Effects of urea, metal ions and surfactants on the binding of baicalein with bovine serum albumin
Atanu Singha Roy, Amit Kumar Dinda, Nitin Kumar Pandey, Swagata Dasgupta
Journal of Pharmaceutical Analysis
The interaction of baicalein with bovine serum albumin (BSA) has been investigated with the help of spectroscopic and molecular docking studies. The binding affinity of baicalein towards BSA was estimated to be in order of 105 M−1 from fluorescence quenching studies. Negative ΔH° (−5.66±0.14 kJ/mol) and positive (ΔS°) (+79.96±0.65 J/mol K) indicate the presence of electrostatic interactions along with the hydrophobic forces that results in a positive ΔS°. The hydrophobic association of baicalein with BSA diminishes in the presence of SDS (Sodium dodecyl sulfate) due to probable hydrophobic association of baicalein with SDS, resulting in a negative ΔS° (−40.65±0.87 J/mol K). Matrix-assisted laser desorption ionization/time of flight (MALDI-TOF) experiments indicate a 1:1 complexation between baicalein and BSA. The unfolding and refolding phenomena of BSA have been investigated in the absence and presence of baicalein using steady-state and fluorescence lifetime measurements. It was observed that the presence of urea ruptured the non-covalent interaction between baicalein and BSA. The presence of metal ions (Ag+, Mg2+, Ni2+, Mn2+, Co2+and Zn2+) increased the binding affinity of ligand towards BSA. The changes in conformational aspects of BSA after ligand binding have also been investigated using circular dichroism (CD) and Fourier transform infrared (FT-IR) spectroscopic techniques. Site selectivity studies following molecular docking analyses indicated the binding of baicalein to site 1 (subdomain IIA) of BSA.
Circular dichroism, Secondary structure, Ligand binding, Pharmaceutical, Biochemistry