The sliding columnar phase: A new phase of matter in DNA-lipid complexes

Under appropriate conditions, DNA and cationic and neutral lipids in water solutions form lamellar complexes in which the DNA strands form two-dimensional smectic-like structures in the galleries between lipid-bilayer lamellae. The subject of this presentation is the possible equilibrium phases these DNA-cationic-lipid lamellar complexes may exhibit. The DNA can form a two-dimensional centered rectangular columnar phase, a nematic lamellar phase in which the DNA has nematic orientational rather than smectic positional order at the longest length scales, or possibly a new phase of matter, which we call the sliding columnar phase. The latter phase is characterized by strong but not long-range smectic correlations, a vanishing shear modulus for sliding DKA planes across each other, and unusual exp(- ln(2) r) behavior of the DNA structure function.".