FRAGMENTATION OF SINGLY-PROTONATED, ARGININE-CONTAINING, PEPTIDES WITH A SECOND BASIC RESIDUE: SEQUENCES THAT PROMOTE LOW ENERGY b+H_2O~+ PRODUCTION

摘要

The presence of a C-terminal basic residue in the sequences RAAAAX promotes C-terminal loss to form [b+H_2O]~+ and [MH-H_2O]~+ ions by a low energy pathway. While the position of the N-terminal arginine residue has little effect ion the energy or selectivity of these fragmentation pathways, the position of the C-terminal basic residue is critical. A salt-bridged intermediate in volving the basic C-terminal residue is hypothesized to play a key role in promoting this low energy fragmentation pathway.