Perturbation of anionic surfactant induced amyloid fibrillation by chemical chaperone: A biophysical study

Abstract

The formation of amyloid fibrils causes different degenerative diseases. For example, the polypeptide hormone insulin, comprising 51 amino acids, is directly linked to type II diabetes due to the formation of amyloid-like aggregates. Herein, insulin was used as a model protein to evaluate the solubilizing potential of alpha-cyclodextrin (α-CD) on the sodium dodecylbenzene sulfonate (SDBS) induced amyloid fibril at pH 2.0. Turbidity, Rayleigh light scattering, binding of Thioflavin T dye, and far-ultraviolet circular dichroism analyses were used to characterize the structural conversion induced by α-CD. ThT binding assay showed the formation of amyloid-like aggregates in the insulin in the presence of 0.5 mM of SDBS. The aggregation was solubilized by α-CD in a dose-dependent manner. At low α-CD concentrations (≤5.0 mM), SDBS-induced amyloid fibrils were not inhibited or solubilized. However, amyloid fibrils completely disappeared or solubilized at α-CD >7.0 mM and the native-like secondary structure of insulin was restored. The results clarify the molecular mechanism underlying the effect of α-CD on amyloid fibrillation of insulin induced by SDBS.