Mechanical Properties Of Microtubules: Continuum Description And MD Simulation

As the basic element of life, there have been a lot of studies on the mechanical behaviors of cell. The cytoskeleton(CSK) is a self-organizing filaments network in all eukaryotes, The CSK is a dynamic, living structure that defines the cell's shape and bulk mechanical properties, Many cellular functions such as cell division, motility, signal transduction, etc. are mediated by the physical properties of CSK. The CSK network consists of three primary protein filaments:microtubules(MTs), intermediate filements, and actin filements. Among the three types of CSK filaments, microtubules are the most rigid. so the microtubules play an essential roles in the mechanical properties of cell. This thesis is focusing on investigating the mechanical behaviors of MTs. The specific works finished are listed below:●A nonlocal Timoshenko beam model with consideration of the wormlike chain model(WLC) has been developed for the MTs. A new persistence length prediction formula with consideration of the small scale effect has been presented. The predicated results of our model indicate that the persistence length increases while the contour length of the MT is increasing, and the persistence length tends to a constant value while the contour length is large enough. The Euler beam model shows the persistence length is a constant value, which is always considered unable to explain the length-dependence of microtubules.●Base on the nonlocal Timoshenko beam model, the buckling behavior of the MT surrounded by the cytosol under axial compression has been investigated. The intermediate filaments are assumed as an elastic medium, The analytical expression of the buckling growth rate has been presented. The results show that the buckling growth rate is related with not only the material parameter, but also with the small scale parameters eoa. In addition, the results can explain the short wave buckling behavior which is in excellent agreement with the experiments.●Based on the Coarse-grained molecular dynamics models for proteins, the axial tension behavior of MT is simulated. The Stress-strain relation and the Young's modulu of MT are also obtained from the Coarse-grained MD simulation.