Three-dimensional reconstruction of membrane protein crystals

Computer graphic display method for visualizing three-dimensional biological structures

A computer graphic display method that produces two-dimensional perspective views of three-dimensional objects is presented. The method is applied to the reconstruction at a resolution of 2.2 nanometers of the neck of bacteriophage phi 29, obtained from transmission electron micrographs processed by the direct Fourier method. The combined use of directed illumination, reflectance models, color, and different levels of transparency provides a powerful tool for a better interpretation of the three-dimensional structure, allowing improved correlation with genetic, structural, and biochemical data.

Nucleosome reconstruction via phosphorus mapping

Electron spectroscopic imaging was combined with reconstruction algorithms to derive the three-dimensional structure of the nucleosome core particle to a resolution of 1.5 nanometers. Images of phosphorus distributions within individual nucleosomes were interpreted as projections of a supercoil of DNA. These were used to orient the corresponding individual nucleosome images, making it possible to reconstruct the entire nucleosome in three dimensions. The structure is consistent with known biochemical and biophysical data and explains site-specific nuclease sensitivity, although differing in part with other nucleosome models.