Noncovalent Complexes of Polysaccharides

Although many complexing systems for polysaccharides have been investigated, the data published can only represent a fraction of the field when there are considered all the complexes and associations in which polysaccharides and the polysaccharide parts of glycoproteins and proteoglycans must be involved in natural processes. 

Probably the best known polysaccharide complex is the blue, starch-iodine complex. This reaction between iodine and the amylose component of starch involves the polymerization of iodine atoms inside the linear cavity of helically coiled, amylose macromolecules. The kinetics of complex-formation for many starches follow the same rate-equation as that for pure amylose, and, thus, the presence of amylopectin does not significantly affect the reaction. The differences between the 

0-(Carboxym.ethyl)celluIose azide amino acids and polypeptides 449,465 

Many other amylose complexes are water-insoluble, and the complexes with methanol, 1-propanol, acetone, and butanone may be precipitated from solutions of amylose in methyl sulfoxide, as well as from aqueous solution. As amylose frequently forms crystalline complexes. X-ray diffraction patterns have been obtained for a number of them. Amylose-methyl sulfoxide complexes have a structure almost identical to those of amylose-ethylenediamine complexes, in which the complexing ratio is one ethylenediamine molecule per two n-glucose residues. The helix packing-diameter of the complexes, at least for complexes with linear aliphatic ketones, is dependent upon the chain-length of the molecule complexed, although other factors are also involved.  

The complex-formation of polysaccharides with alkali metals and alkaline-earth metals has already been discussed in this Series. A dextran-iron complex has been used in the experimental therapy of synovitis, and chondroitin sulfate-iron colloids have been prepared. The swelling of cellulose in aqueous solutions of zinc chloride depends on the formation of a complex with the vicinal 2- and 3- hydroxyl groups of the repeating unit.  

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