Glycosidic linkages analysis

Xylans as true homopolymers occur in seaweeds of the Palmariales and Nemaliales, however, their backbone consists of Xylp residues linked by -(1 3) (Type X3, Fig. la) or mixed -(1 3, 1 -> 4)-glycosidic linkages (Type Xmy Fig. lb). They are assumed mainly to have a structural function in the cell-wall architecture, but a reserve function cannot be ruled out [4]. From the microfibrils of green algae (Siphonales) such as Caulerpa and Bryop-sis sp., X3 was isolated and the structure confirmed by methylation analysis, C-NMR spectroscopy [7], as well as by mass spectrometry of enzymically released linear oligosaccharides up to a degree of polymerization (DP) of... 

The lipoarabinomannan (LAM) capsule is the major vimlence factor of M. tuberculosis [88]. The multifaceted architecture, shown as 143 (Figure 5.2) by Turnbull ct al. [89], anticipates the complexity of any synthetic scheme aimed to its conquest. However, a simple analysis of the molecule shows that the mannan and arabino segments possess 1,2-trans glycosidic linkages, which point toward a retrosynthesis in which NPOEs could be the donors of choice. 

The conformational behaviour in solution of a dermatan-derived tetra-saccharide has been explored by means of NMR spectroscopy, especially by NOE-based conformational analysis. RDCs were also measured for the tetrasaccharide in a phage solution and interpreted in combination with restrained MD simulations. The RDC-derived data substantially confirmed the validity of the conformer distribution resulting from the NOE-derived simulations, but allowed an improved definition of the conformational behaviour of the oligosaccharides in solution, which show a moderate flexibility at the central glycosidic linkage. Differences in the shapes of the different species with the IdoA in skew and in chair conformations and in the distribution of the sulphate groups were also highlighted.28... 

The conformational properties of a glyconucleoside containing an. S -glycosidic linkage have been also studied and compared to those of the corresponding O-disaccharide. A / and NOE data examination allowed a full pseudorotational analysis, showing a switch in the conformational preferences between the two molecules, the natural and the mimetic one.59... 

Methylation analysis Permethylation of intact oligosaccharides Hydrolysis of glycosidic linkages Reduction to monosaccharide alditols Acetylation of free hydroxyl groups previously involved in link-... 

This article is a discussion of cleavage of glycosidic linkages useful for the analysis of oligo- and poly-saccharides. 

It should be noted that this reaction is referred to incorrectly by many authors as the Smith degradation. This designation should only be used when advantage is taken of the relative acid-labilities of acetal and glycosidic linkages (see Section XIV, p. 98). As the method here under discussion is an alternative procedure for end-group analysis, it may conveniently be referred to as the Smith end-group analysis. 

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