Dextran chemical structure

Of great interest is the possible determination of structures of pneumococcus polysaccharides by comparison with a known chemical structure such as dextran. The extent of the cross-precipitation reactions43 of dextran with various pneumococcus antisera indicates the closeness of the relationships between the structures of dextran and of the various pneumococcus polysaccharides. 

The chemical structures of five dextrans were partially determined by methylation, and found to be branched molecules having the following types of substitution (a) 6-0 and 3,6-di-O, (b) 6-0, 3-0, and 3,6-di-O, (c) 6-0,3,6-di-O, and 2,3-di-O, (d) 6-0, 4-0, and 3,4-di-O, and (e) 6-0 and 2,3-di-O. At 27° and pH 7 (external, Me4Si standard), the 13C shifts ofO-substituted, non-anomeric carbon atoms were C-2 (76.5), C-3 (81.6), and C-4 (79.5). The C-l resonances were also recorded, and may be used for reference purposes. Some variation of chemical shifts, relative to each other, was observed with changing temperature. (The work serves to emphasize the importance of accurately measuring the temperature of the solution when determining chemical shifts.102)... 

The emulsifying properties of these polymeric surfactants demonstrate that the chemical structure influences the kinetic behaviour of interfacial tension reduction. An increase of sulfopropyl moieties reduces the interfacial tension slower while an increase in 2-hydroxy-3-phenoxy propyl moieties reduces the interfacial tension faster. The ionic strength of the emulsion appears to increase the rate of tension reduction. The average droplet size of oil-in-water emulsions in presence of previously dissolved 2-hydroxy-3-phenoxy propyl sulfopropyl dextran is around 180 nm immediately after preparation and increases with time. The presence of ionic moieties appeared to facilitate emulsification at low polymer concentrations due to electrostatic repulsions between the oil droplets [229]. 

Figure 1. Chemical structure ofpullulan containing maltotriose units and of dextran containing a-1,6 linked anhydroglucose units with a-1,3 branch points.

Fig. 16 a Chemical structures of dextran immobilized on a QCM plate through an avidin-biotin linkage, and b hydrolysis schemes of the dextran on the QCM plate catalyzed by isomalto-dextranase (wUd type, D198N, D266N, and D313N) and kinetic parameters obtained in this work... 

Fig. 34.6 Chemical structure of (A) anionic and (B) cationic mitomycin C-dextran conjugates.

To date the ehemical struetures of dextrans synthesized by Leuconostoc species have been the most thoroughly investigated, although an increasing interest is being evinced in the chemical structures of dextrans produced by streptococci, because of their implication in the development of oral disease (see p. 433). Serological tests - have indicated that Lactobacilli convert sucrose into dextrans few confirmatory structural studies have, however, been reported. - ... 

As indicated earlier in the present Section, dextrans vary greatly in chemical structure. These differences are reflected in the types of gels formed by different dextrans the gel may have prc rties approaching those of a sol or a syneresed gel. 

The water-soluble dextrans produced by a strain of Streptococcus mutans have been fractionated by gel chromatography into three types having different molecular sizes, chemical structures, and serological properties. One of the fractions and a water-insoluble dextran, also synthesized by the organism, appear to represent different physical states of an inherently identical D-glucan. 

Pullulan is a neutral glucan (like amylose, dextran, cellulose), with a chemical structure more or less depending on carbon source, producing microorganisms (different strains of Aureobasidium pullulans) and the fermentation conditions. ... 

FIGURE 53.3 Chemical structure of dextran, where m and n stand for whole numbers signifying the number of monomers present in the polymeric form. 

The most commonly used cationic polysaccharides in gene delivery, such as chitosan, CD, dextran, carbohydrate copolymers, etc., are discussed exhaustively in this section. The chemical structures of the listed pol3miers are given in Figure 9.2. 

Figure 11.1 Chemical structures of (A) chitosan, (B) dextran, (C) a-CD-PEO polyrotaxane, (D) polyethylenimine and (E) polj L-lysine).

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