Gated escaping of ligand out of protein

We construct a new gating model and develop a new theory to study the escaping process of a ligand out of a spherical cavity with a puncture ~or gate! on the surface. The gate undulation can be regulated by any time-dependent function and the motion of the ligand inside the spherical cavity is mapped into a two-dimensional entropy potential surface. Hence the driving force of our model is entropy only. For a static gate, the escaping process corresponds to climbing a two-dimensional entropy barrier. When the gate open angle is small, the escaping rate is proportional to the square of the opening angle. The prefactor of the escaping rate constant depends on the curvature of the entropy potential surface. For coherent gating, the survival time depends not only on the gate undulation frequency but also on how the initial state is defined. On the escaping from protein, our escaping rate shows it is qualitatively consistent with the experimental result of ligand recombination in myoglobin. © 2000 American Institute of Physics. @S0021-9606~00!50801-0#