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. Author manuscript; available in PMC: 2012 Apr 1.
Published in final edited form as: J Proteome Res. 2011 Feb 23;10(4):2095–2103. doi: 10.1021/pr1012174

Figure 1.

Figure 1

A workflow of peptide/protein ratio estimation using 18O-water labeling. Two samples are separately alkylated and digested with trypsin. One of the samples (normally treatment sample) is subjected to trypsin mediated 16O/18O exchange in 18O-water. Then, the labeled and unlabeled samples are mixed and analyzed in a LC-MS/MS system. Peptides and proteins are identified using tandem mass spectra and protein sequence databases. Quantification software MassXplore was used to estimate relative ratios of heavy and light peptide pairs from their mass profiles.