Monosaccharides structural features

While the hemicelluloses obtained from the germ, aleuron, and caryopsis coat cell walls all showed a similar monosaccharide composition, this was not the case for the endosperm tissue. Thus, a major difference in the structure of hemicellulosic polysaccharides exists between the preparations obtained from the endosperm cell walls and those from the cell walls of the other parts of the grain, i.e., rice bran. (Rice bran consists of the caryopsis coat, aleuron layer and germ.) Comparison of the detailed structural features of the hemicellulosic polysaccharides of endosperm and bran cell walls will be discussed in the following sections. 

A great diversity of monosaccharide structures is a characteristic feature of bacterial polysaccharide chains, especially of O-specific chains of lipopolysaccharides from Gram-negative bacteria. Several surveys of monosaccharide components of bacterial polysaccharides have been published.95 98... 

Methyl a-D-glucopyranoside and methyl B-D-fructo-furanoside, which have structural features in common with sucrose were the most effective monosaccharides for eliciting a neural response. (3) The lengths of superimposed Dreiding models of a pentitol and sucrose coincide almost perfectly. (This could account for the leveling off of the response to the polyols as the... 

D-Glucose is the most common of the monosaccharides, occurring in the free state in the blood of animals and in the polymerized state, inter alia, as starch and cellulose. Tens of millions of tons of these polysaccharides are made by plants and photosynthetic microbes annually. A detailed study of the structure of glucose is justified on these grounds, and many of the structural features of all monosaccharides can be illustrated using glucose as an example. 

Hemicelluloses are a family of four basic types of polysaccharides, composed of two or more monosaccharide residues. All have structural features similar to cellulose in that they have their main chains that are -(1 4) linked, with the exception of the arabinoglactans that are /3-(l—>3) linked. The main chains are homopolysaccharides composed of a single monosaccharide residue, but they are highly branched by one or two different kinds of monosaccharides that are linked for the most part to give single monosaccharide branches. 

Active transport mechanisms for the intestinal absorption of amino acids, oligopeptides, monosaccharides, monocarboxylic acids, phosphate, bile acids, and a number of vitamins have been identified and the review by Tsuji and Tamai provides an excellent summary of those mechanisms. The potential use of intestinal peptide and hepatic bile acid carriers to enhance drug absorption also has been reviewed. Structural and molecular modeling studies have postulated molecular structural features necessary for substrate recognition by the intestinal peptide carrier and the bile acid carrier. ... 

Disaccharides are glycosides formed from two molecules of monosaccharide, either the same monosaccharide or different monosaccharides, by dehydration between OH substituents. To identify a disaccharide, the following structural features must be specified ... 

It has been demonstrated in previous sections of this chapter that some substrates (e.g., furfuryl alcohols, vinylene carbonate telomers, etc.) are capable of being transformed, in a limited number of synthetic steps, into the full variety of stereoisomeric sugars. These syntheses are fairly general. In this section, carbohydrate preparations are described which start from some peculiar substrates and by exploitation of specific reactions lead to a single monosaccharide or, at most, to a limited number. Natural products have often been used for the purpose. Their structural features usually predetermine the type of sugar that can be obtained. These substrates, being optically active, afford eventually enantiomeric products. The usually troublesome resolution of racemic intermediates of final... 

French et al. have provided some insight into the ability of MM2 and MM3 to correctly predict the strengths of nonbonded interactions between sugar residues by computing the crystal lattice energies of microcrystalline ensembles of monosaccharides.. 3 Although simulations of carbohydrate crystal structures have been reported, the published investigations have focused primarily on the structural features.3 23.i04 worthwhile to note that these... 

So far we have represented the monosaccharides as open-chain polyhydroxy aldehydes and ketones. These representations are useful in discussing the structural features and stereochemistry of monosaccharides. However, we learned in Section 4.3 that aldehydes and ketones react with alcohols to form hemiacetals and hemiketals. When these functional... 

Nature produces numerous kinds of polysaccharides in an appropriate biological environment. The structural diversity of the natmal polysaccharide is fully commensurate with a diverse array of molecules that can be generated from only a limited number of monosaccharides as building blocks by linking them in a variety of ways. This structural feature of polysaccharide characterized by diversity is in sharp contrast to that of other natural polymers such as polynucleotides and peptides with very regular, uniform and well-identified nanostructures. 

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