Abstract
A procedure is described for determining the activity of the individual carbon atoms in D-fructose labelled with C14, which is suitable for as little as 1 milli-mole of the sugar. The D-fructose is degraded by lead tetraacetate oxidation and the product is hydrolyzed to glycolic acid, formic acid, and D-glyceraldehyde. Glycolic acid is oxidized to formaldehyde (car-bon-1) and carbon dioxide (carbon-2), and formic acid to carbon dioxide (carbon-3). D-Glyceraldehyde is degraded to carbon dioxide (carbons -4 and -5, combined) and formaldehyde (carbon-6); after reduction of a second portion of the D-glyceraldehyde to glycerol, the degradation products obtained are carbon dioxide (carbon-5) and formaldehyde (car-bons-4 and -6, combined). The activity of carbon-1, -2, -3, -5, or -6 is thus determined directly, and of carbon-4 by difference in two ways. The procedure should also be applicable to C14-labelled L-sorbose. Lead tetraacetate oxidation of sedohepulose followed by hydrolysis yields glycolic acid, formic acid, and D-erythrose. These three fragments are degraded in turn to afford a method for partial determination of the C14-distribution in samples of this important heptulose.
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