Inexact three-dimensional reconstruction of a biological macromolecule from a restricted number of projections.

A computer-generated three-dimensional model of Lumbricus terrestris hemoglobin has been obtained by reconstruction from four STEM low-dose computer-averaged micrographs. X-ray projections of a wooden model constructed from the calculated two-dimensional sections through the molecule were generally consistent with the original STEM projections of the hemoglobin and suggest the presence of large gaps between the central regions of adjacent 1/12th subunits of opposite tiers.