dansylating the virus protein and then separating the dansylated N-terminal amino acids from the hydrolysis products by thin layer chromato- graphy, Laporte identified threonine, leucine and iso-leucine as N-terminal amino acids, thus furnishing evidence for at least three polypeptides

Further evidence has been obtained which confirms that foot-and-mouth disease virus contains several structural proteins. By electrophoresis in urea-polyaerylamide gels, virus of type O gave six distinct bands. In sodium dodecyl sulphatepolyacrylamide gels four proteins with molecular weights of 34, 3o, 26 and Iy5 x io 3 were clearly demonstrated. When virus preparations were labelled with a single amino acid, in both sodium dodecyl sulphate-polyacrylamide and ureapolyacrylamide gel electrophoresis, the fastest migrating protein contained no arginine and only traces of cysteine. This protein also stained differently from the other bands with Coomassie Blue and was absent from the I2S protein subunit prepared by mild acid (pH 6"5) disruption of the virus. This protein was separated from the I2S subunit by sucrose gradient centrifugation and by ion exchange chromatography on Amberlite IRC-5o.