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Smectic phase in suspensions of gapped DNA duplexes.

  • Author(s): Salamonczyk, Miroslaw
  • Zhang, Jing
  • Portale, Giuseppe
  • Zhu, Chenhui
  • Kentzinger, Emmanuel
  • Gleeson, James T
  • Jakli, Antal
  • De Michele, Cristiano
  • Dhont, Jan KG
  • Sprunt, Samuel
  • Stiakakis, Emmanuel
  • et al.
Abstract

Smectic ordering in aqueous solutions of monodisperse stiff double-stranded DNA fragments is known not to occur, despite the fact that these systems exhibit both chiral nematic and columnar mesophases. Here, we show, unambiguously, that a smectic-A type of phase is formed by increasing the DNA's flexibility through the introduction of an unpaired single-stranded DNA spacer in the middle of each duplex. This is unusual for a lyotropic system, where flexibility typically destabilizes the smectic phase. We also report on simulations suggesting that the gapped duplexes (resembling chain-sticks) attain a folded conformation in the smectic layers, and argue that this layer structure, which we designate as smectic-fA phase, is thermodynamically stabilized by both entropic and energetic contributions to the system's free energy. Our results demonstrate that DNA as a building block offers an exquisitely tunable means to engineer a potentially rich assortment of lyotropic liquid crystals.

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