic skeleton CDE was reached at once in a single step. The ACDE tetracyclic moiety should be quickly accessible after few modifications of the initial strategy
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Hasegawa, Jun-ya. "Theoretical Study on the Excited States and Electron Transfer Reactions in Photosynthetic Reaction Center." Kyoto University, 1998. http://hdl.handle.net/2433/77871.
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Yaghoubi, Houman. "Bio-Photoelectrochemical Solar Cells Incorporating Reaction Center and Reaction Center Plus Light Harvesting Complexes." Scholar Commons, 2015. http://scholarcommons.usf.edu/etd/5803.
Повний текст джерелаАнотація:
Harvesting solar energy can potentially be a promising solution to the energy crisis now and in the future. However, material and processing costs continue to be the most important limitations for the commercial devices. A key solution to these problems might lie within the development of bio-hybrid solar cells that seeks to mimic photosynthesis to harvest solar energy and to take advantage of the low material costs, negative carbon footprint, and material abundance. The bio-photoelectrochemical cell technologies exploit biomimetic means of energy conversion by utilizing plant-derived photosystems which can be inexpensive and ultimately the most sustainable alternative. Plants and photosynthetic bacteria harvest light, through special proteins called reaction centers (RCs), with high efficiency and convert it into electrochemical energy. In theory, photosynthetic RCs can be used in a device to harvest solar energy and generate 1.1 V open circuit voltage and ~1 mA cm-2 short circuit photocurrent. Considering the nearly perfect quantum yield of photo-induced charge separation, efficiency of a protein-based solar cell might exceed 20%. In practice, the efficiency of fabricated devices has been limited mainly due to the challenges in the electron transfer between the protein complex and the device electrodes as well as limited light absorption. The overarching goal of this work is to increase the power conversion efficiency in protein-based solar cells by addressing those issues (i.e. electron transfer and light absorption). This work presents several approaches to increase the charge transfer rate between the photosynthetic RC and underlying electrode as well as increasing the light absorption to eventually enhance the external quantum efficiency (EQE) of bio-hybrid solar cells. The first approach is to decrease the electron transfer distance between one of the redox active sites in the RC and the underlying electrode by direct attachment of the of protein complex onto Au electrodes via surface exposed cysteine residues. This resulted in photocurrent densities as large as ~600 nA cm-2 while still the incident photon to generated electron quantum efficiency was as low as %3 × 10-4. 2- The second approach is to immobilize wild type RCs of Rhodobacter sphaeroides on the surface of a Au underlying electrode using self-assembled monolayers of carboxylic acid terminated oligomers and cytochrome c charge mediating layers, with a preferential orientation from the primary electron donor site. This approach resulted in EQE of up to 0.06%, which showed 200 times efficiency improvement comparing to the first approach. In the third approach, instead of isolated protein complexes, RCs plus light harvesting (LH) complexes were employed for a better photon absorption. Direct attachment of RC-LH1 complexes on Au working electrodes, resulted in 0.21% EQE which showed 3.5 times efficiency improvement over the second approach (700 times higher than the first approach). The main impact of this work is the harnessing of biological RCs for efficient energy harvesting in man-made structures. Specifically, the results in this work will advance the application of RCs in devices for energy harvesting and will enable a better understanding of bio and nanomaterial interfaces, thereby advancing the application of biological materials in electronic devices. At the end, this work offers general guidelines that can serve to improve the performance of bio-hybrid solar cells.
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Channa, Aravinda Wijesinghe W. M. "Photosynthetic antenna-reaction-center mimicry." Diss., Wichita State University, 2012. http://hdl.handle.net/10057/5369.
Повний текст джерелаАнотація:
The research presented in this dissertation discusses the mimicry of primary events in natural photosynthesis via artificial molecular constructs. Photosynthesis involves two major steps, absorption of light by antenna pigments and transfer of the excitation energy to the reaction center where charge separated entities are formed via photoinduced electron transfer (PET).
