Bhattacharya Santanu, Bajaj Avinash
Department of Organic Chemistry, Indian Institute of Science, Bangalore 560 012, India.
J Phys Chem B. 2007 Dec 6;111(48):13511-9. doi: 10.1021/jp0750203. Epub 2007 Nov 9.
Membrane-forming properties of five new gemini cationic lipids possessing an aromatic backbone between the headgroup and hydrocarbon chains have been presented. These gemini lipids differ by the number of polymethylene units [-(CH(2))(n)-] between the cationic ammonium -[N(+)(CH(3))(2)]- headgroups. The membrane-forming properties of these gemini lipids have been studied in detail by transmission electron microscopy (TEM), dynamic light scattering (DLS), X-ray diffraction (XRD), high-sensitivity differential scanning calorimetry (DSC), Paldan fluorescence studies, and UV-vis absorption spectroscopy. The electron micrographs and dynamic light scattering of their aqueous suspensions confirmed the formation of vesicular-type aggregates. The vesicle sizes and morphologies were found to depend strongly on the n-value of the spacer. Information on the thermotropic and hydration properties of the resulting vesicles was obtained from differential scanning calorimetry and temperature-dependent Paldan fluorescence studies, respectively. Examination of the thermotropic phase-transition properties of the lipid aggregates revealed interesting features of these lipids, which were found to depend on the length of the spacer chain. Paldan fluorescence studies indicate that the membranes of the gemini lipids are less hydrated as compared to that of the monomeric counterpart in their solid-gel state. In contrast in their fluid, liquid-crystalline phase, the hydration of gemini lipid aggregates was found to depend strongly on the length of the spacer. UV-vis absorption studies suggest an apparent H-type aggregate formation in the gemini lipid membranes in the gel states. In fluid state of the lipid membranes, H-aggregate formation was found to be enhanced depending on the length of the spacer. Such an understanding of the properties upon membrane formation from this new class of gemini lipids will be useful for further development of related gene delivery systems.
本文介绍了五种新型双子阳离子脂质的成膜特性，这些脂质在头基和烃链之间具有芳香主链。这些双子脂质的区别在于阳离子铵基[-N+(CH3)2]-头基之间的亚甲基单元[-(CH2)n-]数量不同。通过透射电子显微镜（TEM）、动态光散射（DLS）、X射线衍射（XRD）、高灵敏度差示扫描量热法（DSC）、帕尔丹荧光研究和紫外可见吸收光谱等方法，详细研究了这些双子脂质的成膜特性。其水悬浮液的电子显微镜照片和动态光散射证实了囊泡型聚集体的形成。发现囊泡大小和形态强烈依赖于间隔基的n值。分别从差示扫描量热法和温度依赖性帕尔丹荧光研究中获得了所得囊泡的热致和水合性质信息。对脂质聚集体的热致相变性质的研究揭示了这些脂质的有趣特征，发现这些特征取决于间隔链的长度。帕尔丹荧光研究表明，与单体对应物的固体凝胶态相比，双子脂质的膜水化程度较低。相反，在其流体液晶相中，发现双子脂质聚集体的水化程度强烈依赖于间隔基的长度。紫外可见吸收研究表明，在凝胶态的双子脂质膜中明显形成了H型聚集体。在脂质膜的流体状态下，发现H聚集体的形成根据间隔基的长度而增强。对这类新型双子脂质成膜性质的这种理解将有助于相关基因递送系统的进一步开发。
