The conformation of circular DNA molecules of various lengths adsorbed in a 2D conformation on a mica surface is studied. The results confirm the conjecture that the critical exponent $\nu$ is topologically invariant and equal to the self-avoiding walk value (in the present case $\nu =3/4$), and that the topology and dimensionality of the system strongly influence the crossover between the rigid regime and the self-avoiding regime at a scale $L\approx 7{\ell }_p$. Additionally, the bond correlation function scales with the molecular length $L$ as predicted. For molecular lengths $L\le 5{\ell }_p$, circular DNA behaves like a stiff molecule with an approximately elliptic shape.

• Received 2 June 2008

DOI:https://doi.org/10.1103/PhysRevLett.101.148103