The synthesized artificial molecular systems are comprisedof porphyrin-fullerene, donor-acceptor entities due to their well studied photophysical properties which are essential to yield long-lived charge-separated states. Covalent and non covalent binding strategies have been employed in the design and synthesis of these novel artificial antenna-reaction centers.
The synthesized molecular systems are characterized using standard spectroscopic techniques. Their properties and performances in terms of an artificial photosynthetic model are evaluated by electrochemical, computational, time resolved emission, and transient absorption spectral studies. The systems studied reveal their potential in transferring excitation energy and yielding long-lived charge separated states with fast charge separation and slow charge recombination. The photoelectrochemistry of some of the compounds reveal their ability to convert light into electricity. Some triads show better performance as dyes in dye sensitized solar cells giving around 12% IPCE, incident photon-to-photocurrent conversion efficiency.Thesis (Ph.D.)--Wichita State University, College of Liberal Arts and Sciences, Dept. of Chemistry
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Gautrey, Charlotte. "The biomechanics of the dynamic defence mechanism." Thesis, University of Hertfordshire, 2013. http://hdl.handle.net/2299/13905.
Повний текст джерелаАнотація:
Context: It has been suggested that muscle fatigue can lead to injury, however, research investigating this phenomenon in functional ankle instability (FAI) subjects is lacking. Aim: The purpose of this thesis was to research postural sway and muscular latency in FAI subjects and healthy controls, both before and immediately after localised and globalised fatigue protocols. Subjects: All subjects used in this project were males, between the ages of 18 and 25 years, and participated in regular (>2 x week) aerobic exercise. Subjects were categorised into healthy subjects, or subjects with a history of FAI using the FAI questionnaire. Methods: Neuromuscular control was analysed in FAI subjects and healthy controls through measures of muscular latency and postural sway. These measures were repeated both before and immediately after localised and globalised fatigue protocols. Results: The induction of localised and globalised fatigue had no effect on muscle latency in the FAI or healthy subjects. However, postural sway was significantly increased in the FAI subjects, following localised and globalised fatigue, with globalised fatigue also significantly increasing postural sway in the healthy subjects. The globalised football-specific fatigue protocol caused the greatest deficits in the FAI subjects, but also the healthy controls. Conclusions: In terms of muscle latency individuals that participate in sports, as well as sports clinicians and coaches, should not be concerned about the theorised relationship between the onset of fatigue and an increased injury risk at the ankle. However, in terms of postural sway the globalised football-specific fatigue protocol caused the greatest deficits. This highlights that the fatigued individual may be at greater risk of musculoskeletal injury during prolonged exercise that involves multiple joints, such as a football match.
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Wilkinson, Jon N. "Regioselective reactions at a diruthenium centre." Thesis, University of Bristol, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.266954.
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Moccellin, Ana Silvia. "Adaptações no controle postural estático e dinâmico durante a gestação." Universidade Federal de São Carlos, 2011. https://repositorio.ufscar.br/handle/ufscar/5279.
