Carbohydrates constitution

Since carbohydrates constitute an inexpensive and highly modular chiral source for preparing chiral ligands," Claver et al. have reported the use of a series of thioether-phosphite" and thioether-phosphinite furanoside ligands" in the test palladium-catalysed allylic substitution reaction. In the first type of ligand, a systematic variation of the donor group attached to the carbon atom C5 indicated that the presence of a bulky phosphite functionality had a positive effect on the enantioselectivity. Indeed, the enantioselectivity was controlled mainly by the phosphite moiety. This was confirmed by the use of a ligand... 

Building blocks derived from microbial transformations are usually employed as the key units of fluorinated analogs of appropriate natural products or synthetic biologically active materials [42-45]. Among such useful compounds, trifluoromethylated carbohydrates constitute one of the most interesting fields for intensive study. Novel and efficient routes to access a variety of chiral... 

Carbohydrates constitute a major class of naturally occurring organic compounds, including sugars, starches, and celluloses. They are essential to the maintenance of plant and animal life. Carbohydrates are classified into three major groups monosaccharides, oligosaccharides,1 and polysaccharides. Monosacchandes are the simplest carbohydrate units. Oligosaccharides contain two or more of these simple mono sacchande units, and polysaccharides contain hundreds or thousands of them. 

As discussed in Section V, the spectrum of substrates and substrate proxies currently used to measure enzyme activities in marine systems is limited and most likely does not adequately represent the macromolecules actually available to aquatic microbial communities. Despite progress in recent years, our knowledge of the molecular structure and composition of dissolved organic matter is still only rudimentary. Although carbohydrates constitute an estimated 25-50% of DOC in seawater (Benner et al., 1992),... 

The triphenylmethyl ethers of the carbohydrates constitute a group of derivatives of particular interest because of the special properties inherent in the trityl group. Before entering into a discussion of these carbohydrate derivatives, a few words regarding the preparation, properties and special behavior of trityl ethers would appear to be in order. 

Fig. 20.4. Predicted changes (A) in the ratio of serum totai choiesterol to HDL-C and in LDL- and HDL-C concentrations when carbohydrates constituting 1% of energy are replaced isoenergetically with saturated, cis monounsaturated, cis poiyunsaturated, or trans monounsaturated fatty acids. P<0.05 +P<0.01 P<0.001.

Of all the dissolved oi anic components present at the beginning of the experiment, organic C and carbohydrates constituted the major part (39 and 16 mg r ). This is due to the considerable amount of coloured humus compounds, found in the initial water. The experimental evidence (Bikbulatov and Skopintsev, 1974) strongly su ested that the addition of phenol-sulphuric reagent to such water caused a considerable increase in light absorption in the 480—490 nm sector. This is evidently caused by (a) the conversion of organic components of the high sulphuric acid medium into more coloured forms, and (b) the hydrolysis of carbohydrate compounds of the coloured water humus. 

In the human diet, carbohydrates constitute approximately half the total caloric intake, yet only 1% of tissue weight is carbohydrate. Explain this fact. 

Carbohydrates constitute the main constituents of plants, with.cellulose the most abundant. In addition, are the various hemicelluloses or polysaccharides, pentosans and polyuronides. Most of these substances, especially cellulose, are readily attacked by many species of soil microorganisms. The result is that the carbohydrate content of humus is very different from that of the plant residues from which most of the humus is derived (Gupta, 1962 Gupta et al, 1963 Gupta and Sowden, 1964). Humus usually contains little cellulose but does contain hemicelluloses and polyuronides. These substances are in part the residues of the original plant materials but most of them are the synthesized gums, slimes and cell walls of the microorganisms that are responsible for decomposition and the formation of humus. 

A major proportion of the organic matter on Earth is plant tissue ( biomass ) and is composed of carbohydrates, principally cellulose. This is the structural support polymer of land plants and the material used since ancient times in the form of cotton and linen textiles, and later as paper. Chitin is a polymer related to cellulose that has skeletal function in arthropods and fungi. Other polymeric carbohydrates constitute the structural support framework for marine plants and the cell walls of microorganisms. The sweet carbohydrate of sugar cane, now termed sucrose, has been a dietary item for at least 10 millennia. 

Polysaccharides are the most abundant macromolecules in the biosphere. These complex carbohydrates constituted of glycosidic bonds are often one of the main structural elements of plants and animals exoskeleton (cellulose, carrageenan chltin). The... 

Carbohydrates constitute one the of most complex structures occurring in nature (with nucleic acids and proteins) due to i) the monosaccharide diversity, ii) the type of linkage and iii) the nature of carbohydrate-linked molecules. As a result, GHs present a wide range of activities, which have necessitated the creation of a specific classification more explicit than the lUB Enzyme Nomenclature. In 1998, the Carbohydrate-Active Enzymes (CAZy) database was created, gathering glycosidases in famiUes based on amino-acid sequence and protein structures similarities. ... 

The ring contraction of carbohydrates constitutes a very useful route to functionalised and enantiomerically pure carbocycles. These compounds play a significant role in the construction of biologically active compounds such as enzyme regulators [24], the Corey lactone [25] and related prostaglandin intermediates [26], just to mention a few. 

As a more recent example, microchip electrophoresis has been coupled to a copper-nanowire electrochemical detector that exhibited electrocatalysis toward carbohydrates, constituting a selective and sensitive detector that was applied in the fast and reliable analysis of monosaccharides in honey samples (Garcia and Escarpa, 2014). Glucose and fructose were separated in less than 250 s, the obtained results agreeing, with errors lower than 10%, with those obtained by high-pressure EC (HPLC)-refractive index. 

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