The Role Of Solutal Convection In Protein Crystal Growth-a New Dimensionless Number To Evaluate The Effects Of Convection On Protein Crystal Growth

摘要

According to the experiments by Vekilov et al., the crystal growth rate, G_c of tetragonal lysozyme crystal initially increases up to 200 μm/s with increasing flow velocity, u_m and then decreases monotonically. While in the lower supersaturated solution, G_c decreases monotonically with increasing u_m, and the growth cessation occurs at u_m = 1450 μm/s. In this paper, we propose a new theory to explain these complicated experimental results. We consider one protein molecule near the crystal surface and define a dimensionless number r, the ratio of the velocity of convective flow to the diffusion velocity of a protein molecule. When convection occurs along the crystal surface and a molecule diffuses toward the crystal surface, r indicates the moving direction of the molecule and is closely related with crystal growth rate. We derive the equation to calculate r from experimental parameters. Analyzing the experimental results in the literatures, we find that the dependence of G_c on u_m is related with r and there exist three critical r-values, r_1 ≈4-8, r_2 ≈ 0.01-0.02, r_3≈0.004. When r>r_1 crystal growth cession occurs; when r_1>r>r_2, G_c decreases with u_m; when r_2>r>r_3, G_c increases with u_m; when r