Stability Of Molecular Bonds Upon Varied Loads

Cells can actively sense and respond to different mechanical signals from the extracellular matrix through focal adhesions, which can be represented by a cluster of bonds. A molecular bond is a type of specific interaction between proteins. The study of the stability of the molecular bonds is of significance to biomechanics, medicine, pathology, etc. In this paper, we study the stability of a single or a cluster of different types of molecular bonds under varied load with a coupled of finite element method and Monte Carlo method, and explore the dynamics of molecular bonds, which provides theoretical basis for the future study of biomechanics.Catch bonds can exist in many subcellular biological processes. Their lifetime is counter-intuitively prolonged under loads. Here we establish two types of catch bonds with two-state models to study their dynamics upon varied loads. Our studies have found that one of the two types of catch bonds shows a similar force-lifetime profile under a stable rate load to a preset value. However, the force-lifetime profile and bond strength of an individual molecular bond of either type are very different. Further studies show that the stability of clusters of either type will be undermined by cyclic load.When using the molecular cluster of slip bonds to represent the focal adhesion, a fluctuated force can often weaken the stability of the cluster. However, the molecular cluster will appear abnormal stability enhancement phenomenon, when the load has a relatively low frequency and relatively high amplitude. According to the traditional fracture theory, a fatigue loading can promote the crack propagation, which is contrary to the abnormal phenomenon of the molecular cluster. In order to understand this phenomenon, we have carried out parametric studies on a cluster of slip bonds upon fluctuated loads, and found that the abnormal phenomenon of the cluster is very robust and influenced by stochastic features and loading profile of an individual molecular bond. The inherent fluctuated traction forces within a focal adhesion have relatively low frequencies and relatively high amplitudes, so we can speculate that the inherent fluctuated traction forces might enhance its stability in the similar way.