  The effective interaction between a sphere with an open cavity (lock) and a
spherical macroparticle (key), both immersed in a hard sphere fluid, is studied
by means of Monte Carlo simulations. As a result, a 2d map of the key-lock
effective interaction potential is constructed, which leads to the proposal of
a self-assembling mechanism: there exists trajectories through which the
key-lock pair could assemble avoiding trespassing potential barriers. Hence,
solely the entropic contribution can induce their self-assembling even in the
absence of attractive forces. This study points out the solvent contribution
within the underlying mechanisms of substrate-protein assembly/disassembly
processes, which are important steps of the enzyme catalysis and protein
mediated transport.
