Membrane nanoobjects are very important tools to study biomembrane properties. Two types are described herein: Bicelles and Nanodiscs. Bicelles are obtained by thorough water mixing of long chain and short chain lipids and may take the form of membranous discs of 10–50 nm. Temperature-composition-hydration diagrams have been established for Phosphatidylcholines and show limited domains of existence. Bicelles can be doped with charged lipids, surfactants or with cholesterol and offer a wide variety of membranous platforms for structural biology. Internal dynamics as measured by solid-state NMR is very similar to that of liposomes in their fluid phase. Because of the magnetic susceptibility anisotropy of the lipid chains, discs may be aligned along or perpendicular to the magnetic field. They may serve as weak orienting media to provide distance information in determining the 3D structure of soluble proteins. In different conditions they show strong orienting properties which may be used to study the 3D structure, topology and dynamics of membrane proteins. Lipid Bicelles with biphenyl chains or doped with lanthanides show long lasting remnant orientation after removing the magnetic field due to smectic-like properties. An alternative to pure lipid Bicelles is provided by nanodiscs where the half torus composed by short chain lipids is replaced by proteins. This renders the nano-objects less fragile as they can be used to stabilize membrane protein assemblies to be studied by electron microscopy. Internal dynamics is again similar to liposomes except that the phase transition is abolished, possibly due to lateral constrain imposed by the toroidal proteins limiting the disc size. Advantages and drawbacks of both nanoplatforms are discussed.

膜纳米物体是研究生物膜特性的非常重要的工具。本文描述了两种类型：Bicelles和Nanodiscs。Bicelles是通过长链和短链脂质的充分水混合而获得的，并且可能呈10–50 nm的膜状圆盘形式。已经建立了磷脂酰胆碱的温度-组成-水合图，并显示了存在的有限域。Bicelles可以掺入带电荷的脂质，表面活性剂或胆固醇，并为结构生物学提供多种膜平台。通过固态NMR测量的内部动力学与脂质体在其液相中的动力学非常相似。由于脂质链的磁化率各向异性，圆盘可能沿着磁场或垂直于磁场排列。它们可以用作弱定向介质，以在确定可溶性蛋白质的3D结构时提供距离信息。在不同条件下，它们显示出很强的定向特性，可用于研究膜蛋白的3D结构，拓扑和动力学。由于具有近晶状性质，具有联苯链或掺杂有镧系元素的脂质Bicelles在去除磁场后显示出持久的残余取向。纳米圆盘提供了纯脂质Bicelles的替代产品，其中短链脂质组成的半圆环被蛋白质取代。这使得纳米物体较不易碎，因为它们可用于稳定要通过电子显微镜研究的膜蛋白组件。内部动力学与脂质体类似，只是相变被取消了，可能是由于环形蛋白质施加的侧向约束限制了椎间盘的大小。讨论了两种纳米平台的优缺点。