Isoelectric points of polypeptides of standard poliovirus particles of different serological types and of empty capsids and dense particles of poliovirus type 1.

The isoelectric points of polypeptides of standard and dense poliovirus particles and of empty capsids have been determined by isoelectric focusing in urea and by two-dimensional analysis. Comparing virus strains belonging to the three serological types of poliovirus, differences in the pI of some, but not all of the structural polypeptides are found. The pI of polypeptides of dense particles and of empty capsids are identical with those of standard particles. Polypeptide VPo present in empty capsids has a pI between those of VP4 and VP2.