Polysaccharides salts

The results of a conductivity study on locust-bean gum (a neutral polysaccharide) in aqueous salt solutions led Barry and Halsey28 to conclude that there is no interaction between this carbohydrate and the many ions employed (H , Na , K , Ag , Ba2 , OAc , Cl , NO, , SO,2 , and HSO, ). Hydroxide ion was an exception. The electrolyte concentrations ranged from 0.0005 to 0.1 N, and the maximum concentration of polysaccharide was 0.0277 M (on a monosaccharide-residue bans). The specific conductivity of each polysaccharide-salt solution was identical to that of the corresponding salt solution containing no polysaccharide, strongly indicating the absence of significant adduct formation under the conditions... 

Many naturally occurring ionic polysaccharides are mixed salts of alkali, alkali-earth, and transition metals with different insolubilities. Salts of alkali metals are invariably soluble. Sodium, the most ubiquitous alkali, possesses a single valence electron, large atomic and ionic radii, and very low ionization potential. Na+ hydrates in aqueous solution and retains its coordination water in the solid state. Prior to use, native polysaccharide salts are usually converted to the sodium form whence they acquire functionality. 

Alkali-earth metals (calcium, barium, and magnesium) complex with polysaccharides extensively (Reisenhofer et al., 1984). Calcium has a smaller atomic and ionic radius than does sodium and, because it has two valence electrons, it is endowed with greater polarizing and bonding ability than Na+. Ca and Ca2+ easily form insoluble complexes with oxygenated compounds. Polysaccharide salts of alkali-earth metals are generally insoluble. 

Recovery and purification of 1,3-PD from complex and dilute fermentation broth meet severe challenges, which is mainly attributed to its low volatility, great affinity for water, and the presence of residual glycerol, macromolecules (e.g., proteins, nucleic acids, polysaccharides), salts, and some by-products (e.g., 2,3-BD, ethanol, acetate, lactate, succinate) (Xiu and Zeng, 2008). This becomes the bottleneck of the commercialization of 1,3-PD from renewable resources. 

Tables 1 and 2 Hst the important physical properties of formamide. Form amide is more highly hydrogen bonded than water at temperatures below 80°C but the degree of molecular association decreases rapidly with increa sing temperature. Because of its high dielectric constant, formamide is an excellent ionizing solvent for many inorganic salts and also for peptides, proteias (eg, keratin), polysaccharides (eg, cellulose [9004-34-6] starch [9005-25-8]) and resias.

Gum ghatti is the calcium and magnesium salt of a complex polysaccharide which contains L-arabinose, D-galactose, D-mannose, and D-xylose and D-glucuronic acid (48) and has a molecular weight of approximately 12,000. On dispersion in water, gum ghatti forms viscous solutions of viscosity intermediate between those of gum arabic and gum karaya. These dispersions have emulsification and adhesive properties equivalent to or superior to those described for gum arabic. 

Guar gum is a nonionic, branched-chain polysaccharide, a galactomaiman that is usually hydroxypropylated for use in drilling (52). It produces viscous solutions in fresh or salt water at concentrations of ca 3—6 kg/m (1—2 lb /bbl). It is used in soHds-free and low soflds muds and degrades rapidly above 80°C, limiting its use to shallow wells. 

CS derivatives/salts have found limited use as detergents (25), antistatic coatings for photographic film (26), oil drilling fluids (25), thickeners in food, cosmetics, and pharmaceuticals (27). They have been recommended for use as cation exchangers (28,29). Also, sulfated polysaccharides have recendy shown interesting antiviral activity (30). 

Molecular Interactions. Various polysaccharides readily associate with other substances, including bile acids and cholesterol, proteins, small organic molecules, inorganic salts, and ions. Anionic polysaccharides form salts and chelate complexes with cations some neutral polysaccharides form complexes with inorganic salts and some interactions are stmcture specific. Starch amylose and the linear branches of amylopectin form inclusion complexes with several classes of polar molecules, including fatty acids, glycerides, alcohols, esters, ketones, and iodine/iodide. The absorbed molecule occupies the cavity of the amylose helix, which has the capacity to expand somewhat to accommodate larger molecules. The starch—Hpid complex is important in food systems. Whether similar inclusion complexes can form with any of the dietary fiber components is not known. 

Sephadex. Other carbohydrate matrices such as Sephadex (based on dextran) have more uniform particle sizes. Their advantages over the celluloses include faster and more reproducible flow rates and they can be used directly without removal of fines . Sephadex, which can also be obtained in a variety of ion-exchange forms (see Table 15) consists of beads of a cross-linked dextran gel which swells in water and aqueous salt solutions. The smaller the bead size, the higher the resolution that is possible but the slower the flow rate. Typical applications of Sephadex gels are the fractionation of mixtures of polypeptides, proteins, nucleic acids, polysaccharides and for desalting solutions. 

The gel-like, bead nature of wet Sephadex enables small molecules such as inorganic salts to diffuse freely into it while, at the same time, protein molecules are unable to do so. Hence, passage through a Sephadex column can be used for complete removal of salts from protein solutions. Polysaccharides can be freed from monosaccharides and other small molecules because of their differential retardation. Similarly, amino acids can be separated from proteins and large peptides. 

Nondispersed Inhibited Systems. In these systems, the nondispersed character of the fluids is reinforced by some inhibition system, or combination of systems, such as (1) calcium ions, lime or gypsum (2) salt-sodium chloride or potassium chloride (3) polymers such as Polysaccharides, polyanionic cellulose, hydrolyzed polyacrylamide. 

Separations of polysaccharides by fractionation on a preparative scale were also examined. Stemming from earlier work in his laboratory on the isolation of acidic polysaccharides by precipitation as their insoluble Cetavlon salts, Stacey and coworkers showed that it was possible to fractionate neutral polysaccharides by selective precipitation with Cetavlon after the formation of borate complexes. 

Observations on the Properties of Cetyltrimethylammonium Salts of some Acidic Polysaccharides, ... 

Mutant YE-2 of Rhizobium meliloti excretes a mixture of soluble polysaccharides that include a complex succinoglycan having a branched octasaccharide repeat as well as a simple galactoglucan (22) having a linear disaccharide repeat.102 In contrast to the case of the succinoglycan, oriented fibers of the potassium salt of 22 have yielded good X-ray data and its three-dimensional structure has been established.39 The polymer forms a two-fold helix of pitch... 

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