Aldoses composition

Aldose composition P. pouchetii and P. globosa Exponential Stationary 2-11% 0-51% Compiled in this study... 

Extra-colonial DOM rich in carbohydrates was reported in cultures of Phaeocystis (Table 5 and references therein). Carbohydrates similar in aldose composition to that of mucopolysaccharides form a major contribution to this DOM... 

Neutral aldose compositions of hydrolysate mixtures from marine plankton and HMW DOM from surface seawater. Both samples are characterized by similar relative sugar compositions with the major exceptions of lyxose, ribose and galactose relative to glucose. Abbreviations Lyx, lyxose Ara, arabinose Rib, ribose Xyl, xylose Rha, rhamnose Fuc, fucose Man, mannose Gal, galactose Glc, glucose. From McCarthy et al. (1998). 

IV, Composition in Aqueous Solution Aldoses 1. Aldohexoses and Aldopentoses... 

Whereas the composition of solutions of the unsubstituted aldoses and ketoses has been systematically investigated, very few studies have been conducted on substituted and on derived sugars, such as amino sugars,... 

Water is the only solvent in which the composition of sugars has been systematically explored. Stevens1674 has determined the composition of several aldoses in pyridine-d5 by -n.m.r, spectroscopy at 300 MHz. There are scattered data on solutions in organic solvents (mainly pyridine, dimethyl sulfoxide, and N,N-dimethylformamide), but only rarely have four (or more) components of such solutions been quantitatively determined. The data that have been encountered are collected in Table VII undoubtedly, there are others that have been missed. 

The simple sugars, or monosaccharides, are poly-hydroxyaldehydes (aldoses) or polyhydroxyketones (ketoses).1-5 All have the composition (CH20)n, hence the family name carbohydrate. A typical sugar, and the one with the widest distribution in nature, is glucose. 

The composition of many aldoses and two ketoses has been determined14 by, 3C-n.m.r. spectroscopy the results agreed well with those from previous determinations made from H-n.m.r. spectra. 

The Composition (%) of Aldoses and Some of Their Deoxy Derivatives in D20... 

Table 1.3 Composition of some aldoses at equilibrium in aqueous solution...

Following the production of 1,2-enol forms of aldose and ketose amines, a series of degradations and condensations results in the formation of melanoidins. The a-fi-dicarbonyl compounds enter into aldol type condensations, which lead to the formation of polymers, initially of small size, highly hydrated, and in colloidal form. These initial products of condensation are fluorescent, and continuation of the reaction results in the formation of the brown melanoidins. These polymers are of nondistinct composition and contain... 

A second compound, 155, contains a reaction product with ethylenediamin and two moieties of mannose. Although the structure of the pentacuprate is quite complex, the composition of 155 could be derived from the simple educts. Besides oxidation, the building of iV-glycosides is another reaction of the aldoses. 

As the name implies, carbohydrates are characterized by a nominal (CH20) composition. Next to proteins, carbohydrates combined into polysaccharides are generally the most abundant (Table 8.6) and widely distributed biopol5miers in living organisms. (However, there are some plankton in which the lipid concentration exceeds that of carbohydrates (Wakeham et al, 1997).) The fundamental monomeric rmits of most carbohydrates are five- (pentose) and six-(hexose) carbon sugars, of which there are roughly ten common forms (Fig. 8.9). These structural units usually occur as either aldoses or ketoses, in which either the first (aldose) or second (ketose) carbon... 

Monosaccharides can exist as aldehydes or ketones and are called aldoses or ketoses, respectively. For example, (Figure 9.3) shows the structures of glyceraldehyde, an aldo-triose, and dihydroxyacetone, a keto-triose. Glyceraldehyde and dihydroxyacetone have the same atomic composition, but differ only in the position of the hydrogens and double bonds. Moreover, they can interconvert via an enediol intermediate (Figure 9.4). When the structures of molecules are related in these ways, the molecules are called tautomers. 

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