Observation of the orientation of membrane protein crystals grown in high magnetic force fields

Crystallization of membrane proteins in magnetic fields is thought to reveal the magnetic orientations of crystals, and is expected to enhance crystal quality for X-ray crystallographic analysis. The light-harvesting complex 2 (LH2) from a photosynthetic bacterium, Thermochromatium tepidum was crystallized in steep-gradient magnetic fields. The rod-shaped crystals of LH2 grown in the magnetic fields were oriented parallel to the magnetic field direction. An X-ray diffraction experiment indicated that the overall R value and crystal mosaicity are improved for the magnetically oriented crystal, and the helix bundles of LH2 were located parallel to the magnetic field direction in the crystal packing.

► Magnetic orientation of the crystals of a membrane protein was observed.
► Overall R value and crystal mosaicity of the oriented crystals were improved.
► Helix axis of the molecule was parallel to the magnetic field direction.