Fig. 5.

LC-NSI-MS of Permethylated Isomers.A, extracted ion chromatograms showing individual (A–D) or a mixture (E) of four O-glycan tetrasaccharide isomers that only differ by the cyclic form of a single sugar [pyranose (p) or furanose (f)] or a single linkage (differences indicated in green). Separation was performed using a PepMap Acclaim C18 column in 1 mM lithium acetate-containing mobile phases with a modified gradient (35–40% B over 170 min) and detected using a Thermo Velos Pro ITMS. F, summary table of isomers used with retention times converted to reversed phase glucose units (RP g.u.; referenced to ¹³C-permethylated isomaltooligosaccharide standards separated using the same gradient). LC-NSI-MS, liquid chromatography-nanospray ionization-mass spectrometry.