Sialic acid isolation

L-Lactyl groups described as occurring at 0-9 of sialic acids isolated from different tissues (see Section II) are analyzed either as their hy-droxylamine derivatives, by t.l.c., or, in a more specific way,97 by L-lac-tate dehydrogenase and NAD+ in the presence of hydrazine, after O-deacylation with 0.05 M NaOH. 

Neuraminic (Sialic) Acids, Isolation and Determination of (Whitehouse and... 

The biotinylated glycans on the cell surfaces subsequently may be probed with (strept)avidin reagents to detect the azido-sialic acid modifications. Alternatively, the cells may be lysed and the glycoproteins isolated using an immobilized (strept)avidin or monomeric avidin affinity resin. 

In about 1936, sialic acid was discovered by Blix, who found it to be a component of submaxillary-gland proteins, and who described many of its properties. However, little notice was taken of this work at the time it was published. In 1941, Klenk, who was working on glycolipids of the brain, described a compound, later shown to be a methyl glycoside of sialic acid, that had been obtained by treatment of a lipid fraction with 5% methanolic hydrogen chloride at 105°. In 1954, Klenk and Faillard reported the first isolation of pure N-acetyl-neuraminic acid from animal sources. 

For enveloped viruses such as the influenza viruses it has been shown that similar binding affinities are found for the hemagglutinin (HA) Hg-and sialic acid using either isolated HA or the whole virus [37,40] using simple H NMR titration experiments. In contrast to structural proteins of non-enveloped viruses, HA is a membrane protein and thus not as rigid as proteins as part of, e.g., icosahedral particles. For the application of STD NMR... 

N-Acetvlneuraminic Acid Aldolase. A new procedure has also been developed for the synthesis of 9-0-acetyl-N-acetylneuraminic acid using the aldolase catalyzed reaction methodology. This compound is an unusual sialic acid found in a number of tumor cells and influenza virus C glycoproteins (4 ). The aldol acceptor, 6-0-acetyl-D-mannosamine was prepared in 70% isolated yield from isopropenyl acetate and N-acetyl-D-mannosamine catalyzed by protease N from Bacillus subtilis (from Amano). The 6-0-acetyl hexose was previously prepared by a complicated chemical procedure (42.) The target molecule was obtained in 90% yield via the condensation of the 6-0-acetyl sugar and pyruvate catalyzed by NANA aldolase (Figure 6). With similar procedures applied to KDO, 2-deoxy-NANA and 2-deoxy-2-fluoro-NANA were prepared from NANA. 

These two polypeptides have been shown to have identical amino acid composition (Table 9) but to differ from each other in sialic acid content. Da and D4 have 1 and 2 moles of sialic acid per mole of protein, respectively (A5, A6, B9, BIO, E5). A third form without sialic acid has been isolated by preparative isoelectric focusing (A5). Both D3 and D4 have the same NHa-terminal (serine) and COOH-terminal (alanine) amino acid residue and a molecular weight of about 10,000. The complete amino acid sequence has recently been announced (B6) and is reported in Fig. 7. These studies show that the polysaccharide having sialic acid as its terminal sugar, is linked to threonine 74 of the polypeptide chain. 

Naturally occurring oligosaccharides have also been isolated by gel chromatography. Ohman and Hygstedt94 have reported the isolation, from colostrum, of sialic acid oligosaccharides, including di-O-sialoyl-lactose [0-A/-acetylneuraminoyl-(2 — 8)-0-(N-acetylneur-... 

D-Galactose tends to be the next innermost sugar in nonreducing, terminal positions. Thus, about 70-80% of the D-galactose residues of sialic acid-free fetuin,248,319 or of a glycopeptide isolated from it,248 were released by the action of /3-D-galactosidase. Similar results were... 

Sialic acids generally occur in vertebrates, as is summarized in Refs. 19-21. Neu5Ac was isolated in our laboratory from the secreted mucus of the cyclostome Mi/xine glutinosa,20 a discovery in contrast to an earlier report by Wessler and Werner.3 The sialic acid content of the dried mucus is 0.5%. The greatest variety of N- and O-acyl derivatives of Neu was found in mammals, as will be reported later. 

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