We have been studying numerical models of the protein depletion zones (PDZ) and the impurity depletion zones (IDZ) around crystals in terrestrial gravity and in microgravity and have shown that all sections of the crystals are surrounded by different supersaturation levels of protein and different concentrations of impurities when growing in the steady state model and in the transient state model. This suggests that the extent of molecular order may depend on the position in the crystal. Therefore, we prepared three kinds of lysozyme samples which contained different amounts of impurities and crystallized them in terrestrial gravity and in microgravity. Then we ran grid scans using these crystals to obtain diffraction data and found that the unit cell volume of the outer layer of the crystal increased when 50% purified lysozyme was crystallized in terrestrial gravity. The results were consistent with the numerical analysis. From these results, we conclude that the quality of diffraction data may depend on which part of the crystal the focused X-ray beam is applied. Therefore, it may be important to select the position in the crystal to aim the X-ray beam for a better diffraction dataset collection.
