Showing papers in "Discussions of The Faraday Society in 1958"

Order-Disorder Transitions in Structures Containing Helical Molecules

Abstract: The most commonly considered types of disorder in a crystal containing long-&& molecules are those in which the individual chain molecules are either rotated about their long axes or else translated along the fibre axis. However, since many fibrous polymers are helical in structure, we should also expect the possibility of screw disorder; that is, a combination of the above two types. A disorder of this kind can be shown to exist orientated gels of tobacco mosaic virus and in fibres of polytetrafluoroethylene (PTFE) at 20°C. R e method by which screw disorder may be deduced from X-ray diagram is described, and the order-disow transitions in the two substances discussed. The me&. anism of the transition in PTFE is of particular interest in connection with its remarkably low coefficient of friction. Attention is also drawn to a related type of disorder found in stretched fibres of deoxyribonucleic acid.

Optical rotation and infra-red spectra of some polypeptide and protein films

Abstract: IT is well known that the α-helix configuration of Pauling and Corey1 is associated with a carbonyl stretching mode in the neighbourhood of 1,652–1,655 cm.−1 in films of simple enantiomorphic polypeptides2,3. Since this frequency is also found in the infra-red spectra of films prepared from a number of native proteins4–6 it is of interest to know whether other configurations besides the α-helix are associated with it, for some X-ray diffraction photographs of fibrous proteins suggest a mixture of crystalline and amorphous forms. In the case of water-soluble films of Bombyx mori silk fibroin7, a completely amorphous X-ray diffraction pattern can be obtained, along with a carbonyl band in the infra-red spectrum at 1,660 cm.−1. It is difficult to think that an α-helix arrangement would not produce sufficient order to reveal the characteristic intensity diffraction pattern of this helix.

Electron transfers among transition elements in magnesium oxide

Abstract: : All single crystals of MgO which have been available contain iron-group impurities in quantities easily detectable by e.s.r. absorption. For a given impurity, the fractions in the di- and tri-valent states depend in part upon the past heat treatment and upon the concentrations of the other impurities. Energetic radiation may cause electron transfer to occur among the impurities. Oxygen of the crystal may partake in these transfers.