Aggregation of the protein of tobacco mosaic virus with and without combination with nucleic acid

The protein produced by splitting tobacco mosaic virus with alkali has a smaller electrophoretic mobility at pH 7 than the virus, and recombining the protein with the nucleic acid increases its mobility almost to that of the original virus. Nevertheless the nucleic acid does not seem to contribute appreciably to the surface potential either of the original virus or of the particles of the reconstituted nucleoprotein because the surface potential of disks and cylinders produced by the protein alone when it is aggregated at pH 7 by exposure to ultraviolet radiation also have a surface potential approaching that of the original virus. This and other evidence suggests that the surface charge density of the protein fragments is nonuniform and that when the fragments form cylindrical aggregates the parts of the surface that are oriented outward are the most negatively charged.