Figure 18-7: Surface lattice arrangements predicted for petite, isometric, intermediate, and normal-length T4 heads (above). The definitions of the lattice parameters are shown below. For the isometric phage, the surface lattice is defined completely by the triangulation number (T), given as T(m,n) = m2 + mn + n2; in the drawing m = 3, n = 1, and T = 13. For an icosahedron elongated along a fivefold axis, another number, Q, is used to define the extent of elongation. The Q number can be any integer greater than T and is defined by the coordinates m' and n'. For the intermediate phage shown, m' = 3, n' = 2, and Q = 17. The normal-length head shown has m' = 3, n' = 3, and Q = 21; data from the laboratory of M. Rossmann et al. show that Q=20 for their sample of T4 (113). (for better image quality, click here for tif image, which may be quite large; may also require screen refreshing plus special software to view; or view larger tif in separate window)

Figure 18-1, Figure 18-2, Figure 18-3, Figure 18-4, Figure 18-5, Figure 18-6, Figure 18-7, Figure 18-8

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