The C. Eugene Bennett Department of Chemistry, West Virginia University, Morgantown, West Virginia 26505, USA.
Langmuir. 2012 Sep 18;28(37):13411-22. doi: 10.1021/la302705f. Epub 2012 Sep 5.
It has been demonstrated that many biological processes are influenced by mechanical changes in membranes comprised of a variety of lipid components. As a result, the ability to map physicomechanical properties of surfaces with high temporal and spatial resolution is desirable. Tapping mode atomic force microscopy (AFM) has proven to be a useful technique for imaging biological surfaces due to its ability to operate in solution; however, access to information concerning the mechanical properties of these surfaces can also be obtained by reconstructing the time-resolved tip/sample force interactions during the imaging process. An advantage of such an approach is the direct correlation of topographical features with mechanical properties. Reconstruction of the tip/sample force is achievable by a technique called scanning probe acceleration microscopy (SPAM), which treats the cantilever as an accelerometer. The acceleration, which is directly related to the tip/sample force, of the cantilever is obtained by taking the second derivative of the cantilever deflection signal during a tapping mode AFM experiment in solution with standard cantilevers. Herein, we describe the applicability of SPAM to study mechanical properties of supported lipid bilayers with nanoscale spatial resolution via numerical simulations and experiment. The maximum and minimum tapping forces respond to changes in specific surface mechanical properties. Furthermore, we demonstrate how these changes can be used to map relative changes in the Young's modulus and adhesive properties of supported total brain lipid extract bilayers containing exogenous cholesterol. Finally, the ability of SPAM to distinguish nanoscale lipid raft domains based on changes in local mechanical properties is demonstrated.
已经证明，许多生物过程受到由各种脂质成分组成的膜的机械变化的影响。因此，能够以高时间和空间分辨率绘制表面物理机械性能的能力是理想的。由于能够在溶液中操作，因此， tapping 模式原子力显微镜（AFM）已被证明是一种用于成像生物表面的有用技术；然而，通过重建成像过程中时变的针尖/样品力相互作用，也可以获得有关这些表面机械性能的信息。这种方法的一个优点是形貌特征与机械性能直接相关。通过一种称为扫描探针加速显微镜（SPAM）的技术来实现针尖/样品力的重建，该技术将悬臂梁视为加速度计。在溶液中使用标准悬臂梁进行 tapping 模式 AFM 实验时，通过对悬臂梁挠度信号的二阶导数来获得与针尖/样品力直接相关的悬臂梁加速度。在此，我们通过数值模拟和实验描述了 SPAM 用于通过纳米级空间分辨率研究支撑脂质双层的机械性能的适用性。最大和最小敲击力响应特定表面机械性能的变化。此外，我们展示了如何使用这些变化来映射含有外源性胆固醇的总脑脂质提取物支撑双层的杨氏模量和粘附性能的相对变化。最后，展示了 SPAM 根据局部机械性能的变化来区分纳米级脂质筏域的能力。
