Analysis of the chain length of oligomers and polymers of sialic acid isolated from Neisseria meningitidis group B and C and Escherichia coli K1 and K92

Abstract

A series of (2----8)-alpha-, (2----9)-alpha-, and alternate (2----8)-alpha- and (2----9)-alpha-linked oligomers of sialic acid (N-acetylneuraminic acid, NeuNAc) was prepared by digestion with bacteriophage or by partial hydrolysis at pH 7.0 and 100 degrees of polymers of sialic acid produced by Neisseria meningitidis and Escherichia coli. The oligosaccharides were purified by gel filtration or by anion-exchange chromatography, and their chain lengths were determined by colorimetric measurement of the formaldehyde released from the non-reducing end residue after periodate oxidation, radiolabelling of the reducing end residue by reduction with borotritiide, and determination of the ratio of the non-reducing end and internal residues by g.l.c. of the trimethylsilyl derivatives of the methyl ester methyl beta-ketosides. 1H-N.m.r. spectroscopy was used to confirm the chain length of two oligosaccharides. These methods were used to determine the average chain-length of the sialic acid polysaccharides produced by N. meningitidis and E. coli and the percentage of chains with covalently bound lipid moieties at the reducing end.