Oligosaccharides unusual

As impressive as the oligosaccharide domain is, calicheamici-none, the aglycon sector 7 (see Scheme 3) is the most striking substructure of calicheamicin y. The rigid bicyclic framework of 7 accommodates an unusual allylic methyl trisulfide and a novel pattern of unsaturation that had not been encountered in natural products before. 

Xylanases from A. niger with unusual hydrolysis specificities were recently reported (54), and five xylanases were isolated and purified. Xylanase 1 attacked soluble larchwood arabinoglucuronoxylan and xylose oligosaccharides of DP > 3, to mainly Xyl2 and xylose, but was inactive towards an insoluble xylan fraction (larchwood) prepared by dissolving the aforementioned xylan in water and separating the undissolved fraction... 

Fig. 4.5.4 Identification of mutations in the transferrin protein by neuraminidase treatment. Unusual patterns in the IEF of serum transferrin might lead to pitfalls in CDG diagnostics. These varying patterns are often due to mutations of charged amino acids in the protein backbone of the transferrin molecule, which might lead, for example, to an accumulation of trisialo transferrin bands (lane 3, indicated by a question mark). Further investigations are carried out by cleaving off charged sialic acid monosaccharide moieties from transferrin-linked oligosaccharides by neuraminidase treatment, followed by IEF and transferrin antibody staining. In the case of protein mutations, additional bands below (lane 4) or above (not shown) the desialylated transferrin form appear...

Apart from the complexity of its monosaccharide composition and the presence of the mannose 6-phosphate derivative, this glycolipid is also unusual, in that fucose is located inside the oligosaccharide chain, which is the first time that this has been found in glycolipids. 

Table I, which lists a number of mono-, oligo-, and polysaccharides and derivatives whose motional descriptions are available based on qualitative arguments, summarizes the experimental conditions and types of measurements used to obtain those descriptions. Table II deals specifically with those carbohydrates for which a quantitative treatment and dynamic modeling have been undertaken. In naming the compounds listed in Tables I and II, IUPAC rules are used for monosaccharide and less complex oligosaccharide molecules. However, empirical names are used for unusual oligosaccharides involving a complex aglycon substituent and polysaccharides. The gross motional features of a number of the compounds in Table I have been discussed in references 6-8, and will be mentioned here only if necessary for further clarification or for comparison with quantitative results.

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