Retention time (RT) alignment has been important for
robust protein
identification and quantification in proteomics. In data-dependent
acquisition mode, whereby the precursor ions are semistochastically
chosen for fragmentation in MS/MS, the alignment is used in an approach
termed matched between runs (MBR). MBR transfers peptides, which were
fragmented and identified in one experiment, to a replicate experiment
where they were not identified. Before the MBR transfer, the RTs of
experiments are aligned to reduce the chance of erroneous transfers.
Despite its widespread use in other areas of quantitative proteomics,
RT alignment has not been applied in data analyses for protein turnover
using an atom-based stable isotope-labeling agent such as metabolic
labeling with deuterium oxide, D2O. Deuterium incorporation
changes isotope profiles of intact peptides in full scans and their
fragment ions in tandem mass spectra. It reduces the peptide identification
rates in current database search engines. Therefore, the MBR becomes
more important. Here, we report on an approach to incorporate RT alignment
with peptide quantification in studies of proteome turnover using
heavy water metabolic labeling and LC-MS. The RT alignment uses correlation-optimized
time warping. The alignment, followed by the MBR, improves labeling
time point coverage, especially for long labeling durations.