X-Ray diffraction data for β-(1 → 3)-<scp>D</scp>-glucan

The conformation of a bacterial β-(1 → 3)-D-glucan (curdlan) was studied by X-ray diffraction measurements on fiber diagrams. The glucan fiber, prepared by extruding a dimethyl sulfoxide solution of the glucan into methanol and washing in water (A) was of low crystallinity but with a characteristic diffraction and orientation 'as spun'. The same fiber annealed in water, under tension, at 140 °C, in a closed bomb, was of higher crystallinity and occurred as two reversible crystalline polymorphs: one at high relative humidity (B) and the other at relative humidities less than 20% (C). All three X-ray diagrams displayed the X-shaped patterns characteristic of helical conformations; equatorial diffraction corresponded to hexagonal packing. The fiber axis data for B and C coupled with a conformational study and density data leads to a proposed three-stranded helical structure with P6 3 symmetry.Curdlan in water forms an irreversible gel when a 2–4% solution is heated above 55 °C. The same gel given the annealing treatment described above undergoes syneresis and the gel properties are lost.