Study of the binding interactions between uric acid and bovine serum albumin using multiple spectroscopic techniques

The binding interactions between bovine serum albumin (BSA) and a large excess of uric acid (UA) have been analyzed in aqueous solution at pH = 7.4, using UV-vis absorption and steady-state, time-resolved, synchronous and three-dimensional fluorescence spectra techniques. The observed effects verify the formation of pi-pi stacked non-covalent and non-fluorescent complexes in the system BSA-UA. All the calculated parameters, the binding, fluorescence quenching and bimolecular quenching rate constants, as well as the measurements of fluorescence decay times and Forster resonance energy transfer parameters validate the mechanism of static quenching. The changes in the synchronous fluorescence spectra indicate that the BSA fluorescence quenching originates both from Trp and Tyr residues, but their involvement is not equivalent. The interaction with UA induces the diverse alterations of BSA tertiary structure: folding of the polypeptide chains around Trp residues and concurrently their extension around Tyr residues. The obtained outcomes suggest that the presence of the excessive amount of UA in blood could interfere with the physiological functions of serum albumin, especially in case of UA overproduction. (C) 2018 Elsevier B.V. All rights reserved.