  The interplay between bending of the molecule axis and appearance of
disruptions in circular DNA molecules, with $\sim 100$ base pairs, is
addressed. Three minicircles with different radii and almost equal content of
AT and GC pairs are investigated. The DNA sequences are modeled by a mesoscopic
Hamiltonian which describes the essential interactions in the helix at the
level of the base pair and incorporates twisting and bending degrees of
freedom. Helix unwinding and bubble formation patterns are consistently
computed by a path integral method that sums over a large number of molecule
configurations compatible with the model potential. The path ensembles are
determined, as a function of temperature, by minimizing the free energy of the
system. Fluctuational openings appear along the helix to release the stress due
to the bending of the molecule backbone. In agreement with the experimental
findings, base pair disruptions are found with larger probability in the
smallest minicircle of \textit{66-bps} whose bending angle is $\sim 6^{o} $.
For this minicircle, a sizeable untwisting is obtained with the helical repeat
showing a step-like increase at $\tau =\,315K$. The method can be generalized
to determine the bubble probability profiles of open ends linear sequences.
