Derivatives of polysaccharides

As cotton fabrics are cellulose-based, the dyeing of polysaccharides has been studied as an art for centuries, but the underlying reactions have now been studied. Although this Section is concerned with the covalent dye derivatives of purified polysaccharides, and not general dyeing of fibers, it is not always possible to deduce from the literature the exact structures of the derivatives. This situation arises because attention has mainly been paid to the dyeing of polysaccharides simply to color them, and because commercially available dyes whose overall structures have not necessarily been disclosed are usually used. 

Traditional methods for dyeing cotton depended on formation of insoluble dye molecules on the fibers, or of hydrogen bonds between the dye molecules and the fibers, or both. However, two classes of dyes that react covalently have now been used extensively in the production of colored polysaccharide derivatives. The diazine and triazine types of 

Cibachron Blue, a monochlorotriazinyl dye, has proved valuable for the covalent dyeing of amylose, starch, cross-linked 

The structure of Blue Dextran 2000, a water-soluble commercial derivative, involves a triazine type of dye covalently linked to dextran, and, in a way analogous to that used for other dyed polysaccharides, has been employed for the assay of dextranase. The ability of Blue Dextran 2000 to bind proteins cannot be attributed to formation of a covalent link, because no chloro groups remain on the triazinyl rings. The binding must involve an ionic bond between the protein and the sulfonic groups of the dye residue, and, in one case, the association could be reversed by using 0-(2-diethylaminoethyl) cellulose to abstract the dyed polysaccharide. Other chlorotriazinyl dyes have been used in the preparation of dyed derivatives of amylopectin, laminaran, dextrans, pectin, pelvetian, zosterine, and cellulose. As already mentioned, triazine-dyed polysaccharides are useful in enzyme insolubilization. 

Reactone dyes, which contain trichloropyrimidinyl groups, react with polysaccharides in an analogous way to chlorotriazinyl dyes, but the extent of reaction is somewhat less, at least in their reaction with cellulose. Reactone Red 2B derivatives of amylose, amylopectin, starch, and barley )8-glucan provide substrates for amylases and y3-glucanases in the assay of these enzymes. 

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Biopolymers have diverse roles to play in the advancement of green nanotechnology. Nanosized derivatives of polysaccharides like starch and cellulose can be synthesized in bulk and can be used for the development of bionanocomposites. They can be promising substitutes of environment pollutant carbon black for reinforcement of rubbers even at higher loadings (upto SOphr) via commercially viable process. The combined effect of size reduction and organic modification improves filler-matrix adhesion and in turn the performance of polysaccharides. The study opens up a new and green alternative for reinforcement of rubbers. 

In the third paper of the series, concerned with the formation of -(copper thiolthiocarbonyl) derivatives of polysaccharides, Lieser and Hackl reviewed the few earlier studies on polysaccharides other than cellulose. They claimed that the starch xanthates obtained by Cross, Sevan, and Briggs and by Ost and his colleagues had been given incorrect formulas,... 

Cyclic sulfates can be prepared from cyclic but not acyclic carbohydrate units by reaction with sulfuryl chloride in pyridine [98] or phenyl chlorosulfate and sodium hydride [99]. The reactivity of cyclic sulfates is quite similar to that of epoxides. Thus, they can be used to form fluoro or azido derivatives of polysaccharides by highly regiospecific approaches, usually, but not always, leading to trans-diaxial products from which the sulfate can be easily removed by mild, acid-catalyzed hydrolysis [100,101]. 

The sulfate esters and sulfonate derivatives of polysaccharides and lignin form chemical complexes with the enzyme pepsin. These complexes have no proteolytic activity. Bc-cau.se polysulfatcs and polysulfonates arc ptxirly absorhol from the GI tract, specific chemical complexaiion appeals to be a desirable mechanism of pepsin inhibition. Unfoitu-nately. these polymers are also potent anticoagulants. 

