Negative-ion electrospray ionisation-mass spectrometry (ESI-MS) as a tool for analysing structural heterogeneity in kappa-carrageenan oligosaccharides

Oligosaccharides, enzymically produced from kappa-carrageenan, have been in vestigated by electrospray ionisation mass spectrometry (ESI-MS). The techn ique was used without prior derivatisation of the oligosaccharide originall y obtained by size-exclusion chromatography (SEC). The structure of the oli gosaccharides was mainly 4-sulphated neocarrabiose (A-G4S) with an increasi ng length ranging from di- to dodecasaccharides. However, in the larger oli gosaccharides, structural motifs deviating from the perfect alternating A-G 4S structure were detected, i.e. (A2S-G4S). Although resulting in reduced s ignal intensity, samples to which NaCl was added also gave rise to reliable mass spectra. Desulphation was induced at elevated cone voltages and in ac idic or alkaline salt solutions. (C) 2001 Elsevier Science Ltd. All rights reserved.