Infrared spectroscopy of cationized arginine in the gas phase: direct evidence for the transition from nonzwitterionic to zwitterionic structure.

ABSTRACT: The gas-phase structures of protonated and alkali metal cationized arginine (Arg) and arginine methyl ester (ArgOMe) are investigated with infrared spectroscopy and ab initio calculations. Infrared spectra, measured in the hydrogen-stretch region, provide compelling evidence that arginine changes from its nonzwitterionic to zwitterionic form with increasing metal ion size, with the transition in structure occurring between lithium and sodium. For sodiated arginine, evidence for both forms is obtained from spectral deconvolution, although the zwitterionic form is predominant. Comparisons of the photodissociation spectra with spectra calculated for low-energy candidate structures provide additional insights into the detailed structures of these ions. Arg*Li+, ArgOMe*Li+, and ArgOMe*Na+ exist

SUBMITTER: Bush MF 

PROVIDER: S-EPMC2675882 | biostudies-literature | 2007 Feb

REPOSITORIES: biostudies-literature