Quantification of proteins by label-free LC-MS/MS.

Quantitative proteomic profiling is becoming a widely used approach in systems biology and biomarker discovery. There is a growing realization that quantitative studies require high numbers of non-pooled samples for increased statistical power. We present a descriptive protocol for label-free quantitation of proteins by LC-MS/MS that enables to obtain both quantitative and qualitative information in one study without the need to pool samples or label them.