Light-Scattering Study of Tobacco Mosaic Virus Solutions When Subjected to Electric Fields

Abstract

The results of the light-scattering study are presented. Measurements made in the absence of an applied electric field gave size parameters and a molecular weight for this rodlike molecule which are in good agreement with results obtained by other workers. These are a molecular weight of 49.5×106 and a radius of gyration of 940(±28) Å corresponding to a length of 3200 Å and a diameter of about 150 Å. The sample was very monodisperse. The second osmotic virial coefficient was zero. The application of alternating electric fields to solutions of polar or electrically anisotropic molecules results in changes of the angular distribution of the intensity of the scattered light and the introduction of an alternating scattered intensity component of twice the frequency of the applied field. The way in which these effects can be used to determine the electrical characteristics of the molecules is described. The solutions were subjected to fields up to about 500 V cm−1 at frequencies up to 30 kc/sec, and it was found that the molecules possessed both a permanent dipole moment μ and electrical anisotropy β. The values obtained were μ=4.1×104 D and β=4.3×104 D and these are in agreement with previously reported values. Consideration of the frequency dependence of the intensity changes enabled a value for the rotary diffusion constant to be estimated.

Electric Field X-ray Scattering Measurements on Tobacco Mosaic Virus

“…The cultures were exposed to these factors during the exponential phase of their growth. Highly purified preparations of the various growth inhibitors (9) were added at increasing concentrations to subconfluent monolayers of the retinal cells and tested for their effects on DNA synthesis and on cell number.…”

“…It is mainly this second possibility that prompted us to perform the feasibility expeniments described below, because there is some advantage in the study of fibrous systems like chromatin (4) in being able to unequivocally assign specific features of the solution scattering patterns to meridional or equatorial contributions in the pattern of oriented specimens. As an obvious test object for these experiments we chose tobacco mosaic virus (TMV), which is perhaps the system most thoroughly studied by electric dichroism and birefringence (5)(6)(7)(8) and electric field light scattering (9). Furthermore, magnetic field orientation methods (10, 11) have been used on very concentrated TMV samples that display liquid crystalline behavior.…”

Sur les propriétés optiques linéaires et non linéaires des atomes et des molécules

“…11 est dommage que nous ne connaissions pas encore les parametres de deformation non lineaire optique de la molecule C6H5NO2 et que, de ce fait, nous ne puissions pas 6valuer la variation correspondante de D due a la diffusion d'ordre deux. On pourrait s'attendre a des effets plus consid6rables lors de la diffusion par les macromolécules, comme c'est le cas pour le champ 6lectrique constant [38,39].…”