Abstract
Glycoproteomic analysis requires efficient separation and sensitive detection to enable the comprehensive characterization of glycan heterogeneity. Here, we report the use of capillary zone electrophoresis-electrospray ionization-mass spectrometry (CZE-ESI-MS) with an electrokinetically-pumped nanospray interface for the study of protein glycosylation microheterogeneity. A fast separation was developed that resolved intact glycopeptides generated from standard proteins within ~9min. Differentially terminal-galactosylated and sialylated species with the same glycosylation sites were well resolved. The concentration detection limits for CZE were three times higher than for nanoLC methods; however, a 200-fold smaller injection volume was used in CZE, which reflects the use of an extremely efficient electrospray interface in our CZE-ESI-MS setup. The resulting glycopeptide mass detection limit was two orders of magnitude superior to a nanoLC method. We also observed a 1.5% and 7% average relative standard deviation in peak migration time and glycopeptide relative abundance, and a four order of magnitude linear dynamic range in signal intensity. With CZE-ESI-MS, 40 haptoglobin glycopeptides were identified from roughly 40 fmol of digest.