The study on characterization of interaction between casticin and model proteins using spectroscopic and computational methodologies

The present studies were conducted to investigate the interaction of casticin to model proteins (BSA, HSA, OVA and HEL) using fluorescence spectra, Fourier transform infrared spectra, molecular docking and molecular dynamics simulation methodologies. Our work displayed that the endogenous fluorescence intensities of BSA, HSA, OVA and HEL were quenched by various concentrations of casticin were the typical static quenching process. The binding constants (K_a) of casticin for these model proteins were in the range of 10⁴–10⁵ mol·L^-1, with the highest affinity for HSA. On the basis of thermodynamic parameters and computational simulation studies, it was suggested that the binding force of casticin to BSA, HSA, OVA and HEL were mainly hydrogen bonds, van der Waals forces and hydrophobic interactions. The spectral results illustrated that the binding of casticin to BSA, HSA, OVA and HEL induced conformational and microenvironmental changes. Casticin could decrease the α-helix percentages of BSA, HSA and OVA, but increase that of HEL. Binding substitution studies confirmed that casticin bound to the Sudlow site I of BSA and HSA. Molecular docking predicted the binding models of casticin to BSA, HSA, OVA and HEL, followed closely by molecular dynamic simulations to assess the binding stability.