  Two-dimensional semiflexible polymer rings are studied both by imaging
circular DNA adsorbed on a mica surface and by Monte Carlo simulations of
phantom polymers as well as of polymers with finite thickness. Comparison of
size and shape of the different models over the full range of flexibilities
shows that excluded volume caused by finite thickness induces an anisotropic
increase of the main axes of the conformations, a change of shape, accomplished
by an enhanced correlation along the contour.
