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Structural studies of Klebsiella capsular polysaccharides Yang, Mo-Tai


The genus Klebsiella belongs to the family Enterobacteriaceae. Eighty types of Klebsiella have been serologically classified using the capsular polysaccharides as antigens. In order to understand the chemical basis of serological reactions, structural studies of the capsular polysaccharides from three strains of Klebsiella, namely, K5, K62 and K18 were carried out by means of conventional methods (such as hydrolysis, methylation and periodate oxidation) as well as modern methods (such as circular dichroism (c.d.) for the assignment of the D or L configuration of monosaccharides, gas-liquid chromatography (g.l.c.) and mass spectrometry for isolation and identification of sugar moieties). In the course of the present investigation, p.m.r. spectroscopy at 95° for the assignment of anomeric configurations of the constituent sugars, and Sephadex gel filtration for the separation of a series of acidic oligosaccharides obtained from the partial hydrolysis of polysaccharides for sequential analysis have been developed. The repeating units of K5, K62 and K18 are as follows. The structure of K5 capsular polysaccharide lacks any side chain and is also unusual in affording the first example of a 4,6-0-(l-carboxyethylidene)-D-raannose unit In a natural product. Capsular polysaccharide of K.62 belongs to the prevailing structural pattern so far published in this genus which is composed of a repeating unit involving a single sugar in the side chain with three to four monosaccharides in the backbone. Capsular polysaccharide from K18 is unusua complex in that it consists of two L-rhamnoses in the hexasaccharlde repeat unit which renders the polysaccharide less viscous and acid labile. Finally, an attempted immunological study on K5 is briefly discussed.

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