  Effect of bending anisotropy on a planar DNA loop, using energy minimization
and neglecting entropic effects, is studied. We show that the anisotropy
results in polygonal shape of the loop and increasing the anisotropy makes the
edges sharper. Calculating the energy of such a loop lets us to find effective
persistence length as the geometrical mean of hard and soft rigidities, which
is quite different from harmonic mean for an unconstrained long DNA.
