Liquid Crystal Ordering of Four-Base-Long DNA Oligomers with Both G–C and A–T Pairing

We report the liquid crystal (LC) ordering in an aqueous solution of four-base-long DNA oligomers 5′-GCTA-3′. In such systems, the formation of the chiral nematic (N*) LC phase is the result of a continuous self-assembly process in which double helix stability is achieved only through linear chaining of multiple DNA strands. The thermal stability of the aggregates and their LC phase diagram have been experimentally investigated, quantitatively interpreted with theoretical models and compared with recent results on four-base sequences with only G–C or only A–T pairing motifs. N* phase is found at GCTA concentration, cDNA, between 240 and 480 mg/mL and at temperature T < 30 ◦C. The twist of the nematic director is found to be left-handed with pitch (p) in the optical range, increasing with cDNA and decreasing with T.