Impurity-induced defect and its effect on protein crystal perfection

The rocking curve widths of tetragonal lysozyme crystals were measured. Typical full-width half-maximum (FWHM) of the rocking curve of crystals grown from a pure lysozyme solution were 0.004–0.006°, while those crystals containing 5% lysozyme dimer were 0.006–0.010°. X-ray topography experiments revealed that dislocations existed in crystals containing the lysozyme dimer. These dislocations are one of the causes of rocking curve width broadening. 2×104 cm−2 pits were observed on the {1 0 1} face in contaminated crystals, but few, if any pits were observed in either face of the pure crystals.