Biphasic Role of β-Cyclodextrin in Anionic Surfactant-induced Lysozyme Aggregation and Refolding

This study explores the role of β-cyclodextrin (β-CD) on the aggregation and refolding of hen egg white lysozyme (HEWL) induced by an anionic surfactant, i.e., sodium dodecylbenzenesulfonate (SDBS). Different biophysical techniques (Spectrophotometer, Flurometer, and Circular Dichroism) were employed to measure the conformational changes and aggregation propensity. UV-Vis spectroscopy revealed a biphasic turbidity response: initial β-CD concentrations (<0.4 mM) enhanced HEWL aggregation, whereas higher concentrations (>0.4 mM) solubilized the SDBS-induced aggregates, thereby restoring a native-like HEWL structure. Intrinsic fluorescence and circular dichroism analyses indicated that β-CD mitigated SDBS-induced structural disruptions, facilitating HEWL refolding. Thioflavin T assays confirmed the formation of amyloid-like fibrils in the SDBS-HEWL complex, which were solubilized upon addition of higher β-CD concentration, correlating with a decrease in turbidity,the regain of tertiary and secondary structure. Right-angle light scattering kinetic measurements supported these findings, showing rapid aggregate solubilization at higher β-CD concentrations. The study suggests that β-CD forms inclusion complexes with SDBS, thereby reducing its availability to interact with HEWL and mitigating aggregation, while promoting refolding. These findings underscore the potential of β-CD as a chemical chaperone in modulating protein aggregation, with implications for the formulation of therapeutic proteins and the understanding of protein misfolding diseases.