The role of metal ions in the behavior of bovine serum albumin molecules under physiological environment

Abstract

Metal ions released from metallic implants can affect the conformation and structural stability of proteins in biological fluids, which eventually affects the biocompatibility of implants. The present study aimed at understanding the interactions between the metal ions (Mn2+, Fe2+, Fe3+, Co2+, Cu2+, and Zn2+) and bovine serum albumin (BSA) molecules in physiological context. The structural information of BSA molecules and the microenvironment of functional groups were investigated using UV, Raman, and circular dichroism spectroscopy. The results revealed that addition of Fe3+, Fe2+, and Cu2+ ions alters the tertiary structure of BSA molecules and exposes the aromatic heterocyclic hydrophobic group of BSA amino acid residues. The addition of Fe3+ and Cu2+ ions results in increased viscosity and decreased intensity of the water peak in the BSA solution. Furthermore, Fe3+ and Cu2+ ions evidently promote the α-helix to β-sheet transformation of BSA molecules due to decreased disulfide bond stability. Tryptophan residues of BSA and metal ions containing BSA (Me+/BSA) solutions were found to be in a hydrophilic environment. Moreover, the addition of metal ions to BSA results in several of tyrosine residues acting as hydrogen-bond donors. Coomassie brilliant blue staining revealed that the addition of Cu2+ ions promotes the aggregation of BSA molecules. The findings of this study will be helpful for evaluating the biocompatibility of metallic implants.