Methods and compositions for determining the three dimensional structure of
a particle are provided. In the subject methods, a plurality of images of
the identically heavy atom labeled particles of interest is obtained. Each
of the images in the plurality is obtained by rigidly attaching at least
four heavy atom clusters to the particle of interest and imaging the
particle in an electron microscope. The three-dimensional structure of the
particle is then derived from the plurality of images of the labeled
particle. This derivation step preferably includes an alignment step in
which the orientation of the images is determined using the heavy atom
cluster projections. In preferred embodiments, the heavy atom clusters
serve to reveal particle homogeneity, particle location, particle
orientation, image artifacts, and image parameters required for
computational image restoration. The subject methods are particularly
suited for use in determining the three dimensional structure of
biological particles, e.g. proteins.