Identification of S-Glutathionylated Cysteine Residues in Murine Hepatic Proteins by nLC-CID-ETD MS/MS following Immunoaffinity Enrichment

摘要

IP enrichment allowed for direct detection of a significant number of S-glutathionylated peptides from a complex mixture. (See Table 3). Due to the multiple neutral losses incurred during CID, S-glutathionylated peptides are poorly scored by search algorithms and thus difficult to detect. Alternating CID/ETD yielded the best results. ETD spectra yield the diagnostic oxonium ion characteristic of glutathionylated peptides. This ion is routinely observed with the exception of from doubly charged precursor ions. Methodology facilitating detection of this modification will permit future studies aimed at identifying S-glutathionylated peptides from more complex mixtures and determining the functional role of this modification.