Negative Ion fast atom bombardment (FAB) mass spectra were found to allow the determination of the linkage position and sugar sequences In a series of (underivatized) dlsaccharkles and of linear oligosaccharides. Discrimination of 1-4, 1-6, 1-3, and 1-2 linkage type and determination of the reducing end and of the monosaccharide sequence Is made possible by the analysis of the negative metastable Ions produced In linked scans FAB MS. The peculiarity of negative Ionization Is believed to consist In a selective deprotonatlon of the anomeric hydroxyl (reducing end of the oligosaccharide chain), which Is more acidic with respect to the remaining OH groups. Once the negative charge Is localized at the oligosaccharide reducing end, the Ion fragmentation of this ring occurs rapidly and the mass losses observed are found to be diagnostic of the glycoside linkage type between adjacent sugar units. The overall negative Ions fragmentation process outlined above allows the simultaneous Identification of the reducing end of the chain, of the monosaccharide units sequence, and of the linkage type between adjacent units.

The spectra recorded by matrix-assisted laser desorption/ionization time-of-flight/time-of-flight tandem mass spectrometry (MALDI-TOF/TOF-MS/MS) of complex carbohydrates from human milk are presented. Besides ions originating from glycosidic cleavages and from sugar ring fragmentations, these spectra show intense peaks that may be assigned to ions produced by three new fragmentation pathways involving a six-atom rearrangement. These ions, together with the A fragments from sugar ring fragmentations, open the possibility of obtaining a complete mapping of the linkage positions present in the carbohydrates investigated by MALDI-TOF/TOF.

In this paper we report matrix-assisted laser desorptionlionization (MALDI) mass spectra of dextrans up to 100 OOO Da molecular weight and compare these measurements with those obtained by conventional sizeexclusion chromatography with low-angle laser light scattering (SEULALLS). These results extend the usefulness of MALDI-MS to higher molecular weight polysaccharides and give some insights into the MALDI process.

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High molar mass random poly(butylene succinate-co-butylene sebacate), P(BS-co-BSe), and poly(butylene succinate-co-butylene adipate), P(BS-co-BA), with different composition, were synthesized and subjected to enzymatic hydrolysis by Lipase from Mucor miehei or from Rhizopus arrhizus. The enzymatic hydrolysis of P(BS-co-BSe)s and P(BS-co-BA)s films produced a mixture of water-soluble monomers and co-oligomers that were separated and identified by on-line high performance liquid chromatography/electrospray ionization mass spectrometry (HPLC/ESI-MS). Optimization of the HPLC analysis allowed the separation of isobar co-oligomers, differing only for the co-monomers sequence. Oligomers with the same monomer composition and molar mass but different sequence were identified by HPLC/ESI-MS-MS on-line analysis. The results obtained show a preferential hydrolytic cleavage induced by the lipases used. In particular, these enzymes prefer cleaving sebacic ester bonds in P(BS-co-BSe) copolymers, whereas succinic ester bonds appear to be hydrolyzed faster than adipic ester bonds in P(BS-co-BA) copolyesters. 1H NMR analysis further substantiates these findings. The primary products generated by lipase hydrolysis of polyester films underwent further degradation at longer reaction times. The HPLC/ESI-MS analysis of these mixtures at various times provided the first evidence that lipase catalysis is active also in water solution, a hydrophobic effect induced by the aliphatic units of these polyesters.