Probing the Drug-Protein Interactions Using Multi-Spectroscopic Approaches: Characterizing the Interactions of...

The binding behavior of the antioxidant supplement chromium picolinate (CPN) with bovine serum albumin (BSA) was examined under simulated physiological conditions using a variety of spectroscopic techniques, including Fourier transform infrared (FTIR), fluorescence, and UV-visible absorption spectroscopy, complemented by molecular docking analyses. Fluorescence quenching studies revealed that the formation of the BSA-CPN complex resulted in the quenching of HSA's intrinsic fluorescence. A portion of the quenching arises from the inner filter effect (IFE), while the remainder occurs through a dynamic mechanism, with a binding affinity of 3.47 × 10⁷ L mol^-1 at 298 K. Thermodynamic analysis via the van't Hoff equation provided key parameters, with an enthalpy change (ΔH°) of -238.89 kJ mol^-1 and an entropy change (ΔS°) of -671.146 J mol^-1 K^-1. These values, along with spectral data, suggested that the stability of the BSA-CPN complex was primarily governed by hydrogen bonding and van der Waals forces. Further structural analysis using FTIR and UV-vis spectroscopy pointed out that CPN binding made conformational changes in BSA, particularly altering its secondary structure due to interactions with hydrophobic pocket residues. Competitive binding assays with site-specific probes suggested that CPN is likely binding to BSA at a location analogous to Site I.