Improvement in Quality of Protein Crystals Grown in a High Magnetic Field Gradient

Space-based microgravity environments have been utilized to obtain a highly ordered crystal because of the lack of gravity-induced convection. A superconducting magnet-based quasi-microgravity is also expected to contribute to the enhancement of the quality of protein crystals. We here report a case study on protein crystallization using fifteen kinds of samples in a magnetic field gradient, which was sufficient for magnetic levitation of water droplets. In three cases, rod-type crystals were aligned perpendicular to the crystallization plate, exhibiting magnetic orientation parallel to the direction of the magnetic field. Five proteins showed improvement in crystal quality evaluated by the resolution limit in X-ray diffraction experiments and the overall B-factor of the crystal. Our data support the idea that the reduced-gravity environment produced by a high magnetic field gradient can be used to obtain enhanced-quality protein crystals, aiding in the determination of their precise crystal structures.