Dorothy Wrinch

Nature of the Cyclol Bond

THE confirmation by X-ray data1,2 of C2, the A 288-residue cage structure proposed for the insulin molecule3, makes it of interest to consider the nature of the cyclol bond, upon the postulation of which this structure and the cyclol theory of protein structure in general4 depend.The making and breaking of a cyclol bond between an NH group of a polypeptide chain and a CO group of the same or of another polypeptide chain, requires only the migration of an H atom thus:

The Cyclol Hypothesis

FIVE sets of experiments have been reported in the past few years which have been claimed to bear on the cyclol hypothesis.

An Introduction to Combinatory Analysis

IN this little book Major P. A. MacMahon has given a short introduction to his two volumes on combinatory analysis which were published in 1915–16. The theories of combination, permu tation, arrangement, order, and distribution which are dealt with in those volumes present technical difficulties; it is, therefore, a great advantage that such an introduction should exist, for the gradual development of the subject by easy stages will prove interesting to the reader and whet his appetite for the larger tomes which await him.An Introduction to Combinatory Analysis.By Major P. A. MacMahon. Pp. viii + 71. (Cambridge: At the University Press, 1920.) 7s. 6d. net.