Interactions of Pyrene with Human Serum Albumin and Bovine Serum Albumin: Microenvironmental Polarity Differences at Binding Sites

The interactions of pyrene (Pyr), a microenvironmental hydrophobic fluorescent probe,with human serum albumin (HSA) or bovine serum albumin (BSA) were investigated using steady-state fluorescence,fluorescence resonance energy transfer technology, and molecular docking methods. It was observed that the average values of I-1/I-3 of the Pyr in the presence of HSA or BSA are 1.36 and 0.92, respectively. The binding constants of Pyr with HSA or BSA has been decreased from 1.86x10(7) L/mol to 1.71x10(5) L/mol. The apparent distances of Pyr to tryptophan residues in HSA or BSA were calculated to be 2.37 and 2.34 nm. The binding sites of Pyr in HSA or BSA were located in subdomain. B and subdomains. A, respectively. The polarity of amino acid residues around the binding sites was one of the main factors affecting the I-1/I-3 value of Pyr. The experimental results suggested that there were significant differences in the binding sites and its microenvironmental polarity of BSA and HSA with Pyr.