Tandem mass spectrometry post-source decay

Peptide sequencing via post-source decay and tandem mass spectrometry. 339... 

Figure 5. Methods employed for identifiying and characterizing proteins separated by 2DE. Abbreviations used 2DE, two-dimensional electrophoresis ESI, electrospray ionization HPLC, high performance liquid chromatography IR, infrared M, relative molecular mass MALDI, matrix-assisted laser desorption ionization MS, mass spectrometry MS/MS tandem mass spectrometry p/, isoelectric point PSD, post-source decay.

A reflectron TOF analyzer also permits tandem mass spectrometry studies. For this, an ion gate is needed to select the desired precursor ion among those produced in the source. A deflector electrode can serve as the gate, which is pulsed off at a selected time to allow the passage of a specific precursor ion (Figure 1.23). Post-source decay (PSD) of this ion between the gate and the... 

Post-source Decay Tandem Mass Spectrometry The potential of PSD has also been exploited to identify phosphopeptides [61,62]. This technique is used for MALDI-generated ions in a reflectron TOP instrument. PSD can also distinguish any serine-threonine phosphorylation from tyrosine phosphorylation. Phosphotyrosine-containing peptides mostly yield the [MH — HP03J+ (loss of 80 Da) ion, whereas phosphoserine- and threonine-containing peptides produce [MH - H3P041+ (loss of 98 Da) and [M - HP03]+ ions. 

Lattova, E. Perreault, H. Krokmn, O. Matrix-assisted laser desorption/ionization tandem mass spectrometry and post-source decay fragmentation study of phenylhydrazones of N-linked oligosaccharides from ovalbumin. J. Am. Soc. Mass Spectrom. 2004, 15, 725-735. 

The loss of 44 5 uma was also observed in the mass spectrum of poly-BFl synthesized by anionic polymerization with PhLi as the initiator (Fig. 39), recorded using the dithranol as matrix. In this case, the difference between the two most intense peaks belonging to each cluster is about 77 Da, suggesting that the most intense peaks correspond to the macromolecular chains terminated with a phenyl group (Ph) at one end, as expected since PhLi was used as initiator [23]. Since very similar mass spectra were recorded using other matrices, such as CHCA (a-cyano-4-hydroxycinnamic acid), DCTB [tra/25-2-[3-(4-t rt-butylphenyl)-2-methyl-2-pro-penylidene]malononitrile], and HABA [2-(4-hydroxylphenylazo)benzoic acid], the question about the loss of a compound with a mass 44 5 requires appropriate investigations by means of post-source decay (PSD) and CID (collision induced dissociation) MALDI-TOF/TOF tandem mass spectrometry methods. 

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