Multiple-step method for making exceptionally well-oriented liquid-crystalline sols of macromolecular assemblies.

X-ray fiber diffraction is potentially powerful in solving the atomic structure of filamentous assemblies of macromolecules, as demonstrated for tobacco mosaic virus. However, it requires extremely well-oriented sols to allow for extraction of intensities on closely located layer-lines. A high degree of orientation requires a high filament concentration to restrain the orientational freedom, but orienting concentrated sols is hampered by their high viscosity. Here, we report a systematic method that reproducibly produces extremely good orientation, which involves three steps; liquid crystallization, centrifugation and magnetic orientation. We found that a slow centrifugation can trigger a dynamic self-orientation process to form perfectly homogeneous liquid-crystalline sols, and further centrifugation to concentrate sols followed by magnetic orientation produces exceptionally well-oriented sols. The best-oriented flagellar sol showed a disorientation angle of 0.6 degrees as 1sigma of its Gaussian distribution. The new method has been successfully applied to many other systems, such as tobacco mosaic virus and F-actin. Copyright 1998 Academic Press Limited.