Dextran residues

D-Glucose residue 1 would therefore appear as 2,3,4,6-tetramethyl-D-glucose on hydrolysis of methylated dextran D-glucose 2 as 2,3-dimethyl-D-glucose and the other three D-glucose residues as 2,3,4-tri-... 

This simple strategy can be used to add amine residues to polysaccharide molecules after formation of aldehydes by periodate or enzymatic oxidation (Section 4.4, this chapter). Thus, glycoconjugates or carbohydrate polymers such as dextran may be derivatized to contain amines for further conjugation reactions. 

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. 

The main disadvantage in using poly(acrylamide) systems is that they are not biodegradable and the monomers are toxic. Extensive purification is also required to remove the organic solvents, anionic surfactants, and residual monomers. Edman et al. [74] produced biodegradable poly(acryldextran) particles by incorporating dextran into the poly(acrylamide) chain. These particulate systems were metabolized and eliminated faster, both in vivo and in vitro, than poly(acrylamide) particles. 

As previously stated, our C-13 n.m.r. spectral analysis was first applied to dextrans. In the spectral analysis hypotheses described above, it is an inherent assumption that each residue... 

Assuming that all a-[l->6)-linkages are in the dextran backbone, our permethylation g.l.c.-m.s. data [which indicate that only the residues shown above are present in this series of dextrans) are consistent with a polymeric structure that is comb-like with side branches a single residue long. 

Comparison of two series of dextran data shows the importance of considering the spectra in terms of specific residue type. One... 

The feature of immediate interest in the above general structure is that relatively large (and for dextran B-1355 fraction S, very large) percentages of 3-0-substituted a-D-glucopyranosyl residues are present with relatively small proportions of the 3,6-di-O-substituted a-D-glucopyranosyl residues. Careful examination of the 75--85-p.p.m. region for the above polymers shows that the major resonance is now respectively at 83.31,... 

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