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Int J Biol Macromol. 2018 Jul 1;113:1032-1040. doi: 10.1016/j.ijbiomac.2018.02.116. Epub 2018 Feb 21.

Thimerosal changes protein conformation and increase the rate of fibrillation in physiological conditions: Spectroscopic studies using bovine serum albumin (BSA).

Author information

1
Laboratório de Instrumentação e Desenvolvimento em Química Analítica (LINQA), Instituto de Química e Biotecnologia, Universidade Federal de Alagoas, Maceió, AL 57072-900, Brazil.
2
Grupo de Estudos em Química Orgânica e Biológica (GEQOB), Departamento de Química, Universidade Federal de Minas Gerais, Belo Horizonte, MG 31270-901, Brazil.
3
Laboratório de Instrumentação e Desenvolvimento em Química Analítica (LINQA), Instituto de Química e Biotecnologia, Universidade Federal de Alagoas, Maceió, AL 57072-900, Brazil. Electronic address: josue@iqb.ufal.br.

Abstract

The interaction between bovine serum albumin (BSA) and thimerosal (TM), an organomercury compound widely employed as a preservative in vaccines, was investigated simulating physiological conditions and using different spectroscopic techniques. The results, employing molecular fluorescence showed the interaction occurs by static quenching through electrostatic forces (ΔH < 0 and ΔS > 0), spontaneously (ΔG = -4.40 kJ mol-1) and with a binding constant of 3.24 × 103 M-1. Three-dimensional fluorescence studies indicated that TM causes structural changes in the polypeptide chain of the BSA, confirmed by circular dichroism that showed an increase in α-helix (from 43.9 to 47.8%) content after interaction process. Through synchronized fluorescence and employing bilirubin as a protein site marker, it was confirmed the preferential interaction of TM in the subdomain IB of BSA. The interaction mechanism proposed in this work is based on the reaction of TM with BSA through of free Cys34 residue, forming the adduct BSA-HgEt with the thiosalicylic acid release, which possibly interacts electrostatically with positive side chain amino acids of the modified protein. Finally, it was proven that both TM and EtHgCl accelerate the protein fibrillation kinetics in 42 and 122%, respectively, indicating the toxicity of these compounds in biological systems.

KEYWORDS:

BSA and ethylmercury; Interaction mechanism; Protein fibrillation; Thimerosal

PMID:
29476861
DOI:
10.1016/j.ijbiomac.2018.02.116
[Indexed for MEDLINE]
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