Homobifunctional Hydrazides

4-Butanediol diglycidyl ether is a viscous liquid having a density of 1.45 at 20°C. It is a hygroscopic, corrosive compound with a displeasing odor that should be handled with care in a fume hood. Aqueous solutions of the bis-epoxide usually possess a characteristic oily film on their surfaces, indicating the limited solubility of the reagent. 

An example of the use of 1,4-butanediol diglycidyl ether for the activation of soluble dex-tran polymers is given in Chapter 25, Section 2.3. One end of the fezs-epoxide reacts with the hydroxylic sugar residues of dextran to form ether linkages, which terminate in epoxy functionalities. The epoxides of the activated derivative then can be used to couple additional mol-ecules-containing nucleophilic groups to the dextran backbone. 

These techniques have been used to target, detect, or assay glycoproteins in solution or on cell surfaces by using hydrazide-activated enzymes, avidin, or streptavidin (Chapter 13, Section 5) (Bayer and Wilchek, 1990 Bayer etai, 1987a,b 1990) and to form conjugates with glycoproteins. 

Bis-hydrazide-containing molecules also can be used to activate soluble polymeric substances containing aldehyde groups. For instance, dextran may be periodate-oxidized to create numerous formyl functional groups on each molecule. Subsequent reaction with a homobifunctional hydrazide in excess results in a hydrazide-activated polymer having multivalent binding capability toward aldehydes or ketones (Chapter 15, Section 2.2). Insoluble support matrices suitable for affinity chromatography have been activated in a similar fashion to create the hydrazide derivative (O Shannessy and Wilchek, 1990). 

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