Multiple orientation responses of lysozyme crystals to magnetic field when paramagnetic salts are used as the crystallization agents

We investigated the effect of paramagnetic salts (NiCl₂, CoCl₂, and MnCl₂) on the magnetic orientation of henegg white lysozyme (HEWL) crystals at different pHs. Multiple orientation responses of the crystals to magnetic fields were discovered when NiCl₂ and CoCl₂ were used as the crystallization agents (the c-axis and the (110) orientations for NiCl₂ solution, and the c-axis, the a-axis and the (110) orientations for CoCl₂ solution). Only the normal c-axis orientation was found when MnCl₂ was used as the crystallization agent. The multiple orientation responses were sensitive to the variations in the pH. These phenomena are discussed in the context of the incorporation of paramagnetic cations into lysozyme. Although anions affect the crystallization of lysozyme, the effect of cations on the crystallization of lysozyme has been considered marginal. This study reveals that cations can also exhibit profound effects on the crystallization of lysozyme.