Some factors affecting particle length distribution in tobacco mosaic virus preparations

Abstract

The length of tobacco mosaic virus (TMV) particles in crude extracts of infected tobacco leaves and in preparations purified by ultracentrifugation and by precipitation with ammonium sulfate have been determined by electron microscopy. Preparations with high proportions of particles longer than 300 mμ were prepared by treating virus preparations with acetate buffer, pH 4.8. Preparations with high proportions of particles shorter than 300 mμ were obtained when phosphate buffer, pH 7.2, was used. The particle-length distribution in these preparations was readily reversed by dialysis against the appropriate buffer for 3 days at 4 °. TMV preparations purified by ammonium sulfate precipitation or by ultracentrifugation and resuspending pellets in buffer at pH 4.8 or 7.2, all had similar infectivity in spite of their different particle-length distributions. Virus purified by ammonium sulfate precipitation, when dialyzed against phosphate buffer, pH 7.2, contained an increased proportion of particles shorter than 300 mμ yet its infectivity increased slightly. It is suggested that particles shorter than 300 mμ may enhance the infectivity of particles 300 mμ or longer.