Smectic phase in suspensions of gapped DNA duplexes

Area of Science:

• Biophysics
• Materials Science
• Liquid Crystals

Background:

• Aqueous solutions of stiff double-stranded DNA typically do not form smectic liquid crystal phases, despite forming other mesophases like chiral nematic and columnar.
• Flexibility in lyotropic systems usually destabilizes smectic phases.

Purpose of the Study:

• To investigate the formation of a smectic-A phase in DNA solutions by modifying DNA flexibility.
• To characterize the structure and thermodynamic stability of this novel DNA-based liquid crystal phase.

Main Methods:

• Synthesizing double-stranded DNA fragments with a single-stranded DNA spacer to introduce flexibility.
• Observing liquid crystal phase formation in aqueous solutions.
• Utilizing simulations to model the conformation and interactions of the gapped DNA duplexes.

Main Results:

• A smectic-A type phase, designated smectic-fA, was unambiguously formed by introducing flexibility into DNA duplexes.
• Simulations suggested gapped duplexes adopt a folded conformation within the smectic layers.
• Both entropic and energetic factors were identified as stabilizing the smectic-fA phase.

Conclusions:

• DNA flexibility, introduced via a single-stranded spacer, can stabilize a smectic-A phase in aqueous solutions, contrary to typical lyotropic behavior.
• The engineered gapped DNA duplexes form a unique folded structure within the smectic layers.
• DNA serves as a versatile building block for engineering tunable lyotropic liquid crystals with diverse mesophases.