Dextran, acetate

Recently, Brich and coworkers (40) reported the synthesis of lactide/glycolide polymers branched with different polyols. Polyvinyl-alcohol and dextran acetate were used to afford polymers exhibiting degradation profiles significantly different from that of linear poly-lactides. The biphasic release profile often observed with the linear polyesters was smoothened somewhat to a monophasic profile. Further, the overall degradation rate is accelerated. It was speculated that these polymers can potentially afford more uniform drug release kinetics. This potential has not yet been fully demonstrated. 

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... 

Deuterium-labelled glycogen, III, 246 Dextran, 2,3-dimethyl-D-gIucose from methylated, V, 161 Dextran acetate, II, 218 Dextran beers, IV, 333 Dextran esters, II, 218 Dextran ethers, II, 218 Dextran triacetate, II, 210, 212 Dextran tribenzoate, II, 210, 212 Dextrans... 

Reaction of carbohydrate with quaternary ammonium hydroxide Dextran acetate Ester derivative of dextran Dextran ether esters Mixed benzyl and butyl ethers... 

Dextran acetate Dextran benzyl ether Dextran benzyl ether Acetone-soluble benzyldextran Dextran ether Benzyl ether of dextran Lacquer with benzyl ether of dextran -etherify or esterify in me-Dextran dium benzyl -soft, rubbery ether ether -from separated dextran... 

The preparations of dextran, and certain ethers and esters of dextran have been the subjects of about fifteen recent patents. The dextran (of L. mesenteroides or dextraniczim) may be precipitated first from the culture by the addition of ethanol or acetone, or the culture itself may be treated directly with the appropriate halide and sodium hydroxide in either a single stage or a two-stage procedure. The benzyl ether of dextran, formed by the reaction of dextran with benzyl chloride and sodium hydroxide at 75-185° for three to ten hours, is soluble in acetone and other solvents, and may be used in lacquers. Mixed ether and ester derivatives of dextran, e. g., benzyl and phthalate or butyl and benzoate, have been used for forming films, coatings or molded products. A preparation of dextran acetate has also been patented. ... 

To 200 mL acetone was added 4.35 g dextran acetate A, which was methylated with NaOH (30%, 300 mL) and 110 mL dimethyl sulfate over a period of 3 h. The bath temperature was kept at 25°C for the first 2 h, and at 55°C for 1 h it was then raised to 100°C for 0.5 h. The excess alkali was neutralized, and the reaction mixture was dialyzed. The dialyzed material was concentrated to a small volume, and the methylation was repeated four times in the same way with the bath temperature maintained at 55°C acetone was added in to keep the product in solution. After the fifth methylation the product was extracted with chloroform, and the extract was washed with dilute acetic acid and water and concentrated to give 3.39 g syrup. The syrupy product was methylated with 50 mL methyl iodide (50 mL) and 6 g silver oxide, added in 12 portions under continual stirring and refluxing for 22 h. The product was extracted with chloroform, and after the removal of solvent it was remethylated four times in the same manner to give 1.96 g product with a methoxyl content of 44.93%. On fractionation of the methylated dextran from chloroform with petroleum ether, 90% of the product precipitated at 90-92% petroleum ether, a second... 

Marchessault, Sarko etal. [10, 11] have investigated the chiroptical properties of amylose xanthates extensively. The CD of amylose triacetate in trifluoroethanol shows, apart from the expected acetyl z -> tt transition at about 230 nm, an additional shortwave peak. This is again explained by assuming a helical conformation of the amylose chain. Dextran acetates and mycodextran acetates, on the other hand, do not show conformational effects. The considerable changes in the CD spectra of amylose triacetate films when the temperature increases from 30 to 190°C are particularly remarkable. As X-ray diffraction analysis shows, these effects are connected with crystallisation processes and transformation during annealing. 

Dextran [9004-54-0] Mf 6,000-220,000. Solutions keeps indefinitely at room temperature if 0.2mL of Roccal (10% alkyldimethylbenzylammonium chloride) or 2mg phenyl mercuric acetate are added per lOOmL solution. [Scott and Melvin Anal Biochem 25 1656 7955.]... 

