Schmidt Sebastian W, Pill Michael F, Kersch Alfred, Clausen-Schaumann Hauke, Beyer Martin K
Munich University of Applied Sciences, Department of Applied Natural Sciences and Mechatronics, Lothstr. 34, 80335 Munich, Germany.
Faraday Discuss. 2014;170:357-67. doi: 10.1039/c3fd00119a.
AFM-based dynamic single-molecule force spectroscopy was used to stretch carboxymethylated amylose (CMA) polymers, which have been covalently tethered between a silanized glass substrate and a silanized AFM tip via acid-catalyzed ester condensation at pH 2.0. Rupture forces were measured as a function of temperature and force loading rate in the force-ramp mode. The data exhibit significant statistical scattering, which is fitted with a maximum likelihood estimation (MLE) algorithm. Bond rupture is described with a Morse potential based Arrhenius kinetics model. The fit yields a bond dissociation energy De = 35 kJ mol(-1) and an Arrhenius pre-factor A = 6.6 × 10(4) s(-1). The bond dissociation energy is consistent with previous experiments under identical conditions, where the force-clamp mode was employed. However, the bi-exponential decay kinetics, which the force-clamp results unambiguously revealed, are not evident in the force-ramp data. While it is possible to fit the force-ramp data with a bi-exponential model, the fit parameters differ from the force-clamp experiments. Overall, single-molecule force spectroscopy in the force-ramp mode yields data whose information content is more limited than force-clamp data. It may, however, still be necessary and advantageous to perform force-ramp experiments. The number of successful events is often higher in the force-ramp mode, and competing reaction pathways may make force-clamp experiments impossible.
基于原子力显微镜（AFM）的动态单分子力谱技术被用于拉伸羧甲基化直链淀粉（CMA）聚合物，这些聚合物通过在pH 2.0条件下的酸催化酯缩合反应，共价连接在硅烷化玻璃基底和硅烷化AFM探针之间。在力斜坡模式下，测量了断裂力随温度和力加载速率的变化。数据呈现出显著的统计散射，采用最大似然估计（MLE）算法进行拟合。用基于莫尔斯势的阿累尼乌斯动力学模型描述键的断裂。拟合得到键解离能De = 35 kJ mol⁻¹和阿累尼乌斯前因子A = 6.6 × 10⁴ s⁻¹。该键解离能与之前在相同条件下采用力钳模式的实验结果一致。然而，力钳结果明确显示的双指数衰减动力学在力斜坡数据中并不明显。虽然可以用双指数模型拟合力斜坡数据，但拟合参数与力钳实验不同。总体而言，力斜坡模式下的单分子力谱得到的数据，其信息含量比力钳数据更有限。然而，进行力斜坡实验可能仍然是必要且有利的。在力斜坡模式下，成功事件的数量通常更多，并且竞争反应途径可能使力钳实验无法进行。
