SYNTHESIS OF POLYSIALIC ACID ANALOGS
Margaret McGowen, H.J. Jennings and W.F. Vann

Poly-alpha(2,8)-N-acetyl neuraminic acid (polysialic acid, PSA) has been implicated in the pathogenic mechanism of Escherichia coli K1 urinary tract infection and neonatal meningitis. The three dimensional structure of PSA rationalized as random coil with localized helices of n = 9-11. We were interested in studying the role of the C9 hydroxyl moiety in PSA interactions. Our approach is to synthesize sialic acid analogs modified at C9 and incorporate them into polymer. 9-Azidosialic acid was charged with CMP using recombinant CMP-NeuNAc synthetase. The membrane of a mutant E. coli K1, EV241, which can neither synthesize nor degrade sialic acid was the source of sialyltransferase used to synthesize modified alpha(2,8)-PSA de novo. The 9-modified PSA was isolated associated with membrane vesicles by ultra-centrifugation. It was then purified by gel filtration and anion exchange chromatography. The structure of the polymer was then confirmed by 13C NMR spectroscopy to be alpha(2,8)-PSA analog