Random-Sequence\nDNA Oligomers Make Liquid Crystals:\nA Case of Collective Ordering in a Superdiverse Environment

The availability of synthetic, analytical, and predictive\ntools\nmakes DNA an ideal platform, not yet considered, to investigate statistical\nand soft matter physics. Here we report and interpret the equilibrium\ncollective ordering in solutions of random-sequence DNA (rsDNA) oligomers\nof lengths <i>L</i> = 8 and <i>L</i> = 12. Despite\nthe extreme molecular diversity inherent in rsDNA solutions, which\nfor <i>L</i> = 12 are composed of 20 million distinct molecular\nspecies, these systems develop long-range columnar liquid crystal\n(LC) ordering when equilibrated at high osmotic pressure. By a combination\nof experimental models and computed statistics, we demonstrate that\nthe residual end-to-end attraction between rsDNA duplexes, which typically\nterminate with various forms of pairing errors, is indeed sufficient\nto drive LC ordering. The resulting narrow range of isotropic-LC phase\ncoexistence, in seeming contrast with the variety of phase behaviors\nof the species composing rsDNA, demonstrates that the (nearly) continuum\ndistribution of molecular interaction strengths effectively reduces\nthe tendency for demixing instead of enhancing it, in line with theoretical\nmodeling.