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Figure 1 | Genome Biology

Figure 1

From: Is mass spectrometry ready for proteome-wide protein expression analysis?

Figure 1

LC MS/MS analysis of a peptide mixture obtained by proteolysis of a complex protein mixture. (a) The total ion chromatogram (sum of the signals of all peptides as a function of time) of peptides obtained by tryptic digestion of a complex protein mixture is shown, as obtained by liquid chromatographic separation and online analysis by mass spectrometry. (b) As an example, the mass spectrum of peptides eluting at 18.08 minutes after the start of the analysis is shown. (c) The doublet starting at 633.79 indicates a pair of peptides that are chemically identical yet differ in mass due to stable isotope incorporation in the two different samples. Their relative intensities reveals the relative abundance of the protein from which they derive in the two protein populations that were mixed - in this case approximately 0.9:1.0. The protein is then identified by fragmentation of the peptides. m/z is the mass/charge ratio.

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