Electrospray tandem mass spectrometric studies of phosphopeptides and phosphopeptide analogues

✍ Scribed by Tholey, Andreas; Reed, Jennifer; Lehmann, Wolf D.

• Publisher: John Wiley and Sons
• Year: 1999
• Tongue: English
• Weight: 284 KB
• Volume: 34
• Category: Article
• ISSN: 1076-5174
• DOI: 10.1002/(sici)1096-9888(199902)34:2<117::aid-jms769>3.0.co;2-v

✦ Synopsis

A set of synthetic phosphopeptides and phosphopeptide analogues was studied by tandem nano-electrospray mass spectrometry. The inÑuence of the collision o †set and of the charge state of the molecular ion on phosphate-speciÐc fragmentation processes was investigated in detail. H-D exchange experiments and structural considerations support a six-centered transition being present in the neutral loss of from serine, threonine and homoserine H 3 PO 4 phosphopeptides, where the C-a hydrogen of serine or threonine or the C-b hydrogen of homoserine is transferred to the protonated phosphate group. Neutral loss of at moderate collision o †set potential represents a very H 3 PO 4 abundant fragmentation process for serine, threonine and homoserine phosphopeptides. The most speciÐc feature for discrimination of these phosphopeptides from tyrosine phosphopeptides is the m/z 79 : 97 ratio in the negative ion product spectra, which is consistently elevated in tyrosine phosphopeptides as compared with serine, threonine and homoserine phosphopeptides. The fragment ions of methylphosphono-and H-phosphonopeptides can be explained by the same mechanisms as are applicable to phosphopeptides.