Comprehensive investigation of binding of some polycyclic aromatic hydrocarbons with bovine serum albumin: Spectroscopic and molecular docking studies.

The interactions of phenanthrene (PHTN), fluorene (FLRN) and fluoranthene (FLRT) as polycyclic aromatic hydrocarbons (PAHs) with bovine serum albumin (BSA) were explored employing spectroscopic approaches and molecular docking simulations. Based on fluorescence quenching analysis FLRT showed higher binding affinity to BSA comparing with PHTN and FLRN. PHTN/FLRN/FLRT quenched the intrinsic fluorescence of BSA in the form of the mixed mechanism. Synchronous fluorescence spectroscopy, UV-Vis and circular dichroism spectroscopy demonstrated that presence of PHTN/FLRN/FLRT induced conformational alterations in BSA molecules. Based on the Förster resonance energy transfer (FRET) theory, the binding distances between the donor (BSA) and the acceptor (PHTN/FLRN/FLRT) were 3.85, 2.34 and 2.69 nm, respectively. Molecular docking simulations of 16 EPA priority PAHs were carried out to disclose their preferred binding modes. Docking analysis demonstrated that PAHs were bound to BSA stronger as the number of aromatic rings increased. Moreover, the results revealed the role of differences in the location of aromatic rings in PAHs on their interactions with BSA despite equivalent number of aromatic rings. Van der Waals forces dominated the formation of the. BSA-PAHs complexes. Most studied PAHs were bound to the IIIB region of BSA; however, the sterically bulky PAHs like benzo[g,h,i]perylen and indeno[1,2,3cd]pyrene were located in the IIIA and IIB regions of BSA. Naproxen, the co-crystalized ligand, was redocked to the crystal structure of BSA and root mean square deviation value was found to be 1.96 Å highlighting the predictive accuracy of the docking protocol.