Mechanistic insights into the interaction of pyrene-based chalcone derivatives with bovine serum albumin: a combined spectroscopic and computational study.

The interaction of small bioactive molecules with serum albumins plays a crucial role in their transport, distribution, and pharmacokinetic behaviour. In this study, the binding mechanism of pyrene-chalcone derivatives, including (2E)-1-phenyl-3-(pyren-1-yl)prop-2-en-1-one and its methoxy-, fluoro-, chloro-, and nitro-substituted analogues, with bovine serum albumin (BSA) was investigated using UV-visible spectroscopy, fluorescence spectroscopy, molecular docking, molecular dynamics (MD) simulations, and MM-GBSA binding free-energy calculations. UV-visible absorption spectra exhibited a bathochromic shift from 278 to 282 nm, indicating alterations in the microenvironment of aromatic residues. Fluorescence quenching studies revealed a predominantly static quenching mechanism. Stern-Volmer analysis yielded Ksv values of 663.50 and 363.86 M-1, corresponding to Kq values of 6.64 × 1010 and 3.64 × 1010 M-1 s-1, which exceed the diffusion-controlled limit and support the formation of ground-state complexes. Among the compounds studied, PPPO displayed higher quenching efficiency than FPPO, indicating substituent-dependent differences in binding affinity. Molecular docking and MD simulations demonstrated that the pyrene-based chalcone derivatives preferentially bind at Site I in subdomain IIA of BSA through hydrophobic interactions, π-π stacking with Trp213, and electrostatic contributions. MM-GBSA calculations revealed more favourable binding energetics for the chalcone derivatives than the control ligand, consistent with enhanced hydrophobic packing and strong aromatic interactions. Overall, the results indicate stable binding of pyrene-based chalcone derivatives to BSA and highlight the importance of the extended π-conjugated scaffold in governing protein-ligand interactions.