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Previous issue date: 2011-02-25Universidade Federal de Minas Gerais
Pregnancy causes considerable physiologic, hormonal and anatomic changes in women that may affect the lower limbs and trunk movements, lead to instability of postural control and increased risk of falls, causing a direct impact on mother´s health and quality of life. We conducted three studies to examine the changes in static postural control (STUDY I), in dynamic postural control (STUDY II) and the relationship of these changes with quality of life (STUDY III) of 13 pregnant women during the gestational period (G1, G2 and G3), and a control group of 29 non-pregnant women. For static postural control assessment, a force plate (Bertec®) was used and to assess the quality of life was used the WHOQOL-Bref. In STUDY I posturographic tests were applied in four still standing positions, for three trials, with a combination of different visual conditions (eyes open - EO/eyes closed - EC) and support base configurations. The variables analyzed, derived from the center of pressure (COP), were statokinesigram, displacement amplitude, displacement velocity and sway frequency. In STUDY II were analyzed variables of ground reaction force during the stance phase of gait: time and value of the first peak (P1), second peak (P2) and the valley of the vertical component; time and maximum and minimum value found in the anteroposterior horizontal component (max Fy / min Fy) and the difference between the maximum and minimum values in the mediolateral horizontal component ( max min Fx). And in the STUDY III we used data from the first two studies, plus the assessment of quality of life of pregnant women. The results demonstrate that, early in pregnancy, the woman's body seems to be already adapted for postural control, probably due to hormonal factors, and during the trimesters there was a decrease in postural stability. Compared to the control group, pregnant women had larger areas, an increase in the amplitudes and velocities of COP displacement, more time in the first phase of weight acceptance, lower values of peak 1 and 2 of the vertical component and lower maximum and minimum values of anteroposterior horizontal component of ground reaction force, possibly indicating a reduction in speed and thrust of the gait. With respect to quality of life, the physical domain was the most affected in the first trimester, with lower values mainly during late gestation.
A gestação ocasiona consideráveis alterações fisiológicas, hormonais e anatômicas na mulher que podem afetar os membros inferiores e os movimentos do tronco, levar a uma instabilidade do controle postural e aumentar o risco de quedas, podendo gerar um impacto direto na saúde e qualidade de vida da gestante. Foram realizados três estudos com o objetivo de analisar as adaptações no controle postural estático (ESTUDO I), no controle postural dinâmico (ESTUDO II) e a relação dessas adaptações com a qualidade de vida (ESTUDO III) de 13 gestantes, ao longo dos trimestres gestacionais (G1, G2 e G3), além de um grupo controle formado por 29 mulheres não-gestantes. Para avaliação do controle postural utilizou-se uma Plataforma de Força (Bertec®), e para a avaliação da qualidade de vida utilizou-se o instrumento WHOQOL-bref. No ESTUDO I foram aplicados testes posturográficos em quatro posições eretas estáticas, por três tentativas, combinando diferentes condições visuais (olhos abertos OA/ olhos fechados OF) e diferentes configurações da base de suporte. As variáveis analisadas, relacionadas com o centro de pressão, foram a área elíptica do estatocinesigrama, a amplitude de deslocamento, a velocidade de deslocamento e a freqüência de oscilação. No ESTUDO II foram analisadas as variáveis da força de reação do solo na fase de apoio da marcha: tempo e valor do primeiro pico (P1), segundo pico (P2) e vale da componente vertical; tempo e valor máximo e mínimo encontrado na direção ântero-posterior da componente horizontal (max Fy/min Fy) e a diferença entre os valores máximo e mínimo na direção médiolateral do componente horizontal (max-min Fx). E no ESTUDO III foram utilizados dados dos dois primeiros estudos, acrescidos da avaliação da qualidade de vida das gestantes. Os resultados mostraram que, logo no início da gestação, o organismo feminino pareceu já sofrer adaptações no controle postural, provavelmente por fatores hormonais e, no decorrer dos trimestres, ocorreu uma tendência à redução da estabilidade postural. Comparadas ao grupo controle, as gestantes apresentaram maiores áreas, amplitudes e velocidades de deslocamento do centro de pressão, maior período de tempo na primeira fase de aceitação do peso, menores valores dos picos 1 e 2 da componente vertical e menores valores máximo e mínimo da componente horizontal ântero-posterior da força de reação do solo, possivelmente indicando uma redução na velocidade e na força de propulsão da marcha. Com relação à qualidade de vida, o domínio físico foi o mais afetado logo no primeiro trimestre, apresentando menores valores principalmente ao final da gestação.
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Rodier, Fabien. "Nouvel accès chimio-, régio- et stéréosélectif aux motifs spirolactones polycycliques via une réaction de cycloaddition [3+2]." Thesis, Aix-Marseille, 2012. http://www.theses.fr/2012AIXM4324.
