Binding of a bcl-2 Family Inhibitor to Bovine Serum Albumin: Fluorescence Quenching and Molecular Docking Study

Abstract

Both fluorescence spectroscopic and molecular docking methods were used to investigate the interaction between bovine serum albumin (BSA) and a known Bcl-xl/Bcl-2 inhibitor HA 14-1. Based on the spectral overlap between the emission of BSA and absorption of HA 14-1, Forster energy transfer was proposed to be the possible quenching mechanism. The Stern-Volmer constants are 2.49 x 10⁴, 2.04 x 10⁴ and 0.90 x 10⁴ M⁻¹ at 293, 303 and 318 K, respectively, indicating that a static quenching process dominates. Thermodynamic parameters were further obtained. The derived negative Δ H (-27.51 kJ mol⁻¹) and Δ S (-11.11 J mol⁻¹ K⁻¹) values suggest hydrogen bond interaction and van der Waals force are the main binding force. The docking study was performed on BSA model. According to the docking score and the number of hydrogen bonds, the potential binding site for HA 14-1 is proposed to be the site IIA, also known as drug site 1.