Assignments of B-Type Fragments in Post-Source Decay of Negative-Ion Matrix-Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry of Neutral Lactooligosaccharides

Abstract

We describe a detailed assignment strategy for B-type fragments of neutral lactooligosaccharides derived from negatively charged precursor ions in matrix-assisted laser desorption/ionization mass spectrometry (MALDI MS). The post-source decay (PSD) ions produced by the loss of 180 u were assigned to the B-type fragments. The existing analyses of a series of lactooligosaccharides, as summarized in a previous report [T. Yamagaki, et al., J. Am. Soc. Mass Spectrom., 17, 67 (2006)], assisted us in the correct assignments. A clarification of B-type fragment assignments was essential, since we considered that the generation of B-type fragments from negatively charged precursor ions was typical of MALDI PSD, as opposed to the products of electrospray ionization MS low-energy collision induced dissociation.

Production and fragmentation of negative ions from neutral N‐linked carbohydrates ionized by matrix‐assisted laser desorption/ionization

“…Preparation of such adducts is readily achieved by addition of ammonium chloride to a suitable matrix such as the β‐carboline used by Suzuki et al . and Yamagaki et al . A layered target consisting of matrix, analyte and additive was reported to give the best results.…”