Повний текст джерелаАнотація:
Le système spirocyclique (7,5) est un motif récurrent dans un certain nombre de produits naturels tels que les Micrandilactones ou les Rubriflordilactones. Ces structures polycycliques représentent un réel défi synthétique pour les chimistes organiciens puisqu'elles présentent au moins neuf centres stéréogènes dont plusieurs sont quaternaires. L'objectif principal de ce travail était de développer de nouvelles réactions de cycloaddition [3+2] et de les utiliser comme étape clé afin d'obtenir rapidement et efficacement le squelette polycylique de ces composés. La première partie de ces travaux a été consacrée au développement d'une réaction de cycloaddition [3+2] intra- et intermoléculaire mettant un jeu un nouveau partenaire dipolarophile, les γ-alkylidènes-buténolides. Cette étape clé conduit à la formation de cycloadduits hautement fonctionnalisés de façon rapide et efficace avec d'excellents rendements et de façon hautement chimio-, régio- et diastéréosélective. De plus, des calculs théoriques ont permis d'appréhender le mécanisme réactionnel entre un 2-diazo-1,3-cétoester et la protoanémonine catalysé par un sel de rhodium mis en jeu dans ce type de processus et ainsi d'expliquer les résultats obtenus.Dans une deuxième partie, deux approches aux cœurs ABC et CD de la micrandilactone C ont été développées mettant respectivement en jeu une cycloaddition [3+2] formellement intermoléculaire utilisant un lien de type acétal de silicium et suivie par une réaction de Diels Alder. Ainsi, le motif tétracyclique devrait être rapidement accessible après quelques aménagements de la voie de synthèse initialeThe spiro (7, 5) ring system is a recurring structural moiety in numerous natural products such as Micrandilactones and Rubriflordilactones. In term of complexity, these polycyclic structures represent a synthetic challenge for organic chemist. Indeed, these molecules present at least nine stereogenic centres including several quaternary ones. The main goal of this work was to use unprecedented partners in the [3+2] cycloaddition reaction to obtain quickly and efficiently the polycyclic core of those natural products. The first part of these studies was dedicated to the development of an intra- and intermolecular [3+2] cycloaddition using for the first time a γ-alkylidene-butenolide dipolarophile. This approach provides rapid and facile access to highly functionalised polycyclic molecules along with excellent regio-, chemo- and stereoselectivities. In addition, thanks to computational studies an overall picture of the mechanism of the intermolecular rhodium catalysed [3+2] cycloaddition between 2-diazo-1,3-ketoester and protoanemonin was apprehended, and experimental results have been rationalised.Finally, two approaches to the ABC and CD cores of Micrandilactone C were developed using respectively a formal intermolecular [3+2] cycloaddition reaction in presence of a silicon acetal linker followed by a Diels Alder reaction. The ACDE tetracyclic moiety should be quickly accessible after few modifications of the initial strategy
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Wigginton, James Richard. "The reactions of diynols at a diruthenium centre." Thesis, University of Bristol, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.274641.
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Soltau, Carl Peter. "Nitroxide trapping of radical species formed from the reaction of sulfoxides with reactive oxygen species." Thesis, Queensland University of Technology, 2021. https://eprints.qut.edu.au/210339/1/Carl_Soltau_Thesis.pdf.
Повний текст джерелаАнотація:
This project focussed on an in-depth evaluation of an established methodology that uses dimethyl sulfoxide (DMSO) as a reactive solvent with a profluorescent nitroxide (PFN) to detect and quantify particulate matter-derived ROS (Reactive Oxygen Species). Additionally, a novel approach which utilized cyclic sulfoxide tetrahydrothiophene-1-oxide (THTO) as the reactive solvent was investigated. The reactions of these sulfoxides with ROS generated from multiple sources in the presence of nitroxide radical scavengers were investigated. The results of these experiments show that nitroxides can display much broader reactivity than the simple radical scavenging processes that have previously been accepted.
