Polysaccharides classes

Xylan has the general properties of insolubility in water, solubility in alkaline solutions, ease of acid hydrolysis, high negative optical rotation, and non-reducing action toward Fehling s solution. It can be placed in three general polysaccharide classes (1) pentosan, (2) glycan, and (3) hemicellulose. It is classed as a pentosan because it is principally a polymer of a pentose. It is by far the most abundant pentosan. 

For the Eq. (11) verification the data of Ref. [17] for biopolymer of polysaccharides class (rodexman) were used, for which Maik-Kuhn-Hou-wink has a look like ... 

Carrageenan. The term carrageenan [19000-07-1] is the generic description for a complex mixture of sulfated polysaccharides that are extracted from certain genera and species of the class Fhodophjceae red seaweed. 

Plant stmctural material is the polysaccharide cellulose, which is a linear P (1 — 4) linked polymer. Some stmctural polysaccharides iacorporate nitrogen iato thek molecular stmcture an example is chitin, the material which comprises the hard exoskeletons of kisects and cmstaceans. Chitki is a cellulose derivative whereki the OH at C-2 is replaced by an acetylated amino group (—NHCOCH ). Microbial polysaccharides, of which the capsular or extracellular (exopolysaccharides) are probably the most important class, show more diversity both ki monomer units and the nature of thek linkages. 

Since polysaccharides are the most abundant of the carbohydrates, it is not surprising that they comprise the greatest part of industrial utiliza tion (9,22). Most of the low molecular weight carbohydrates of commerce are produced by depolymerization of starch. Polysaccharide materials of commerce can be thought of as falling into three classes cellulose, a water-insoluble material starches, which are not water-soluble until cooked and water-soluble gums. 

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. 

The structural polysaccharides have properties that are dramatically different from those of the storage polysaccharides, even though the compositions of these two classes are similar. The structural polysaccharide cellulose is the most... 

We have already seen several cases in which the synthesis of a class of biomolecules is conducted differently from degradation (glycolysis versus gluconeoge-nesis and glycogen or starch breakdown versus polysaccharide synthesis, for... 

This class of polysaccharide was well known in sugar refineries as the causative agent of ropiness it was formed from cane or beet sugar by bacteria of the Leuconostoc genus. Over many years, numerous papers were published, mainly with E. J. Bourne [Adv. Carbohydr. Chem. Biochem., 34 (1977) 1-22] and S. A. Barker as co-authors, describing the isolation, purification, properties, and structural features of dextrans. 

Polysaccharides composed of only one kind of monosaccharide are described as homopolysaccharides (homoglycans). Similarly, if two or more different kinds of monomeric unit are present, the class name heteropolysaccharide (heteroglycan) may be used. (See 2-Carb-39.)... 

Based on the current stage of knowledge, hemicelluloses can be divided into four general classes of structurally different cell-wall polysaccharide types, i.e.,... 

Hence polysaccharides have been viewed as a potential renewable source of nanosized reinforcement. Being naturally found in a semicrystalline state, aqueous acids can be employed to hydrolyze the amorphous sections of the polymer. As a result the crystalline sections of these polysaccharides are released, resulting in individual monocrystalline nanoparticles [13]. The concept of reinforced polymer materials with polysaccharide nanofillers has known rapid advances leading to development of a new class of materials called Bionanocomposites, which successfully integrates the two concepts of biocomposites and nanometer sized materials. The first part of the chapter deals with the synthesis of polysaccharide nanoparticles and their performance as reinforcing agents in bionanocomposites. 

Shortly afterwards, Westphal, Liideritz, and their coworkers using the newly developed method of paper chromatography, found a new class of sugars in lipopolysaccharides (LPS) from Gram-negative bacteria, and identified them as 3,6-dideoxyhexoses. This work is summarized in Ref. 4. These discoveries initiated more-systematic investigations of hydrolyzates from bacterial polysaccharides, and a number of new monosaccharides were completely or partially identified. This development has been summarized by Ashwell and Hickman. ... 

