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Structural studies of Klebsiella capsular polysaccharides Choy, Matthew Yuen-Min

Abstract

Eighty types of Klebsiella are recognised on the basis of immunochemical tests. Qualitative analyses of the capsular polysaccharides produced by these bacteria have been provided by Nimmich. Nevertheless very few detailed structures are known in contrast to the qualitative data published. The present investigation deals with the structural studies of capsular polysaccharides from four strains of these bacteria, for example K20, K21, K24 and K56. Besides the classical methods used, new techniques have been used or developed in order to obtain detailed information on the structures. Modern methods used include the circular dichroism (c.d.) for the assignment of the D or L configuration of sugar constituents. Gas-liquid chromatography (g.l.c.) and mass spectrometry (m.s.) were used to analyse the partially methylated sugars which can be characterized further by demethylation and reacetylation to give crystalline derivatives. In the course of our studies, p.m.r. spectroscopy at 95° has been developed and becomes a very powerful tool for the assignment of the anomeric linkages of oligosaccharides and polysaccharides. It has also been found to be an excellent method for the detection and quantitative assay of other functional groups such as O-acetyl or pyruvic acid without degrading the polymer. The application of the above modern techniques together with use of the classical methods affords the detailed structures of K20, K21, K24 and K56, the repeating units of which are as follow: [See Thesis for Diagram]. The structure of K20 is the first of these Klebsiella capsular polysaccharides to be encountered with an aldobiouronic acid side chain. The capsular polysaccharides K21 and K24 each contains the same-type of aldobiouronic acid with branching on the D-glucuronic acid. The capsular polysaccharide K56 has a L-rhamnose side chain. The acidity of the polysaccharide is due only to the pyruvic acid present and this constitutes the first investigation of those Klebsiella polysaccharides lacking uronic acid.

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