Institute for Bioengineering of Catalonia, University of Barcelona, Barcelona, Spain.
Biophys J. 2012 Jan 4;102(1):66-74. doi: 10.1016/j.bpj.2011.10.051. Epub 2012 Jan 3.
How do metal cations affect the stability and structure of phospholipid bilayers? What role does ion binding play in the insertion of proteins and the overall mechanical stability of biological membranes? Investigators have used different theoretical and microscopic approaches to study the mechanical properties of lipid bilayers. Although they are crucial for such studies, molecular-dynamics simulations cannot yet span the complexity of biological membranes. In addition, there are still some experimental difficulties when it comes to testing the ion binding to lipid bilayers in an accurate way. Hence, there is a need to establish a new approach from the perspective of the nanometric scale, where most of the specific molecular phenomena take place. Atomic force microscopy has become an essential tool for examining the structure and behavior of lipid bilayers. In this work, we used force spectroscopy to quantitatively characterize nanomechanical resistance as a function of the electrolyte composition by means of a reliable molecular fingerprint that reveals itself as a repetitive jump in the approaching force curve. By systematically probing a set of bilayers of different composition immersed in electrolytes composed of a variety of monovalent and divalent metal cations, we were able to obtain a wealth of information showing that each ion makes an independent and important contribution to the gross mechanical resistance and its plastic properties. This work addresses the need to assess the effects of different ions on the structure of phospholipid membranes, and opens new avenues for characterizing the (nano)mechanical stability of membranes.
金属阳离子如何影响磷脂双层的稳定性和结构？离子结合在蛋白质插入和生物膜整体力学稳定性中扮演什么角色？研究人员已经使用不同的理论和微观方法来研究脂质双层的力学性质。尽管这些方法对于此类研究至关重要，但分子动力学模拟仍然无法跨越生物膜的复杂性。此外，在准确测试离子与脂质双层结合方面仍然存在一些实验困难。因此，需要从纳米尺度的角度建立一种新的方法，因为大多数特定的分子现象都发生在这个尺度上。原子力显微镜已成为研究脂质双层结构和行为的重要工具。在这项工作中，我们使用力谱法通过一种可靠的分子指纹（表现为接近力曲线中的重复跳跃）来定量表征电解质组成对纳米力学阻力的影响。通过系统地探测一组不同组成的双层膜，这些双层膜浸入由各种单价和二价金属阳离子组成的电解质中，我们获得了大量信息，表明每个离子对总机械阻力及其塑性特性都有独立且重要的贡献。这项工作解决了评估不同离子对磷脂膜结构影响的需求，并为膜的（纳米）力学稳定性提供了新的研究途径。
