FIGURE 1. Structure of epsilon15 bacteriophage.

a, 200-kV CCD image of epsilon15 particles embedded in vitreous ice. b, Surface rendering of the 20 Å resolution three-dimensional map of entire epsilon15 bacteriophage reconstructed without symmetry imposition. The capsid (dark green) exhibits good icosahedral symmetry as indicated by the icosahedral lattice (grey). c, d, The structural components of epsilon15 bacteriophage are annotated in the central section density (c) and the cut-away surface view (d) of the three-dimensional density map. Each of the structural components is coloured differently and the same colour scheme is used in Figs 1–3. e, A slightly tilted view of the coaxially packed dsDNA genome. Only portions of the first and second layers of dsDNA are shown so that the three outermost layers can be viewed. Colour gradient (light blue to darker blue) is used in d and e to indicate the likely packaging order of the dsDNA starting from the outer layer towards inner layers and ending as the central straight segment of terminus.