title: Identification of Phosphorylated Human Peptides by Accurate Mass Measurement Alone.
abstract: At sufficiently high mass accuracy, it is possible to distinguish phosphorylated from unmodified peptides by mass measurement alone. We examine the feasibility of that idea, tested against a library of all possible in silico tryptic digest peptides from the human proteome database. The overlaps between in silico tryptic digest phosphopeptides generated from known phosphorylated proteins (1-12 sites) and all possible unmodified human peptides are considered for assumed mass error ranges of ±10, ±50, ±100, ±1,000, and ±10,000 ppb. We find that for mass error ±50 ppb, 95% of all phosphorylated human tryptic peptides can be distinguished from nonmodified peptides by accurate mass alone through the entire nominal mass range. We discuss the prospect of on-line LC MS/MS to identify phosphopeptide precursor ions in MS1 for selected dissociation in MS2 to identify the peptide and site(s) of phosphorylation.
authors.affiliation: Department of Chemistry and Biochemistry, Florida State University, 95 Chieftain Way, Tallahassee, Florida 32306, United States.
authors.forename: Yuan
authors.initials: Y
authors.lastname: Mao
authors.forename: Leonid
authors.initials: L
authors.lastname: Zamdborg
authors.forename: Neil L
authors.initials: NL
authors.lastname: Kelleher
authors.forename: Christopher L
authors.initials: CL
authors.lastname: Hendrickson
authors.forename: Alan G
authors.initials: AG
authors.lastname: Marshall