Sliding Contact Dynamic Force Spectroscopy Method for Interrogating Slowly Forming Polymer Cross-Links

Dynamic single-molecule force spectroscopy (SMFS), conducted most commonly using AFM, has become a widespread and valuable tool for understanding the kinetics and thermodynamics of fundamental molecular processes such as ligand–receptor interactions and protein unfolding. Where slowly forming bonds are responsible for the primary characteristics of a material, as is the case in cross-links in some polymer gels, care must be taken to ensure that a fully equilibrated bond has first formed before its rupture can be interpreted. Here we introduce a method, sliding contact force spectroscopy (SCFS), that effectively eliminates the kinetics of bond formation from the measurement of bond rupture. In addition, it permits bond rupture measurements in systems where one of the binding partners may be introduced into solution prior to binding without tethering to a surface. Taking as an example of a slowly forming bond, the “eggbox” junction cross-links between oligoguluronic acid chains (oligoGs) in the commercially...