PNNL

Abstract

L-cysteine S sulfate Cys S SO 3 H and its derivatives play essential roles in biological chemistry and p harmaceutical synthesis , yet their intrinsic molecular properties have not been studied to date. In this contribution , the deprotonated anion cysS SO 3 was introduced in the gas phase by electrospray and characterized by size selected cryogenic negative ion photoelectron spectroscopy technique. The electron affinity of the cysS SO 3 radical is determined to be 4.95± 0.10 eV. In combination with theoretical calculations, it has been found that the most stable structure of cysS SO 3 S 1 ) is stabilized via three intramolecular hydrogen bonds ( HBs), i.e. e., one O-H??N between COOH and NH 2 group and two N-H??O HBs between NH 2 and SO 3 , in which the amino group serves as both HB acceptor and donor I n addition, a nearly iso energetic conformer ( S 2 ) with the formation of O-H??N-H??O-S chain-type binding motif competes with S 1 in the source . The most reactive site of the molecule susceptible for electrophilic attacks is the linkage S atom . T heoretically predicted infrared spectra indicate O-H and N-H stretching modes are the fi ngerprint region (2800 to 3600 cm 1 ) to distinguish different isomers.