*MEMPHYS-Center for Biomembrane Physics, Department of Physics, Chemistry, and Pharmacy, University of Southern Denmark, DK-5230 Odense M, Denmark.
†Membrane Biophysics and Biophotonics Group, Department of Biochemistry and Molecular Biology, University of Southern Denmark, DK-5230 Odense M, Denmark.
Essays Biochem. 2015;57:1-19. doi: 10.1042/bse0570001.
All biological membranes consist of a complex composite of macromolecules and macromolecular assemblies, of which the fluid lipid-bilayer component is a core element with regard to cell encapsulation and barrier properties. The fluid lipid bilayer also supports the functional machinery of receptors, channels and pumps that are associated with the membrane. This bilayer is stabilized by weak physical and colloidal forces, and its nature is that of a self-assembled system of amphiphiles in water. Being only approximately 5 nm in thickness and still encapsulating a cell that is three orders of magnitude larger in diameter, the lipid bilayer as a material has very unusual physical properties, both in terms of structure and dynamics. Although the lipid bilayer is a fluid, it has a distinct and structured trans-bilayer profile, and in the plane of the bilayer the various molecular components, viz different lipid species and membrane proteins, have the capacity to organize laterally in terms of differentiated domains on different length and time scales. These elements of small-scale structure and order are crucial for the functioning of the membrane. It has turned out to be difficult to quantitatively study the small-scale structure of biological membranes. A major part of the insight into membrane micro- and nano-domains and the concepts used to describe them have hence come from studies of simple lipid bilayers as models of membranes, by use of a wide range of theoretical, experimental and simulational approaches. Many questions remain to be answered as to which extent the result from model studies can carry over to real biological membranes.
所有的生物膜都是由大分子和大分子组装体组成的复杂复合材料，其中流体脂质双层成分是关于细胞封装和屏障特性的核心元素。流体脂质双层还支持与膜相关的受体、通道和泵的功能机制。该双层由弱物理和胶体力稳定，其性质是水相中的两亲分子自组装系统。脂质双层的厚度约为 5nm，但仍包裹着直径大三个数量级的细胞，因此作为一种材料，它具有非常特殊的物理性质，无论是在结构还是动力学方面。尽管脂质双层是一种流体，但它具有独特的、结构化的跨双层轮廓，在双层平面内，各种分子成分，即不同的脂质种类和膜蛋白，具有在不同长度和时间尺度上的不同区域进行侧向组织的能力。这些小尺度结构和有序性的元素对于膜的功能至关重要。事实证明，定量研究生物膜的小尺度结构具有一定的难度。因此，对膜微区和纳米区的深入了解以及用于描述它们的概念主要来自于对简单脂质双层的研究，这些研究使用了广泛的理论、实验和模拟方法。对于模型研究的结果在多大程度上可以推广到真实的生物膜，仍有许多问题需要回答。
