Correction of systematic errors in single-molecule force spectroscopy with polymeric tethers by atomic force microscopy
Correction of systematic errors in single-molecule force spectroscopy with polymeric tethers by atomic force microscopy
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DOI：
10.1021/jp065530h
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发表时间：
2007-03-01
影响因子：
3.3
通讯作者：
Akhremitchev, Boris B.
中科院分区：
文献类型：
--
作者：
Ray, Chad;Brown, Jason R.;Akhremitchev, Boris B.
单分子力谱已成为研究各种分子缔合物的分子间能量分布的重要工具。原子力显微镜（AFM）通常被用作这些测量的实验技术，并且Bell-Evans模型通常用于断裂力的统计分析。贝尔-埃文斯模型的大多数应用都考虑了施加在分子间键上的力的恒定加载速率。数据分析往往是不一致的，因为无论是探头速度或表观加载速率被用作一个独立的参数。这些方法在基于AFM的实验中使用时提供不同的结果。结果中的显着变化产生的AFM力传感器的相对刚度相比，与聚合物系链的刚度，链接研究中的分子的固体表面。这里提出的分析模型占力谱参数的系统误差所产生的非线性负载引起的聚合物系绳。所提出的分析模型是基于贝尔-埃文斯模型的强制解离动力学和渐近模型的系绳拉伸。分析了两种最常用的数据处理方法，给出了系统误差的解析表达式。该模型表明，屏障的宽度被低估，解离速率显着高估时，力谱数据进行分析，不考虑聚合物系链的弹性。给出了渐近自由连接链和蠕虫状链聚合物模型的系统误差估计。的分析模型的基础上的渐近自由连接的链拉伸的分析和校正的双系绳力谱实验的结果分离的“疏水键”之间的个别十六烷分子，通过共价连接的聚（乙二醇）连接基的不同长度的衬底和AFM探针。校正算法的应用降低了数据从平均值的扩展，这对于解离速率的测量是特别重要的，并且将屏障宽度增加到0.43 nm，这可能指示理论上预测的疏水去湿。
Single-molecule force spectroscopy has become a valuable tool for the investigation of intermolecular energy landscapes for a wide range of molecular associations. Atomic force microscopy (AFM) is often used as an experimental technique in these measurements, and the Bell-Evans model is commonly used in the statistical analysis of rupture forces. Most applications of the Bell-Evans model consider a constant loading rate of force applied to the intermolecular bond. The data analysis is often inconsistent because either the probe velocity or the apparent loading rate is being used as an independent parameter. These approaches provide different results when used in AFM-based experiments. Significant variations in results arise from the relative stiffness of the AFM force sensor in comparison with the stiffness of polymeric tethers that link the molecules under study to the solid surfaces. An analytical model presented here accounts for the systematic errors in force-spectroscopy parameters arising from the nonlinear loading induced by polymer tethers. The presented analytical model is based on the Bell-Evans model of the kinetics of forced dissociation and on the asymptotic models of tether stretching. The two most common data reduction procedures are analyzed, and analytical expressions for the systematic errors are provided. The model shows that the barrier width is underestimated and that the dissociation rate is significantly overestimated when force-spectroscopy data are analyzed without taking into account the elasticity of the polymeric tether. Systematic error estimates for asymptotic freely jointed chain and wormlike chain polymer models are given for comparison. The analytical model based on the asymptotic freely jointed chain stretching is employed to analyze and correct the results of the double-tether force-spectroscopy experiments of disjoining "hydrophobic bonds" between individual hexadecane molecules that are covalently tethered via poly(ethylene glycol) linkers of different lengths to the substrates and to the AFM probes. Application of the correction algorithm decreases the spread of the data from the mean value, which is particularly important for measurements of the dissociation rate, and increases the barrier width to 0.43 nm, which might be indicative of the theoretically predicted hydrophobic dewetting.