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Open Access Publications from the University of California

Smectic phase in suspensions of gapped DNA duplexes

  • Author(s): Salamonczyk, M
  • Zhang, J
  • Portale, G
  • Zhu, C
  • Kentzinger, E
  • Gleeson, JT
  • Jakli, A
  • De Michele, C
  • Dhont, JKG
  • Sprunt, S
  • Stiakakis, E
  • et al.

© The Author(s) 2016. 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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