Magnetic Image Force for Biophysical Force Measurements

Current methods for measuring biomolecular interactions such as atomic force microscopy (AFM), biomembrane force probe (BFP), and optical tweezing (OT) have various logistical limitations. Most importantly, these methods can study only one molecule at a time, which greatly limits the ability to observe the ensemble mechanical properties. We investigated a new highly parallel molecular force spectroscopy approach in which up to thousands of bonds can be studied simultaneously. This new method utilizes the concept of ``image forces'' arising in suspension of nonmagnetic beads, which is purely repulsive and tunable with the applied field. We have shown that it is possible to directly measure the rupture force between the bead and substrate which is mediated through ideally single Biotin-Streptavidin (B-S) bonds. We have measured for the first time the rupture force for single B-S bonds at the lowest ever force loading rates ($<$1fN/s). Rupture force vs. loading rate diagrams for B-S bonds will be discussed.