Brasnett Christopher, Longstaff Georgia, Compton Laura, Seddon Annela
H.H. Wills Physics Laboratory, Tyndall Avenue, University of Bristol, Bristol, BS8 1FD, UK.
Bristol Centre for Functional Nanomaterials, HH Wills Physics Laboratory, Tyndall Avenue, University of Bristol, Bristol, BS8 1FD, UK.
Sci Rep. 2017 Aug 15;7(1):8229. doi: 10.1038/s41598-017-08438-4.
Inverse bicontinuous cubic structures formed by lipids have been demonstrated in a wide variety of applications, from a host matrix for proteins for crystallisation, to templates for nanoscale structures. Recent work has focused on tuning their properties to realize such applications, often by manipulating the structure by introducing other lipids with different properties such as charge or packing. However, they are often prepared in the presence of solutions containing salt, counteracting the effects, for example, charged lipids, and fundamentally changing the structures obtained. Here, we demonstrate the delicate interplay between electrostatic swelling in bicontinuous structures formed by monoolein (MO) doped with both negatively charged dioleyl phosphatidylglycerol (DOPG), and zwitterionic dioleyl phosphatidylethanolamine (DOPE), with the addition of mono- and divalent salts. The effect of adding salt to the charged phase changes the structure from the primitive cubic ([Formula: see text]) to the double diamond phase ([Formula: see text]) whilst still allowing for modest increases in lattice parameter of up to a nanometer. Contrasting this, the addition of salts to the non-charged phase, has minimal effect on the lattice parameter but now the transition from the ([Formula: see text]) to the inverse hexagonal phase (H ) is observed occurring at higher mole fractions of DOPE than in pure water.
由脂质形成的反向双连续立方结构已在广泛的应用中得到证实，从用于蛋白质结晶的主体基质到纳米级结构的模板。最近的工作集中在调整它们的性质以实现此类应用，通常是通过引入具有不同性质（如电荷或堆积）的其他脂质来操纵结构。然而，它们通常是在含有盐的溶液存在下制备的，这会抵消例如带电脂质的作用，并从根本上改变所获得的结构。在这里，我们展示了在由掺杂有带负电荷的二油酰磷脂酰甘油（DOPG）和两性离子二油酰磷脂酰乙醇胺（DOPE）的单油酸甘油酯（MO）形成的双连续结构中，静电膨胀与添加单价和二价盐之间的微妙相互作用。向带电相添加盐会使结构从原始立方相（[公式：见原文]）转变为双菱形相（[公式：见原文]），同时仍允许晶格参数适度增加至纳米级。与此形成对比的是，向不带电相添加盐对晶格参数的影响最小，但现在观察到从（[公式：见原文]）到反六角相（H ）的转变在比纯水中更高的DOPE摩尔分数下发生。
