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ETUDE DE L'INFLUENCE DE LA TEMPERATURE ET DE LA PRESSION SUR LA STRUCTURE ET LA DYNAMIQUE DE L'INHIBITEUR DE LA TRYPSINE PANCREATIQUE BOVINE.
UNE ETUDE PAR DIFFUSION DE NEUTRONS

Abstract : The subject of this PhD thesis concerns a protein belonging to the enzymatic catalysis : the bovine pancreatic trypsin inhibitor or BPTI which is a model system much studied by several techniques but less by neutron scattering. It is a small protein ( 58 amino acid residues, a molecular weight of 6500 Da) which has a very high stability since it cannot be denatured at temperatures below 95°C or at pressures below 14 kbar. This stability is due to the presence of three disulphide bridges and three salt bridges. We have studied the structure and the dynamics of native state and thermal and pressure denatured states of BPTI by neutron scattering technique. By small angle neutron scattering we have observed an increase of the radius of gyration of the protein in solution at 95°C and a reduction of this radius under 6000 bar. The ellipsoidal shape of the molecule in the native state do not change between 22°C and 95°C but we have observed an increase of the volume of BPTI. Indeed, the shape of BPTI is modified from an ellipsoidal one to a spherical one at 3000 bar, while it is well represented by a micelle when applied pressure values reach 5000 and 6000 bar.
Further experiments by infrared spectroscopy and by UV-visible spectroscopy as a function of temperature and pressure allowed us to confirm our results. Quasielastic neutron scattering allowed us to observe an opposite effect of temperature and pressure on global motions and internal dynamics of BPTI in solution. Increasing temperature induces a faster dynamics of these global and internal Motions whereas increasing pressure induces a slowing down of these motions.
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Marie-Sousai Appavou. ETUDE DE L'INFLUENCE DE LA TEMPERATURE ET DE LA PRESSION SUR LA STRUCTURE ET LA DYNAMIQUE DE L'INHIBITEUR DE LA TRYPSINE PANCREATIQUE BOVINE.
UNE ETUDE PAR DIFFUSION DE NEUTRONS. Physique [physics]. Université Paris Sud - Paris XI, 2005. Français. ⟨tel-00232529⟩

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