Hydrogen-Deuterium Exchange and Selective Labeling of Deprotonated Amino Acids and Peptides in the Gas Phase

Hydrogen-deuterium exchange reactions of deprotonated amino acids and small peptides were studied. Selective labeling can be carried out at the α-amino group of lysine (2 of 4 labile hydrogens undergo exchange with CF₃CH₂OD) and the guanidine side chain of arginine (3 of 6 labile hydrogens undergo exchange with CH₃CH₂OD and C₆H₅CH₂OD). Differential labeling of peptides also was accomplished, and the extent of H/D exchange is dependent on the amino acids which are present as well as their order in the chain.