15N Metabolic Labeling of Mammalian Tissue with Slow Protein Turnover

We previously reported the metabolic 15N labeling of a rat where enrichment ranged from 94% to 74%. We report here an improved labeling strategy which generates 94% 15N enrichment throughout all tissues of the rat. A high 15N enrichment of the internal standard is necessary for accurate quantitation, and thus, this approach will allow quantitative mass spectrometry analysis of animal models of disease targeting any tissue. Keywords: Brain • Proteomics • Quantification • Labeling • SILAM