Of neutral polysaccharides

Although the glycosidic bonds of uronic acid residues are usually more resistant to acid hydrolysis than those of neutral polysaccharides,218 these linkages in heparin are more readily cleavable then those between the hexosamine and the uronic acid residues. Disaccharides obtained by exhaustive hydrolysis of heparin with 0.5 MHC1 at 80° contained hexu-... 

The situation that exists in the case of the biosynthesis of neutral polysaccharide chains of streptococcal cell-wall is still very uncertain. In S. sanguis, assembly of the trisaccharide derivative (45, X = an unidentified, hydro-phobic group) from UDP-GlcNAc, dTDP-Rha, and UDP-Glc on an... 

Using distribution between chloroform and water, Jones and asso-ciates have separated an acetylated mixture of neutral polysaccharide, which dissolved in the chloroform, and an acidic polysaccharide, which formed an emulsion between the two phases. Such mixtures were shown by Scott < to be easily separated by precipitation of the acidic component with such quaternary ammonium salts as cetyltrimethylammonium (Cetavlon) or cetylpyridinium halides. Polysaccharides which differ in acidity can also be separated by this method, and, as the solubility of the precipitate increases with increasing ionic strength, the separation can also be done as... 

Kent and coworkers briefly reported the detection, after application of zone electrophoresis in barbiturate and other buffers, of a number of neutral polysaccharides, although no details of mobilities were noted. In a borate buffer at pH 8.0, amylopectin was observed to migrate toward the cathode and to be stained red with iodine, whereas amylose is stained blue and remains stationary. 

An interesting study of the behavior of a range of neutral polysaccharides on subjection to boundary electrophoresis in the presence of borate has been described by Northcote. ... 

The presence of accompanying polysaccharides Heparinoids usually contain some of the original polysaccharide, while commercial heparin, as shown by the presence of anthrone-reducing substance, also usually contains such material. The elevation of body temperature, leucocytosis and thrombocytosis associated with pyrogens, can be due to the presence of extremely minute amounts of certain polysaccharides. One should suspect reactions of this nature as being due to traces of neutral polysaccharides. 

Electrophoresis. —The use of the free boundary method, in which molecules migrate in solution under the influence of an applied electric field, has found limited application to polysaccharide solutions as a separation method. This applies even to acidic polysaccharides, such as plant gums and mucilages, bacterial polysaccharides, and mucopolysaccharides, which will migrate directly. Electrophoretic separation of neutral polysaccharides in alkali appears to be limited to a gross separation of neutral... 

A complete list of semi-synthetic heparinoids is outside the scope of this article. Products of sulfation of neutral polysaccharides include sulfates of starch, cellulose, - - xylan, dextran, " guaran, and synthetic polymers of o-glucose. A somewhat closer simulation of the structure of heparin was attempted by sulfating polysaccharides containing amino sugars or uronic acids or both, such as chitin and chitosan, " and the corresponding N-formyl, N-(car-boxymethyl), O-(carboxymethyl), and 5-carboxylated - deriva-... 

Carbon atoms of neutral polysaccharides may be converted into carboxyl groups by oxidation with dinitrogen tetraoxide, and the mechanism, at least for cellulose, possibly involves an intermonomeric contribution to the transition state by adjacent C-6 groups. Cellulose " " and ivory-nut mannan have been oxidized in this way, and, in both products, keto groups are formed at secondary carbon atoms in side reactions. Oxidation with dinitrogen tetraoxide has also been employed in the pro-... 

L. Hough, Periodate oxidation of neutral polysaccharides Oxidation to formaldehyde. Methods Carbohydr. Chem., 5 (1965) 370-377. 

Thus, the amount of bound water, Vo/c, can be estimated from at infinite dilution with the following assumptions (1) the solute is incompressible (3,=0), (2) the. compressibility of bound water is the same as that of ice (32=18xl0 cm /dyne) since the hydration of neutral polysaccharide would be mainly due to hydrogen bonds between water and OH groups of the polymer, and (3) v =V2. 

The above dependence on pH of the precipitation of acidic polyelectrolytes with cationic surfactant clearly affords means of separating mixtures of such polymers based on their acid strength. In an interesting development, it was shown (115) that the method can be applied to the separation of neutral polysaccharides by working at sufficiently high pH to ionize their hydroxyl groups. A more convenient method, however, to develop polyanionic character and hence precipitability with added cationic surfactants is to form the borate complex of the polysaccharide by simple addition of borate ion (116). 

If the polysaccharide is composed of uronic acid residues, it can be specifically precipitated by lowering the pH. Different pH values between 5 and 1 can be used to precipitate polysaccharides with different amounts and kinds of uronic acids [6]. Likewise, mixtures of neutral polysaccharides can. sometimes be precipitated by differential alcohol precipitation in which the polysaccharides have different water solubilities due to differences in their degrees of branching [7]. Saccharides with certain specific structures can be selectively separated by using lectins (see section 12.10). 

A number of authors have been interested in the adsorption of neutral polysaccharides (dextran and related polyglucosides), e.g., (Parfitt and Greenland, 1970a Olness and Clapp, 1973, 1975). The adsorption of neutral polysaccharides onto kaolinite as well as onto montmorillonite has been studied (Chenu et al, 1987). 

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