Jamming Proteins with Slipknots and Their Free Energy Landscape

Theoretical studies of stretching proteins with slipknots reveal a surprising growth of their unfolding times when the stretching force crosses an intermediate threshold. This behavior arises as a consequence of the existence of alternative unfolding routes that are dominant at different force ranges. The existence of an intermediate, metastable configuration where the slipknot is jammed is responsible for longer unfolding times at higher forces. Simulations are performed with a coarse-grained model with further quantification using a refined description of the geometry of the slipknots. The simulation data are used to determine the free energy landscape of the protein, which supports recent analytical predictions.