Actin polymerization is coupled with the hydrolysis of adenosine triphosphate (ATP). The hydrolysates of ATP are adenosine diphosphate (ADP) and inorganic phosphate (Pi). Therefore, each protomer within the actin filament can exhibit three different nucleotide states corresponding to bounded ATP, ADP/Pi and ADP molecules. These protomer states cause the filaments to form different spatial patterns, which will change various properties of the filament. The related model has been made to simulate the process of polymerization, depolymerization and hydrolysis via Brownian dynamics simulations, where the time evolution of depolymerization and hydrolysis is described as a continuous-time Markov process. In this paper, we focus on how to realize the chemical equilibrium between two ends of the filament, and study the growth behavior of long filaments as a function of ATP-actin monomer concentration.

Key words: brownian dynamics, actin filament, polymerization, depolymerization