Reproducing Biological Catch Bonds in Simple Newtonian Mechanical Systems

  • Dansuk, Kerim Can (Bogazici University)

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Common intuition suggests that tensile force shortens chemical bond lifetimes; however, biological "catch bonds" defy this notion by strengthening under load. While catch bonds are critical for cell adhesion, the physical principles underlying their function in allosteric proteins like P-selectin, often described by the sliding-rebinding model, remained disputed, hindering the development of synthetic analogs. In this work, we introduce a simple, Newtonian molecular system that reliably reproduces catch bond behavior under thermal excitation, effectively bridging the gap between biological complexity and synthetic design. Our model mimics the allosteric regulation of P-selectin using a coarse-grained, hinged geometry controlled by a "switch" mechanism. In the closed state, the ligand is subjected to a vertical peeling force (Low Affinity). When external force ruptures the switch, the system reorients, aligning the force with the binding plane in a sliding configuration (High Affinity). We demonstrate that this behavior arises when the switch possesses a wider energy well than the ligand, allowing a soft, low-frequency conformational mode to couple with high-frequency binding dynamics. Remarkably, this minimalistic system produces a lifetime curve reminiscent of highly complex catch bond protein networks. The significance of this study lies in distilling the complex physics of allostery into accessible mechanical design rules. By validating a mechanism where force-induced tilting of energy landscapes drives functional transitions, we provide a blueprint for synthetic systems, such as DNA-based catch bonds and nanoparticle networks. These findings pave the way for novel, mechanically active materials that can reconcile the trade-off between high tensile strength and dynamic reconfiguration.