Determining the solution conformational entropy of oligosaccharides by size-exclusion chromatography with on-line viscometry detection
Mallory J. Morris, Andre Striegel
Introduced here is a method for determining the solution conformational entropy of oligosaccharides (-S) that relies on the on-line coupling of size-exclusion chromatography (SEC), an entropically-controlled separation technique, and differential viscometry (VISC). Results from this SEC/VISC method were compared, for the same injections of the same sample dissolutions and under identical solvent/temperature conditions, to results from a benchmark SEC/differential refractometry (SEC/DRI) method which has been applied successfully over the last decade to determining -(delta S) of a variety of mono-, di-, and oligosaccharides. The accuracy (as compared to SEC/DRI) and precision of SEC/VISC were found to be excellent. Also, and contrary to expectations, the viscometer's sensitivity in the oligomeric region was quite good, even when analyzing disaccharides. The experiments presented here contrast three sets of beta-(1-4)-linked oligosaccharides, namely manno-, cello-, and N-acetylchitooligosaccharides of degree of polymerization (DP) 2 through 6. For each series, the dependence of -(delta S) on DP was found to be monotonic while, between series, differences at each DP could be ascribed to either the additional degrees of freedom imparted by large, multi-atomic substituent groups, or to the presence or absence of additional hydrogen bonds, depending on the axial versus equatorial arrangement of particular hydroxyl groups. We also advance a hypothesis to help explain the unexpectedly high sensitivity of viscometric detection for low-molar-mass analytes. The method presented can be extended to the analysis of oligosaccharides other than those presented here.
and Striegel, A.
Determining the solution conformational entropy of oligosaccharides by size-exclusion chromatography with on-line viscometry detection, Biomacromolecules, [online], https://doi.org/10.1016/j.carbpol.2014.02.027, https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=914431
(Accessed May 28, 2023)