Time-Resolved Observation of Product Ions Generated by 157 nm Photodissociation of Singly Protonated Phosphopeptides

Vacuum UV photodissociation tandem mass spectra of singly charged arginine-terminated phosphopeptides were recorded at times ranging from 300 ns to ms after photoexcitation, to investigate when the phosphate group falls off from the precursor and product ions and whether loss of phosphate can be eliminated in tandem mass spectra. For peptide ions containing phosphoserine and phosphothreonine, little loss of 98 Da from the product ions was observed up to 1 μs after photoexcitation. However, neutral losses from the precursor ions were considerable just 300 ns after photoactivation. Loss of 98 Da from product ions first appears about 1 μs after laser irradiation and becomes more common 13 μs after photoexcitation. Consistent with previous reports, phosphotyrosine was more stable than either phosphoserine or phosphothreonine.

Graphical AbstractStudy of nano- to milli-second time-resolved photofragmentation of singly charged phosphopeptides using 157 nm vacuum UV light.Figure optionsDownload full-size imageDownload high-quality image (146 K)Download as PowerPoint slide