Interactions between hydroxylated polycyclic aromatic hydrocarbons and serum albumins: multispectral and molecular docking analyses.

Hydroxylated polycyclic aromatic hydrocarbons (OH-PAHs) can bind to serum albumin and influence their distribution and elimination in organisms. Here, multispectral analysis and molecular docking methods were used to investigate the binding mechanism of two OH-PAHs, 1-hydroxyphenanthrene (1-OHPhe) and 9-hydroxyphenanthrene (9-OHPhe), with two homologous serum albumins, human serum albumin (HSA) and bovine serum albumin (BSA). The quenching constants of HSA with 1-OHPhe and 9-OHPhe were much larger than those for BSA. Energy transfer from the tryptophan (Trp) residues in HSA to 1-OHPhe and 9-OHPhe was more probable than from Trp in BSA. The interactions of 1-OHPhe and 9-OHPhe with Trp in HSA and BSA altered the microenvironment of Trp. Molecular docking results revealed that the binding modes and binding forces of 1-OHPhe and 9-OHPhe with HSA and BSA were different. The two OH-PAHs were used as fluorescent probes to analyze the microenvironmental hydrophobicities of HSA and BSA, which were distinctly different. The structural difference between HSA and BSA induced significant variations in their binding behaviour with 1-OHPhe and 9-OHPhe. Moreover, HSA was more susceptible to 1-OHPhe and 9-OHPhe than BSA. This work suggests that the differences between the two serum albumins should be considered in related studies.