Zn²⁺, Cd²⁺ and Cu²⁺ mediated formation of amyloid like fibrils by the monomers of β-sheet rich peanut agglutinin

Abstract

A broad spectrum of peptides and proteins can self assemble to form amyloid or amyloid like fibrils under appropriate conditions. Although amyloid fibrils have recently been exploited for their potential use as biomaterials, their applications remain challenging. In this paper, we have shown the formation of amyloid like fibrils of peanut agglutinin isolated from leguminacea class that is rich in beta sheet secondary structure under thermal conditions in the presence of Zn²⁺, Cd²⁺ and Cu²⁺. Formation of such fibrils has been followed and also assayed by different spectroscopy techniques. This was further evaluated by transmission electron microscopy, atomic force microscopy and scanning electron microscopy revealing their morphological features at the nano-scale. The blue-green fluorescence of these fibrils treated with dansyl chloride was micrographed. The role of these metal ions has been revealed by carrying out the experiments in the presence of EDTA that chelates these metal ions. Furthermore, the Energy Dispersive X-ray Analysis clearly showed that the fibrils are enriched with these metal ions. During the formation of fibrils, the presence of granular, sponge-like, network-like and proto-filaments has been witnessed. In order to demonstrate the utility of such self assembled fibrils induced by metal ions, these were shown to bind and possess circular – PBR322 plasmid, and hence are expected to have potential applications in gene delivery and related therapy.