2-Phenyl-1,3-dithiolanylium ion is generated as a transient intermediate by flash photolysis of aqueous ethanol and acetonitrile solutions of 2-methoxy and other dithiolane derivatives with a xenon lamp. Decay of the absorption (342 nm) of the cation generated from the 2-methoxy derivative follows pseudo-first-order kinetics. Rate constants were measured for the reaction of the cation with various nucleophiles. Decay curves for the cations generated from 2-arylthio and 2-sulfonyl derivatives are steep and show second-order kinetic character owing to the recombination of the cation with the counter anions (thiolate and sulfinate).
Hydrogen−Deuterium Exchange and Selective Labeling of Deprotonated Amino Acids and Peptides in the Gas Phase
作者:Zhixin Tian、Lev Lis、Steven R. Kass
DOI:10.1021/ja076599l
日期:2008.1.1
Hydrogen-deuterium exchange reactions of deprotonated aminoacids and small peptides were studied. Selective labeling can be carried out at the alpha-amino group of lysine (2 of 4 labile hydrogens undergo exchange with CF3CH2OD) and the guanidine sidechain of arginine (3 of 6 labile hydrogens undergo exchange with CH3CH2OD and C6H5CH2OD). Differential labeling of peptides also was accomplished, and the extent of