  The computational modelling of DNA is becoming crucial in light of new
advances in DNA nanotechnology, single-molecule experiments and in vivo DNA
tampering. Here we present a mesoscopic model for double stranded DNA (dsDNA)
at the single nucleotide level which retains the characteristic helical
structure, while being able to simulate large molecules -- up to a million base
pairs -- for time-scales which are relevant to physiological processes. This is
made possible by an efficient and highly-parallelised implementation of the
model which we discuss here. We compare the behaviour of our model with single
molecule experiments where dsDNA is manipulated by external forces or torques.
We also present some results on the kinetics of denaturation of linear DNA.
