Carbohydrate chain conformation

In conclusion, we have developed a general methodology particularly suitable for modeling of unbranched complex carbohydrates, since it lends itself to a modular analysis of a long carbohydrate chain. This methodology is based on MD/EM calculations with NMR derived constraints introduced into the calculations to generate conformations compatible with the experimental data. 

Jarvis, M.C., Apperley, D.C. (1995). Chain conformation in concentrated pectic gels evidence from 13CNMR. Carbohydrate Research, 275, 131-145. 

The role of the carbohydrate chains in the digoxin family of compounds is analyzed from the conformational point of view. Digitoxose could be shown by -NMR spectroscopy to adopt in both the a- and the P-anomeric forms, predominantly the... 

G. M. Lipkind, V. E. Verovskii, and N. K. Kochetkov, Conformational analysis of the carbohydrate chains of blood-group substances, Bioorg. Khim., 8 (1982) 963-970. 

In considering the overall conformations of carbohydrate chains it is useful to start by distinguishing between (1) ordered conformations, in which the values of the torsion angles are fixed by cooperative interactions between residues and (2) disordered conformations, in which continuous fluctuation occurs. 

Fig. 11. Interresidue linkages in carbohydrates chains (illustrated for some glucose dimers). Linkage conformation is defined by the dihedral angles 4>, ij/) or (4>, j/, o>). The intramolecular hydrogen bonds are also indicated.

It is not the purpose of this article to discuss in detail the gelation properties of these macromolecules, as consideration of this can be found elsewhere (see, for example, Ref. 12). The glycoproteins found in submandibular and submaxillary secretions will also not be considered. Although these substances are also referred to as mucins, they have somewhat different characteristics (namely, a considerably lower proportion of carbohydrate, shorter carbohydrate chains of different structure and composition) and properties (such as a lower viscosity). A study has however shown that they have a greater overall homology with other mucins in terms of assembly and conformation than was perhaps originally presumed. 

The B chain contains two N-linked oligosaccharide side-chains which contain only A-acetylglucosamine and mannose [27, 35]. One of these carbohydrate side-chains can be removed from the B chain by endoglycosidase H or F, whereas both can be removed after denaturation of the polypeptide by SDS [35, 38], This indicates that the N,N -diacetylchitobiose core of the second carbohydrate chain is normally protected by the polypeptide conformation. 

A sixth level of control must determine which of the core units added to a mannoprotein are elongated and which are not. Thus, external invertase has 9-10 carbohydrate chains per protein subunit ( l), and over half of them appear to consist solely of the core unit ( 6). A simple explanation could be that these units are sequestered inside when the invertase folds into its native conformation, and only those core units still exposed on the surface of the protein have the outer chain added. 

Yang, L. and Zhang, L. M. (2009). Chemical structure and chain conformational characterization of some bioactive polysaccharides isolated from natural sources. Carbohydr. Polym. 76, 349-361. 

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