Quantitative proteomics chemical labelling method

One of the main problems to overcome in order to realise quantitative proteomics is that mass spectrometry is not strictly a quantitative technique with respect to molecular abundance. One approach to overcome this problem is to perform comparative experiments in parallel where one sample is labelled with an isotope (such as 0 or H) and the other is unlabelled. Mass differences between labelled and unlabelled samples may be observed in a mass spectrometer and the relative ratios quantified (Figure 9.21). Obviously this method of quantification relies on equivalent mass expression by both samples in spite of the isotopic labelling of the one and not the other. In other words, in spite of the labelling, both samples should behave identically chemically. The simplest way to effect labelling is to use isotope-coded affinity tags (ICATs). According to this technique, two identical populations of proteins... 

---