An X-ray scattering investigation of broad bean mottle virus in solutions of various electron densities

Abstract

Low-angle X-ray scattering data to a resolution of 30 Å are presented for broad bean mottle virus suspended in buffer and in solutions of higher electron density produced by the addition of sucrose or the trisaccharide melezitose. Comparison of the scattered intensity distributions with those of simple model particles are made and radial electron density distributions are obtained. The results indicate that in buffer the virus particle has a radius of gyration of 117 Å, a mean outer radius of about 147 Å, and a nearly hollow core of about 60 Å radius. The scattering data for the virus in sugar solutions supports these results and indicates that much of the region within the virus open to water is also open to penetration by the sugar molecules. Melezitose can penetrate about 60% of the volume of the virus open to water while sucrose can penetrate nearly 90%. The region of the virus within 90 Å from the center is more easily penetrated by these sugars than the region from 90 Å to the surface. It is concluded that the virus at this resolution appears as a hollow, approximately spherically symmetric object with a high density and probably well organized RNA region enclosed by a protein shell into which some of the RNA penetrates.