Interactions of pyrene and/or 1-hydroxypyrene with bovine serum albumin based on EEM-PARAFAC combined with molecular docking

The interactions of pyrene (Pyr) and/or 1-hydroxypyrene (1-OHPyr) with bovine serum albumin (BSA) in binary and ternary systems were investigated using the excitation-emission matrix (EEM)-parallel factor analysis (PARAFAC) method combined with fluorescence quenching analysis and the molecular docking method. The results showed that the PARAFAC approach could be used to decompose the EEM spectra of Pyr, 1-OHPyr, and BSA in the binary and ternary systems. The binding constants of Pyr and 1-OHPyr with BSA increased from 1.01 x 10(6) and 1.62 x 10(6) L mol(-1) to 2.09 x 10(6) and 1.86 x 10(7) L mol(-1) in the ternary systems compared with the binary systems, respectively. Molecular docking revealed that in both binary and ternary systems, Pyr was bound between II A and III A regions of BSA, whereas 1-OHPyr was located in the I B region. Van der Waals forces dominated the formation of the BSA-Pyr complexes; however, for BSA-1-OHPyr complexes, in addition to Van der Waals forces, hydrogen bonds also played an important role in their binding as a hydrogen bond formed between 1-OHP and the amino residue of BSA. Moreover, the coexistence of Pyr and 1-OHPyr aggravated the conformation changes of BSA and led to a prominent decrease in the hydrophobicity of the micro-environment around tryptophan (TRP) residues. 1-OHPyr has a more severe influence on BSA conformation than Pyr in the ternary systems. This study will help to understand the combined effects of PAHs and their hydroxyl metabolites on proteins at the molecular level.