Non-covalent interaction of BODIPY-benzimidazole conjugate with bovine serum albumin–A photophysical and molecular docking study.

• A synthesized BODIPY-benzimidazole conjugate (BDZ) displays high binding affinity towards BSA with a binding constant of (1.38 ± 0.09) × 104 M−1. • Binding of BDZ with BSA casues significant modulations in the photophysical properties of BDZ due to structural immobilization of the dye inside the binding pocket of BSA. • Ionic strength dependent measurements suggest the prominence of hydrophobic interactions between BDZ and BSA. • Molecular docking calculations suggests site IB of BSA to be the most probable binding site for BDZ. Non-covalent interactions of different dyes/drugs with various biological agents, which lead to large modulations in photophysical properties, have attracted attention of many scientists over the decades due to their versatile applicability in different fields. Herein, we report the spectroscopic investigation of non-covalent interaction of a synthesized BODIPY-benzimidazole conjugate (BDZ) dye with bovine serum albumin (BSA), which results in distinctive modulations in the photophysical properties of the dye. The structural immobilization, and reduced propensity of forming the weakly emissive intramolecular charge transfer (ICT) state of the dye, inside the confined BSA cavity, results into a significant increase in fluorescence intensity, which is also supported by the increase in the excited-state lifetime and fluorescence anisotropy decay time of the dye. Molecular docking calculations and competitive binding experiments reveal that the BDZ dye binds selectively to site IB with a reasonably high binding constant K b ˜ 1.38 × 104 M−1. The BDZ-BSA complex shows a notable decrease in fluorescence intensity in the presence of guanidinium hydrochloride, indicating the selective binding of the dye with the native form of the BSA protein as compared to its denatured form. Formation of BDZ-BSA complex, which emits in the biologically favorable red region, makes the studied system a probable choice to monitor the denatured form of the BSA protein, biological sensing study, and to understand the transport mechanism of similar kind of drugs and other metabolites with serum albumin protein. [ABSTRACT FROM AUTHOR]