Inventors:
Xiangping Zhu - Grafton MA, US
Stephen Hattan - Roslindale MA, US
Xunming Chen - Bedford MA, US
Ioannis Papayannopoulos - Ashland MA, US
Assignee:
Applera Corporation - Framingham MA
MDS Inc. - Concord
International Classification:
G06F019/00
G01N033/48
G01N033/50
Abstract:
In various aspects, provided are methods for identification of the presence of modified peptides using at least in part mass spectrometric signals from metastable ions that are formed in the field free region of the analyzer. For example, in various embodiments where the modified peptides are phosphopeptides, such metastable ions can appear approximately 95 u lower than the precursor ion m/z value from which they were formed when the peptide contains a phosphate group. In various embodiments, detection of such metastable ions in a MALDI-TOF mass spectrum can identify the modified peptide. In various aspects, provided are methods for identification of the presence of modified peptides using at least in part MS/MS data from two or more of modified peptides, de-modified peptides and non-modified peptides by comparing the sequence and/or site of modification information for two or more of these three forms of a peptide.