基于原子力显微镜的单分子力谱技术在高分子表征中的应用

Application of Atomic Force Microscopy(AFM)-based Single-molecule Force Spectroscopy(SMFS)in Polymer Characterization

基于原子力显微镜(atomic force microscopy,AFM)的单分子力谱技术以其操作简便、适用面广等优势,成为了单分子领域应用最为广泛的技术之一.本文阐述了该技术的基础原理与实验技巧,包括仪器构造、工作原理、探针与基底的选择、样品固定、实验操作、单分子信号的获得以及数据处理.介绍了基于AFM的单分子力谱技术在合成高分子及生物大分子表征中的典型应用及前沿进展.AFM单分子力谱技术将有助于建立合成高分子的链结构、链组成与单链弹性以及链间相互作用与其宏观力学性能间的关联,帮助理解生物大分子的结构、相互作用与其生物功能之间的联系.

Atomic force microscopy(AFM)-based single-molecule force spectroscopy(SMFS)has been used widely in the investigation of molecular forces because of its friendly user interface(e.g.,easy to operate and can work in liquid,air and high vacuum phase)and worldwide commercialization.This review is aimed to introduce the principle and protocol of AFM-based SMFS including the setup,the working principle,typical curves,the choice of AFM tip and substrate,immobilization of samples,manipulation of the device,empirical criteria for single-molecule stretching and data analysis.Recent progresses on the application of AFM-based SMFS in the characterization of synthetic polymers and biopolymers were reviewed.For synthetic polymers,the effects of primary chemical compositions,side groups,tacticity and solvents on the single chain elasticities were discussed.The applications of AFM-SMFS in disclosing the structure of unknown molecule,polymer-interface interactions and polymer interactions in polymer assemblies(e.g.,polymer single crystal)were introduced.In addition,the nature of mechanochemical reactions and characterization of supramolecular polymers were realized via this technic.For biopolymers,the effects of base-pair number,the force-loading mode(unzipping or shearing)on the stability of short double-stranded DNA(dsDNA)were reviewed.According to this knowledge,the single molecule cut-and-paste based DNA assembly was then discussed.The typical force fingerprints of long dsDNA,proteins and polysaccharides as well as the force-fingerprint-based investigation of molecular interactions were illustrated.Finally,the application of AFM-SMFS in revealing the intermolecular interactions and the mechanism of virus disassembly as well as the antivirus mechanism of tannin in tobacco mosaic virus were reviewed.Therefore,AFM-based SMFS is essential for revealing the relationship between the conformation/composition of polymer chains and micro/macro-mechanical properties of polymer materials as well as correlating the molecular structure/interaction of biopolymers with their biofunctions.