Influence of the ionic strength on the amyloid fibrillogenesis of hen egg white lysozyme

Abstract

The study investigates the role of the electrostatic interactions in the fibrillation of the hen egg white lysozyme (HEWL). In order to achieve this aim the influence of the cations Na⁺, Mg²⁺ and Al³⁺ on the amyloid fibril formation and amorphous aggregation was tested. The amyloids are formed in the solution without added salt but the Thioflavin T fluorescence gives the false-negative result. In these conditions, the HEWL fibrils are long and curvy. If the ionic strength of the solution is sufficiently high, the formed amyloids are shorter and fragmented. Our study shows that the addition of the aluminium salt promotes protein fibrillation. The amorphous aggregation dominates in the high concentration of electrolyte. The in vitro amyloid fibril formation seems to be regulated by universal mechanisms. The theories implemented in the polymer science or for colloidal solutions give the qualitative description of the aggregation phenomena. However, the specific interactions and the additional effects (e.g. fibril fragmentation) modulate the amyloidogenesis.

Keywords: Aluminium ions; Amyloid; Hen egg white lysozyme; Ionic strength; Protein aggregation.