Dual binding modes of Quercetin to BSA: Insights from spectroscopy and molecular simulations in amyloid suppression.

The rising incidence of neurodegenerative disorders linked to protein fibrillation in aging populations highlights the need for efficient, low-toxicity fibrillation inhibitors. Quercetin, a natural flavonoid, shows potential in both suppressing fibrillation and disaggregating mature fibrils. However, its mechanisms require further investigation. This study examines the dual binding modes of Quercetin to bovine serum albumin (BSA) using spectroscopic and molecular simulation techniques. These approaches reveal hydrophobic-driven complexation and polar interaction-mediated structural interference. Together, they provide insight into its role in amyloid suppression. Through Thioflavin-T (ThT), 8-anilino-1-naphthalenesulfonic acid (ANS), and Congo Red (CR) analysis, we confirm that Quercetin inhibits BSA fibrillation kinetics and prevents amyloid-like aggregation. Ultraviolet-visible (UV-vis) and variable-temperature fluorescence spectroscopy show that static quenching is the dominant interaction. This interaction is driven by entropy and hydrophobic burial at Sudlow site I (subdomain IIA). A 1:1 binding stoichiometry is also supported. Competitive displacement assays and molecular docking reveal that Quercetin binds preferentially to subdomain IIA through π-π stacking and hydrogen bonds (e.g. Trp-214, Ser-192). Scanning electron microscopy (SEM) further validates Quercetin's suppression of fibrillar growth. This study uncovers the interaction mechanism between Quercetin and BSA. It also provides theoretical support for its potential in anti-fibrillation therapy. Additionally, it highlights the advantages of combining spectroscopic and molecular simulation methods to study biomolecular interactions.