Characterization of interaction and the effect of carbamazepine on the structure of human serum albumin

The binding of carbamazepine (CBZ) to human serum albumin (HSA) was investigated under simulative physiological conditions. In this study, intrinsic fluorescence of tryptophan-214 in HSA was monitored upon the addition of CBZ. Binding constant of CBZ–HSA was calculated by the remarkable static quenching effect of CBZ and found to be (2.081 ± 0.023) × 10⁴ M⁻¹. The fluorimetric results revealed that the hydrophobic interaction was a predominant intermolecular force for stabilizing the complex, which is also in agreement with the results obtained from voltammetric approach. Three site probes, warfarin, ibuprofen and digitoxin, were employed in fluorescence displacement experiments to locate the exact binding site for CBZ in HSA. The alteration in secondary structure of protein in the presence of CBZ was confirmed by the evidences from circular dichroism and FT-IR spectroscopy. Further, the distance r between donor (Trp-214) and acceptor (CBZ) was obtained according to fluorescence resonance energy transfer (FRET).