Brownian dynamic simulations are used to elucidate some of the underlying transport processes of protein molecules in protein crystallization. The dominant forces are modeled from colloidal interactions between a lysozyme molecule (sphere) and tetragonal lysozyme crystal (wall), both heterogeneously charged. The electrostatic portion is obtained by solving the linearized Poisson-Boltzmann equation with a boundary elements method; the van der Waals force is treated as a function of only the Hamaker constant and sphere-wall separation. Simulation results show that protein molecules have greater translational diffusivity and are more concentrated near a highly charged crystal surface than near a weakly charged one. This suggests that ordered protein assembly as a precursor to crystal growth is more likely to occur at the crystal surface than in bulk solution.