The mierostrycture of DNA-egg yolk phosphatidylcholinegemini surfactants complexes: effect of the spacer length

摘要

Background: The length of spacer of gemini surfactants affects the DNA packing in DNA-neutral phospholipid-gemini surfactant complexes. Methods: The microstructure of complexes DNA-egg yolk phosphatidylcholine (EYPC)-alkane-alpha,omega-diyl-bis(dodecyl-dimethylammonium bromides) (CnGS, spacer n=2-12, n is even) was studied using small angle X-ray diffraction. Results: At EYPC:CnGS=1:1 mol/mol, the condensed lamellar phase was identified in complexes with CnGS, n=2-4, whereas longer spacer (n>=6) induced a hexagonal phase. The condensed lamellar phase L_alpha~c was observed in the range 2< = EYPC:GnGS< =10 (mol/mol) in all complexes. The distance between adjacent DNA strands increases linearly with decreasing surface charge density of EYPC-CnGS vesicles. We determined the increase in d_(DNA) 0.40+-0.03 nm/l mol of EYPC from the slope of d_(DNA)=f (molEYPC/molCnGS) in the range of molar ratios 2< =EYPC:CnGS<=5. At lower surface charge density, EYPC:CnGS>5 mol/mol, the length of CnGS spacer (n=6-10) modulates the DNA-DNA distance. Conclusions: Both the short spacer of CnGS and the low molar ratio EYPC:CnGS result in the closest DNA-DNA packing. A high surface charge density of membrane was reported as a key parameter for transfection efficiency of L_alpha~c phase-forming complexes.