Polysaccharides with hydrazine

One of the first polysaccharide derivatives used for insolubilization was the acid azide (or hydrazide) of 0-(carboxymethyl)cellulose. Treatment of the methyl ester of O-(carboxymethyl) cellulose with hydrazine gives the hydrazide 31 which, with nitrous acid, yields the azide (32). The azido group evidently reacts with the free functional groups of lysyl, tyrosyl, cysteinyl, and seryl residues (see Ref. 436), and evidence for formation of a covalent bond, as in 33, comes from the fact that the... 

Scheme 1.19 Modification of polysaccharides using hydrazines, with subsequent reduction with sodium cyanoborohydride.

The hydrazide derivative can be used to modify aldehyde- or ketone-containing molecules, including cytosine residues using the bisulfite activation procedure described in Chapter 17, Section 2.1. The sulfonyl hydrazine group of Texas Red hydrazide reacts with aldehydes or ketones in target functional groups to form hy-drazone bonds (Fig. 218). Carbohydrates and glycoconjugates can be specifically labeled at the polysaccharide portion if the required aldehydes are first formed by periodate oxidation or another such method (Chapter 1, Section 4.4). 

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