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Robert, Bruno. "Etude de la structure et des interactions au sein des complexes proteine pigments impliques dans la photosynthese bacterienne : contribution de la spectrometrie raman de resonance." Paris 6, 1987. http://www.theses.fr/1987PA066603.
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Figueredo, Michael. "Reactive architecture : Urban Recreational center." FIU Digital Commons, 2005. https://digitalcommons.fiu.edu/etd/3595.
Повний текст джерелаАнотація:
This thesis explores how architecture can be designed to react to changing conditions. In the design I address how the occupants of a building may change the exterior façade based on a change of events or on group size. This creates an architectural language on the façade for pedestrians and motorists to read those activities that are occurring.
The design project is a hybrid recreational center and plaza that is designed for the use of small groups and can be adapted for larger groups. By manipulating the ground plane I create spaces where the spectator becomes the display and the display becomes the spectator. The public spaces at the center are a casual stage for movement, while private spaces at the edge offer places for spectators to overlook events. The movements at the center and edge are displayed on the façade creating a system of information.
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Smyth, R. M. "Studies of nuceophilic reactions at unsaturated centres." Thesis, University of Kent, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.233495.
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Fyfe, Paul Kelman. "Biophysical investigations of photosynthetic reaction centres from Rhodobacter sphaeroides." Thesis, University of Glasgow, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.263434.
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Crystall, Ben. "Time resolved fluorescence studies of photosystem 2 reaction centres." Thesis, Imperial College London, 1990. http://hdl.handle.net/10044/1/47831.
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Booth, Paula Jane. "Thermodynamics of electron transfer in photosystem 2 reaction centres." Thesis, Imperial College London, 1990. http://hdl.handle.net/10044/1/47779.
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Rastelli, Julia. "Latent Epstein-Barr virus infection and the germinal center reaction." Diss., lmu, 2007. http://nbn-resolving.de/urn:nbn:de:bvb:19-105021.
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Balelli, Irène. "Fondements mathématiques de la maturation d’affinité des anticorps". Thesis, Sorbonne Paris Cité, 2016. http://www.theses.fr/2016USPCD091/document.
Повний текст джерелаАнотація:
Le système immunitaire adaptatif est capable de produire une réponse spécifique contre presque tous le pathogènes qui agressent notre organisme. Ceci est dû aux anticorps qui sont des protéines secrétées par les cellules B. Les molécules qui provoquent cette réaction sont appelées antigènes : pendant une réponse immunitaire, les cellules B sont soumises à un processus d’apprentissage afin d’améliorer leur capacité à reconnaitre un antigène donne. Ce processus est appelé maturation d’affinité des anticorps. Nous établissons un cadre mathématique très flexible dans lequel nous définissons et étudions des modelés évolutionnaires simplifies inspirés par la maturation d’affinité des anticorps. Nous identifions les éléments constitutifs fondamentaux de ce mécanisme d’évolution extrêmement rapide et efficace : mutation, division et sélection. En commençant par une analyse rigoureuse du mécanisme de mutation dans le Chapitre 2, nous procédons à l’enrichissement progressif du modelé en ajoutant et analysant le processus de division dans le Chapitre 3 ,puis des pressions sélectives dépendantes de l’affinité dans le Chapitre 4. Notre objectif n’est pas de construire un modèle mathématique très détaillé et exhaustif de la maturation d’affinité des anticorps, mais plutôt d’enquêter sur les interactions entre mutation, division et sélection dans un contexte théorique simplifie. On cherche à comprendre comment les différents paramètres biologiques influencent la fonctionnalité du système, ainsi qu’à estimer les temps caractéristiques de l’exploration de l’espace d’états des traits des cellules B. Au-delà des motivations biologiques de la modélisation de la maturation d’affinité des anticorps, l’analyse de ce processus d’apprentissage nous a amenée à concevoir un modèle mathématique qui peut également s’appliquer à d’autres