Rappolt Michael, Amenitsch Heinz, Strancar Janez, Teixeira Cilaine V, Kriechbaum Manfred, Pabst Georg, Majerowicz Monika, Laggner Peter
Institute of Biophysics and X-Ray Structure Research, Austrian Academy of Sciences, Schmiedlstrasse 6, A-8042 Graz, Austria.
Adv Colloid Interface Sci. 2004 Nov 29;111(1-2):63-77. doi: 10.1016/j.cis.2004.07.004.
In this work, we report on recent investigations, both on the global and on the local molecular architecture of supported phospholipid model membranes. A brief theoretical introduction explains how global structural information on supramolecular lipid ensembles can be retrieved from surface X-ray diffraction measurements as well as how spin-label electron paramagnetic resonance spectroscopy (EPR) provides complementary information on the local environment of probe molecules. The combination of especially designed X-ray cells with the technique of small- and wide-angle X-ray surface scattering makes it possible to explore various fields of lipid research and its applications. Examples for different physico-chemical conditions are presented: (i) in situ chemistry under excess of water conditions demonstrating how solid-supported lipid films sense salinity, (ii) the 3D electron density reconstruction of a vesicle-fusion intermediate under controlled humidity, and (iii) complementary temperature and pressure effects on oriented phospholipid samples. Further, special attention has been given to the influence of different film preparation techniques with respect to quality and the defect structure manifestation. To resolve the proportions and local properties of defects in a hydrated lipid-deposited surface, spin-label EPR was applied. The results from 9.6 GHz EPR as well as from 1.2 GHz EPR suggest the alignment to be in the range between 30% and 80%. In addition, slow time-dependent EPR measurements point to nano-structural rearrangements due to water flow and reduction of alignment quality.
在这项工作中，我们报告了关于支撑磷脂模型膜的全球和局部分子结构的最新研究。简短的理论介绍解释了如何从表面X射线衍射测量中获取超分子脂质聚集体的全局结构信息，以及自旋标记电子顺磁共振光谱（EPR）如何提供关于探针分子局部环境的补充信息。特别设计的X射线池与小角和广角X射线表面散射技术的结合，使得探索脂质研究及其应用的各个领域成为可能。给出了不同物理化学条件的例子：（i）在水过量条件下的原位化学，展示了固体支撑脂质膜如何感知盐度；（ii）在受控湿度下囊泡融合中间体的三维电子密度重建；（iii）对取向磷脂样品的互补温度和压力效应。此外，还特别关注了不同膜制备技术对质量和缺陷结构表现的影响。为了确定水合脂质沉积表面缺陷的比例和局部性质，应用了自旋标记EPR。9.6 GHz EPR以及1.2 GHz EPR的结果表明排列率在30%至80%之间。此外，缓慢的时间依赖性EPR测量表明由于水流和排列质量降低导致纳米结构重排。
