The use of haemocyanin to determine the molecular weight of Nudaurelia cytherea capensis β virus by direct particle counting

Abstract

The giant haemocyanin of the molluse Burnupena cincta is shown to be a useful reference standard for the simple determination of molecular weights of viruses by the particle counting technique. Haemocyanin of known concentration and molecular weight is mixed with a known concentration of virus, and the respective particles counted on an electron photomicrograph. A particle ratio is determined from which the molecular weight may be determined with the appropriate equation. The method was tested with tobacco mosaic virus. A value of 41.8 × 10 6 determined for the molecular weight was in good agreement with values found by several authors. The particle counting method was applied to a nonoccluded virus of the saturniid Nudaurelia cytherea capensis. The calculated molecular weight of 16.3 × 10 6 was in good agreement with the molecular weight found by the velocity method, involving sedimentation and diffusion coefficients and partial specific volume. As additional controls the molecular weight was calculated from the diffusion coefficient and intrinsic viscosity, diffusion coefficient and frictional ratio and sedimentation coefficient and frictional ratio. Reasonable agreement with the value from particle counting was obtained.