Understanding the binding of quinoline amines with human serum albumin by spectroscopic and induced fit docking methods.

Seven new quinoline-based bioorganic compounds were prepared by solvent-free synthesis and characterized using spectral techniques. The binding of these compounds with human serum albumin (HSA) was investigated by multi-spectroscopic methods. The quenching of Trp fluorescence upon addition of these compounds to HSA confirmed their significant binding. The quenching analysis at three different temperatures revealed that the complex formation is static and the reaction is entropy driven, spontaneous, and exothermic. Hydrogen bonds and van der Waals forces mainly contributed in the interactions as confirmed by the negative Δ and Δ values as well as molecular docking. The results from the circular dichroism (CD) spectroscopy indicated the minimal conformational changes of the protein upon binding with these quinoline compounds. The specific binding site and mode of interactions with HSA were also modeled using induced fit molecular docking procedure and their binding site was found to be in the interface of domains II and III, which is similar to the binding of the drug iodipamide with serum albumin. Communicated by Ramaswamy H. Sarma.