A simple protocol is reported for consistently obtaining large single crystals of hen egg‐white lysozyme (HEWL) greater than 2 mm in the longest dimension. Comparative crystallization experiments with different sources of HEWL showed that the simple addition of glass capillaries, `crystal hangers', reduced excessive nucleation and resulted in large single crystals regardless of the commercial source of HEWL.

The effect of coupling the salt concentration gradient crystallization method with the use of the paramagnetic salt MnCl2 and a magnetic field is reported. The use of a simple magnetic device is shown to have a significant effect on hen egg-white lysozyme crystal growth.

The three-dimensional structure of the proteins, including the location of the hydrogen atoms can be analyzed by using neutron diffraction. In order to grow single crystals for neutron diffraction experiments, we developed a simple magnetic field device with the commercial magnets and succeeded in growing hen egg-white lysozyme single crystals of more than 1 mm 3 in volume using this device. The crystals grown with a magnetic field were larger and had perfect transparency, whereas the crystals grown without a magnetic field had micro-cracks. The result of the X-ray measurement showed a good resolution and small mosaicity for the crystals grown in the presence of a magnetic field.