Investigation of the binding affinity in vitamin B12—Bovine serum albumin system using various spectroscopic methods

Abstract

The binding affinity between vitamin B12 (VitB12) and bovine serum albumin (BSA) has been investigated in aqueous solution at pH=7.4, employing UV–vis absorption and steady-state, synchronous and three-dimensional fluorescence spectra techniques. Representative effects noted for BSA intrinsic fluorescence resulting from the interactions with VitB12 confirm the formation of π-π stacked non-covalent and non-fluorescent complexes in the system VitB12-BSA. All the determined parameters, the binding, fluorescence quenching and bimolecular quenching rate constants (of the order of 104Lmol−1, 103Lmol−1 and 1011Lmol−1s−1, respectively), as well as Förster resonance energy transfer parameters validate the mechanism of static quenching. The interaction with VitB12 induces folding of the polypeptide chains around Trp residues of BSA, resulting in a more hydrophobic surrounding. Presented outcomes suggest that the addition of VitB12 can lead to the more organized BSA conformation and its more folded tertiary structure, what could influence the physiological functions of bovine serum albumin, notably in case of its overuse or abnormal metabolism.