  To simulate long time and length scale processes involving DNA it is
necessary to use a coarse-grained description. Here we provide an overview of
different approaches to such coarse graining, focussing on those at the
nucleotide level that allow the self-assembly processes associated with DNA
nanotechnology to be studied. OxDNA, our recently-developed coarse-grained DNA
model, is particularly suited to this task, and has opened up this field to
systematic study by simulations. We illustrate some of the range of DNA
nanotechnology systems to which the model is being applied, as well as the
insights it can provide into fundamental biophysical properties of DNA.
