title: Equilibrium sedimentation of turnip yellow mosaic virus.
abstract: Sedimentation equilibrium was achieved with turnip yellow mosaic virus at low speeds (600 rpm) in a magnetic ultracentrifuge. The experiments were carried out in the newly installed constant-speed rotor, equipped with automatic control and an electromagnetic drive. A particle mass of 5.55 x 10(6) daltons was calculated for the virus at vanishing concentrations, in essential agreement with the earlier results using the more tedious procedure with a freely coasting rotor. In order to interpret the observed departure from ideal behavior (nonassociating conditions), preferential interaction experiments were carried out by magnetic densimetry. These showed that a strong Donnan effect exists at pH 7, which contributed > 10(3) times more to the nonideality than did the excluded volume effect. A net negative charge of about 3.5 x 10(3) per particle was estimated at this pH.
mesh_terms: D003720:Densitometry; D006863:Hydrogen-Ion Concentration; D008280:Magnetics; D008970:Molecular Weight; D009029:Mosaic Viruses / Q000032:analysis*; D010942:Plant Viruses / Q000032:analysis*; D012367:RNA, Viral / Q000032:analysis; D014461:Ultracentrifugation; D014764:Viral Proteins / Q000032:analysis
chemical_list: D012367:RNA, Viral; D014764:Viral Proteins