Figure 2.

(A) Small-angle X-ray scattering data for DOTAP/DOPC/cholesterol–DNA complexes, where Φ_DOTAP = 0.3 and DOPC is gradually replaced by cholesterol (Φ_DOPC + Φ_cholesterol = 0.7). The structure of these CL–DNA complexes remains lamellar with increasing Φ_cholesterol (first and second order of the lamellar peak are marked by q₀₀₁ and q₀₀₂). At Φ_cholesterol ≥ 0.4, phase coexistence of CL–DNA complexes and cholesterol monohydrate crystals is observed (q_chol, marked by grey arrows). Black arrowheads point to the DNA peak at q_DNA. (B) The interaxial spacing between DNA molecules (d_DNA) obtained from X-ray scattering data acquired at the isoelectric point of the CL–DNA complexes. At this point (lipid/DNA charge ratio = 1), d_DNA is directly correlated with the membrane charge density of the lipid bilayer because the negative charge of DNA precisely neutralizes the positive charge on the adjacent lipid bilayers. (C) Lamellar spacing d of cholesterol-containing CL–DNA complexes obtained from X-ray scattering data. The lamellar spacing rises from 70 Å to 72 Å and then drops to 65 Å as a function of increasing cholesterol content. In B and C, the transition from single-phase regime (all cholesterol is incorporated in the membrane) to multiphase regime (coexistence of CL–DNA complexes and cholesterol monohydrate crystals) is marked by a dashed line.