Polysaccharide-Polysaccharide

Polysaccharides. Polysaccharides, also called glycans, are the nutrient and stmctural materials of plants. They are a principle part of the carbohydrate portion of the biomass. The most prevalent monomeric carbohydrate is glucose. Common polysaccharides are all polymers of glucose (Pig. 

Most carbohydrates exist in the form of polysaccharides. Polysaccharides give stmcture to the cell walls of land plants (cellulose), seaweeds, and some microorganisms and store energy (starch in plants and glycogen in animals). They are important in the human diet and in many commercial apphcations. 

An Antigenic Polysaccharide, Polysaccharide II, Isolated from Tuberculin, Florence B. Seibert, M. Stacey, and P. W. Kent, Biochim. Biophys. Acta, 3 (1949) 632-640. 

CA of Polysaccharides. Polysaccharides adopt a wide variety of shapes that depend on their composition and their environment. In solution, polymers are almost always random coils that have local regions that might be similar to conformations that are found in the solid state. The chapter by Brant and Christ discusses conformations of polysaccharides in solutions both in terms of these local regions and by the overall shape of the random coil in terms of end-to-end distance, etc. The following discussion concerns only linear (unbranched) molecules, and refers only to regular polymers, i.e., those that have repeated sequences of monomeric residues located by screw-axis (helical) symmetry. 

Polysaccharides Polysaccharides are composed of a huge number of monosaccharide units, and the number forming the molecule is often approximately known. For example, cellulose and starch are polysaccharides composed of hundreds of glucose units. 

Nowadays it is well established that the interactions between different macromolecular ingredients (i.e., protein + protein, polysaccharide + polysaccharide, and protein + polysaccharide) are of great importance in determining the texture and shelf-life of multicomponent food colloids. These interactions affect the structure-forming properties of biopolymers in the bulk and at interfaces thermodynamic activity, self-assembly, sin-face loading, thermodynamic compatibility/incompatibility, phase separation, complexation and rheological behaviour. Therefore, one may infer that a knowledge of the key physico-chemical features of such biopolymer-biopolymer interactions, and their impact on stability properties of food colloids, is essential in order to be able to understand and predict the functional properties of mixed biopolymers in product formulations. 

Non-reserve polysaccharides seem to function in biological tissues through the part they play in cohesion, the retention of water and salts, the physical organization, and the elasticity and general texture. Polysaccharide conformation and association, as well as chemical structure, are obviously involved in the control of such properties. The polysaccharide-polysaccharide interactions considered in this Section can be regarded (in the nomenclature of protein biochemistry) as showing secondary, tertiary, and quaternary structure.4W>2W8 The... 

Solubility is a very important criterium for the different uses of polysaccharides in pharmacy. Table 4 lists the solubility criteria of some polysaccharides in water. Solutions containing sugars and alcohol generally depress the solubility of polysaccharides. Polysaccharides containing carboxyl groups, i.e., pectins, alginates, and carboxy-methylcellulose, are insoluble at low pH values. They will be precipitated when the pH is lowered below 3. 

Most carbohydrates in nature exist as high-molecular-weight polymers called polysaccharides. Polysaccharides are composed of simple or derived sugars connected by gly-cosidic bonds. In this chapter we restrict ourselves to a description of homopolymers of glucose because they are the most important in energy metabolism. 

Biological Functions of Oligosaccharides and Polysaccharides. Polysaccharides serve two important biological roles. Glycogen and starch are polymers of glucose units linked in a(l —> 4) linkages that serve as carbohydrate reserves for animals, bacteria, and plants. Because these polymers are readily converted to intermediates for pathways that yield metabolic energy, they can also be... 

Carbohydrates generally supply about 45% of our energy requirement. Dietary carbohydrates include monosaccharides (such as glucose and fructose), disaccharides (such as sucrose and lactose), and the longermonosaccharide units arc classed as oligosaccharides.) Dietary polysaccharides include starches, such as amyJose and amylopectin, and some of the dietary fibers. 

Molecular conformations [71,72] and associations can be determined by CP-MAS- C-NMR and two-dimensional NMR methods [73], but the primary means of determining molecular conformations has been X-ray fiber diffraction analysis coupled with molecular modeling as practiced by Chandraskeran and co-workers. Examples are found in references [74,75,76,77,78,79,80,81,82,83,84]. The technique has also been used to study polysaccharide-polysaccharide interactions [85]. Recently, powder diffraction data has been used to determine a molecular conformation [86]. Modeling alone has been used to predict possible conformations [87]. 

Just as two monosaccharides combine to form a disaccharide, many monosaccharides or disaccharides can combine to form a long chain called a polysaccharide. Polysaccharides may be represented by the general formula below or by structural models such as the ones shown in Figures i and 2. 

Polysaccharides. Polysaccharides possess readily accessible hydroxyl groups that may be derivatized for selective protein immobilization. We will consider the two most commonly used immobilization reactions, the triazine and the cyanogen bromide reactions. 

Lii, C.-y. et al., Polysaccharide polysaccharide interactions in pastes, Pol. J. Food Nutr. Sci., submitted, 2001a. 

In the range up to overlapping concentration (co - c ), macroscopic material qualities become increasingly influenced by polysaccharide-polysaccharide interaction phenomena. However, individual... 

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