Abstract
Nano-scale structures of individual single molecules and supra-molecular networks of xanthan gum were investigated using atomic force microscopy (AFM). AFM images of xanthan dissolved in water at ambient temperatures revealed branched fibrous structures, the cross-sectional dimensions of which typically ranged from 1 to 1.5 nm. Individual molecular chains, the cross-sectional dimensions of which were around 0.5 nm, were observed after heating at 90°C. Renaturation behavior upon successive cooling was dependent on the concentration of xanthan and the temperature. At 60°C, the formation of an anti-parallel double-stranded helix from an isolated molecule was evident. Air-drying of aqueous solutions containing either 1 or 10 μg/mL xanthan at room temperature resulted in the formation of nanometer- or micrometer-sized networks, respectively. These networks appeared to be composed of multiple filaments aggregated in parallel alignment to form thicker bundles with varied thicknesses, typically ranging from 0.5 to 2 nm.
