Systematic analysis of supersaturation and lysozyme crystal quality

A systematic study of the correlation between supersaturation and protein c rystal quality was carried out employing atomic force microscopy (AFM) and X-ray crystallography with synchrotron radiation (SR). The surface morpholo gy and growth rates of hen egg-white (HEW) lysozyme crystals soaked in vari ous supersaturated solutions were first investigated by AFM. The results sh owed 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 betwe en the surface morphology, growth rate and the crystal quality, X-ray diffr action 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 resu lts strongly suggested that the molecular misorientation at high supersatur ation affected the crystal quality.