RESUMO
Many quantitative proteomics methods rely on protein and peptide labeling with stable isotopes. We have recently found that the introduction of ¹5N into organisms via in vivo metabolic labeling affects protein expression levels as well as metabolic pathways and behavioral phenotypes. Here, we present further evidence for a stable isotope effect based on the plasma proteome analysis of ¹5N-labeled mice. We compared plasma proteomes of ¹5N-labeled and unlabeled (¹4N) mice by quantitative MS. We found a number of protein level differences, some of which were verified immunochemically. In addition, we observed divergent chromatographic retention time and peak full width at half maximum (FWHM) between ¹5N-labeled and ¹4N tryptic peptides. Our data point toward a systemic effect of the introduction of heavy isotopes in vivo.
