Physikalische und chemische Untersuchungen am broad bean mottle-Virus

Abstract

Broad bean mottle virus (BBMV) contains 15.2 percent N and 1.83 percent P; the N/P ratio is 8.4 ± 0.3. The protein of BBMV contains 15.6 percent N and no P; the NA has a N/P ratio of about 1.85. From these data a NA content of about 22 percent can be evaluated. This value agrees with that of 23 percent obtained by orcinol reactions. The sedimentation constant at infinite dilution is 83 ± 2 S, the diffusion constant 1.44 ± 0.04 · 10-7 cm2/sec, and the partial specific volume 0.75 cm3/gram. From these data a molecular weight of 5.6 ± 0.5 millions for the unhydrated particles can be calculated. The diameter of these particles is about 24 mµ, which agrees fairly well with determinations made with the electron microscope 1. Estimations of molecular weight and diameter of the hydrated particles reveal about 10 millions and about 30 mu respectively. Purified BBMV was stable in neutral buffer solutions at 3 °C for some weeks and remained infective. Exhaustive dialysis of such virus suspensions against dist. water caused a considerable increase in turbidity, and, later on, precipitation of the virus. It was not possible to resuspend this virus completely by adding neutral buffer or salt solutions. Density gradient centrifugations showed these resuspensions to be inhomogeneous, whereas non-dialyzed virus suspensions in buffer gave only one narrow zone in the gradient tubes, indicating the homogeneity of the particles. In buffers of different pH , virus suspensions showed a maximum turbidity at about pH 4.5. For precipitations of BBMV with ammonium sulfate, higher salt concentrations were necessary than for most other viruses. The UV light absorption (corrected for light scattering) of BBMV as well as of its protein and its NA was measured. It could be shown that the absorption coefficient of BBMV protein is much lower than that of most other viruses, presumably because of the low content of aromatic amino acids as determined by chemical analysis recently 2. The estimation of the NA content of BBMV from UV absorption data is discussed.