Chapter 2.2 - Physico-chemistry of (1,3)-β-Glucans

Abstract

This chapter describes the methods and results of studies into the conformations adopted by (1,3)-β-glucans in solid, solution and native states, and characterization of the physical behavior of (1,3)-β-glucans in dilute solutions, concentrated solutions and gel networks. The physico-chemical properties exhibited by (1,3)-β-glucans are based primarily on the nature and stability of ordered conformations that are present under hydrated conditions. X-ray fiber diffraction analysis has shown unambiguously that a triple helix can be formed under both anhydrous and hydrated solid state conditions for linear (1,3)-β-glucans; similar diffraction behavior for side-chain-substituted (1,3)-β-glucans suggests a similar triple helical form with reduced lateral aggregation of glucan backbones due to the presence of side chains. Solid state 13C nuclear magnetic resonance (NMR) provides evidence that triple helical conformations are present within gels and some native forms of (1,3)-β-glucans. Light scattering, electron microscopy and atomic force microscopy data show the presence of triple helices for a range of substituted (1,3)-β-glucans in dilute aqueous solution, and are consistent with single-chain forms in solutions of alkali and dimethyl sulfoxide (DMSO).