OBSERVATION OF A RECTANGULAR COLUMNAR PHASE IN CONDENSED LAMELLAR CATIONIC LIPID-DNA COMPLEXES

We report on a synchrotron x-ray diffraction study of saturated cation ic lipid complexed with DNA. In the lipid gel phase L-beta(c), the com plexes exhibit Bragg reflections due to lamellar lipid bilayer stackin g and three nonintegral peaks in agreement with an intercalated center ed rectangular columnar superlattice of DNA. The diffuse broadening of the DNA peaks is caused by in-plane translational disorder of the DNA strands and is approximated by Lorentzians with positional correlatio n lengths of xi(y) approximate to 250 Angstrom out of plane and xi(x) > 2000 Angstrom in plane. We interpret our results in terms of a syste m of interacting two-dimensional smectic layers. [S0031-9007(98)07820- X].