Carbohydrates, complex

The cell wall of fungi is a complex, multilayered structure formed by at least two major polysaccharides. These major polysaccharides have been used as a taxonomic criterion for fungi, as some of them contain chitin-glucans, and others, glucomannans.123 

The primary cell-wall of plants is formed by microfibrils of cellulose in a complex matrix of polysaccharides, proteins, and glycoproteins. The structure and relationship of the different components is under continuous study and revision, and most of them can now be identified and their biosynthesis studied.124 126 

In fungi, and in higher plants, the cell wall is a dynamic structure, changing during growth and differentiation, or in response to environmental factors. The main polysaccharides found in plant cell-walls are listed in this Section. The biosynthesis of those which are synthesized by way of lipid intermediates (see Table V) will be analyzed later. 

Polymer Precursor Source Product linkage Lipid intermediates References 

Vigna sinensis is the current name for Phaseolus aureus. b n.d., Not determined. 

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The per capita consumption of rice in the United States has doubled since 1960 to approximately 10 kg in 1989. Over the last decade U.S. rice consumption has benefited from a growing trend in U.S. diets away from high fat animal products and toward grain-based foods. Many health groups encourage use of the complex carbohydrates found in grain products such as rice. Also, increases in the Asian and Hispanic segments of the U.S. 

Celluloses. Complex carbohydrates including gums, cellulose, methylceUulose, and carboxymethylceUulose also have found appHcation ia fat replacemeat. A good summary of the appHcatioa of these materials is available (21). 

Acarbose is a nonabsorbable a-glucosidase inhibitor which blocks the digestion of starch, sucrose, and maltose. The digestion of complex carbohydrates is delayed and occurs throughout the small intestine rather than in the upper part of the jejunum. Absorption of glucose and other monosaccharides is not affected. Acarbose is adrninistered orally three times a day and chewed with the first mouthful of food. 

The notion that complex carbohydrates eHcit a gradual, steady secretion of insulin while sugars cause a sudden release of this hormone accompanied by a rapid drop in blood glucose has fostered the behef that hypoglycemia is affected by sucrose ingestion. However, research does not support this conclusion (63). 

N. Sharon, Complex Carbohydrates, Addison-Wesley PubUshiag Co., Reading, Mass., 1975. 

Class of colloidal substances prepared from plants. Composed of complex carbohydrates and organic acids that swell in water. Also, a number of natural resins are gums. 

Extracellular matrix The surfaces of animal cells are covered with a flexible and sticky layer of complex carbohydrates, proteins, and lipids. This complex coating is cell-specific, serves in cell-cell recognition and communication, creates cell adhesion, and provides a protective outer layer. 

Complex carbohydrate (Section 25.1) A carbohydrate that is made of two or more simple sugars linked together. 

Combinatorial library, 586 Complex carbohydrate, 974 Computer chip, manufacture of, 505-506... 

When a-glucosidase activity is inhibited, carbohydrate digestion is prolonged and takes place further along the intestinal tract. This in turn delays and spreads the period of glucose absorption, which reduces the extent of the postprandial rise in blood glucose concentrations. The effectiveness of a-glucosidase inhibitors is dq en-dent on the consumption of a meal rich in complex carbohydrate. 

Tannins comprise various polyhydroxyphenols and polysaccharides (polysaccharoses), which are complex carbohydrates (polyhydroxy aldehydes or ketones) and include starches and cellulose, and their... 

Between academic terms in the period 1929-1933, he traveled regularly to the London School of Hygiene and Tropical Medicine to participate, on a part-time basis, in research at Professor Raistrick s laboratory on the complex carbohydrates of molds and bacteria. Stacey s Ph.D. thesis, Investigation into the Ascent of The Series and High Polymers in the Carbohydrate Group, based on work carried out in both Birmingham and London, was presented in May 1932. 

Figure 13-10. Glucosamine (2-amino-D-glucopyra-nose) a form). Galactosamine is 2-amino-D-galactopy-ranose. Both glucosamine and galactosamine occur as N-acetyl derivatives in more complex carbohydrates, eg, glycoproteins.

Coelenterates and Echinoderms. Coelenterate and echinoderm toxins range from small molecular weight amines, to sterols, to large complex carbohydrate chains, to proteins of over 100,000 daltons. Molecular size sometimes reflects taxonomy, e.g., sea anemones (Actiniaria) all possess toxic polypeptides varying in size from 3,000 to 10,000 daltons while jellyfish contain toxic proteins (ca. 100,000 daltons). Carotenoids have been isolated from Asterias species (starfish), Echinoidea (sea urchins), and Anthozoans such as Actiniaria (sea anemones) and the corals. These are sometimes complexed with sterols (J5). 

Asymmetric epoxidation is another important area of activity, initially pioneered by Sharpless, using catalysts based on titanium tetraisoprop-oxide and either (+) or (—) dialkyl tartrate. The enantiomer formed depends on the tartrate used. Whilst this process has been widely used for the synthesis of complex carbohydrates it is limited to allylic alcohols, the hydroxyl group bonding the substrate to the catalyst. Jacobson catalysts (Formula 4.3) based on manganese complexes with chiral Shiff bases have been shown to be efficient in epoxidation of a wide range of alkenes. 

In line with the policy of Advances to provide periodic coverage of major developments in physical methodology for the study of carbohydrates, A. Dell (London) here surveys the use of fast-atom-bombardment mass spectrometry in application to carbohydrates. This technique has achieved rapid prominence as the soft ionization technique of choice for structural investigation of complex carbohydrate sequences in biological samples. The author s extensive personal involvement in this field makes her chapter a critical, state-of-the-art overview for the specialist, as well as a valuable primer for the reader unfamiliar with this technique. 

The spore coats make up a major portion of the spore, consisting mainly of protein with smaller amounts of complex carbohydrates and Bpid and possibly large amounts of phosphorus. The outer spore coat contains the alkali-resistant protein fraction and is associated with the presence of disulphide-rich bonds. The alkali-soluble fraction is... 

Complex Carbohydrate Research Center and Department of Biochemistry and Molecular Biology, University of Georgia, 220 Riverbend Road, Athens, GA 30602-4712, USA... 

This research was supported in part by the United States Department of Energy (DOE) grant DE-FG05-93ER20115 (to AGD) and by the DOE-funded PE-FG09-93ER20097) Center for Plant and Microbial Complex Carbohydrates. 

Many thanks are due to Mr. Jean-Paul Lepoutre (Laboratoire des ArSmes et des Substances Naturelles, BPV, INRA, Montpellier, France) for EIMS and CIMS analyses and to Dr. Malcolm O Neill (Complex Carbohydrate Research Center, The University of Georgia, USA) for his help in the identification of TMS derivatives. 

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