The Study of Interaction between Human Serum Albumin and Emtricitabine Using Multi-Spectroscopy and Molecular Docking

This study investigates the interaction between the antiretroviral drug Emtricitabine and human serum albumin under physiological conditions, employing fluorescence spectroscopy, circular dichroism, and molecular docking techniques. Fluorescence quenching analysis revealed a moderate binding affinity (association constant, Ka = 16.601 M–1) and a spontaneous interaction between Emtricitabine and HSA in phosphate buffer (0.05 M, pH 7.4) at 25°C. CD spectroscopy indicated an increase in the α-helical content of HSA from 61.1 to 64.84% upon Emtricitabine binding, suggesting conformational changes in the protein’s secondary structure. Molecular docking studies identified subdomain IIA of HSA as the optimal binding site for Emtricitabine. Thermodynamic and docking analyses revealed that the interaction is primarily driven by hydrophobic forces and hydrogen bonding. Specifically, Emtricitabine formed hydrophobic contacts with residues Gln196(A), Leu219(A), Arg222(A), and Ala291(A), and established two hydrogen bonds with Arg257(A), with bond lengths of 3.25 and 2.88 Å, respectively. The estimated Gibbs free energy for the most favorable binding model was –6.4 kcal/mol (–26.496 kJ/mol). Notably, the theoretical predictions were in strong agreement with the experimental observations.