Disaccharides mass spectra

Chitinase from Bacillus sp. was added to a solution of Xyl (l— 4)GlcNAc oxazoline 13 dissolved into a phosphate buffer. The consumption rate of 13 was accelerated by the enzyme addition and chitin-xylan hybrid polysaccharide 14 was produced. During the polymerization, the reaction proceeded homogenously throughout the reaction. The yield was 76% and its average molecular weight value of 14 was M = 1500 with MJMa = 1.76, determined by GPC. Furthermore, MALDI-TOF mass spectrum of 14 indicated the peaks at every m/z 335, which corresponds to the molecular mass of the repeating disaccharide unit. 

A (l->6)-linked disaccharide having a nonreducing 2-acetamido-2-deoxyhexose residue is characterized by a fragment at m/e 552 corresponding to m/e 583 in a per(trimethylsilyl)ated aldohexosyl-(l- 6)-aldohexose. In the mass spectrum of a-D-Glcp-(l—>6)-n-GlcNAc, the... 

Fig. 24. Monomer analysis of methylated glucans by ESI-MS/CID after perdeuteriomethylation and partial hydrolysis. As an exan le, evaluation of daughter mass spectrum of monomethylated disaccharides, m/z 464, is demonstrated for details see Ref. 256.

A characteristic peak at m/e 353 is present in the mass spectrum of the 1 — 6 linked disaccharide 20 (48). It arises from the potentially reducing unit by cleavage between C-1 and C-2 and migration of a methoxyl group probably from C-3 (Scheme 20). Table I summarizes some characteristic peaks in the mass spectra of methylated disaccharides. The hrst identification of N-glycoIyl-muramic acid as a cell wall constituent has been... 

It should be mentioned that analogous elimination of 101 mass units from the a ring is not traced, as the spectra of (1— 2)- and (1—>4)-hexosyl-hexosides contain no peak at m/e 353 this may be due to rapid degradation of the corresponding ion, leading to ion m/e 279, the corresponding peak being a very intense one in the spectrum of methylated disaccharides ... 

MALDI-TOF was successfully utilized for determination of the molar mass of low molar mass HA samples [283]. Fig. (16) shows a MALDI-TOF spectrum of a HA fraction separated using an SEC system. The MALDI-TOF spectrum clearly shows the major mass differences between the peaks corresponding to a mass of the disaccharide repeating unit of HA, (378 Da), and the minor peaks correlated to the molar masses of the two monosaccharide components of HA. 

After completion of the enzymatic reaction, a white precipitate was separated by centrifugation, and the supernatant was analyzed by MALDI-TOF/MS, and NMR measurements. From the MALDI-TOF/MS spectrum, the peaks appeared at every m z 365, corresponded to the molecular mass of the repeating disaccharide unit of 3. and NMR spectra supported that the resulting product is a cellulose-chitin hybrid polysaccharide. Furthermore, it has been proven by CP/MAS NMR spectrum that the white precipitate is also hybrid polysaccharide 3. 

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