Analysis of Binding Interaction between Bovine Serum Albumin and the Cobalt(II) Complex with Salicylaldehyde-2-phenylquinoline-4-carboylhydrazone

The interaction between bovine serum albumin (BSA) and the cobalt(II) complex with salicylaldehyde-2-phenylquinoline-4-carboylhydrazone (Co-SPC) was investigated using fluorescence spectroscopy, UV absorption, and circular dichroism (CD) under simulated physiologic conditions for the first time. Fluorescence data and UV absorption spectra revealed that the intrinsic fluorescence of BSA was strongly quenched by Co-SPC in terms of a static quenching process at a lower concentration of the complex and a combined quenching process at a higher concentration of the complex. Binding constants and binding sites were evaluated. The average binding distance between Co-SPC and BSA was obtained (2.28 nm) on the basis of Förster's theory. The thermodynamic parameters indicated that hydrophobic force played a major role in the binding. The binding of Co-SPC to BSA leads to changes in the conformation of BSA according to synchronous fluorescence spectra and CD data.