Figure 1
From: Protein structure similarity from principle component correlation analysis
(a) Ribbon representation of 1IP9, showing two α helixes and four β strands, and (b) the corresponding symmetric interaction matrix (defined in eq. 2), where h3 and h5 are the two α helices, and h1, h2, h4 and h6 are the four β strands. The gray-level values denote the distance between any two Cα atoms with white corresponding to the shortest distance, i.e., 0.