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UBC Theses and Dissertations

Use of 2D N.M.R. and bacteriophages in structural studies of some E. coli antigens Kuma-Mintah, Agyeman


The capsular polysaccharide of Escherichia coli K31 has been found by methylation analysis and n.m.r. spectroscopy to be based on the hexasaccharide shown. The sequence of the repeating unit was deduced from the combined results of β-elimination, lithium ethylenediamine degradation, and hydrogen fluoride and selective hydrolyses. The nature of the anomeric linkages, established by chromic acid oxidation, was confirmed by ¹Hcoupled ¹³C-n.m.r. spectroscopy. Two dimensional n.m.r. studies on a low molecular weight polymer obtained by bacteriophage depolymerization confirmed the structure given below. [See Thesis for Diagram] The importance of bacteriophage-borne enzymes in the generation of lower polymers very suitable for homonuclear (¹H) two dimensional n.m.r. studies is demonstrated. E. coli K33 has been shown to cross react with Klebsiella K58. Chemical and two-dimensional n.m.r. studies gave the K antigen of E. coli K33 as a tetrasaccharide repeating unit [See Thesis for Diagram] and this structure is quite identical to that of Klebsiella K58. The use of homonuclear two-dimensional ¹H-spin correlated n.m.r. experiment as a very convenient method for the location of acetate in the repeating unit of a polysaccharide is illustrated using E. coli K33 polysaccharide as an example. The identification of a phosphate ester in the repeating unit of E. coli K46 using n.m.r. spectroscopy is reported. Detailed n.m.r. study on this antigen is well documented in this communication. The first occurrence of a 3,6-dideoxyamino sugar residue in an E. coli K antigen (i.e. E. coli K45 K antigen) and the finger print of its proton chemical shifts is also shown.

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