Improved Sensitivity for Protein Turnover Quantification by Monitoring Immonium Ion Isotopologue Abundance

We
describe an analytical strategy allowing for the direct quantification
of stable isotope label incorporation in newly synthesized proteins
following administration of the stable isotope tracer deuterium oxide.
We present a demonstration of coupling high-resolution mass spectrometry,
metabolic stable isotope labeling, and MS/MS-based isotopologue quantification
for the measurement of protein turnover. Stable isotope labeling with
deuterium oxide, followed by immonium ion isotopologue quantification,
is a more sensitive strategy for determining protein fractional synthesis
rates compared to peptide centric mass isotopomer distribution analysis
approaches when labeling time and/or stable isotope tracer exposure
is limited and, as such, offers a great advantage for human studies.