Influence of Anomeric Configuration, Degree of Polymerization, Hydrogen Bonding, and Linearity versus Cyclicity on the Solution Conformational Entropy of Oligosaccharides

In their various incarnations oligosaccharides have roles that are oftentimes conformationally dependent, where this dependency can be dictated by the anomeric configuration, glycosidic linkage, and/or hydrogen bonding (H-bonding) of the sugar molecules. Examples of this phenomenon are linkage- and configuration-selective aptameric binding to oligosaccharides and taste responses that appear to depend on the H-bonding-controlled shape of sugars. Differences in the behavior and use of oligosaccharides as a function of degree of polymerization are also well-known, a classic example being the case of cyclodextrins (CDs) and the different uses and properties of α-, β-, and γ-CD. Here, we have measured the solution conformational entropy of three homologous series of oligosaccharides, linear malto- and cellooligosaccharides and cyclodextrins, using high-resolution oligomeric size-exclusion chromatography (SEC), an entropically controlled separation method. We measured the change in Δ S of the malto- and cello- series as a function of degree of polymerization (DP) and compared the effects of α vs β anomeric configuration at each DP. By comparing select maltooligosaccharides with CDs, we also measured the effect of linearity vs cyclicity on Δ S . Additionally, by performing all of these studies under both hydrogen-bond-accepting and non-hydrogen-bond-accepting conditions, we were able to isolate the effects of H-bonding on the Δ S of the malto- and cellooligosaccharides and cyclodextrins as well.