Two-dimensional condensation of DNA molecules on cationic lipid membranes

DNA molecules adsorbed onto supported cationic lipid membranes are highly condensed. The 2-D condensation requires the presence of free DNA molecules in the solution for a period about 12 h, in which the ratio of adsorbed DNA to the free DNA is about 5% or less. Once condensed, the adsorbed DNA molecules remain on the membrane after removing free DNA molecules in the solution. The adsorption-condensation of both the linear and the circular forms of DNA onto the cationic membrane is independent of the length of DNA. For the condensed DNA, the interhelical distance increases with increase in the concentration of monovalent Na+ ions. The fluidity of the membrane is essential to induce the close packing of the adsorbed DNA. Possible mechanisms of our findings are discussed.