Izumi Yoshizaki

Systematic analysis of supersaturation and lysozyme crystal quality

A systematic study of the correlation between supersaturation and protein crystal quality was carried out employing atomic force microscopy (AFM) and X-ray crystallography with synchrotron radiation (SR). The surface morphology and growth rates of hen egg-white (HEW) lysozyme crystals soaked in various supersaturated solutions were first investigated by AFM. The results showed that the formation of two-dimensional islands increased as a function of supersaturation. The growth rate (molecule intake speed) also increased as a function of supersaturation. In order to examine the correlation between the surface morphology, growth rate and the crystal quality, X-ray diffraction experiments were performed. It was confirmed that crystals grown at lower supersaturations diffracted better with higher signal-to-noise ratios, including better agreement between symmetry-related reflections. The results strongly suggested that the molecular misorientation at high supersaturation affected the crystal quality.

Systematic analysis of the effect of supersaturation on protein crystal quality

We proved the correlation between supersaturation and the quality of Hen Egg White (HEW) lysozyme crystal by X-ray crystallography and confirmed that crystals grown in lower supersaturated solution diffracted better with higher signal-to-noise ratios. The surface morphologies of lysozyme crystals grown in various supersaturated solutions were investigated by AFM. The observations revealed that no major crystal defects existed in tetragonal lysozyme crystals. We also investigated the step growth rates in various supersaturated conditions. The step kinetic constant β tended to increase as the supersaturation increased. The results strongly suggested that the molecular misorientation brought about at high supersaturation affected the crystal quality.