Mechanical behavior of actin monomers under axial tensile loads: A molecular dynamics study

This paper deals with atomistic modeling of nanomechanical behavior of actin monomer. The major cytoskeletal protein of most cells is actin, which is responsible for the mechanical properties of the cells. Actin also plays critical mechanical roles in many cellular processes which gives structural support to cells and links the interior of the cell with its surroundings. Based on the accuracy of atomistic-based methods such as molecular dynamics simulations, in this paper, we perform a series of steered molecular dynamics simulations on both ATP and ADP single actin monomers to determine their intrinsic molecular strength. The effect of virtual spring of steered molecular dynamics on the mechanical behavior of actin monomer is investigated. The results reveal increasing the virtual spring constant leads to convergence of the stiffness. The stiffness of ADP actin and ATP actin calculated as 215.16 and 228.24 pN/Å, respectively. The results also show higher stiffness and Young’s modulus for ATP G-actin in comparison to ADP G-actin. In order to compare the behavior of ATP and ADP G-actins, the number of hydrogen bonds and nonbonded energies between the nucleotide and the protein is analyzed. The obtained persistent length is 15.61 µm which is in good agreement with the other reported literature values.