Carbohydrates, acidic derivatives alkaline hydrolysis

The discovery of a small proportion of a nucleoside containing thymine42 in the ribonucleic acid of two strains of Escherichia coli, in Aerobacter aero-genes, and in commercial, yeast-ribonucleic acid emphasizes the point made previously,26-28 namely, that the nucleic acids may contain constituents other than those heretofore identified. Alkaline hydrolysis of the ribonucleic acid from E. coli gave nucleotides42 (probably the 2- and 3-phosphate esters) which were converted to the nucleoside with prostatic phospho-monoesterase.62 Enzymic hydrolysis of the nucleic acid preparation also led to the nucleoside, which was degraded further to thymine by hydrolysis with perchloric acid.42 There can be little doubt that this carbohydrate derivative of thymine is intimately bound as part of the polynucleotide chain of this particular ribonucleic acid. 

The acetone-soluble fraction was known to contain a large percentage of free fatty acids in addition to the fatty esters. Some of these fatty acids were found by Anderson to be of a type hitherto unknown. In common with the waxes, this fat did not contain any free glycerides. Alkaline hydrolysis of the fat derived from human strain bacilli yielded a water-soluble carbohydrate. This was identified as trehalose by isolation of the crystalline sugar. Corresponding fats isolated from the bovine and avian strains of bacilli were examined. The presence of glycerol could not be detected nor could the carbohydrate components be identified. 

Fig. 1. Determination of the structure of MGDG from wheat flour (adapted from Carter et al., 1961a,b). Methylation of MGDG, followed by alkaline saponification, yields partially methylated derivatives. Periodate oxidation of these substances gives 1 mol uptake with the formation of formaldehyde. After acidic hydrolysis, MGDG derivatives give 2,3,4,6-tetra-O-methyl-D-ga-lactose and glycerol. Consequently, these results clearly deflne the structure of MGDG as a 1,2-diacyl-sn-glycerol with a carbohydrate moiety attached in the C-3 position.

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