Casper—a computerised approach to structure determination of polysaccharides using information from n.m.r. spectroscopy and simple chemical analyses
✍ Scribed by Per-Erik Jansson; Lennart Kenne; Göran Widmalm
- Publisher
- Elsevier Science
- Year
- 1987
- Tongue
- English
- Weight
- 672 KB
- Volume
- 168
- Category
- Article
- ISSN
- 0008-6215
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✦ Synopsis
ABsTRAcr
A computer program, CASPER, has been developed for the determination of the structure of polysaccharides composed of regular repeating-units. The program utilises the '3Cn.m.r. spectrum of the polysaccharide and information from sugar and methylation analyses. Based on the identity of the monosaccharides present in the repeating unit and the positions of the linkages, all possible permutations are constructed. With the aid of a database containing l3Gn.m.r. substituent shifts obtained from disaccharides, the spectra of the alternative structures are simulated and the best fit with the observed spectrum is selected. The program has been tested on two polysaccharides of known structures, for both of which the correct structure was selected.
INTRODUCI'ION
Until recently, the elucidation of polysacchatide structures involved specific degradations and analysis of the products. In recent years, n.m.r. spectroscopy has become increasingly important in such studies and the structures of several oligoand poly-saccharides have been determined mainly or exclusively by n.m.r. techniques. The n.m.r. data were generally compared with data obtained from monosaccharide derivatives. Compilations of l3Cn.m.r. spectra's2 and the rationalisation of some substituent shifts3 have been reported.
The lH-and '3Gn.m.r. chemical shifts of the resonances of a monosaccharide residue within a larger saccharide depend mainly on the structure of the monosaccharide and on the nature of the flanking sugar residues. In 'H-n.m.r. spectroscopy, the resonances of some protons have chemical shifts outside the "bulkregion" (8 3.54) and these resonances have been assigned to structural reporter *Resented at the xmth International Carbohydrate Symposium,