Mucin glycopeptides were isolated from rat small intestinal mucosa after reduction/alkylation, trypsin digestion and gel chromatography. The oligosaccharides were released by using alkaline-NaBH4, separated into neutral and acidic species and permethylated. The derivatized mixtures were analysed with fast atom bombardment mass spectrometry and gas chromatography-mass spectrometry using thin film columns. Permethylated neutral oligosaccharides with up to seven sugars could be chromatographed and detected with mass spectrometry. The complex mixture revealed was partly due to the linkage GalNAc being substituted at both position 3 and 6. The approach will be very useful when analysing small amounts of mucins and mucin fragments.
