Abstract
Treatment of foot-and-mouth disease virus with 4% glutaraldehyde increases the diam. of the particles by 25% and makes them permeable to phosphotungstic acid so that they appear empty. The treated particles also resemble naturally-occurring empty particles in their low sedimentation coefficient (about 75S) but, in contrast to empty particles, they have a normal content of RNA and a higher than normal buoyant density in caesium chloride. The RNA can be removed from fixed particles by ribonuclease. Two models are suggested which account for these alterations in the structure of the virus particles. These results show that fixation with glutaraldehyde, far from maintaining the structural integrity of the virus particles, leads to considerable alterations in the arrangement of the RNA and protein subunits.