Department of Physical Chemistry, Faculty of Chemical and Food Technology, Slovak University of Technology, Radlinského 9, SK-812 37 Bratislava, Slovakia.
Biophys Chem. 2012 Jan;160(1):35-45. doi: 10.1016/j.bpc.2011.09.002. Epub 2011 Sep 22.
Liposome dispersions obtained from the mixture of gemini surfactants of the type alkane-α,ω-diyl-bis(alkyldimethylammonium bromide) and helper lipid DOPC create complexes with DNA showing a regular inner microstructure, identified by small angle X-ray diffraction as condensed lamellar phase (L(α)(c)). In addition to the L(α)(c) phase, a coexisting lamellar phase L(B) was also identified in the complexes formed, with periodicities in the range ~8.8-5.7nm, at ionic strengths corresponding to 50-200mM NaCl. The periodicities of L(B) phase did not correspond to those identified in liposome dispersion without DNA using small angle neutron scattering. The observed phase separation is shown to depend on the interplay between the surface charge density of cationic liposomes, ionic strength and method of complex preparation. The effect of ionic strength on complex formation was studied by isothermal titration calorimetry and zeta potential measurements. High ionic strength reduces the fraction of bound DNA in the complexes, and the isoelectric point is attained at a ratio of DNA/gemini surfactant which is lower than the one that can be estimated by calculation based on nominal charges of CLs and DNA.
由双子表面活性剂（烷烃-α，ω-二基-双（烷基二甲基溴化铵）和辅助脂质 DOPC 的混合物获得的脂质体分散体与 DNA 形成复合物，显示出规则的内部微观结构，通过小角 X 射线衍射鉴定为凝聚的层状相（L(α)(c)）。除了 L(α)(c)相外，还在形成的复合物中鉴定出了共存的层状相 L(B)，其周期性在~8.8-5.7nm 范围内，在对应于 50-200mM NaCl 的离子强度下。L(B)相的周期性与使用小角中子散射在没有 DNA 的脂质体分散体中识别的周期性不对应。观察到的相分离显示取决于阳离子脂质体的表面电荷密度、离子强度和复合物制备方法之间的相互作用。通过等温热滴定法和 zeta 电位测量研究了离子强度对复合物形成的影响。高离子强度会降低复合物中结合的 DNA 分数，等电点在 DNA/双子表面活性剂的比例达到低于可以根据 CLs 和 DNA 的名义电荷计算估计的值。
