Spontaneous and X-ray–Triggered Crystallization at Long Range in Self-Assembling Filament Networks

Abstract

X-rays to Order Self-assembly of molecules is often irreversible. Cui et al. (p. 555 , published online 17 December; see the Perspective by Safinya and Li ) examined the ordering of a short peptide sequence (Ala 6 Glu 3 ) terminated with an alkyl chain. Aqueous solutions of this molecule could form hexagonally ordered filaments, but more dilute solutions were disordered. However, prolonged x-ray exposure caused these arrays to become ordered. These arrays were stable for several hours but eventually returned to a disordered state; the addition of salts slowed the ordering processes. It is possible that during the ordering process, X-ray–induced charging affected the repulsive forces that balance tension within the filament.