Before 1983, branched-chain sugars had not been found in bacterial polysaccharides, but there are now five examples belonging to this class. The LPS from Coxiella burned phase I contains both 6-deoxy-3-C-methyl-L-gulose (L-virenose) as pyranoside (12) and 3-C-(hydroxymethyl)-L-lyxose as furan-oside (13). Another 6-deoxy-3-C-methylhexose, having the manno configuration, is a component of the Nitrobacter hamburgiensis 0-antigen. ... 

A number of 3-deoxyglyculosonic acids have been identified. These substances are acid-labile and are decomposed on hydrolysis with acid under normal conditions, and have therefore often escaped detection in the past. The simplest member of this class, 3-deoxy-L- /yccro-pentulosonic acid (26), occurs as terminal groups in the capsular polysaccharide from Klebsiella K38. Pyranosidic 3-deoxy-D-r/ircohexulosonic acid is a component of the Vibrio parahaemolyticus 07 and 012 LPS. The same acid, as )3-py-ranosyl groups, is also present in the extracellular polysaccharide from Azo-tobacter vinelandii. ... 

A 3-deoxyheptulosaric acid has been found in the LPS from Acineto-bacter calcoaceticus NCTC 10305. Another acid of this class, 3-deoxy-o-/yxo-heptulosaric acid ° (30), is a component of a plant polysaccharide. One 4-deoxyhexulosonic acid, of unknown configuration, is known and is a component of the E. coli K3 capsular polysaccharide. "... 

There are solitary examples of other alditol phosphates as components of this class of polymers. Arabinitol 1-phosphate is part of the S. pneumoniae type 17F capsular polysaccharide. o-Glucitol 6-phosphate is a component of the group-specific polysaccharide from group B Streptococcus, which has a most unusual, ramified structure. In a polysaccharide from Nocardia... 

Some antigens, such as type 3 pneumococcal polysaccharide, EPS and other polymeric substances such as dextrans (poly-D-glucose) and levan (poly-D-fructose) can induce antibody synthesis without the assistance of TH cells. These are known as T-independent (Ti) antigens. Only one class of immunoglobulin (IgM) is synthesized and there is a weak memory response. 

Plant cell walls provide the obvious functions of stmctural support and integrity and can vary tremendously in size, shape, composition and stmcture depending on cell type, age and function within the plant body. Despite this diversity, plant cell walls are composed of only three major classes of polysaccharides cellulose, hemicellulose and pectins. Pectins, or polyuronides, are imbedded throughout the cell wall matrix and are particularly abundant in the middle lamella region. Pectins generally account for 10-30% of the cell wall dry weight and... 

Rha, Ara and Gal are the neutral sugar components from all the fractions. Xyl is not present in Fla and is significantly present in the hemicellulose fractions, indicating that this monosaccharide is component of hemicellulosic polymers. Chemical composition of the water fractions were determined (Table V). High protein contents and the presence of O-acetyl-groups were observed in four aqueous fractions. Neutral sugar and uronic acid composition points to inclusion of these polymers in the class of pectic polysaccharides. 

The FTIR spectra of citrus pectin and wheat straw XRPP (Figure 1) appeared to be similar. Both of the spectra have absorptions at 1740, 1608, 1430, 1360, 1244, 1080, 1060, 1035, 890 and 524 cm. The pectic substances belong to a class of carboxy poly saccharides which differ from neutral polysaccharides, with an intense band in the region 1740 cm l (for salts 1608 cm ) related to vibrations of the carboxyl group... 

It would be easier to describe those classes of compounds not normally separated by RPLC than to catalogue the applications to which RPLC has been turned. Applications for reversed phase can be found in virtually every area of analysis and are reviewed regularly in the journal Analytical Chemistry. RPLC has not been in general use for the analysis of inorganic ions, which are readily separated by ion exchange chromatography polysaccharides, which tend to be too hydrophilic to separate by RPLC polynucleotides, which tend to adsorb irreversibly to the reversed phase packing and compounds which are so hydrophobic that reversed phase offers little selectivity. 

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