A Spectroscopic Investigation into the Interactions of 3′-O-Carboxy Esters of Thymidine with Bovine Serum Albumin

Binding studies of 3'-O-carboxy esters of thymidine, reported inhibitors of ribonucleases, with bovine serum albumin (BSA) have been explored in this report. Fluorescence spectroscopy in combination with Fourier transform infrared (FTIR) and circular dichroism (CD) spectroscopy have been used to determine the nature and mode of binding. The binding and quenching parameters were determined from tryptophan fluorescence quenching by Scatchard plots and modified Stern-Volmer plots. The association constants are of the order of 10(4) M-1 for both the ligands. Thermodynamic parameters suggest that apart from an initial hydrophobic association, hydrogen bonding and van der Waals interactions play a decisive role during protein-ligand complex formation. Minor changes were observed in the secondary structures Of human serum albumin (HSA) as revealed by FTIR and CD. Docking studies suggest that the ligands are close to Trp 213, which causes fluorescence quenching. (C) 2009 Wiley Periodicals, Inc. Biopolymers 91: 737-744, 2009.