Fluctuations of Quasi-Two-Dimensional Smectics Intercalated between Membranes in Multilamellar Phases of DNA-Cationic Lipid Complexes

We theoretically elucidate lamellar phases of DNA-cationic lipid complexes as the very first realization of a decoupled phase of strongly fluctuating 2D smectic DNA manifolds weakly interacting across membranes. Because of couplings between adjacent 2D smectic $L_x\times L_y$ planes, recently observed ordinary 2D smectic behavior of DNA in-plane undulations, with $〈u^2〉\sim L_y^{1/2}\sim L_x$, must cross over, at long scales, to a novel fluctuation behavior, with $〈u^2〉\sim \left(\ln L_y{)}^2\sim \right(\ln L_x{)}^2$.