Figure 1

Protein Blocks. From left to right and top to bottom, RASTER 3D [42, 43] images of the 16 Protein Blocks of the structural alphabet. Each prototype is five residues in length and corresponds to eight dihedral angles (φ,ψ). The PBs m and d can be roughly described as prototypes for the central α-helix and the central β-strand, respectively. For each PB, the N cap extremity is on the left and the C-cap on the right.