Quadruple Helix Formation of a Photoresponsive Peptide Amphiphile and Its Light-Triggered Dissociation into Single Fibers

摘要

Building well-defined higher-order architectures through supra-molecular chemistry is one of the challenges in nanotechnology and is critical for our understanding of biological self-assembly. Secondary structures, such as α-helices and β-sheets in proteins and the double-helix of nucleic acids, generate stable tertiary and quaternary structures with critical roles in the three-dimensional architectures in biology. Furthermore, conformational changes of proteins can switch functional states such as enzymatic activities. Inspired by these switchable structures seen in biomolecules, we have investigated here the synthesis of photoresponsive peptide amphiphiles (PAs), well-known to self-assemble into supramolecu-lar nanofibers. The single-handed helical structure has always been an attractive target, and more recently, there is also interest in multiple helices. Here we report the discovery of a quadruple helical fiber formed by photoresponsive PA 1 and its conversion into single fibers upon photochemical cleavage of the 2-nitrobenzyl group in 1.