  Short, partially complementary, single-stranded (ss)DNA strands can form
nanostructures with a wide variety of shapes and mechanical properties. It is
well known that semiflexible, linear dsDNA can undergo an isotropic to nematic
(IN) phase transition and that sufficiently bent structures can form a biaxial
nematic phase. Here we use numerical simulations to explore how the phase
behaviour of linear DNA constructs changes as we tune the mechanical properties
of the constituent DNA by changing the nucleotide sequence. The IN phase
transition can be suppressed in so-called DNA 'nunchakus': structures
consisting of two rigid dsDNA arms, separated by a sufficiently flexible
spacer. In this paper, we use simulations to explore what phase behavior to
expect for different linear DNA constructs. To this end, we first performed
numerical simulations exploring the structural properties of a number of
different DNA oligonucleotides, using the oxDNA package. We then used the
structural information generated in the oxDNA simulations to construct more
coarse-grained models of the rodlike, bent-core, and nunchaku DNA. These
coarse-grained models were used to explore the phase behavior of suspensions of
the various DNA constructs. The approach explored in this paper makes it
possible to 'design' the phase behavior of DNA constructs by a suitable choice
of the constituent nucleotide sequence.
