Sugar components

As is well-known, nucleic acids consist of a polymeric chain of monotonously reiterating molecules of phosphoric acid and a sugar. In ribonucleic acid, the sugar component is represented by n-ribose, in deoxyribonucleic acid by D-2-deoxyribose. To this chain pyrimidine and purine derivatives are bound at the sugar moieties, these derivatives being conventionally, even if inaccurately, termed as pyrimidine and purine bases. The bases in question are uracil (in ribonucleic acids) or thymine (in deoxyribonucleic acids), cytosine, adenine, guanine, in some cases 5-methylcytosine and 5-hydroxymethylcyto-sine. In addition to these, a number of the so-called odd bases occurring in small amounts in some ribonucleic acid fractions have been isolated. 

The sugar component in RNA is ribose, and the sugar in DNA is 2 -deoxy-ribose. (The prefix 2 -deoxv indicates that oxygen is missing from the 2 position of ribose.) DNA contains four different amine bases, two substituted purines (adenine and guanine) and two substituted pyrimidines (cytosine and thymine). Adenine, guanine, and cytosine also occur in RNA, but thymine is replaced in RNA by a closely related pyrimidine base called uracil. 

In two articles published in this Series in 1946, the chemistry of bacterial polysaccharides was discussed. All the sugar and non-sugar components of such polysaccharides that were known at that time had previously been isolated from plant or animal polysaccharides. It was thus not known that... 

For most of the sugar components, little or nothing is known about their biosynthesis. Nucleoside hexosyl-4-ulose diphosphates are, however, almost certainly key intermediates in the biosynthesis of several of these sugars, as discussed in Ref 7. The biosynthesis of the 6-deoxyheptoses is probably analogous to that of the 6-deoxyhexoses, and proceeds by way of nucleoside heptosyl-4-ulose diphosphates. 

Rha, Ara and Gal are the neutral sugar components from all the fractions. Xyl is not present in Fla and is significantly present in the hemicellulose fractions, indicating that this monosaccharide is component of hemicellulosic polymers. Chemical composition of the water fractions were determined (Table V). High protein contents and the presence of O-acetyl-groups were observed in four aqueous fractions. Neutral sugar and uronic acid composition points to inclusion of these polymers in the class of pectic polysaccharides. 

Terrab, A., Vega-Perez, J. M., Diez, M. J., and Heredia, F. J. (2002). Characterization of northwest Moroccan honeys by gas chromatographic mass spectrometric analysis of their sugar components. /. Sci. Food Agric. 82,179-185. 

More-specific methods are available for identifying and quantitating the typical, amino sugar component of heparin (and some heparan sulfate species), namely, 2-deoxy-2-sulfoamino-D-glucose. Most of these methods are based on conversion of these residues into 2,5-anhydro-D-mannose by deamination with nitrous acid (see Section VIII,2). The 2,5-anhydro-D-mannose residues may be determined either colorimetrically,52-54 or fluorimetrically.55... 

Oligonucleotides with modified sugar components are another alternative to PNAs work in this direction was begun by Albert Eschenmoser, a famous synthetic chemist who was interested in the question as to why nature chose certain biomolecules for the processes of life and not others (Eschenmoser, 1991). This group carried out studies on the sugar components of the nucleic acids, in order to find out why D-ribose was used rather than another sugar. 

In the two nucleic acids, the sugar component consists solely of D-ribose or D-deoxyribose. 

The oligosaccharide components play a direct and central role in the biosynthesis, secretion, serum half-life and potency of the gonadotrophins. The sugar components attached to the a-subu-nits play an important role in dimer assembly and stability, as well as hormone secretion and possibly signal transduction. The sugars associated with the P-subunit, while contributing to dimer assembly and secretion, appear to play a more prominent role in clearance of the hormone from circulation. 

The difficulties inherent in obtaining correct sugar analyses for a polysaccharide containing three different amino sugars are obvious. It therefore seems possible that S4 is composed of tetrasaccharide repeating-units, containing one residue each of the four different sugar components. 

By means of gel electrophoresis on cross-linked, hydrolyzed starch,99 with simultaneous checking for proteins, lipids, and pectinesterase activity, it was found, however, that the product isolated after the separation on CM-Sephadex C-50 constitutes but one of five multiple forms of tomato pectinesterase, and is the one present in preponderant proportion98 (see Fig. 4). The accompanying lipid and sugar components were separated from this pectinesterase form in the course of the purification procedure. After analysis of the hydro-lyzate of the final product for fatty acids, as well as for carbohydrate components, it was possible to exclude the possibility of a lipoprotein,30 as well as glycoprotein,100 character of this form of tomato pectinesterase. 

Cuscutic resinoside A (1 tetradecanoic acid, (115)-[[6-deoxy-3-(9-(6-deoxy-a-L-mannopyranosyl)-4-0-[(2/ ,3R)-3-hydroxy-2-niethyl-l-oxobutyl]-a-L-nianno-pyranosyl]oxy]-intramol. l,2 -ester) was obtained from the ethyl acetate-soluble fraction of a methanol extract prepared from the seeds of Cuscuta chinensis Lam. The purification of this compound employed a combination of column and preparative-scale HPLC. The structure was deduced from spectroscopic evidence and acid hydrolysis 14). The degradative process gave convolvuUnolic acid, nilic acid, and L-rhamnose. The sugar components were identified by GC analysis after being converted to their thiazolidine derivatives. This disaccharide has a unique macrocyclic lactone, which is placed between C-1 and C-2 of the first rhamnose moiety. 

The natural antibiotic novobiocin (Fig. 3) is an example of diversity enhancement by the combination of building blocks from different pathways, such as aromatic rings, isoprenoid, amino acid, and sugar components, finished by post-modification [22]. 

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