Posted by Web Master (June 14, 2004)

iTRAQ modification data added to Unimod

Applied Biosystems have released details of their new iTRAQ™ multiplexed quantitation chemistry. This chemistry is ideal for database searching because the tag is isobaric, meaning that the peptide precursor masses and the MS/MS fragment ion masses are the same for all four channels. The channel dependent reporter mass, used for quantitation, is ignored by Mascot, so the same modifications work for all four channels: iTRAQ (K) and iTRAQ (N-term). Modification details are on Unimod. The tag targets primary amine groups, but a low-level reaction with tyrosine may also be observed. iTRAQ (Y) has been defined as a separate modification so that it can be specified as a variable modification, while iTRAQ (K) and iTRAQ (N-term) are specified as fixed.

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