systèmes d’évolution, mais aussi à l’étude de la propagation de rumeurs ou de virus. Notre travail théorique s’accompagne de nombreuses simulations numériques qui viennent soit l’illustrer soit montrer que certains résultats demeurent extensibles a des situations plus compliquéesThe adaptive immune system is able to produce a specific response against almost any pathogen that could penetrate our organism and inflict diseases. This task is assured by the production of antigen-specific antibodies secreted by B-cells. The agents which causes this reaction are called antigens: during an immune response B-cells are submitted to a learning process in order to improve their ability to recognize the immunizing antigen. This process is called antibody affinity maturation. We set a highly flexible mathematical environment in which we define and study simplified mathematical evolutionary models inspired by antibody affinity maturation. We identify the fundamental building blocks of this extremely efficient and rapid evolutionary mechanism: mutation, division and selection. Starting by a rigorous analysis of the mutational mechanism in Chapter 2, we proceed by successively enriching the model by adding and analyzing the division process in Chapter 3 and affinity-dependent selection pressures in Chapter 4. Our aim is not to build a very detailed and comprehensive mathematical model of antibody affinity maturation, but rather to investigate interactions between mutation, division and selection in a simplified theoretical context. We want to understand how the different biological parameters affect the system’s functionality, as well as estimate the typical time-scales of the exploration of the state-space of B-cell traits. Beyond the biological motivations of antibody affinity maturation modeling, the analysis of this learning process leads us to build a mathematical model which could be relevant to model other evolutionary systems, but also gossip or virus propagation. Our method is based on the complementarity between probabilistic tools and numerical simulations
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Grimshaw, M. D. "Reactions of propargyl alcohols and propargyl amines at a diruthenium centre." Thesis, University of Bristol, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.274617.
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Raave, DA. "The control and auxiliary equipment of the national accelerator centre precision = 1,5m scattering chamber." Thesis, Cape Technikon, 1987. http://hdl.handle.net/20.500.11838/1111.
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Thesis (Maters Diploma(Electrical Engineering)--Cape Technikon, Cape Town, 1987A variable-energy separated sector cyclotron with a K value of 200 MeV as well as an 8 MeV solid pole injector cyclotron has been completed at the national Accelerator Centre complex at Faure. These accelerators will produce bith light-ion and heavy-ion beams for Nuclear Physics, Radiotherapy and Isotope production.
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Tetreault, Michelle Lynn. "Investigation of the docking and electron transfer reactions between cytochrome c₂ and the reaction center from the photosynthetic bacteria Rhodobacter sphaeroides using site-directed mutants /." Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC IP addresses, 1999. http://wwwlib.umi.com/cr/ucsd/fullcit?p9945781.
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Wynne, Graham M. "Oxygen centred radical fragmentations in polycycle constructions." Thesis, University of Nottingham, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.294257.
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Mauthe, Silvia [Verfasser]. "Mimicking the reactive center of photosystem II : analysis of the reaction behavior of free tetrameric and pentameric (Calcium-)manganese-oxide cluster ions / Silvia Mauthe." Ulm : Universität Ulm, 2021. http://d-nb.info/1228439087/34.
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Chuang, Jessica I.-Jane. "Understanding unidirectional electron transfer in the photosynthetic reaction center using protein engineering /." May be available electronically:, 2007. http://proquest.umi.com/login?COPT=REJTPTU1MTUmSU5UPTAmVkVSPTI=&clientId=12498.
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Becton, J. Bret Feild Hubert S. "Candidate reactions to three assessment center exercises a field study /." Auburn, Ala., 2005. http://repo.lib.auburn.edu/2005%20Summer/doctoral/BECTON_J._14.pdf.
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