Sugar chains

Conformational depictions of acyclic sugar chains are conveniently expressed by locating certain atoms in the plane of the paper and orientating the remaining atoms or groups appropriately above and below that plane, as shown for D-arabinitol and xylitol (it should be recognized that the favoured conformation does not necessarily have all the carbon atoms in the same plane) ... 

Figure 5.31 LC-electrospray-MS-MS spectrum of the column eluate at around 22 min in the analysis of the peptide mixture from the tryptic digest of glycoprotein TIME-EA4 from silkworm diapause eggs. Reprinted from Bioorg. Med. Chem., 10, Kurahashi, T., Miyazaki, A., Murakami, Y., Suwan, S., Franz, T., Isobe, M., Tani, M. and Kai, H., Determination of a sugar chain and its linkage site on a glycoprotein TIME-EA4 from silkworm diapause eggs by means of LC-ESI-Q-TOF-MS and MS/MS , 1703-1710, Copyright (2002), with permission from Elsevier Science.

Osada T., Takezawa S., Itoh A., Arakawa H., et al. (1999). The distribution of sugar chains on the vomeronasal epithelium observed with an atomic force microscope. Chem Senses 24, 1-6. 

Manya, H., et al. (2000). Comparative study of the asparagine-linked sugar chains of human lipocalin-type prostaglandin D synthase purified from urine and amniotic fluid, and recombinantly expressed in Chinese hamster ovary cells. 

Endo, T., Wright, A., Morrison, S.L., and Kobata, A. (1995) Glycosylation of the variable region of immunoglobulin G-site specific maturation of the sugar chains. Mol Immunol. 32(13), 931-940. 

A comparative analytical study, by means of paper chromatography, has confirmed the conclusion that, in the condensation of aldoses with ethyl acetoacetate, the yield of the furan derivatives increases as the length of the sugar chain is decreased.17... 

Thioureas are most commonly prepared from reaction of isothiocyanates with amines. Also there are some reports on reactions of anime or carbodiimides with several thionating reagents. AA -Disubstituted thioureas bearing double NH groups have been developed as sensors, and as catalysts because of their hydrogen bonding ability. A,A -Disubstituted thiourea-linked sugar chains have been prepared by the reaction of isothiocyanate with amine. 

Conversely, concanavalin A relieves desensitization of kainate receptors, presumably via interaction with surface sugar chains, but has insignificant effects on AMPA receptors. 

Fig. 36 Example of synthesis of an imino sugars by insertion of the nitrogen on the sugar chain and subsequent cyclization at the anomeric centre.

A consideration of the individual carbon atoms of the sugar chain thus leads to the conclusion that this trimethylglucose is the 2,3,6-isomer and ample confirmation of this conclusion has been forthcoming. To mention only two cases (a) oxidative degradation yields L-threo-di-methoxysuccinic acid,143 and (b) the sugar does not condense with acetone.130... 

The cyanohydrin synthesis of higher sugars, which involves intermediate aldonolactones, allows the introduction of a 14C label in the sugar chain. Thus, for example, L-[5-l4C]arabinose was synthesized (12) from D-xylose, which was first converted, by addition of K14CN and hydrolysis, into D-[ 1-... 

Matsuo, L Isomura, M. Walton, R. Ajisaka, K., A new strategy for the synthesis of the core trisaccharide of asparagine-hnked sugar chains. Tetrahedron Lett. 1996,37, 8795-8798. 

The enzyme transpeptidase cross-Unks the peptide chains of adjacent amino-sugar chains. 

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