Spectroscopic studies on the interaction of azelnidipine with bovine serum albumin

Interaction between azelnidipine and bovine serum albumin (BSA) was investigated by fluorescence spectroscopy and circular dichroism (CD). Azelnidipine effectively quenched the intrinsic fluorescence of BSA via a combination of static and dynamic quenching, forming azelnidipine-BSA complex with binding constant (K-a) of the order of 10(5). The thermodynamic parameters obtained from van't Hoff equation revealed that both Delta H degrees and Delta S degrees were negative, that is, -49.77 kJ mol(-1) and -64.47 J mol(-1) K-1, respectively, suggesting that the binding is mainly driven by the enthalpy and hydrogen bonding plays major role in stabilizing azelnidipine-BSA complex. The binding of azelnidipine to BSA leads to changes in the conformation of BSA according to synchronous fluorescence spectra and CD data. The presence of metal ion decreases the binding constant of azelnidipine-BSA complex. (C) 2007 Elsevier B.V. All rights reserved.