Preservation of 2-D crystals of tubulin for electron crystallography

Zinc-induced sheets of tubulin are two-dimensional crystalline polymers that constitute an ideal sample for high resolution studies of tubulin by electron crystallography. We show that these 2-dimensional tubulin crystals can be stabilized by taxol against low-temperature depolymerization and degradation with time, easing the way for the preparation of electron microscopy samples. The preservation of the crystals to high resolution has been tested with different embedding media. While glucose-embedded samples diffract poorly, samples embedded in tannin consistently diffract to a resolution of at least 3.5 A. Even better results are obtained by embedding with a combination of tannin and glucose, which improves the flatness of the crystals and allows the collection of isotropic high-resolution data from tilted specimens.