Prediction Method for Improvement of Protein Crystal Quality Grown in Microgravity

Abstract

It is said that the microgravity environment has a positive effect on protein crystallization because concentration depletion zones (CDZ) are positively formed due to minimized convection fluid motion and sedimentation. However, the microgravity experiment was thought to have a limited contribution to structural biology. In the JAXA's protein crystallization project since 2002, high viscosity of the precipitant solution had positive effects on the quality of the protein crystal grown in microgravity. Thus, we developed the method for estimating ‘D/β’ for the evaluation of CDZ formation using values of the diffusion coefficient (D) and kinetic coefficient (β) by a simple experiment. The D/β indicates that CDZ is formed around the crystal in microgravity if it is low enough. Since we can predict the effects of microgravity on the protein crystal growth before performing space experiment, it is possible to select samples and crystallization conditions which have high possibility to improve the crystal quality. Moreover, if we could modify the crystallization condition to lower D/β, the improvement of the crystal quality will be expected.