Polymorphism of DNA/multi-cationic lipid complexes driven by temperature and salts

The structural polymorphism of DNA/lipopolyamine (multi-cationic lipid) com plexes has been studied by X-ray diffraction and cryo-electron microscopy. Monovalent salt and temperature effects have been analyzed. Depending on th e treatment applied to the lipidic solution prior to DNA addition, two type s of structure can be obtained for identical final conditions: a classical lamellar structure and a more complex structure, The latter was shown to ap pear when the lipidic solution prepared in high salt condition is vortexed and quenched below the hydrocarbon chain melting temperature, before additi on to the DNA solution. It corresponds to some small facetted vesicles. Sim ilar behavior is observed for the poly(styrene-sulfonate)/lipid system.