Single-molecule pulling experiments are widely used to extract both thermodynamic and kinetic data on ligand-receptor pairs, typically by fitting different models to the probability distribution of rupture forces of the corresponding bond. Here, a theoretical model is presented that shows how a measurement of the number of binding and unbinding events as a function of the observation time can also give access to both the binding ( k on ) and the unbinding ( k off ) rates of bonds, which combined provide a well-defined bond free-energy Δ G bond . The connection between Δ G bond and the ligand-receptor binding constant measured by typical binding essays is critically discussed. The role played by the molecular construct used to tether ligands and receptors to a surface is considered, highlighting the various approximations necessary to derive general expressions that connect its structure to its contribution, termed Δ G cnf , to the bond free-energy. In this way, the validity and the assumptions underpinning widely employed formulas and experimental protocols used to extract binding constants from single-molecule experiments are assessed. Finally, the role of Δ G cnf in processes mediated by ligand-receptor binding is briefly considered, and an experiment to unambiguously measure this quantity proposed.

中文翻译：

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通过单分子实验对动力学和热力学的解释

单分子牵引实验被广泛用于提取配体-受体对的热力学和动力学数据，通常是通过将不同的模型拟合到相应键的断裂力的概率分布。在这里，提出了一个理论模型，该模型显示了作为观察时间函数的结合和解绑事件数量的测量如何也可以访问结合 (k on ) 和解离 (k off ) 键率，其结合提供了明确的键自由能 Δ G 键。批判性地讨论了 Δ G 键与通过典型结合论文测量的配体-受体结合常数之间的联系。考虑了用于将配体和受体连接到表面的分子结构所起的作用，强调导出通用表达式所需的各种近似值，这些表达式将其结构与其对键自由能的贡献（称为 Δ G cnf ）联系起来。通过这种方式，评估了用于从单分子实验中提取结合常数的广泛采用的公式和实验方案的有效性和假设。最后，简要考虑了 ΔG cnf 在配体-受体结合介导的过程中的作用，并提出了明确测量该数量的实验。