Elementary smectic ordering of “gapped” DNA duplexes*

We used small angle X-ray scattering and optical microscopy to study the liquid crystalline behavior of “gapped” DNA duplexes in aqueous solution. Our previous work¹ revealed the occurrence of a smectic-A phase for DNA concentrations in the range _^~230 to _^~300 mg/ml and for a single-strand “gap” between duplexes of 20 thymine bases. Here we describe evidence for two coexisting/competing smectic-A-like layer structures, whose relative population varies with temperature and “gap” length. Smectic layering occurs for gap lengths down to 4 bases but disappears when the gap is reduced to 2 bases. Transitions from smectic to cholesteric/nematic state are observed as a function of temperature.

Reference
(1) Salamonczyk, M.; Zhang, J.; Portale, G.; Zhu, C.; Kentzinger, E.; Gleeson, J. T.; Jakli, A.; De Michele, C.; Dhont, J. K. G.; Sprunt, S.; et al. Smectic Phase in Suspensions of Gapped DNA Duplexes. Nat. Commun. 2016, 7, 13358.