Polysaccharides overview

Polysaccharides are ubiquitous in nature. They can be classified into three separate groups, based on their different functions. Structural polysaccharides provide mechanical stability to cells, organs, and organisms. Waterbinding polysaccharides are strongly hydrated and prevent cells and tissues from drying out. Finally, reserve polysaccharides serve as carbohydrate stores that release monosaccharides as required. Due to their polymeric nature, reserve carbohydrates are osmotically less active, and they can therefore be stored in large quantities within the cell. 

Polysaccharides that are formed from only one type of monosaccharide are called homo-glycans, while those formed from different sugar constituents are called heteroglycans. Both forms can exist as either linear or branched chains. 

The table gives an overview of the composition and make-up both of the glycans mentioned above and of several more. 

In addition to murein, bacterial polysaccharides include dextrans—glucose polymers that are mostly al 6-linked and al 3-branched. In water, dextrans form viscous slimes or gels that are used for chromatographic separation of macromolecules after chemical treatment (see p.78). Dextrans are also used as components of blood plasma substitutes (plasma expanders) and foodstuffs. 

The starches, the most important vegetable reserve carbohydrate and polysaccharides from plant cell walls, are discussed in greater detail on the following page. Inulin, a fructose polymer, is used as a starch substitute in diabetics dietary products (see p.l60). In addition, it serves as a test substance for measuring renal clearance (see p.322). 

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Table 1 An overview of the pectic type structures and bioactivities of the polysaccharides presented in this review...

This essay was written in an attempt to explain our overview of primary cell walls and to reach consensus on the nomenclature of primary cell wall polysaccharides. We present evidence supporting the hypothesis that cellulose, xyloglucan, arabinoxylan, homogalacturonan, RG-I, and RG-II are the six polysaccharides common to all primary cell walls of higher plants. In many cells, these six polysaccharides account for all or nearly all of the primary wall polysaccharides. Like the physically interacting proteins that constitute the electron transport machinery of mitochondria, the structures of the six patently ubiquitous polysaccharides of primary cell walls have been conserved during evolution. Indeed, we hypothesize that the common set of six structural polysaccharides of primary cell walls have been structurally... 

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. 

Partially hydrolyzed polyacrylamides, carboxymethylcellulose, polysaccharides, and acrylamido methylpropane sulfonate have been screened to investigate the performance of aluminum citrate as a chelate-type crosslinker. An overview of the performance of 18 different polymers has been presented in the literature [1646]. The performance of the colloidal dispersion gels depends strongly on the type and the quality of the polymer used. The gels were mixed with the polymers at two polymer concentrations, at three polymer-to-aluminum ratios, and in different concentrations of potassium chloride. The gels were quantitatively tested 1,7, 14, and 28 days after preparation. 

Here we report an overview of the different heterogeneously-catalyzed pathways designed for the selective conversion of carbohydrates. On the basis of these results, we shall try to determine the key parameters allowing a better control of the reaction selectivity. Water being commonly used as solvent in carbohydrate chemistry, we will also discuss the stability of solid catalysts in the aqueous phase. In this review, heterogeneously-catalyzed hydrolysis, dehydration, oxidation, esterification, and etherification of monosaccharides and polysaccharides are reported. 

Kobayashi, H., K. Matsunaga, Y. and Oguchi. 1995. Antimetastatic effects of PSK (krestin), a protein bound polysaccharide obtained from basidiomycetes an overview. Cancer Epidemiol. Biomarkers Prev. 4 275-281. 

Berteau, O. and Mulloy, B. (2003). Sulfated fucans, fresh perspectives Structures, functions, and biological properties of sulfated fucans and an overview of enzymes active toward this class of polysaccharide. Glycobiology 13, 29R-40R. 

Walstra, P. Smulders, I., Making Emulsions and Foams An Overview in Food Colloids Proteins, Lipids and Polysaccharides, Bergen-stahl, E. Dickinson, E. (Eds.), Royal Society of Chemistry Cambridge, 1997, pp. 367-381. 

Sect. 2 below summarizes some of the important structures containing pyruvic acid acetals. The structural diversity, methods for structure elucidation, biosynthesis and biological function of these oligo- and polysaccharides will be briefly discussed. Sect. 3 gives an overview of the synthetic methods for the stereoselective preparation of pyruvated building blocks for oligosaccharide synthesis. Here, special attention is paid to pyruvated glycosyl donors, and their application to the synthesis of selected structures is presented in Sect. 4. 

Over 70 pyruvated saccharide structures from natural sources are known today, but only a few representative examples are summarized here. The choice has been determined by the synthesis of pyruvated saccharides as discussed in the Sections below. Reference [2] gives a more concise overview of the great structural diversity found among naturally occurring pyruvated oligo- and polysaccharides. 

A comprehensive technical overview on the epidemiology and prevention of pneumococcal disease, including the use of polysaccharide and conjugate vaccines has been provided (11). 

This chapter will give you an overview of recent approaches for drug development, focusing on the function and roles of carbohydrates. O Section 2 will outline the biochemical functions of polysaccharide (neutral polysaccharide, chitin and chitosan, glycosaminoglycan, and synthetic polysaccharides) and glycopolymers and the perspectives of their medicinal/medical use. O Section 3 will outline recent biopharmaceutical research and development, utilizing... 

Fig. 1 SEM photographs of broken surface olives, adapted from Mafra et al. [7] (a) details of green olive thin-walled parenchyma cells tightly packed (cell adhesion) (b) overview, showing tissues fracturing through the cells of epicarp and mesocarp with no cell separation at the middle lamella (c) details of the black olive parenchyma showing cell separation (by the dissolution of pectic polysaccharides) (d) overview, showing a smaller region of broken cells in comparison to (b), involving only the epicarp and the first layers of the mesocarp...

Polysaccharides are an abundant source of raw materials that are interesting due to the biodegradable, biocompatible and renewable character. Saccharides are expected to play an increasingly bigger role as raw material in the future and to replace petrol-based materials. Already, polysaccharides find their way into many disparate fields of industry a short overview is given in Table 9.1. 

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