دانلود گزارش کارورزی و کار آموزی

چکیده : 

Myosins are typical molecular motor proteins, which convert the chemical energy of ATP into mechanicalwork. The fundamental mechanism of this energy conversion is still unknown. To explain the experimen-tal results observed in molecular motors, Masuda has proposed a theory called the “Driven by Detachment(DbD)” mechanism for the working principle of myosins. Based on this theory, the energy used during thepower stroke of the myosins originates from the attractive force between a detached myosin head andan actin filament, and does not directly arise from the energy of ATP. According to this theory, every stepin the myosin working process may be reproduced by molecular dynamics (MD) simulations, except forthe ATP hydrolysis step. Therefore, MD simulations were conducted to reproduce the docking process ofa myosin subfragment-1 (S1) against an actin filament. A myosin S1 directed toward the barbed end ofan actin filament was placed at three different positions by shifting it away from the filament axis. After30 ns of MD simulations, in three cases out of ten trials on average, the myosin made a close contact withtwo actin monomers by changing the positions and the orientation of both the myosin and the actin aspredicted in previous studies. Once the docking was achieved, the distance between the myosin and theactin showed smaller fluctuations, indicating that the docking is stable over time. If the docking was notachieved, the myosin moved randomly around the initial position or moved away from the actin fila-ment. MD simulations thus successfully reproduced the docking of a myosin S1 with an actin filament.By extending the similar MD simulations to the other steps of the myosin working process, the validityof the DbD theory may be computationally demonstrated.