Annotated IS-CID-SWIFT-2D-MS/MS spectrum of serotype PnP 31. Stepwise patterns are colored to reflect the presence of one, two, and three acetyl groups in yellow, orange, and red respectively. Evenly spaced patterns which are closely related in profiles, especially in them/z600-800 region, result from the characteristic sequential loss of 18 Da (H2O) and 42 Da, the latter generated by both the different degree of acetylation of the molecule itself as well as by the commonly observed sequential loss of CH2O from an A2,4cross-ring fragmentation.
