Serpe Michael J, Whitehead Jason R, Rivera Monica, Clark Robert L, Craig Stephen L
Department of Chemistry, University of Rochester.
Colloids Surf A Physicochem Eng Asp. 2009 Aug 20;346(1-3):20-27. doi: 10.1016/j.colsurfa.2009.05.019.
Single-molecule force spectroscopy, as implemented in an atomic force microscope, provides a rarely-used method by which to monitor dynamic processes that occur near surfaces. Here, a methodology is presented and characterized that facilitates the study of polymer bridging across nanometer-sized gaps. The model system employed is that of DNA-based reversible polymers, and an automated procedure is introduced that allows the AFM tip-surface contact point to be automatically determined, and the distance d between opposing surfaces to be actively controlled. Using this methodology, the importance of several experimental parameters was systematically studied, e.g. the frequency of repeated tip/surface contacts, the area of the substrate surface sampled by the AFM, and the use of multiple AFM tips and substrates. Experiments revealed the surfaces to be robust throughout pulling experiments, so that multiple touches and pulls could be carried out on a single spot with no measurable affect on the results. Differences in observed bridging probabilities were observed, both on different spots on the same surface and, more dramatically, from one day to another. Data normalization via a reference measurement allows data from multiple days to be directly compared.
原子力显微镜中实施的单分子力谱提供了一种鲜少使用的方法，用于监测发生在表面附近的动态过程。在此，我们提出并表征了一种有助于研究聚合物跨越纳米级间隙的方法。所采用的模型系统是基于DNA的可逆聚合物，并且引入了一种自动化程序，该程序可以自动确定原子力显微镜（AFM）针尖与表面的接触点，并主动控制相对表面之间的距离d。使用这种方法，系统地研究了几个实验参数的重要性，例如重复的针尖/表面接触频率、AFM采样的基底表面面积，以及使用多个AFM针尖和基底。实验表明，在整个拉伸实验过程中表面都很稳定，因此可以在单个点上进行多次接触和拉伸，而对结果没有可测量的影响。在同一表面的不同点上，以及更显著地，在不同日期之间，观察到了桥接概率的差异。通过参考测量进行数据归一化处理，可以直接比较来自多天的数据。
