The Cyclic Helix and Cyclic Coil Forms of Polyoma Viral Dna

The DNA extracted from polyoma virus exhibits certain properties which have not been reported for other viral base-paired DNA's. (1) The DNA renatures monomolecularly. The loss of helical configuration does not impair biological activity. Heating at 100° for 10-20 min followed by rapid cooling does not reduce the infective titer. Dulbecco has given evidence suggesting that a fraction of the polyoma DNA molecules are cyclic. (2) This form would in part account for the above properties.