A Simple Mechanical Model for Synthetic Catch Bonds

Abstract

Dansuk and Keten have demonstrated that a simple mechanical design based on a tweezer-like mechanism can exhibit catch bond characteristics under thermal excitations. By introducing a switch design with broader energy landscape than the ligand binding site landscape, they achieve force-dependent kinetics that prolongs ligand lifetime through formation of secondary interactions. This serial arrangement of a soft conformational switch with a stiff ligand interaction results in catch bonds. The force versus lifetime curves are tunable by changing these design parameters.

Detailed Balance Broken by Catch Bond Kinetics Enables Mechanical‐Adaptation in Active Materials

“…These results highlight the role of catch-bonds on fluidity, as well as rigidity, as the latter is principally observed in synthetic systems. [14][15][16][17][18] Furthermore, the non-monotonic change in material fluidity is also observed in biochemical reconstitution experiments that closely resemble our simulations. In the experiments, we alter the "effective" catch through the increase in motor content or F-actin crosslinking by α-actinin ( Figures S9 and S10, Supporting Information).…”

“…[ 13 ] In synthetic systems, mechanical load is applied externally, and catch bonds can increase the mechanical toughness of the material in response, enabling several‐fold increase in allowable strain. [ 14–18 ] While catch bonds in biological systems are also subject to external forces, [ 13 ] active stresses in living matter are generated internally, and the force generating units, in turn, sense and adapt to applied load. [ 19 ] If the source of the endogenous stress also acts as a catch bond, biological activity creates an adaptive feedback between macroscopic mechanical properties and microscopic, internal stress generation.…”

Catch bond-inspired hydrogels with repeatable and loading rate-sensitive specific adhesion

“…On the other hand, the receptor-ligand bond broke by randomly escaping from the potential well. Analogous to the two-pathway model describing cell adhesion [ 28 , 46 ], we used the potential well shown in Fig. 3 A to describe the breaking of the receptor-ligand bond.…”

“…In this case, it was easier to break the bond when the tensile force increased [ 49 ]. Therefore, the reverse reaction rate took the following form [ 28 ] where and were the reverse reaction rate coefficients of the catch-bond and slip-bond, respectively; was the elastic strain energy of a single receptor-ligand bond, which could be expressed as ; and were the characteristic coefficients of the catch-bond and slip-bond, representing the sensitivity of the energy barrier to the tensile force; was the Boltzmann's constant; and was the absolute temperature. The parameters and their values involved in the simulations are summarized in Table S2 .…”

“…In essence, the so-called catch bonds, e.g. , integrin-RGD bonds, are a class of protein-ligand bonds that are easily broken under relatively small tensile forces but tend to have much longer lifetimes when larger tensile forces are applied [ [24] , [25] , [26] , [27] ], which is seemingly counterintuitive and hard to reproduce in most man-made systems [ 28 ].

Fig.

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