Three-dimensional reconstruction of noisy electron microscopy virus particle images

Three-dimensional reconstruction of icosahedral viruses using electron microscopy is similar to computed tomography except that the direction of projection is initially unknown. In addition, the projection images are noisy and low contrast. However, three-dimensional reconstructions are possible by using techniques which take advantage of the high degree of symmetry present in such viruses. In principle, these reconstructions should be routine, highly automated, and of high resolution. Yet the average resolution obtained by these methods is significantly lower than the limit of electron microscopy. We summarize the open problems which are necessary to allow routine high resolution three-dimensional reconstruction of icosahedral viruses using electron microscopy