Monovalent cation-promoted ordering of a glycine-rich cyclic peptide

Abstract

This report describes an accelerated self-assembly of a synthetic cyclic hexapeptide in the presence of alkali metal ions. Time-dependent aggregation of hexapeptide was considerably influenced upon co-incubation with monovalent metal ions, of which K⁺ afforded the most significant effect both on the time-scale required for self-assembly and on the morphology of aged structures. Metal ion adducts formation ability of the hexapeptide was confirmed by electrospray ionization mass spectrometry measurements and ¹³C NMR spectrometry. The effect of metal ion binding on peptide structure was also probed by circular dichroism, optical microscopy, and scanning electron microscopy. K⁺ ions not only interacted more efficiently with the hexapeptide enabling it to reach conformational state(s) conducive for self-assembly, but also altered the morphologies of the aged peptide fibers, when compared to the unmetalated peptide.