Smectic-B phase and temperature-driven smectic-B to -A transition in concentrated solutions of “gapped” DNA

The occurrence of a smectic-B (Sm-B) phase is demonstrated in concentrated aqueous solutions of “gapped” DNA constructs consisting of fully paired duplexes bridged by a flexible, unpaired strand of nucleotides. The Sm-B phase, identified by small and wide angle x-ray scattering measurements and optical microscopy, develops from a smectic-A (Sm-A) phase with increasing DNA concentration at room temperature. It transitions (reversibly) to the Sm-A when the temperature is raised above ∼50^{∘}C.