Combined in vitro optical and in silico docking approaches: evaluating kinetic and thermodynamic parameters in the...

This study investigates the interaction between human serum albumin (HSA) and taurine (2‑aminoethanesulfonic acid) in aqueous solution using a multi-technique biophysical approach. The interaction of taurine (as an additive, supplement, or endogenous metabolite) with HSA is critically important for several interconnected scientific, pharmaceutical, and health-related reasons. This interaction was investigated using fluorescence spectroscopy, UV-visible absorption, zeta potential, surface plasmon resonance (SPR), and molecular docking under physiological conditions. Fluorescence quenching showed K_SV increasing with temperature (2.99 × 10³ to 5.11 × 10³ M^-1), indicating dynamic quenching. Binding constants (K_A) increased with temperature, while K_D decreased, with n ≈ 1, SPR gave a lower K_A (1.7 × 10⁵ M^-1), reflecting surface sensitivity. Thermodynamic parameters (ΔH = +127.4 kJ/mol, ΔS = +0.54 kJ/(mol·K), ΔG =  - 34.41 to - 40.22 kJ/mol) confirmed an endothermic, entropy-driven process governed by hydrophobic forces. Zeta potential shifted from - 39 mV to - 20 mV, and UV-visible showed hypochromism with red shift, indicating conformational changes. Docking revealed binding energy of - 4.5 kcal/mol at domain IIB (fatty acid region). Collectively, taurine binds to HSA via hydrophobic interactions with moderate, temperature-dependent affinity, offering insights into its transport and bioavailability in human circulation.