Biophysics, Faculty of Life Sciences, University of Copenhagen, Denmark.
Phys Chem Chem Phys. 2011 Feb 28;13(8):3161-70. doi: 10.1039/c0cp01074j. Epub 2010 Dec 10.
Nanodiscs™ consist of small phospholipid bilayer discs surrounded and stabilized by amphiphilic protein belts. Nanodiscs and their confinement and stabilization of nanometer sized pieces of phospholipid bilayer are highly interesting from a membrane physics point of view. We demonstrate how the detailed structure of Di-Lauroyl-Phosphatidyl Choline (DLPC) nanodiscs may be determined by simultaneous fitting of a structural model to small-angle scattering data from the nanodiscs as investigated in three different contrast situations, respectively two SANS contrasts and one SAXS contrast. The article gives a detailed account of the underlying structural model for the nanodiscs and describe how additional chemical and biophysical information can be incorporated in the model in terms of molecular constraints. We discuss and quantify the contribution from the different elements of the structural model and provide very strong experimental support for the nanodiscs as having an elliptical cross-section and with poly-histidine tags protruding out from the rim of the protein belt. The analysis also provides unprecedented information about the structural conformation of the phospholipids when these are localized in the nanodiscs. The model paves the first part of the way in order to reach our long term goal of using the nanodiscs as a platform for small-angle scattering based structural investigations of membrane proteins in solution.
纳米碟由小的磷脂双层圆盘组成，周围由两亲性蛋白带环绕和稳定。从膜物理的角度来看，纳米碟及其对纳米尺寸磷脂双层片的限制和稳定是非常有趣的。我们展示了如何通过同时拟合结构模型来确定 Di-Lauroyl-Phosphatidyl Choline (DLPC) 纳米碟的详细结构，该结构模型是在三种不同对比情况下研究纳米碟的小角散射数据得到的，分别是两种 SANS 对比和一种 SAXS 对比。本文详细介绍了纳米碟的基本结构模型，并描述了如何根据分子约束将额外的化学和生物物理信息纳入模型中。我们讨论并量化了结构模型不同元素的贡献，并为纳米碟具有椭圆形横截面和多组氨酸标签从蛋白带边缘突出提供了非常有力的实验支持。该分析还提供了关于磷脂在纳米碟中定位时的结构构象的前所未有的信息。该模型为我们的长期目标铺平了道路，即利用纳米碟作为平台，通过小角散射技术对溶液中的膜蛋白进行结构研究。
