Desnaturação e agregação da albumina mediante aquecimento e mudança de pH estudadas por NEXAFS, fluorescência, eletroforese e cálculos teóricos

Abstract

The chemical processes involved in protein denaturation and aggregation are complex and of great scientific interest. The caracterization of these processes can take us to use them or their products to the benefit of biotechonology, as well as the prevention of diseases caused by them. However, the physicalchemical study of these phenomenons in similiar conditions to fisiological is a challenge. In this work, the NEXAFS spectra at the sulfur 1s edge of albumin in solution were taken, upon variations in temperature and pH. Highly disseminated techniques in the study of proteins were also used, like measures of tryptophan fluorescence and polyacrilamide gel electrophoresis, in addition to theoretical calculations of inner shell transitions of sulfur, simulating the NEXAFS spectrum. With the heating, it was possible to verify changes in the NEXAFS spectrum, indicating denaturation and aggregation phenomena, the latter being highlighted above 60 ° C, in agreement with the other techniques and with that found in the literature. Regarding the pH variation, there was also a variation indicative of the change in the conformation of the protein. Finally, the theoretical calculations had a good agreement with the experimental results, showing that the presence of the disulfide bridges in the albumin structure has a great impact on the spectrum. This work shows that the NEXAFS technique can be an alternative for studying the conformation of proteins in solution and, consequently, in conditions closer to physiological, leading to a greater understanding of the processes of denaturation and aggregation by the influence of physicalchemical factors.