Institute of Applied Beam Science, Ibaraki University^* Kaken.Co.Ltd.^**
○Wakari Iwai^* Daichi Yagi^* Takuya Ishikawa^* Yuki Ohnishi^** Ichiro Tanaka^* Nobuo Niimura^*

In the field of high resolution crystal structure analysis of proteins, high quality single crystals are necessary. High quality crystals of hen egg white lysozyme (HEWL) has been grown at different pH and evaluated by Wilson Plot method¹.
As a crystallization agent, sodium chloride (NaCl) was used by batch method. It has been controlled by adjusting a ratio of phosphoric acid (H₃PO₄) and sodium dihydrogen phosphate (NaH₂PO₄) at low pH, and a ratio of sodium dihydrogen phosphate (NaH₂PO₄) and disodium hydrogenphosphate (Na₂HPO₄) at high pH, respectively. The crystallization of HEWL at different pH has been performed by the following method;
1) Direct crystallization at a defined pH solution.
2) Soaking a crystal grown at a certain easily crystallized pH solution into a defined pH solution.
Direct crystallization was also realized at pH2.5-pH5.5 solution (See the figure.).
The quality of HEWL crystals grown at different pH has been successfully evaluated.

Reference:
1)S.Arai et al, Acta Cryst. D60, (2004)1032-1039