Molecular characterization of polysaccharides dissolved in Me 2NAc-LiCl by gel-permeation chromatography

Abstract

Polysaccharides function in key roles in textiles, biomass, foodstuffs, and plant cell walls, in addition to pharmaceuticals and immunological interactions. Structural information is urgently needed, but the complexity of the polymers, their interactions, and poor solubility have been limiting aspects. The dilute solution behavior of polysaccharides representing typical classes of natural products was investigated via gel-permeation chromatography (GPC) using refractive index and viscometric detectors. The solvent of choice for high-molecular weight cellulose analysis, dimethylacetamide with lithium chloride (Me 2NAc-LiCl), was used for direct polysaccharide dissolution without extraction or derivatization. The utility of this aprotic solvent for effective characterization of carbohydrates was explored. The polysaccharides studied spanned a range of molecular sizes, branching configurations, and linkage types, i.e., celluloses, amyloses, amylopectins, dextrans, pullulans, and curdlan. In addition to molecular weight values and distributions, calculated parameters defining each polysaccharides' dilute solution characteristics (intrinsic viscosity, radius of gyration, Mark-Houwink coefficients) were determined. Comparison between polysaccharides of similar molecular weight differing either in their branching patterns or linkage distribution were made. The calculated values were correlated with theoretical results predicted in the available literature and/or with known results. Relations among polymer linkage type, molecular chain compositions, branching assessments, and solution properties are described.