Kolberg Adrianna, Wenzel Christiane, Hugel Thorsten, Gallei Markus, Balzer Bizan N
Institute of Physical Chemistry, Albert-Ludwigs-Universität Freiburg.
Institute of Physical Chemistry, Albert-Ludwigs-Universität Freiburg; Cluster of Excellence livMatS at FIT - Freiburg Center for Interactive Materials and Bioinspired Technologies, University of Freiburg.
J Vis Exp. 2020 Mar 16(157). doi: 10.3791/60934.
Atomic force microscopy (AFM)-based single molecule force spectroscopy is an ideal tool for investigating the interactions between a single polymer and surfaces. For a true single molecule experiment, covalent attachment of the probe molecule is essential because only then can hundreds of force-extension traces with one and the same single molecule be obtained. Many traces are in turn necessary to prove that a single molecule alone is probed. Additionally, passivation is crucial for preventing unwanted interactions between the single probe molecule and the AFM cantilever tip as well as between the AFM cantilever tip and the underlying surface. The functionalization protocol presented here is reliable and can easily be applied to a variety of polymers. Characteristic single molecule events (i.e., stretches and plateaus) are detected in the force-extension traces. From these events, physical parameters such as stretching force, desorption force and desorption length can be obtained. This is particularly important for the precise investigation of stimuli-responsive systems at the single molecule level. As exemplary systems poly(ethylene glycol) (PEG), poly(N-isopropylacrylamide) (PNiPAM) and polystyrene (PS) are stretched and desorbed from SiOx (for PEG and PNiPAM) and from hydrophobic self-assembled monolayer surfaces (for PS) in aqueous environment.
基于原子力显微镜（AFM）的单分子力谱是研究单个聚合物与表面之间相互作用的理想工具。对于真正的单分子实验，探针分子的共价连接至关重要，因为只有这样才能获得数百条来自同一个单分子的力-伸长曲线。反过来，需要许多曲线来证明所探测的是单个分子。此外，钝化对于防止单探针分子与AFM悬臂尖端以及AFM悬臂尖端与下层表面之间的不必要相互作用至关重要。这里介绍的功能化方案是可靠的，并且可以很容易地应用于各种聚合物。在力-伸长曲线中检测到特征性的单分子事件（即拉伸和平台期）。从这些事件中，可以获得诸如拉伸力、解吸力和解吸长度等物理参数。这对于在单分子水平上精确研究刺激响应系统尤为重要。作为示例系统，聚乙二醇（PEG）、聚（N-异丙基丙烯酰胺）（PNiPAM）和聚苯乙烯（PS）在水性环境中从SiOx（对于PEG和PNiPAM）以及从疏水自组装单分子层表面（对于PS）被拉伸和解吸。
