Neutron small angle scattering on bacteriophage PM2 was used to identify the high molecular weight species and the solvent accessible volume in the structural compartments of the virus spherical shells in a model constructed from the extensive chemical and physical information on PM2. For data analysis the scattering from the model was calculated in such a way as to simulate the real scattering situation, in which the neutron wavelength distribution and beam divergence lead to a significant smearing of the intensity. The calculated convoluted intensity was then fitted to the experimental data by varying the scattering densities and the radii of the spherical shells. Scattering from solutions was studied at low resolution under a wide variety of solvent contrast conditions achieved by varying the H2O2H2O ratio. The dependence of the scattering densities in the shells on the H2O2H2O ratio, obtained on an absolute scale from model fitting, is interpreted in terms of a fractional contribution from solvent and dry species. The amount of protein, lipid and DNA, as well as the solvent volume fraction, are obtained for each shell. Scattering from pellets of PM2 at medium resolution was used to refine the shell radii and the scattering densities evaluated on solutions. An outer shell accommodates all of protein II and a significant amount of protein I. This shell does not penetrate into the viral membrane. The bilayer occupies a second shell; its dimensions agree with X-ray results. Protein III also appears to be in this shell, where it occupies about 50% of the volume. No water is found here. The allocation of protein III to the bilayer is confirmed by the analysis of low angle neutron and X-ray scattering on the nucleocapsid of PM2, where a protein layer extending from 207 Å to 240 Å is detected. The DNA in the inner shell is highly solvated. A fit to higher resolution data could be obtained using two shells for the nucleocapsid region. It is proposed that protein IV is at the interface of the DNA and the bilayer. © 1978.
Mendeley saves you time finding and organizing research
Choose a citation style from the tabs below