IV. Miscellaneous, Short-chain, Primary Derivatives of Polysaccharides. 339... 

The artiele covers the production of all of the known covalent derivatives of naturally occurring polysaccharides, and discusses the reactions in which the polysaccharide chain is maintained largely, if not completely, intact. References are made to the physicochemical properties of the derivatives, and a Section on noncovalent derivatives of polysaccharides is included. The cycloamyloses are often considered together with polysaccharides, and a Section is included on their derivatives. Synthetic polysaccharides and their derivatives, beyond the scope of this article, have already been discussed. In general, papers published before... 

As already indicated, the number of polysaccharide derivatives reported is enormous, and indeed, many papers have been published on particular types, for example, O-(carboxymethyl) cellulose, and enzyme derivatives of polysaccharides. On such derivatives alone, reviews have been, or could be, written the present article must, therefore, of necessity be a condensed form restricted to the principal findings. Where reviews on particular derivatives have been published, this is indicated, and, generally, only subsequent papers are considered here. The reader may also find it useful to refer to other works that consider a number of derivatives of particular polysaccharides, such as cellulose, " chitin, starch, " and others. References to polysaccharide derivatives are now being reported annually in Specialist Periodical Reports. ... 

Treatment of agarose (Sepharose) with epichlorohydrin gives an oxirane derivative (11) that has great potential in the formation of secondary derivatives of polysaccharides (such as insolubilized enzymes and immunoadsorbents), as the epoxide ring can be opened by the attack of... 

Although cyclic and acyclic carbonates of monosaccharides have been known for some time, little interest had been taken in such derivatives of polysaccharides, probably because the conditions could not be controlled to give any degree of specificity. The formation of cyclic carbonate rings involves treatment of the polysaccharide with ethyl chloro-formate heterogeneous reactions occur, and acyclic carbonate (ethy-oxycarbonyl) groups are also formed. The reaction conditions suitable for maximum cyclic carbonate and minimum acyclic substitution have been investigated in detail for cellulose. Other chloroformates have... 

The modification of cellulose with alkaline carbon disulfide to introduce xanthate groups has been extensively exploited in the industrial production of viscose. Early work on the preparation and properties of starch xanthate has been discussed. Xanthate derivatives of cellulose and starch have been discussed with respect to general xanthate chemistry, and the xanthation of cellulose in homogeneous medium is known to be a second-order reaction. Cellulose xanthate shows some potential as a matrix for enzyme insolubilization, " and stable derivatives of this xanthate may be prepared by transesterification. Thermal decomposition of cellulose allyl- and benzyl-xanthates gives 5,6-cellulosene. Some thiocarbonyl derivatives of polysaccharides have been prepared. "... 

Trichloropyrimidinyl and chlorotriazinyl dye derivatives of polysaccharides are considered to be more satisfactory than Ramazol dye derivatives, the ether linkage being considered the weakest of those present. The dyeing of polysaccharides has been advocated as an aid to their identification in gel electrophoresis, gel filtration, and cellulose acetate electrophoresis, although it must be borne in mind that such deriva-tizations alter the characteristics of the polysaccharide under examination. 

The reviews already cited deal adequately with the enzymic properties of insolubilized enzymes, and so, in the present article, appropriate insolubilized enzymes will be discussed as derivatives of polysaccharides. As already mentioned, covalent attachment is the most successful means... 

The use of rafW-2,3-imidocarbonate derivatives of polysaccharides for insolubilization was first made in the field of immunoadsorbents (see Section IX, p. 380). Cyclic imidocarbonates may be considered to react in one of three ways on nucleophilic attack by a free amino group, to give (a) a pseudourea derivative (41), (b) an N-substituted imido-carbonate (42), or (c) an iV-substituted carbonate (43). Although the... 

Polysaccharides, particularly cellulose, have been used almost exclusively in the insolubilization of nucleic acids. The principal, covalent, nucleic acid derivatives of polysaccharides are shown in Table V. Syn-... 

Kennedy, John F., Chemically Reactive Derivatives of Polysaccharides, 29, 305-405... 

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