Low resolution 3D reconstructions of viruses from X-ray crystal diffraction data

We describe low-resolution 3D reconstructions of viral particles based on low-resolution (e.g., 20 /spl Aring/) X-ray crystal diffraction data. The reconstructions are based on parameterized models because the number of data points is small, e.g., 3/spl times/10/sup 2/. Reconstruction is then equivalent to parameter estimation which we perform via nonlinear least squares. The focus is on the structure of the nucleic acid and we demonstrate that inclusion of models for the nucleic acid can reduce the R factor and that the resulting parameter values are in accord with simple physiochemical measurements.