Exploring the binding behaviors between nisoldipine and bovine serum albumin as a model protein by the aid of multi-spectroscopic approaches and in silico

Bovine serum albumin (BSA), a model protein was used to evaluate the binding behavior of nisoldipine and human serum albumin by a series of experiments and in silico in this article. The outcomes suggested that nisoldipine and BSA formed the nisoldipine-BSA complex with a molar ratio of 1:1, caused the fluorescence quenching of BSA, which quenching mechanism was attributable to static quenching. The binding constant of the nisoldipine-BSA complex was (1.3-3.0) x 10(4) M-1 at 298-310 K, indicating that nisoldipine on BSA protein had a moderate affinity. During the complexation of nisoldipine with BSA, nisoldipine can spontaneously insert into the site II (subdomain III A) of BSA and the distance of energy transfer from donor group in protein to acceptor group in nisoldipine was 3.21 nm, which led to the change in the hydrophobicity of the microenvironment surrounding Trp residues and in the secondary structure of BSA. Additionally, the findings also confirmed that the hydrogen bond and van der Waals force were responsible for forming the nisoldipine-BSA complex and the complexation process was a spontaneous exothermic process.Communicated by Ramaswamy H. Sarma