Journal
ANALYTICAL CHEMISTRY
Volume 89, Issue 5, Pages 2956-2963Publisher
AMER CHEMICAL SOC
DOI: 10.1021/acs.analchem.6b04415
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Funding
- National Institutes of Health [R01GM114260, R01AG047928, R01AG053987]
- ALSAC (American Lebanese Syrian Associated Charities)
- NIH Cancer Center [P30CA021765]
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Isobaric labeling quantification by mass spectrometry (MS) has emerged as a powerful technology for multiplexed large-scale protein profiling, but measurement accuracy in complex mixtures is confounded by the interference from coisolated ions, resulting in ratio compression. Here we report that the ratio compression can be essentially resolved by the combination of pre-MS peptide fractionation, MS2-based interference detection, and post-MS computational interference correction. To recapitulate the complexity of biological samples, we pooled tandem mass tag (TMT)-labeled Escherichia coli peptides at 1:3:10 ratios and added in 10-fold more rat peptides as background, followed by the analysis of two-dimensional liquid chromatography (LC) MS/MS. Systematic investigation shows that quantitative interference was impacted by LC fractionation depth, MS isolation window, and peptide loading amount. Exhaustive fractionation (320 X 4 h) can nearly eliminate the interference and achieve results comparable to the MS3-based method. Importantly, the interference in MS2 scans can be estimated by the intensity of contaminated yi product ions, and we thus developed an algorithm to correct reporter ion ratios of tryptic peptides. Our data indicate that intermediate fractionation (40 X 2 h) and yi ion-based correction allow accurate and deep TMT profiling of more than 10 000 proteins, which represents a straightforward and affordable strategy in isobaric labeling proteomics.
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