Small angle X-ray scattering study of the influence of temperature on the structure of DNA/lipid complexes

We report on the synchrotron small-angle X-ray scattering (SAXS) study of self-assembled complex formed by mixing short-chain DNAs with cationic phospholipids in water. The DNA/lipid complex is a sandwiched structure, consisting of alternate layers of DNAs and lipid bilayers with a periodicity of d(D/L). The DNAs at the interfaces are one-dimensionally ordered with a periodicity of d(DNA). When the temperature of the system is increased, the lipid bilayers become soft so that the DNAs are trapped more deeply inside the lipid bilayers. This explains why the measured d(D/L) decreases insignificantly with the increase of temperature. On the other hand, the value of dDNA keeps constant because of the stiffness of the DNAs.