Disaccharide fragments monosaccharides

The list of the most common monosaccharide components of bacterial polysaccharides, shown in Table VI, includes the sugars that were found at the nonreducing end of nine or more different disaccharide fragments of the polymers. The right-hand column of the Table, which shows the total number of such fragments, gives an estimate of the number of different glycosyltransferases that use the activated form of the monosaccharides as... 

Total Number of Isomeric Disaccharide Fragments of the Polysaccharides Composed of the Most Common Monosaccharides"... 

Assuming rigid monosaccharide rings, the source of flexibility in carbohydrates is the glycosidic linkage characterized by the /T torsion angles. In this approximation the complete information about the conformation of a disaccharide fragment is embodied in the conformational distribution function It has been... 

Although other differences in peak intensities can be observed for (l->2)-, (l->3)-, and (l- 4)-linked aldosyl-aldoses, the reason for these differences is not yet well understood, but they may also depend on differences in anomeric configuration and in the monosaccharide components. Therefore, at present, authentic reference-materials should be used for establishing these linkage types by m.s. Disaccharides (l->5)- and (l->6)-linked give almost identical spectra typical for these linkages. The formation of typical fragments at m/e 583 (46 and 47) is shown in Scheme 44. 

Much of our knowledge on the fragmentation patterns of carbohydrate derivatives arises from studies on methylated monosaccharides, but in structural investigations, such compounds are seldom subjected to mass spectrometry. On the other hand, the molecular weight of a permethylated oligosaccharide is significantly less than that of the per(trimethylsilyl) derivative. For this reason, the mass spectra of disaccharides as -their permethylated alditols have been determined by Chizhov and coworkers, Karkkainen, and Krone and Beckey. Trisaccharides have also been studied by Karkkainen, either as permethylated glycosides or as alditols. ... 

Aspects of chemical methods used in the structural elucidation of polysaccharides and complex carbohydrates have been reviewed. In a critical examination of the use of g.l.c.-m.s. in the identification of TMS ethers of monosaccharides, a standardized method, which uses a medium resolution mass spectrometer and short chromatographic columns, has been proposed. TMS Ethers of monosaccharides have been characterized by g.l.c.-chemical ionization m.s. with ammonia as reagent gas. Molecular weights were determined, and fragment ions were produced in a quantity high enough to differentiate between stereoisomers (epimers and anomers). Disaccharides have been determined by permethylation followed by g.l.c. The method has been used in the detection of carbohydrate intolerance secondary to intestinal disaccharidase deficiency. 

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