Study of conformational changes of macromolecules in solutions using X-ray scattering / Estudo de mudanças conformacionais de macromoleculas em solução usando espalhamento de raio-X

AUTOR(ES)
DATA DE PUBLICAÇÃO

2007

RESUMO

During the last decades, the study of conformational changes in biological macromolecules has been a great challenge for the scientists, and continues to be an important subject of biotechnological interest and protein engineering. The process of folding (unfolding) of protein molecules has been intensively studied, because this investigation can contribute to the knowledge of the process of protein synthesis, thus helping to understand the development of some illnesses associated with misfolding or aggregation processes of certain proteins. In this context, the technique of Small Angle X-ray Scattering (SAXS) appears as a valuable technique, because it provides structural information of the molecules in solution. This technique allows dynamical studies and makes possible the study of the protein in physiological conditions. In this work the potentiality of the SAXS technique was evidenced in the study of conformational changes of biological molecules. The process of denaturation of the protein lysozyme in solution was studied using SAXS measurements in equilibrium conditions. Conformational changes were observed during the process of denaturation by the action of urea in the solution and for high temperatures. The results showed that lysozyme is a protein with certain resistance to unfold completely. Even in extreme conditions of high concentration of urea and high temperatures, this protein does not totally lose its compactness. Moreover, only two conformational states (folded and unfolded) were observed. An intermediate state was not observed. This study showed the high cooperativity of the unfolding process of this protein during its denaturation process. Another process studied was the oligomerization of the protein -Lactoglobulin under the effect of gamma irradiation. The protein was studied in the solid form, in different water activities, and in solution, in different concentrations. The samples were exposed to several doses of -radiation. The SAXS technique was used to obtain dimensional parameters of the proteins and models were calculated from the experimental scattering data. Finally, this study showed that the SAXS technique as a versatile and very useful tool for the study of changes in the tertiary and quaternary structures of proteins in solution

ASSUNTO(S)

proteins proteinas conformational changes raios x - espalhamento a baixo angulo small-angle x-ray scattering mudanças conformacionais

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