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Title: Hydrodynamic Versus Size-Exclusion Chromatography Characterization of Alternan and Comparison to Off-Line MALS

Author
item ISENBERG, SAMANTHA - Florida State University
item BREWER, AMANDAA - Florida State University
item Cote, Gregory
item STRIEGEL, ANDRE - Florida State University

Submitted to: Biomacromolecules
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/26/2010
Publication Date: 9/14/2010
Citation: Isenberg, S.L., Brewer, A.K., Cote, G.L., Striegel, A.M. 2010. Hydrodynamic versus size-exclusion chromatography characterization of alternan and comparison to off-line MALS. Biomacromolecules. 11:2505-2511.

Interpretive Summary: Alternan is a very large molecule that can be produced from domestic sugar. It has attracted interest as a potential food ingredient because of its high solubility in water and its relatively low digestibility. However, measuring the size of the molecule has been challenging because of its extremely large size. Most methods tear the molecule into smaller fragments. This paper describes new and improved methods for measuring the size of such large molecules, and helps us understand the relationship between molecular size and physical properties. It should enable researchers to more accurately measure these properties. This knowledge will enable researchers to more accurately measure these properties.

Technical Abstract: Alternan is an ultra-high molar mass polysaccharide composed of two different types of glycosidic linkages and which also possesses long-chain branching. It has great potential in a number of areas, including as a possible domestic replacement for gum Arabic. The high molar mass and large size of alternan, however, complicate its characterization by traditional techniques such as size-exclusion chromatography, wherein the polysaccharide undergoes on-column, flow-induced degradation even using the largest particle size columns available at very low flow rates. To overcome the problems accompanying SEC characterization of alternan, we employed packed-column hydrodynamic chromatography with multi-angle static light scattering and differential refractometry detection. The Mw and RG,z values obtained by HDC/MALS were closer to the values obtained by off-line MALS analysis than were the Mw and RG,z determined by SEC/MALS. Moreover, analysis by HDC was completed in a fraction of the time needed for SEC analysis. Evidence for long-chain branching in alternan was seen in the intrinsic viscosity of the polysaccharide, which is over 300 times lower than would be that of an equivalent-M pullulan, and in the viscometric radius of alternan, which was approximately one seventh that of the equivalent-M pullulan.