The DNA-DNA spacing in gemini surfactants-DOPE-DNA complexes.

ABSTRACT

Gemini surfactants from the homologous series of alkane-α,ω-diyl-bis(dodecyldimethylammonium bromide) (CnCS12, number of spacer carbons n=2-12) and dioleoylphosphatidylethanolamine (DOPE) were used for cationic liposome (CL) preparation. CLs condense highly polymerized DNA creating complexes. Small-angle X-ray diffraction identified them as condensed lamellar phase L(α)(C) in the studied range of molar ratios CnGS12/DOPE in the temperature range 20-60°C. The DNA-DNA distance (d(DNA)) is studied in dependence to CnGS12 spacer length and membrane surface charge density. The high membrane surface charge densities (CnGS12/DOPE=0.35 and 0.4mol/mol) lead to the linear dependence of d(DNA) vs. n correlating with the interfacial area of the CnGS12 molecule.