Observation of NanoDNA Liquid Crystal Phases from Four Base Pair Duplexes at Subambient Temperatures

Based upon conventional Onsager model considerations, liquid crystal (LC) formation in DNA-water mixtures was originally thought to be impossible for DNA polymers of very short length (\textless 100 bases). We originally reported the discovery of chiral nematic (N*), columnar C$_{\mathrm{U}}$ and C$_{2}$ LC phases in NanoDNA oligomers as short as 6 bases in length and have since described additional LC phases involving DNA with random sequences and various blunt or sticky-end duplex architecture, all in the regime of \textless 20 bases. These results suggested a self-assembly motif where hydrophobic forces or hydrogen bond mediated base-pairing enable unusually short polymers to stack into functionally longer units that permit them to exhibit LC phase behavior. We report now the existence of LC phases of ultra short duplexed NanoDNA, 4 bases in length, in blunt-end, sticky-end and random sequence configurations, all observed at temperatures of $\sim$ 5 $^{\circ}$C and not stable \textgreater 13-15 $^{\circ}$C. These oligomers demonstrate an unusual wealth of phase behavior, including the typical N*, C$_{\mathrm{U}}$ and C$_{2}$ phases as well as higher order dark and bright phases, including what we believe to be a Blue Phase.