Abstract
In a nearly salt-free medium, a dilute tobacco mosaic virus solution of rod-shaped virus particles of uniform length forms two phases; the bottom optically anisotropic phase has a greater virus concentration than has the top optically isotropic phase. For a sample containing particles of various lengths, the bottom phase contains longer particles than does the top and the concentrations top and bottom are nearly equal. The longer the particles the less the minimum concentration necessary for two-phase formation. Increasing the salt concentration increases the minimum concentration. The formation of two phases is explained in terms of geometrical considerations without recourse to the concept of long-range attractive forces. The minimum concentration for two-phase formation is that concentration at which correlation in orientation between the rod-shaped particles begins to take place. This concentration is determined by the thermodynamically effective size and shape of the particles as obtained from the concentration dependence of the osmotic pressure of the solutions measured by light scattering. The effective volume of the particles is introduced into the theory of Onsager for correlation of orientation of uniform size rods and good agreement with experiment is obtained. The theory is extended to a mixture of non-uniform size rods and to the case in which the salt concentration is varied, and agreement with experiment is obtained. The thermodynamically effective volume of the particles and its dependence on salt concentration are explained in terms of the shape of the particles and the electrostatic repulsion between them. Current theories of the hydration of proteins and of long-range forces are critically discussed. The bottom layer of freshly purified tobacco mosaic virus samples shows Bragg diffraction of visible light. The diffraction data indicate that the virus particles in solution form three-dimensional crystals approximately the size of crystalline inclusion bodies found in the cells of plants suffering from the disease.
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Selected References
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- Green R. H., Anderson T. F., Smadel J. E. MORPHOLOGICAL STRUCTURE OF THE VIRUS OF VACCINIA. J Exp Med. 1942 Jun 1;75(6):651–656. doi: 10.1084/jem.75.6.651. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Iball J. Antigen Films and Long-Range Forces. Science. 1949 Jan 7;109(2819):18–18. doi: 10.1126/science.109.2819.18-a. [DOI] [PubMed] [Google Scholar]
- Karush F., Siegel B. M. The Structure of Antigen Films and Long-Range Forces. Science. 1948 Jul 30;108(2796):107–108. doi: 10.1126/science.108.2796.107. [DOI] [PubMed] [Google Scholar]
- Oster G. Molecular Weights and Other Properties of Viruses as Determined by Light Absorption. Science. 1946 Mar 8;103(2671):306–308. doi: 10.1126/science.103.2671.306. [DOI] [PubMed] [Google Scholar]
- Pauling L., Delbrück M. THE NATURE OF THE INTERMOLECULAR FORCES OPERATIVE IN BIOLOGICAL PROCESSES. Science. 1940 Jul 26;92(2378):77–79. doi: 10.1126/science.92.2378.77. [DOI] [PubMed] [Google Scholar]
- SCHACHMAN H. K., LAUFFER M. A. The hydration, size and shape of tobacco mosaic virus. J Am Chem Soc. 1949 Feb;71(2):536–541. doi: 10.1021/ja01170a047. [DOI] [PubMed] [Google Scholar]
- Smadel J. E., Pickels E. G., Shedlovsky T., Rivers T. M. OBSERVATIONS ON MIXTURES OF ELEMENTARY BODIES OF VACCINIA AND COATED COLLODION PARTICLES BY MEANS OF ULTRACENTRIFUGATION AND ELECTROPHORESIS. J Exp Med. 1940 Oct 31;72(5):523–529. doi: 10.1084/jem.72.5.523. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Stanley W. M. ISOLATION OF A CRYSTALLINE PROTEIN POSSESSING THE PROPERTIES OF TOBACCO-MOSAIC VIRUS. Science. 1935 Jun 28;81(2113):644–645. doi: 10.1126/science.81.2113.644. [DOI] [PubMed] [Google Scholar]