Phospho-iTRAQ: assessing isobaric labels for the large-scale study of phosphopeptide stoichiometry.The ability to distinguish between phosphopeptides of high and low stoichiometry is essential to discover the true extent of protein phosphorylation.  Our Phospho-iTRAQ method focuses on the unmodified counterparts of phosphorylated peptides, which thus circumvents the ionization, fragmentation, and phospho-enrichment difficulties that hamper quantitation of stoichiometry in most common phosphoproteomics methods.  To demonstrate the flexibility of Phospho-iTRAQ with regards to the experimental setup, the proteome coverage was extended through gel fractionation, while an internal replicate measurement created more stringent data analysis opportunities.  The latest developments in MS instrumentation promise to further increase the resolution of the stoichiometric measurement of Phospho-iTRAQ in the future. 
Phospho-iTRAQ
Phospho-iTRAQ: assessing isobaric labels for the large-scale study of phosphopeptide stoichiometry.The ability to distinguish between phosphopeptides of high and low stoichiometry is essential to discover the true extent of protein phosphorylation.  Our use of isobaric tags for relative and absolute quantitation (iTRAQ) marks the first time that isobaric tags have been applied for the large-scale analysis of phosphopeptides.  Our Phospho-iTRAQ method focuses on the unmodified counterparts of phosphorylated peptides, which thus circumvents the ionization, fragmentation, and phospho-enrichment difficulties that hamper quantitation of stoichiometry in most common phosphoproteomics methods.  Since iTRAQ enables multiplexing, simultaneous (phospho)proteome comparison between internal replicates and multiple samples is possible.  To demonstrate the flexibility of Phospho-iTRAQ with regards to the experimental setup, the proteome coverage was extended through gel fractionation, while an internal replicate measurement created more stringent data analysis opportunities.  The latest developments in MS instrumentation promise to further increase the resolution of the stoichiometric measurement of Phospho-iTRAQ in the future. 
iTRAQ
The latest developments in MS instrumentation promise to further increase the resolution of the stoichiometric measurement of Phospho-iTRAQ in the future. 
MS instrumentation