Chemical Aspects of the Cyclol Hypothesis

Abstract

CONSIDERABLE discussion of the structure of proteins, especially in relation to the cyclol hypothesis, has recently appeared in NATURE1,2,3. This theory assumes that globular proteins consist of a spaceenclosing arrangement of diazine and triazine rings. Most of the evidence produced (including the X-ray diagrams2,3) is, however, not specific for the cyclol theory; many of the points made by Langmuir4 could be equally well used as an argument in favour of any regular geometrical structure which joins peptide chains to form a globular molecule. It is indeed possible to suggest bonds between peptide chains of types already known to exist; thus we are familiar with compounds containing the linkages S—S; CO—S, NH—S or CO—NH—CO, all of which might occur in proteins; in addition, the possibility exists of linkages between hydroxyl groups of hydroxy-amino acids and free carboxyl groups.