Acetylation, of polysaccharides

The degree of influence of the acetylation of polysaccharides on the sorption of peroxidases... 

In contrast to the broad variety of applications of 1 - 4 and 1 3 linked glucans after reaction with (C2 to C4) carboxylic acid anhydrides and chlorides [159], the use of dextran esters of short chain aliphatic acids such as acetates or propionates is rather limited. According to the present knowledge, the commonly applied acetylation of polysaccharides with the acetic acid anhydrides or acetyl chlorides in the presence of triethylamine or pyridine as base does not lead to pure and soluble dextran acetate with significant DS values. In contrast, dextran propionates [160] and butyrates [161] can be... 

The procedure employed for hydrolysis and acetylation of polysaccharides is based on the method of Jones and Albersheim [118], Samples (2-5 mg) are hydrolyzed as follows The polysaccharide samples are dissolved in 1 M NH4OH (1 ml) containing 6 mg of NaBELj and kept at room temperature for 1-3 h. The samples are acidified with acetic acid until no bubbles are produced and 1 ml of methanol is added and then evaporated to dryness at 40 °C with N2 gas. Acetic acid and methanol mixture (10%, w/v) are then added to samples and evaporated tmder N2 gas. The samples and standards (which are usually fiiictose, glucose, xylose, arbinose, galoctose, ribose, rhamnose, and fucose) were treated with acetic anhydride in sealed test tubes at 121 °C for 3 h. After completion of the reaction, the samples were extracted with toluene followed by chloroform and washed with water. The chloroform layer was separated, evaporated, and redissolved in methanol prior to GC analysis. 

Trifluoroacetates of carbohydrates have been prepared 80), These substances, which are quite sensitive to hydrolysis, show some promise as intermediates in synthetic work. Trifluoroacetic anhydride is a powerful impelling reagent for the acetylation of polysaccharides 80),... 

At3g06550 - are deficient in wall-bound acetate. It would be interesting to test their resistance, lignin depositions and other physiological parameters under the influence of pathogens. It may be that these experiments will make clear the role of polysaccharide acetylation. 

Among the spectroscopic methods applicable to polysaccharides, u.v. spectrophotometry is of little value for characterizing heparin, whose main, electronic chromophore (the C02 group) displays a band at 220 nm, that is, in a region where all glycosaminoglycans absorb (also through their N-acetyl chromophores), and where minor proportions of unsaturated or aromatic contaminants cause serious interference.77 With pure heparin preparations, the carboxylate chromophore is most useful for chiroptical measurements, and a semi-quantitative evaluation of the extent of N-acetylation of 2-amino-2-deoxy-D-glucose residues is also possible.78... 

The first practical CSP derived from polysaccharides is cellulose triacetate (21, Figure 3.10) prepared by Hesse and Hagel in 1973.94,95 Since this derivative was prepared by the heterogeneous acetylation of native microcrystalline cellulose (Avicel) in benzene, it has been postulated that its structure is closely related to that of native cellulose (form I). This has been called microcrystalline cellulose triacetate (CTA-I). CTA-I shows characteristic chiral... 

C-N.m.r.-spectroscopic analyses have been successfully made for determination of the position of O-acetyl groups in sialic acids, using the 9-O-acetyl- and 4,9-di-O-acetyl derivatives of Neu-/3-Me methyl ester as model compounds,9 1 or in the sialic acid residues of polysaccharide antigens ofN. meningitidis.166 1... 

In the literature, there are several examples of partial hydrolysis of polysaccharides or glycoconjugates containing 2-amino-2-deoxyhex-ose residues. One example is the hydrolysis of carboxyl-reduced, N deacetylated chondroitin, with the formation of 4-0-(2-amino-2-deoxy-/3-D-galactopyranosyl)-D-glucose.51 Another is the isolation of 6-0-(2-amino-2-deoxy-/8-D-galactopyranosyl)-D-galactose after N-de-acetylation and partial hydrolysis of the pentasaccharide (19) obtained... 

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