Composition polymeric carbohydrates

As we know, from earliest times up to the present days, the substances used as vehicles for writing have been numerous. The papers of one hundred years ago were basically made from rags of cotton and linters. The principal chemical constituent of these sources is cellulose, a polymeric carbohydrate composed of long linear chains of /3-linked anhydroglucopyranose. The chains in cellulose are composed of as many as ten thousand glucose units (degree of polymerization). The composition of wood fibers is quite different from that of cotton, as can be seen from Table I. The chemical constituents of modern papers are compli-... 

Because poiysaccharides are natural macromolecules occurring in all living organisms, the structure of some polysaccharides can be much more complex, as they are not made only from simple monosaccharides. In the composition of natural polymeric carbohydrates, a wide variety of sugars are found. Among these, the most common are pentoses and hexoses. The structural formulas of three common pentoses are shown below. They frequently form cyclic structures with five-member rings (furanoses). 

Water-soluble ohgomeric and polymeric carbohydrate fragments of uncertain composition 5-10... 

Recently, Cady et al. (1993) have described water-dispersible and soluble polymeric carbohydrate compositions for parenteral administration of growth hormones, somatomedins, and growth factors. One-week release of bovine growth hormone from a 25% aqueous dispersion of dextrin was demonstrated, owing to complexation between protein and carbohydrate. Release rates from both dextrin and dextran could be increased by the addition of surfactants. 

In nature, mammalian antibodies occur in five distinct classes IgG, IgA, IgM, IgD, and IgE. These differ in structure, size, amino acid composition, charge, and carbohydrate components. The basic structure of each of the classes of immunoglobulins consists of two identical polypeptide chains linked by disulfide bonds to two identical heavy chains. Differences between classes and subclasses are determined by the makeup of the respective heavy chains. IgG is the major serum immunoglobulin and occurs as a single molecule IgA also occurs as a single molecule but also polymerizes, primarily as a dimer and also associates with a separate protein when secreted. IgM occurs in the serum as a pentamer, with monomers linked by disulfide bonds and the inclusion of an additional polypeptide component, the J-chain. IgD and IgE occur primarily as membrane-bound monomers on -cells, or basophils and mast cells, respectively. 

An alternative approach for screening the composition of phytoplankton exudates is to use either 14C-tracer methods combined with chemical fractionation (Hama and Handa, 1987 Siuda and Wcisko, 1990 Sundh, 1991) or colorimetric methods (Obernosterer and Herndl, 1995 Biddanda and Benner, 1997) to characterize the contribution of different classes of organic compounds (carbohydrates and amino acids in polymeric or monomeric forms) to the total pool of exudates. These studies revealed that monomeric and combined carbohydrates were the major components of exudates, typically accounting for 20-90% of the total extracellularly released DOM. 

To make flour, Jerusalem artichoke tubers are macerated, heated, and spray-dried. In the process, inulin is hydrolyzed to short-chain fructooligosaccharides (Yamazaki et al., 1989). Jerusalem artichoke flour is also used to supplement animal feed. In one study, the composition of a typical Jerusalem artichoke flour was 2.1% (of dry weight) nitrogen, 16.2% insoluble fiber, 4.2% ash, and 77.5% soluble carbohydrate. The carbohydrate comprised fructans with degrees of polymerization of 1 to 2 (33.3%), 3 to 4 (46.4%), and over 5 (20.3%) (Famworth et al., 1993). 

Modification of porous inorganic materials by carbon makes it possible to obtain porous carboniferous composites with high thermal and chemical stability and strength. To introduce carbon into pores, both gas phase pyrolysis and carbonization through thermochemical solid-phase reactions are employed. The formation of carbon structures depends on carbonization conditions process rate, precursor concentration, presence of catalyst, etc. [1-3]. Phenolic resins, polyimides, carbohydrates, condensed aromatic compounds are most widely used as polymeric and organic precursors[4-6]. 

There are two major chemical components in wood lignin (18-35%) and carbohydrate (65-75%). Both are complex, polymeric materials. Minor amounts of extraneous materials, mostly in the form of organic extractives and inorganic minerals (ash), are also present in wood (usually 4-10%). Overall, wood has an elemental composition of about 50% carbon, 6% hydrogen, 44% oxygen, and trace amounts of several metal ions. 

As seen in Tables 16.2.5, 16.2.6, and 16.2.7, many compounds in tobacco smoke are generated from the small molecules. However, polymeric material plays an important role in smoke composition. Carbohydrates, including amidated pectins, Maillard polymers, and proteins, all generate smoke components with important roles in smoke sensorial properties. 

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