Dextrans epichlorohydrin cross-linked dextran

Figure 7.1. Structure of epichlorohydrin cross-linked B-512F dextran. 

Washabaugh and Collins published a very interesting study on the retention of various salts (and also neutral molecules) in Sephadex G-10 columns. This material consists of epichlorohydrin cross-linked dextran in beaded form. Solutes with a weight smaller than 700 Dalton can penetrate the beads resulting in a slower elution than that of molecules with a higher molecular weight. 

Support materials for low-pressure affinity chromatography include agarose (cross-linked with epichlorohydrin), cellulose, dextran, silica, and polyacrylamide 62 in HPLC a rigid, highly porous, hydrophilic polymer is typically used. Large pore sizes are necessary, as either the analyte or the affinity ligand are macromolecules. To provide unhindered access of... 

The soluble linear dextran chains are cross-linked with epichlorohydrin in alkaline solution to yield a three-dimensional gel, which solidifies exothermically. The commercially available dextran gels (Sephadex) are very stable to chemical attack and can be heated up to 110°C in an autoclave for 40 min without impairment of properties. The gels swell to some extent in ethanol, ethylene glycol, formamide, A,A-dimethylformamide (DMF), and dimethylsuKoxide (DMSO). 

These bacterial polysaccharides have been considered to be slimes they are often in reality loose capsules that are produced extracellularly by the bacteria. It was found that low molecular weight L. mesenteroides NRRL B-512F dextran could be used as a blood plasma extender and was produced on a relatively large scale during the cold war , but also found uses as a gel-filtration material when cross-linked by epichlorohydrin to give a family of cross-linked dextrans [41]. 

The trade names of the stationary phase media represent particular polymers formed under well-controlled conditions. Sephadex consists of dextran, cross-linked with epichlorohydrin in alkaline solution. Sephacryl is an allyl dextran, cross-linked with iV.iV -methylenebislacrylamide). Sepharose is a beaded form of agarose gel, where aggregates of the polysaccharide chains are formed. 

Sephadex is a cross-linked dextran polysaccharide, which is prepared by reacting dextran with epichlorohydrin. It is available in several different grades depending on the degree of cross-linking. These different grades of Sephadex allow one to carry out molecular size fractionation experiments over a wide range of molecular sizes. 

Sephadex. Trademark name for a chromatographic gel used in gel permeation chromatography which is composed of an extensively cross-linked gel derived from dextran and epichlorohydrin. 

Sephadex ion exchangers are suitable for separation of large biological molecules. These are prepared from the polysaccharide dextran cross-linked by reaction with epichlorohydrin, followed by the introduction of the desired functional groups on the fiber and pore surfaces [21]. 

Gel permeation chromatography (GPC), sometimes called gel filtration or size exclusion, uses material with a controlled pore size stationary phase. The discovery by Flodin and Porath in 1958 of a suitable cross-linked gel formed by the reaction of dextran with epichlorohydrin provided the breakthrough [44,45]. Subsequently, the commercial development of dextran and similar hydrophilic gels (e.g. agar), ensured rapid acceptance and application... 

Chloro-2-hydroxypropyl derivatives of such polysaccharides as cellulose and cross-linked dextran (Sephadex) may be prepared by treatment with epichlorohydrin in boron trifluoride etherate. These 3-chloro-2-hydroxypropylated polysaccharides may, in turn, react with ammonia, or primary, secondary, or tertiary amines, and the resultant derivatives of cellulose and Sephadex LH-20, particularly an 0-[3-(di-butylamino)-2-hydroxypropyl] derivative of the latter, are useful anion-exchangers. In the amination procedure, between 50 and 100% of the chlorine atoms are utilized, except in the reaction with tertiary... 

Sephadex G-10 Dextran cross-linked with epichlorohydrin 2-10 1-120 <0.7 5... 

The reaction of dextran with epichlorohydrin results in a cross-linked gelatinous product that is used as a molecular sieve for separation and purification of biochemically important macromolecules like proteins, polysaccharides or nucleic acids. Its commercial name Sephadex is derived from SEparation PHArmacia DEXtran and stands for many different successful products including further derivatized materials such as carboxy-methyl, diethylaminoethyl, diethyl(2-hydroxypropyl)-aminoethyl, and sulfo-propyl Sephadex . 

Dextran cross-linked with epichlorohydrin Sephadex G Aqueous 0.1 A/ or 0.5 M NaOH Kraft Ugnin [1,4]... 

Many different types of esters and ethers of dextran pro dde macrmolectiles with diverse properties and negative, positive or neutral charges. Properties depend upon the type and degree of substitution, and the molecular weight of the dextran. The most widely used dextran derivative is obtained by the reaction of an alkaline solution of dextran with epichlorohydrin to give cross-linked chains. The product is a gel that is used as a molecular sieve. With its commercial introduction in 1959 by Pharmacia Fine Chemicals, Ltd, Uppsala, Sweden, cross-linked dextran revolutionized the purification and bio-separation processes. 

Sephadex (a dextran cross-linked with epichlorohydrin) has been used as an affinity matrix for the separation of [ I]-concanavalin A from the unlabelled lectin. If this technique is successful with other I-labelled proteins, it would help to overcome the uncertainty of whether or not biological properties displayed by labelled materials arise from contamination by the unlabelled material. 

Acetylated forms of Sephadex (dextran cross-linked with epichlorohydrin) have been used in the isolation of various proteolipids, and Sephadex has been etherified by reaction with alkaline sodium borohydride and 1-allyloxy-2,3-epoxypropane. Treatment of the etherified Sephadex with mercuric acetate gave a polymer containing covalently-bound, monofunctional mercury, which was used in the separation of nucleotides. 

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