Etudes de diffraction de poudres de protéines

Abstract : Knowledge of the structure of proteins helps in understanding theirbiological function.The main technique used, single crystal diffraction, requires thelimiting step of growing a single crystal.On the other hand, powder diffraction requires only a crystallineprecipitate made of many microcrystals such as those often discardedduring the search for suitable single crystal growth conditions.We present in this thesis different studies of proteins by powder diffraction.Development of new methods for sample preparation and data acquisitionare also presented, as they have been crucial steps to obtain highquality diffraction data.We studied the polymorphism of Urate oxidase by observing thedifferent crystallographic phases resulting from the changes in thecrystallisationconditions.A crystallographic phase of pharmaceutical interest has been identified.Also one phase of urate oxidase complexed with its inhibitor gave apowder pattern sufficient to re-determine and refine its structure.A protocol for cryocooling protein powder samples has been found,extending the lifespan of the sample in the intense X-ray beam.This allowed the refinement from powder data of two forms ofcryocooled human insulin.We present also the determination of a preliminary structure of themayaro virus macro domain, based on a powder diffraction patternobtained on a single urchin-like bundle of needles.A study of the protective protein matrix of two baculoviruses ispresented, showing some current limits of the method.In annexes, the steps for preparing and analysing protein powders are described.
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Agricultural sciences. Université de Grenoble, 2011. French. <NNT : 2011GRENV009>


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Yves Watier. Etudes de diffraction de poudres de protéines. Agricultural sciences. Université de Grenoble, 2011. French. <NNT : 2011GRENV009>. <tel-00605443>

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