Spectroscopic and molecular docking approaches for investigating conformation and binding characteristics of clonazepam with bovine serum albumin (BSA)

Clonazepam, a type of benzodiazepine, is a classical drug used to prevent and treat seizures, panic disorder, movement disorder, among others. For further clarifying the distribution of clonazepam in vivo and the pharmacodynamic and pharmacokinetic mechanisms, the binding interaction between clonazepam and bovine serum albumin (BSA) was investigated using ultraviolet spectroscopy (UV), steady-state fluorescence spectroscopy, synchronous fluorescence spectroscopy, three-dimensional (3D) fluorescence spectroscopy, Fourier transform infrared spectroscopy (FT-IR) and molecular docking methods. The results well confirmed that clonazepam bound on the subdomain III A (Site II) of BSA through van der Waals force and hydrogen bonding interaction, and quenched the intrinsic fluorescence of BSA through a static quenching process. The number of binding sites (n) and binding constant (Kb) of clonazepam-BSA complex were about 1 and 7.94×104M−1 at 308K, respectively. The binding process of clonazepam with BSA was spontaneous and enthalpy-driven process due to ΔG0T|ΔS0| over the studied temperature range. Meanwhile, the binding interaction of clonazepam with BSA resulted in the slight change in the conformation of BSA and the obvious change in the conformation of clonazepam, implying that the flexibility of clonazepam also played an important role in increasing the stability of the clonazepam–BSA complex. [Display omitted] •The fluorescence of BSA quenched by clonazepam due to forming stable clonazepam-BSA complex.•Clonazepam located on the subdomain IIIA (Site II) of BSA•The interaction forces were mainly van der Waal's forces and hydrogen bonding interaction.•There was a slight change in the secondary structure of BSA due to binding clonazepam.•The flexibility of clonazepam played an important role in the binding process.