Stable isotope labeling of mammals (SILAM) for in vivo quantitative proteomic analysis

Metabolic labeling of rodent proteins with 15N, a heavy stable isotope of nitrogen, provides an efficient way for relative quantitation of differentially expressed proteins. Here we describe a protocol for metabolic labeling of rats with an 15N-enriched spirulina diet. As a case study, we also demonstrate the application of 15N-enriched tissue as a common internal standard in quantitative analysis of differentially expressed proteins in neurodevelopment in rats at two different time points, postnatal day 1 and 45. We briefly discuss the bioinformatics tools, ProLucid and Census, which can easily be used in a sequential manner to identify and quantitate relative protein levels on a proteomic scale.