分子间相互作用力的直接测量

结合我们近期的研究工作,着重介绍如何将分子组装与单分子力谱相结合,从单分子水平直接研究分子间相互作用力,包括π-π相互作用、多价作用及嵌入作用.在实验中,将一个相互作用单元通过高分子间隔基共价连接到原子力显微镜针尖上,并将另一相互作用单元共价修饰到基底上,通过压电陶瓷管的移动获得力与拉伸长度的曲线.高分子柔性间隔基团的引入既可用来作为判别单链拉伸的"内标",又可避免非特异相互作用对待测的特异相互作用的影响.研究表明,结合静态和动态力学谱,不仅能够实现分子间相互作用力的直接测量,而且还可获得解离速率和相互作用的距离等参数.

DIRECT MEASUREMENTS OF INTERMOLECULAR INTERACTIONS

Atomic force spectroscopy(AFM)-based single-molecule force spectroscopy(SMFS)can serve as an important tool for studying intramolecular and intermolecular interactions at single-molecule level.On the basis of our recent work,this feature article is aimed to introduce how to combine the delicate SMFS with elegant self-assembly for direct measurements of different intermolecular interactions,including π-π interaction,multivalency and intercalation interaction.To realize the force measurement of single-molecule rupture,one of the interacting components needs to be covalently attached to AFM tip through a flexible polyethylene glycol(PEG)spacer,and the other component to the substrate surface.By the movement of piezo tube,the force-extension curve can be obtained.The introduction of PEG as a spacer provides a means for differentiating the force signal based on the extension length as well as for avoiding the disturbance of the non-specific interaction between the AFM tip and the substrate.In addition,with dynamic force spectroscopy,details about the kinetic of the unbinding and information concerning the length scale of the interaction can be extracted.Therefore,SMFS can investigate not only the intermolecular interactions directly,but also physical insight of the interactions,thus guiding molecular self-assembly.