RT-alignment

Liquid chromatography coupled to mass spectrometry (LC-MS) is the dominant technological platform for proteomics. An LC-MS analysis of a complex biological sample can be visualized as a “map” of which the positional coordinates are the mass-to-charge ratio (m/z) and chromatographic retention time (RT) of the chemical species profiled. Label-free quantitative-proteomics requires the alignment and comparison of multiple LC-MS maps to ascertain the reproducibility of experiments or reveal proteome changes under different conditions. The main challenge in this task lies in correcting retention time shifts, which are inevitable even on the same instrument and under the same elution conditions. For large-scale studies, multiple instruments or multi-week experiments are often required, which exacerbates the problem. We present a new graph-based time alignment algorithm that can align these less similar LC-MS maps, which cannot be effectively handled by existing methods.