Amyloidins

Amyloidins are a proposed class of short peptide sequences that can form amyloid fibrils under physiological-like conditions. The term is used in a limited set of reviews and experimental reports to describe beta-sheet–rich motifs with amyloid-forming potential, distinct from longer disease-associated amyloid proteins. Because the term is not universally standardized, authors differ on inclusive criteria and examples.

Structural features: Amyloidins are typically small peptides, 6–20 residues, enriched in residues that promote beta-sheet structure. They assemble into elongated, unbranched fibrils with the cross-beta architecture characteristic of amyloids. The fibril core is held together by hydrogen bonding and hydrophobic interactions, and fibril surfaces can expose polar or charged residues that influence interactions with solvents and other molecules.

Assembly and kinetics: Formation is often nucleation-dependent; a lag phase precedes rapid fibril growth. Assembly can be influenced by pH, ionic strength, metal ions, and the presence of cofactors. Molecular chaperones or proteases can inhibit or remodel amyloidins, affecting kinetics and final fibril stability.

Biological context: In some organisms and experimental models, amyloidins contribute to structural matrices or serve as models to study aggregation pathways. In materials science, they are explored as tunable nanofibers. The physiological relevance and ubiquity of amyloidins remain debated, and not all reported instances are reproducible.

Detection and study: Researchers rely on Thioflavin T fluorescence, Congo red binding, electron microscopy, and solid-state NMR to characterize amyloidins and their fibrils in vitro; in some studies, spectroscopy and atomic-level simulations are used to probe the aggregation mechanism.

Status and outlook: The term amyloidins lacks a single, widely accepted definition. Ongoing research seeks standardized criteria and nomenclature, clearer distinctions from pathogenic amyloids, and exploration of their potential applications in biology and materials science.