Dextran is one of the most common representatives of polysaccharides, a macromolecule consisting of α-1,6 linkages between glucose units. In addition, α-1,3 (and infrequently α-1,2) linkages can be present, thus creating branches on the main glycan chain (see Figure 1). These materials have a remarkable diversity in physicochemical properties due to the variation in chain length and degree of branching. Dextran’s commercial applications are typically found in the food and pharmaceutical industry, such as vaccines, eye medicines, organ preservation, and blood cell separation. They are also used as blood plasma surrogates.
Pullulan is another widely studied type of polysaccharide. It consists of maltotriose units, made of three glucose monomers with α-1,4 linkages, which are connected by α-1,6 glycosidic bonds (see Figure 2). The coexistence of both types of glycosidic bonds generate an intermediate structure between dextran and amylose. This unique linear structure provides the specific structural flexibility and solubility of pullulan, resulting in distinct film- and fiberforming characteristics which are not exhibited by other polysaccharides. Pullulans have numerous uses in the food, manufacturing, electronic, and pharmaceutical industries, such as wound-healing compositions, pharmaceutical coatings, oral care products, and non-toxic conjugates for vaccines.
As the most abundant natural biopolymer, polysaccharides’ unique chemical and physical properties, as well as their excellent biocompatibility make them materials of choice in many industries. Due to their wide application range and the complexity of their structure, such polymers need to be examined very thoroughly to fully understand their molecular characteristics. For example, to study their diffusion properties, the size of the molecules is an important parameter. Also, the size of dextran is by far the most important determinant of red blood cell aggregation, where low size molecules inhibit aggregation while larger molecules promote aggregation. In addition, a great variety of conformations and branching behaviors make specific polysaccharides either suitable or problematic for certain applications.
This application note explains how size exclusion chromatography (SEC) coupled with multi-angle light scattering (MALS) can be used for the determination of structural changes in polysaccharides, with pullulans and dextrans as examples.
>> Download the Application Note as a PDF
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