Dextrans secondary linkages

Studies on Dextrans and Dextranases. Part X, Types and Percentages of Secondary Linkages in the Dextrans Elaborated by Leuconostoc mesenteroides NRRL B-1299, ... 

Figure 25.13 Polyaldehyde dextran may be used as a multifunctional crosslinking agent for the coupling of amine-containing molecules. Reductive amination creates secondary amine or tertiary amine linkages.

Porath, 1974). B/s-oxirane compounds also can be used to introduce epoxide groups into soluble dextran polymers in much the same manner (Boldicke et al., 1988 Bocher et al., 1992). The epoxide group reacts with nucleophiles in a ring-opening process to form a stable covalent linkage. The reaction can take place with primary amines, sulfhydryls, or hydroxyl groups to create secondary amine, thioether, or ether bonds, respectively (Chapter 2, Section 1.7). 

Fujimoto and coworkers determined that the order of stabilities to acid hydrolysis of D-glucopyranosidic linkages is reversed under the conditions of acetolysis this may be due to steric factors affecting the acetylium ion. In consequence, acetolytic, degradative procedures have enabled secondary-linked disaccharide fragments to be obtained from a large number of native dextrans. The o-D-linked disaccharides obtained by acetolysis and deacetylation of a cross-section of dextrans are listed in Table II. The results may be seen to complement data from periodate... 

Percentages" of Secondary-Glucosidic Linkages in Some Dextrans... 

Fig. 1.—The Actions of P. funiculosum (A) and P. Utadnum (B) Endodextranases on Brandied and Linear Segments of Dextrans. t—O = (l- 6)-linked a-u-gluco-pyranosyl residue °° secondary-linked o-n-glucopyranosyl residue Q— temninal, D- ucose residue % = terminal, n-glucopyranosyl group — linkages resistant to hydrolysis + = ahemative points of hydrolysis that give rise to stable oligosacdiarides.]...

Fig. 2.—Schematic Representations of Possible Types of Dextran Structures. For clarity, short branch-chains are omitted. O = terminal, reducing-end residue — = secondary a-linkages — = chains of (1— 6)-linked [sometimes (l— 3)-linked] a-n-glucopyranosyl residues. ...

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