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

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.