Department of Bionanoscience, Kavli Institute of Nanoscience, Delft University of Technology, Van der Maasweg 9, 2629 HZ, Delft, Netherlands.
School of Physics and Astronomy, University of Manchester, Oxford Road, Manchester, M13 9PL, United Kingdom.
Colloids Surf B Biointerfaces. 2018 Dec 1;172:400-406. doi: 10.1016/j.colsurfb.2018.08.041. Epub 2018 Aug 23.
In this study, we show that dry saturated phospholipid layers prepared by the spin-coating technique could present thinner regions associated to interdigitated phases under some conditions. The morphological characteristics of lipid layers of saturated phosphocholines, such as dilauroylphosphatidylcholine (DLPC), dimyristoylphosphatidylcholine (DMPC), dipalmitoylphosphatidylcholine (DPPC) and distearoylphosphatidylcholine (DSPC), have been measured by Atomic Force Microscopy and revealed that the presence of interdigitated regions is not induced by the same parameters that induce them in hydrated samples. To achieve these results the effect of the lipid hidrocabonated chain length, the presence of alcohol in the coating solution, the spinning velocity and the presence of cholesterol were tested. We showed that DPPC and DSPC bilayers, on the one side, can show structures with similar height than interdigitated regions observed in hydrated samples, while, on the other side, DLPC and DMPC tend to show no evidence of interdigitation. Results indicate that the presence of interdigitated areas is due to the presence of lateral tensions and, hence, that they can be eliminated by releasing these tensions by, for instance, the addition of cholesterol. These results demonstrate that interdigitation in lipid layers is a rather general phenomena and can be observed in lipid bilayers in dry conditions.
在这项研究中，我们表明，在某些条件下，通过旋涂技术制备的干燥饱和磷脂层可能会呈现出与交错相相关的较薄区域。通过原子力显微镜测量了饱和磷脂，如二棕榈酰磷脂酰胆碱（DLPC）、二肉豆蔻酰磷脂酰胆碱（DMPC）、二棕榈酰磷脂酰胆碱（DPPC）和二硬脂酰磷脂酰胆碱（DSPC）的脂质层的形态特征，结果表明交错区域的存在不是由在水合样品中诱导它们的相同参数引起的。为了实现这些结果，测试了脂质氢碳化链长、涂层溶液中存在的醇、旋转速度和胆固醇的存在对结果的影响。我们表明，一方面 DPPC 和 DSPC 双层可以显示出与在水合样品中观察到的交错区域相似高度的结构，而另一方面，DLPC 和 DMPC 则倾向于没有交错的迹象。结果表明，交错区域的存在是由于存在横向张力，因此，通过释放这些张力（例如添加胆固醇）可以消除交错区域。这些结果表明，脂质层中的交错是一种相当普遍的现象，可以在干燥条件下的脂质双层中观察到。
