Bond Orientational Order, Molecular Motion and Free Energy of High Density DNA Mesophases

Abstract

By equilibrating condensed DNA arrays against reservoirs of known osmotic stress and examining them with several structural probes, it has been possible to achieve a detailed thermodynamic and structural characterization of the change between two distinct regions on the liquid crystalline phase digram: a higher-density hexagonally packed region with long-range bond orientational order in the plane perpendicular to the average molecular direction; and a lower-density cholesteric region with fluid-like positional order. X-rays scattering on highly ordered DNA arrays at high density and with the helical axis oriented parallel to the incoming beam showed a six-fold azimuthal modulation of the first order diffraction peak that reflects the macroscopic bond-orientational order. Transition to the less-dense cholesteric phase through osmotically controlled swelling shows the loss of this bond orientational order that had been expected from the change in optical birefringence patterns and that is consistent with a rapid onset of molecular positional disorder. This change in motion was previously inferred from intermolecular force measurements and is now confirmed by ${}^{31}\mathrm{P}$ NMR. Controlled reversible swelling and compaction under osmotic stress, spanning a range of densities between $\sim 120$ mg/ml to $\sim 600$ mg/ml, allows measurement of the free energy changes throughout each phase and at the phase transition, essential information for theories of liquid-crystalline states.

14 pages, 3 figures in gif format available at http://abulafia.mgsl.dcrt.nih.gov/pics.html E-mail: [email protected]

Cited by in corpus (16)

• Charge Fluctuation Forces Between Stiff Polyelectrolytes in Salt Solution: Pairwise Summability Re-examined
• Energies and pressures in viruses: contribution of nonspecific electrostatic interactions
• Equation of state for polymer liquid crystals: theory and experiment
• On the Microscopic Origin of Cholesteric Pitch
• Attraction between DNA molecules mediated by multivalent ions
• Entropy driven formation of a chiral liquid crystalline phase of helical filaments
• Electrostatic Interaction between Long, Rigid Helical Macromolecules at All Interaxial Angles
• Effective interaction between helical bio-molecules
• Positional, Reorientational and Bond Orientational Order in DNA Mesophases
• Generalized liquid crystals: giant fluctuations and the vestigial chiral order of $I$, $O$ and $T$ matter
• Statistical Mechanics of Vacancy and Interstitial Strings in Hexagonal Columnar Crystals
• Ordering of anisotropic polarizable polymer chains on the full many-body level
• Confined chiral polymer nematics: ordering and spontaneous condensation
• Boundary Effects in Chiral Polymer Hexatics
• Coupling between Smectic and Twist Modes in Polymer Intercalated Smectics
• The Casimir free energy of peptide films on a silicon substrate: Impact of dielectric-to-metal transition in silicon and nanoparticles in peptide