Amino acids and glycine ethyl ester as new crystallization reagents for lysozyme

Abstract

Several amino acids and their derivatives are prominent additives in the field of protein chemistry. This study reports the use of charged amino acids and glycine ethyl ester as precipitants in protein crystallization, using hen egg-white lysozyme (HEWL) as a model. A discussion of the crystallization of HEWL using these reagents as precipitating agents is given.

Figure 1

Crystallization experiments with HEWL using amino acids as precipitants at three pH values: (a) pH 4.5, (b) pH 6.5, (c) pH 8.5. The bars show the precipitant concentration ranges in which crystals were formed. Open bars, 50 mg ml⁻¹ HEWL; solid bars, 150 mg ml⁻¹ HEWL. NE indicates that the reagents could not be used because of low solubility.

Figure 2

Representative pictures of HEWL crystals obtained using amino-acid solutions. The results of the crystallization of 150 mg ml⁻¹ HEWL (a) at pH 4.5 in 0.1 M sodium acetate, (b) at pH 6.5 in 0.1 M sodium phosphate and (c) at pH 8.5 in 0.1 M Tris–HCl are shown.