Cationic gemini surfactant (16-4-16) interact electrostatically with anionic plant lectin and facilitates amyloid fibril formation at neutral pH

Abstract

Amyloid are fibrous clumps or aggregates of protein which usually deposited in various organs and tissues which direct their degenration. In neurodenrative disease, these proteincious aggregates leads degeneration of neuronal tissues/organs. In order to develop drug condidate which can dissolve the amyloid fibrils and turned protein functional, it is urgent need to elucidate the mechanism of amyloid fibril formation under different conditions. In this study, we have taken a step to find the mechanism of amyloid fibril formation in concanavalin A (Con A) protein via cationic gemini surfactant (16-4-16) at two different pHs (7.4 and 3.5). We used several biophysical techniques such as Rayleigh light scattering, turbidity, ThT dye binding, intrinsic fluorescence, extrinsic fluorescence, far-UV CD and transmission electron microscopy to characterize the amyloid fibril formation of Con A by cationic gemini surfactant. The results suggest that the Con A form amyloid-like aggregates in the presence of very low gemini concentrations (2.5–125μM) at pH 7.4 while in the presence of higher concentrations (125–1000μM), Con A remained soluble. The Con A was not forming any aggregates or amyloid in the presence of same gemini concentrations at pH 3.5. The possible cause of gemini surfactant-induced amyloid fibril formation of Con A is electrostatic as well as hydrophobic interaction at pH 7.4 and strong electrostatic repulsion at pH 3.5. The far-UV CD spectra of Con A transformed into a cross β-sheet structure when incubated with low gemini surfactants while at higher concentrations the β-sheet structures of Con A transformed into α-helix.