Polysaccharide solubilization

Limitations in possibility of chemical modifications of starch result from steric hindrance of reaction sites, solubility, viscosity of reaction medium, and susceptibility to side reactions among them, depolymerization almost always accompanies intended modification. As a rule, polysaccharides are soluble, although frequently only sparingly, in water and dimethyl sulfoxide. Polysaccharides solubilize on xanthation, i.e., on reaction with CS2 in alkaline medium, to form syrups of xanthates. On acidification polysaccharides could be recovered. Such procedure was utilized for several decades for production of artificial silk from cellulose. 

Phenol/aceticth acid/water. PAW desorbs residual intracellular proteins, some starch, adsorbed deoxycholate, lipids, and pigments from the SDC-residue. The amount of cell wall polysaccharides solubilized is approximately 1% of the dry weight of the purified CWM for potatoes, runner beans, wheat bran, and oats. 

Detergent Methods. The neutral detergent fiber (NDF) and acid detergent fiber (ADF) methods (2), later modified for human foods (13), measure total insoluble plant cell wall material (NDF) and the cellulose—lignin complex (ADF). The easily solubilized pectins and some associated polysaccharides, galactomaimans of legume seeds, various plant gums, and seaweed polysaccharides are extracted away from the NDF. They caimot be recovered easily from the extract, and therefore the soluble fiber fraction is lost. 

Neisseria meningitidis Types A and Ct, Cultures of N. meningitidis of serotypes A and C 1 Precipitation with hexadecyl-trimethyammonium bromide 2 Solubilization and purification 3 Blending 4 Freeze-drying Estimation of capsular polysaccharide content ... 

Other polysaccharides of primary cell walls.-A complex mixture of enzymes including endopolygalacturonase, pectin methylesterase, and/or pectin lyase solubilizes a mixture of polysaccharides from the primary cell walls of fruits [57-64]. Food scientists have referred for some 15 years to this mixture of polysaccharides as the hairy region to describe the highly branched character of the polysaccharides in the fraction and to emphasize the contrast to unbranched homogalacturonan. The recent discovery of rhamnogalacturonan hydrolase [65,66], which selectively cleaves the backbone of RG-I, led to the realization that the hairy... 

This paper begins with a brief description of pectin structure and an overview of the general mechanism of cell wall polysaccharide biosynthesis. This is followed by a summary of previous research on PGA-GalAT and a description of a facile method to synthesize UDP-[ Cj-galacturonic acid. Finally, the paper ends with a summary of our work on the identificadon, partial characterization, and initial solubilization of the homogalacturonan biosynthetic enzyme PGA-GalAT. 

Polysaccharide solubility in aqueous solutions usually is dependent on polymer size and its allied three-dimensional structure. Even water-insoluble carbohydrates may be solubilized by controlled hydrolysis of o-glycosidic linkages to create smaller polysaccharide molecules. Thus, cellulose may be solubilized by heating in an alkaline solution until the polymers are broken up sufficiently to reduce their average molecular weight. Many such soluble forms of common polysaccharides are available commercially. 

The solubilization of polysaccharides such as chitin and cellulose apparently results from the disruption of strong intermolecular hydrogen bonding by the lithium ions in the N,N-dimethylacetamide. Interestingly under identical conditions, cations such as Na+, K" ", Cs+, Ca+, Ba" "" " showed no tendency to solvate the above polymers. Additionally, some specificity was shown for the anion type, i.e., Br-, Cl-, and NO3-. These trends are under further investigation. 

Fig. 10.11 Carbon nanotubes have an absorption peak between 1,000 and 1,500 nm as defined by line (a) in this figure. A decrease in absorption is seen in lines (b) and (c) due to wrapping of polysaccharides around the tubes for water solubilization (Reprinted from Casey et al., 2005. With permission from Elsevier)...

As with fullerenes, carbon nanotubes are also hydrophobic and must be made soluble for suspension in aqueous media. Nanotubes are commonly functionalized to make them water soluble although they can also be non-covalently wrapped with polymers, polysaccharides, surfactants, and DNA to aid in solubilization (Casey et al., 2005 Kam et al., 2005 Sinani et al., 2005 Torti et al., 2007). Functionalization usually begins by formation of carboxylic acid groups on the exterior of the nanotubes by oxidative treatments such as sonication in acids, followed by secondary chemical reactions to attach functional molecules to the carboxyl groups. For example, polyethylene glycol has been attached to SWNT to aid in solubility (Zhao et al., 2005). DNA has also been added onto SWNT for efficient delivery into cells (Kam et al., 2005). 

Abiontic, involving free extracellular enzymes or solubilizing agents, enzymes bound to soil surfaces, enzymes within dead or non-proliferating cells, or enzymes associated with dead cell fragments. Extracellular enzymes are important in the initial stages of organic matter oxidation, in which polysaccharides and proteins are hydrolysed to soluble compounds that can be absorbed by microbial cells and further oxidized in biotic processes. 

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