Single-Shot Proteomics Using Capillary Zone Electrophoresis–Electrospray Ionization-Tandem Mass Spectrometry with Production of More than 1 250 Escherichia coli Peptide Identifications in a 50 min Separation

Capillary zone electrophoresis (CZE)-electrospray ionization-tandem mass spectrometry (ESI-MS/MS) was optimized and applied for analysis of 1-100 ng Escherichia coli protein digests in a single run (single-shot analysis). The system employed an electrokinetically pumped nanospray interface, a coated capillary, and stacking conditions for sample injection. More than 1 250 peptides were identified by optimized single-shot CZE-ESI-MS/MS with 100 ng digest loaded and 50 min analysis time. When 10 ng and 1 ng digests were loaded, about 1 000 and 600 peptides were identified in a single-shot analysis, respectively. Compared with single-shot ultraperformance liquid chromatography (UPLC)-ESI-MS/MS, CZE-ESI-MS/MS produced fewer peptide IDs (1 377 ± 128 vs 1 875 ± 32) for large sample loading amounts (100 ng) with the same mass spectrometer time (50 min). However, when the loaded digest was mass limited (1 ng), CZE-ESI-MS/MS generated many more peptide identifications than UPLC-ESI-MS/MS (627 ± 38 vs 342 ± 113). In addition, CZE-ESI-MS/MS and UPLC-ESI -MS/MS provided complementary peptide level identifications. These results suggest that CZE-ESI-MS/MS may be useful for large-scale, comprehensive, and confident proteomics analysis.