Thermotropic structural changes of saturated-cationic-lipid–DNA complexes
Institut für Biophysik (E22), Physik Department, Technische
Universität München, James Franck Straße 1, D-85747 Garching, Germany
2 European Molecular Biology Laboratory, EMBL c/o DESY, Notkestr. 85, D-22603 Hamburg, Germany
Accepted: 30 October 1998
We investigated the thermotropic behavior of fully hydrated saturated cationic lipid mixture of DMPC/DMTAP (dimyristoylphosphatidyl-choline/dimyristoyl-trimethyl-am monium propane) complexed with DNA. Using simultaneous small- and wide-angle X-ray scattering, we found two condensed lamellar phases, a fluid - and a gel-state -phase. The chain-melting transition was accompanied by a decrease in the bilayer thickness and an expansion of the intercalated one-dimensional DNA rod lattice. The interaxial DNA-DNA spacings are quantitatively described by conservation of local volume fractions for both phases in excess water. The line broadening of the wide-angle scattering exhibited a systematic variation in the hydrocarbon chain tilt as a function of the cationic lipid molar fraction.
PACS: 87.15.By – Structure, bonding, conformation, configuration, and isomerism of bio mole cules / 61.30.Eb – Experimental determinations of smectic, nematic, cholesteric, and other structures / 82.70.Kj – Emulsions and suspensions
© EDP Sciences, 1999