Cationic samples can be adsorbed on the resin by electrostatic interaction. If the polymer is strongly cationic, a fairly high salt concentration is required to prevent ionic interactions. Figure 4.18 demonstrates the effect of increasing sodium nitrate concentration on peak shapes for a cationic polymer, DEAE-dextran. A mobile phase of 0.5 M acetic acid with 0.3 M Na2S04 can also be used. 

Cationic hydrophilic Glycol chitosan, DEAE-dextran, poly(ethyleneimine), poly(trimethylaminoethyl methacrylate) iodide salt 0.5 M acetic acid with 0.3 M NaiSO, or 0.8 M NaNO.,... 

The GBR resin works well for nonionic and certain ionic polymers such as various native and derivatized starches, including sodium carboxymethylcel-lulose, methylcellulose, dextrans, carrageenans, hydroxypropyl methylcellu-lose, cellulose sulfate, and pullulans. GBR columns can be used in virtually any solvent or mixture of solvents from hexane to 1 M NaOH as long as they are miscible. Using sulfonated PDVB gels, mixtures of methanol and 0.1 M Na acetate will run many polar ionic-type polymers such as poly-2-acrylamido-2-methyl-l-propanesulfonic acid, polystyrene sulfonic acids, and poly aniline/ polystyrene sulfonic acid. Sulfonated columns can also be used with water glacial acetic acid mixtures, typically 90/10 (v/v). Polyacrylic acids run well on sulfonated gels in 0.2 M NaAc, pH 7.75. 

PGIP, purified fi om P.vulgaris hypocotyls [11], was immobilized to the sensor ch via amine coupling. A continuous flow of HBS buffer (5 pl/min) was mantained over the sensor surface. The carboxylated dextran matrix of the sensor surface was first activated by a 6-min injection of a mixture of N-hydroxy-succinimide and N-ethyl-N - (3-diethylaminopropyl) carbodiimide, followed by a 7-min injection of PGIP (lOng/pl in 10 mM acetate, pH 5.0). Hie immobilization procedure was con leted by a 7-min injection of 1 M ethanolamine hydrochloride to block the remaining ester groups. 

The most active extracts were obtained8 from L. mesenteroides cultures containing sucrose extracts prepared from L. mesenteroides organisms repeatedly transferred through D-glucose broth were of low potency.48 Active extracts in dilutions of 1 2 or 1 4 produced dextran in 5% sucrose solutions after one to two hours at 23°, and at pH 5.6 with acetate buffer demonstrable amounts of dextran were produced after twenty days with 1/10,000 dilution of the extract. Optimal yields of dextran were less than 5% based on sucrose. Small concentrations of dextran were detected by means of precipitin titrations with pneumococcus antisera Types II or XX (see page 215). 

Another potentially important fermentation is that producing butyric acid. The process is used industrially on only a small scale at present and details have not been disclosed. Many derivatives of butyric acid are used industrially the benzyl, methyl, octyl and terpenyl esters are used in the perfumery and essence trade and amyl butyrate, bornyl and isobornyl butyrates have been described as plasticizers for cellulose esters. Moreover vinyl butyrate is a possible ingredient of polymerizable materials. The mixed acetic and butyric acid esters of polysaccharides are also coming into favor. Cellulose acetate butyrate is marketed as an ingredient of lacquer and is less inflammable than the pure acetate. Dextran (see below) acetate butyrate may have similar uses. 

A good separation of L-rhamnose, 2-acetamido-2-deoxy-D-glucose, D-glucose, and 2-amino-2-deoxy-D-glucose, eluted in that order, was obtained by Zeleznick80 on a small column packed with the highly cross-linked, dextran gel Sephadex G-25, with 62 15 25 (v/v) butyl alcohol-M acetic acid-water as the eluant however, the gel functioned more as a support for partition chromatography than as a molecular sieve. 

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