Abstract
A new procedure for the separation of influenza virus particle ribonucleoproteins (RNPs) by electrophoresis on a slab of polyacrylamide gel resolves five discrete bands. The largest is a triplet containing the three largest RNAs (1 to 3), the intermediate sized RNP is a doublet containing RNAs 5 and 6 and the others each contain a single RNA. In addition, each RNP is composed of NP protein and an amount of M which is independent of the size of the RNP. This suggests that some virus particle M is specifically associated with influenza ribonucleoprotein.