In describing a protein it is now common to distinguish the primary, secondary and tertiary structures. The primary structure is simply the order, or sequence, of the amino-acid residues along the polypeptide chains. This was first determined by [Frederick] Sanger using chemical techniques for the protein insulin, and has since been elucidated for a number of peptides and, in part, for one or two other small proteins. The secondary structure is the type of folding, coiling or puckering adopted by the polypeptide chain: the a-helix structure and the pleated sheet are examples. Secondary structure has been assigned in broad outline to a number of librous proteins such as silk, keratin and collagen; but we are ignorant of the nature of the secondary structure of any globular protein. True, there is suggestive evidence, though as yet no proof, that a-helices occur in globular proteins, to an extent which is difficult to gauge quantitatively in any particular case. The tertiary structure is the way in which the folded or coiled polypeptide chains are disposed to form the protein molecule as a three-dimensional object, in space. The chemical and physical properties of a protein cannot be fully interpreted until all three levels of structure are understood, for these properties depend on the spatial relationships between the amino-acids, and these in turn depend on the tertiary and secondary structures as much as on the primary. Only X-ray diffraction methods seem capable, even in principle, of unravelling the tertiary and secondary structures.[Co-author with G. Bodo, H. M. Dintzis, R. G. Parrish, H. Wyckoff, and D. C. Phillips]
It would be pleasant to believe that the age of pessimism is now coming to a close, and that its end is marked by the same author who marked its beginning: Aldous Huxley. After thirty years of trying to find salvation in mysticism, and assimilating the Wisdom of the East, Huxley published in 1962 a new constructive utopia, The Island. In this beautiful book he created a grand synthesis between the science of the West and the Wisdom of the East, with the same exceptional intellectual power which he displayed in his Brave New World. (His gaminerie is also unimpaired; his close union of eschatology and scatology will not be to everybody's tastes.) But though his Utopia is constructive, it is not optimistic; in the end his island Utopia is destroyed by the sort of adolescent gangster nationalism which he knows so well, and describes only too convincingly.This, in a nutshell, is the history of thought about the future since Victorian days. To sum up the situation, the sceptics and the pessimists have taken man into account as a whole; the optimists only as a producer and consumer of goods. The means of destruction have developed pari passu with the technology of production, while creative imagination has not kept pace with either.The creative imagination I am talking of works on two levels. The first is the level of social engineering, the second is the level of vision. In my view both have lagged behind technology, especially in the highly advanced Western countries, and both constitute dangers.
If we ascribe the ejection of the proton to a Compton recoil from a quantum of 52 x 106 electron volts, then the nitrogen recoil atom arising by a similar process should have an energy not greater than about 400,000 volts, should produce not more than about 10,000 ions, and have a range in the air at N.T.P. of about 1-3mm. Actually, some of the recoil atoms in nitrogen produce at least 30,000 ions. In collaboration with Dr. Feather, I have observed the recoil atoms in an expansion chamber, and their range, estimated visually, was sometimes as much as 3mm. at N.T.P.These results, and others I have obtained in the course of the work, are very difficult to explain on the assumption that the radiation from beryllium is a quantum radiation, if energy and momentum are to be conserved in the collisions. The difficulties disappear, however, if it be assumed that the radiation consists of particles of mass 1 and charge 0, or neutrons. The capture of the a-particle by the Be9 nucleus may be supposed to result in the formation of a C12 nucleus and the emission of the neutron. From the energy relations of this process the velocity of the neutron emitted in the forward direction may well be about 3 x 109 cm. per sec. The collisions of this neutron with the atoms through which it passes give rise to the recoil atoms, and the observed energies of the recoil atoms are in fair agreement with this view. Moreover, I have observed that the protons ejected from hydrogen by the radiation emitted in the opposite direction to that of the exciting a-particle appear to have a much smaller range than those ejected by the forward radiation.This again receives a simple explanation on the neutron hypothesis.