An ASAXS study of bacteriophage T7 near the K-absorption edges of sulfur and phosphorus

The bacteriophage T7 is a bacterial virus containing a double-stranded DNA packed between a protein shell and core. P atoms are constituents of the backbone of DNA and S atoms of the protein. These atoms were used as native labels for in situ structure determination by anomalous small-angle X-ray scattering (ASAXS). The measurements have been performed in the range of the phosphorus K-absorption edge and the sulfur K-absorption edge at HASYLAB. The resonant scattering data obtained were interpreted by model calculations. A protein core in the center of the phage particle is shown directly to exist.