Letter to the editor: Electron diffraction for hydrated crystalline biopolymers: nigeran.

A method is presented to record electron diffraction diagrams on hydrated crystalline biopolymers. It involves quick-freezing of the hydrated crystals, which are maintained at a low temperature throughout the experiment. The technique is illustrated with lamellar single crystals of the linear polysaccharide nigeran. Water of hydration is shown to be in a sheet-like array and its removal is accompanied by development of lateral cracks. This morphological shrinkage coincides with an observed shortening of the b lattice parameter, which is normal to the lateral cracks.