X-Rays and the Cyclol Hypothesis

Abstract

THE purpose of the vector map described by Fankuchen and Riley1 to which Dr. Wrinch has taken exception in her recent letter2 was merely to show that the cyclol C2 skeleton does not contribute anything to the specific character of the observed X-ray reflections from crystalline insulin. No one imagines that insulin contains only (CCN) groups, but these are the only atoms of which the positions have been definitely stated by Dr. Wrinch, and therefore the only ones amenable to exact computation. Dr. Wrinch is, of course, at liberty to place other concentrations of density wherever she likes, but she cannot logically claim in this case that the structure arrived at in this way offers any confirmation of the cyclol hypothesis. Moreover, as has been shown already3, Dr. Wrinch's construction of the vector map from such concentrations4 has been incorrectly carried out, and therefore cannot confirm her proposed model of the insulin structure. Finally, the shape and size of the cyclol molecule do not offer a particularly convincing fit into the cell of insulin. Any spherical molecule of approximately the right molecular weight would fit the cell equally well. The only positive agreement is in the presence of a trigonal axis of symmetry, which can scarcely be claimed to justify the acceptance of such an elaborate construction.