Macrocrystalline patterns of closely packed poliovirus particles in ultrathin sections

Purified preparations of poliovirus MEF 1 (Type II) were spun down into a pellet by means of ultracentrifugation. The virus particles became closely packed and showed macrocrystalline patterns on sectioning. At least two well differentiated patterns were observed. The average spacing was 200–220 Å and the virus particles consisted of osmiophilic, opaque centres which have average diameters of 160 Å. These centres are surrounded by approximately 30 Å thick, less osmiophilic zones.