  We use the oxDNA coarse-grained model to provide a detailed characterization
of the fundamental structural properties of DNA origamis, focussing on
archetypal 2D and 3D origamis. The model reproduces well the characteristic
pattern of helix bending in a 2D origami, showing that it stems from the
intrinsic tendency of anti-parallel four-way junctions to splay apart, a
tendency that is enhanced both by less screened electrostatic interactions and
by increased thermal motion. We also compare to the structure of a 3D origami
whose structure has been determined by cryo-electron microscopy. The oxDNA
average structure has a root-mean-square deviation from the experimental
structure of 8.4 Angstrom, which is of the order of the experimental
resolution. These results illustrate that the oxDNA model is capable of
providing detailed and accurate insights into the structure of DNA origamis,
and has the potential to be used to routinely pre-screen putative origami
designs.
