Internal proton transfer leading to stable zwitterionic structures in a neutral isolated peptide

Abstract

(Figure Presented) No solution for the zwitterion: An acidand base-containing pentapeptide was designed to explore the possibility of zwitterion formation in the gas phase, in the absence of a net charge. Internal proton transfer between peptide side chains in vacuo gave a zwitterion (highlighted in yellow; the canonical form is highlighted in blue), which was identified by gas-phase IR spectroscopy. © 2010 Wiley-VCH Verlag GmbH & Co. KGaA.