Sialic acid oxidation with sodium

Radioactive 3H-labelled prothrombin was prepared by a method described previously (11) sialic acid was oxidized with sodium metaperiodate. The obtained aldehyde was reduced by sodium (3H) -boro-hydride. 

When HeLa cells were.cultured in medium supplemented with 5 mM sodium butyrate, their content of GM3 increased (Fig.2a). Increases varied from 3.5 to 5-fold depending on the experiment (4,8,12,13). When the butyrate was removed and the cells were cultured in normal medium for 24 h, the GM3 levels returned to those found in untreated cells (Fig. 2a). Similar results were observed when N-[acetyl-3H]-D-mannosamine, a precursor of sialic acid, was also included in the culture medium. In the butyrate-treated cells, radioactivity associated with GM3 increased 6.5-fold and 24 h after butyrate was removed, the amount of labeling returned to control values (Fig. 2b). We also were able to label the GM3 by means of a cell surface labeling technique. Control and butyrate-treated cells were exposed to 10 mM sodium periodate and the oxidized sialyl residues were reduced with NaBSfy. There was 5.5-fold more 3h associated with the GM3 recovered from the butyrate-... 

Brief oxidation with 0.025 M-sodium metaperiodate at pH 7, followed by estimation with the resorcinol or thiobarbituric acid reagent, has been used in the simultaneous assay of free and ketosidically bonded sialic acids, respectively." Treatment of 2-acetamido-2-deoxy-3,4 5,6-di-O-isopropylidene-aW liydo-D-glucose (192) or the analogous D-mannose derivative with alkali gave 2-acetamido-2,3-dideoxy-5,6-0-isopropylidene-a-D-eryt/iro-hex-2-enofuranose (193), which afforded the methyl 2-enofuranosides (194) with acidified methanol-acetone (194)... 

Oxidation of nanomole amounts of O-substituted 2-acetamido-2-deoxy-D-galactitol and -glucitol, reduction of the resulting aldehydes with sodium borotri-tiide, and hydrolysis with acid afforded 2-amino-2-deoxy[ct)- H]alditols, which can be separated by t.l.c. and detected by autoradiography. Identification of the 2-amino-2-deoxy[ft>- H]alditols determined the positions of substitution of the 2-acetamido-2-deoxyhexitols. A simple, rapid, and sensitive method for the simultaneous assay of free and ketosidically bonded sialic acids is noted in Chapter 8. 

To investigate the latter possibility, sections of bovine submandibular gland and human colon were oxidized for periods of either 10 or 30 minutes and were then reduced with sodium borohydride. The sections were then reoxidized with periodate for various periods and then stained with Schiff reagent. The results obtained showed that when human colonic mucins were oxidized for an initial period of 10 minutes, some PAS reactivity could be regenerated by a second oxidation period of 60 minutes. When however, the initial oxidation period was extended to 30 minutes, no further PAS reactivity could be generated by a second period of oxidation. These results could be interpreted in two ways either they were the result of the incomplete oxidation of a relatively small number of 9-0-acyl sialic acids or the failure to oxidize other tissue diols. The probability of the latter was lessened by the observation that the oxidation of the crypt mucins of rabbit small intestine which do not contain 0-acylated sialic acids was apparently complete in 10 minutes. 

The hydroxyl groups in the acyclic carbons (C7—C9) of sialic acid may be specifically oxidized by dilute sodium periodate (NaI04) to yield a seven-carbon sugar with a C7 aldehyde which can be reduced with NaB3H4,... 

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