Probing the Drug–Protein Interactions Using Multi‐Spectroscopic Approaches: Characterizing the Interactions of Chromium Picolinate With Bovine Serum Albumin

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.