Characterisation of Amyloid Nanostructures in the Natural Adhesive of Unicellular Subaerial Algae

The composition and nanoscale mechanical characteristics of the adhesive from two species of subaerial green unicellular microalgae (Chlorophyta), Coccomyxa sp. and Glaphyrella trebouxiodes, have been studied using Raman spectroscopy, chemical staining, and atomic force microscopy (AFM). Raman spectroscopy confirmed the adhesive proteins of both species to be predominantly in s-sheet conformations and composed of a number of hydrophobic amino acid residues. Chemical staining with Congo red and thioflavin-T dyes further confirmed the presence of amyloid-like structures. Probing the adhesives with AFM revealed highly ordered and repetitive mechanical responses indicative of highly ordered structures within the adhesive. The repetitive nature of the sawtooth response is typical of a “sacrificial bond” and “hidden length” mechanism, and what we -propose is the result of mechanical manipulation of individual molecules within an intermolecular s-sheet that makes up the generic amyloid structure. The mechanical ...