Amyloid and Hydrogel Formation of a Peptide Sequence from a Coronavirus Spike Protein

We demonstrate that a conserved coronavirus spike protein peptide forms amyloid structures, differing from the native helical conformation and not predicted by amyloid aggregation algorithms. We investigate the conformation and aggregation of peptide RSAIEDLLFDKV, which is a sequence common to many animal and human coronavirus spike proteins. This sequence is part of a native alpha-helical S2 glycoprotein domain, close to and partly spanning the fusion sequence. This peptide aggregates into beta-sheet amyloid nanotape structures close to the calculated pI = 4.2, but forms disordered monomers at high and low pH. The beta-sheet conformation revealed by FTIR and circular dichroism (CD) spectroscopy leads to peptide nanotape structures, imaged using transmission electron microscopy (TEM) and probed by small-angle X-ray scattering (SAXS). The nanotapes comprise arginine-coated bilayers. A Congo red dye UV-vis assay is used to probe the aggregation of the peptide into amyloid structures, which enabled the determination of a critical aggregation concentration (CAC). This peptide also forms hydrogels under precisely defined conditions of pH and concentration, the rheological properties of which were probed. The observation of amyloid formation by a coronavirus spike has relevance to the stability of the spike protein conformation (or its destabilization via pH change), and the peptide may have potential utility as a functional material. Hydrogels formed by coronavirus peptides may also be of future interest in the development of slow-release systems, among other applications.

Characterization of cellulose acetate functional groups synthesized from corn husk (Zea mays)

The use of masks is very important to reduce transmission of the COVID 19 virus. Therefore, an innovation is needed from mask materials is that are environmentally friendly, have good filtration quality and have anti-virus agents. An alternative way to provide masks with good filterability using a raw material of cellulose acetate. Cellulose acetate has fibrils that are bonded together so that it can form dense fibers. Fiber is a semipermeable layer that functions as a particle filtration. Therefore, this study aims to get cellulose from corn husks via delignification. The research method consisted of extracting cellulose from corn husks and further synthesizing cellulose acetate. FTIR results showed an absorption peak at wave numbers 3349 cm-1, 1728 cm-1, 1252 cm-1, and 1031 cm-1. These peaks indicated the presence functional groups of OH, C=O, aryl ether, and C-O. This functional group indicates a cellulose acetate compound.