Supercoiled
When the circular DNA of the SV40 virus is isolated and separated from its associated protein, the DNA duplex is underwound and assumes the supercoiled configuration.[1]
References
1. ^Lodish,H.,Berk,A.,Kaiser,C.A.,Krieger,M.,Bretscher,A.,Ploegh,H., and Amon,A. (2013) Molecular Cell Biology,