SOFTWARE FOR 3-D RECONSTRUCTION FROM IMAGES OF OBLIQUE SECTIONS THROUGH 3-D CRYSTALS

Oblique section reconstruction can produce a 3-D image from electron m icrographs of a sectioned crystal when the orientation of the section plane is not aligned with the principal planes of the unit cell. We de scribe here the reconstruction protocol and the specialized computer s oftware for a Fourier space method that can extract 3-D information fr om 2-D projection images of oblique sections. The protocol encompasses correction for image defects and image distortions, determination and refinement of reciprocal lattices, calculation of the crystal orienta tion in 3-D space, extraction of periodic information, alignment in Fo urier space, determination and deconvolution of section thickness, and calculation of structure factors of the original crystal. A 3-D map o f the unit cell can then be computed by standard crystallographic proc edures. Oblique section reconstruction provides an alternative to tomo graphy for 3-D imaging of crystalline objects with large unit cells. T he method provides an excellent means of obtaining a 3-D transform usi ng electron microscopy for comparison with X-ray diffraction data from native specimens. (C) 1996 Academic Press, Inc.