COORDINATION OF ALKALI-METALS TO OLIGOSACCHARIDES DICTATES FRAGMENTATION BEHAVIOR IN MATRIX-ASSISTED LASER-DESORPTION IONIZATION FOURIER-TRANSFORM MASS-SPECTROMETRY

A correlation is found between the fragment ion yield and the degree o f branching for oligosaccharides analyzed by matrix assisted laser des orption ionization/Fourier transform mass spectrometry (MALDI/FTMS). T he most branched oligosaccharides produced the least amount of fragmen t ion. Another relationship is found between the size of the. alkali m etal ion and the yields of fragment ions. The smallest alkali metal io n produced the greatest amount of Fragment ions. The presence of the q uasimolecular ion is dependent on both the size of the metal ion and t he size of the sugar. A minimum number of saccharide residues are nece ssary to stabilize the complex and produce a quasimolecular ion, Molec ular mechanics calculations were performed and structures obtained con sistent with the observed experimental behavior. The site of coordinat ion plays a dominant role in the yield and types of fragment ions obse rved.