Estudos de interação do timerosal com albumina do soro bovino (BSA) simulando condições fisiológicas e empregando técnicas espectroscópicas: mecanismo e perfil de fibrilação protéica

Abstract

Interaction between bovine serum albumin (BSA) and thimerosal (TM), organic mercury compound, was investigated by spectroscopic methods. The results, by molecular fluorescence, show that the interaction takes place by static quenching with electrostatic forces spontaneously (ΔG = - 4.40 kJ mol-1 at 30°C). The binding constant (Kb) was 3.24 ± 0.01x103 L mol-1 (30°C) is considered a moderate interaction. Fluorescence in three dimensions revealed that TM causes structural involving the the polypeptide chain BSA changes in the polarity of the tryptophan and tyrosine residues confirmed by circular dichroism (CD) showed an increase in α-helix content after interaction with TM. In addition, the TM decreases the surface hydrophobicity of the protein. Bilirubin was used as a marker for the subdomain IB, confirming that TM interacts in this region of the protein. The study of the interaction mechanism proposed that TM is reacted with BSA through the free cysteine residue, forming the adduct BSA-HgEt release of thiosalicylic acid (ATS), which interacts with amino acids with side chain positive. Besides, it was seen that TM accelerates the protein fibrillation kinetics by 42%, with a possible indication of the toxicity of this compound in biological systems.