Crystal and molecular structure of V‐anhydrous amylose

The conformation and crystalline packing of V‐anhydrous amylose has been investigated by a combination of linked atom model building and X‐ray diffraction analysis. The unit cell, the P212121 space group, the left‐handed sixfold helical conformation with all O(6) in gt rotational positions, and the intrahelical O(2)‐‐‐O(3) and O(2)‐‐‐O(6) hydrogen bonds are substantially in agreement with previous studies. A new model for packing of the chains in the unit cell and the presence of crystallographic water is proposed. Packing appears to be stabilized by corner‐to‐center chain O(2)‐‐‐O(2) hydrogen bonds. The nature of the transition from the amylose–DMSO complex to Va‐amylose was considered and it is shown that the transition involves translation of the amylose chains parallel to the a and b unit cell axes with only slight changes in the orientation of the helix. No significant conformational changes result from the transition.