Fig. 4. Topological properties of the yeast protein interaction network constructed from four different databases. (a) Degree distribution. The solid line corresponds to a power law with exponent = 2.5. (b) Clustering coefficient. The solid line corresponds to the function C(k) = B/k². (c) The size distribution of connected components. All the networks have a giant connected component of >1000 nodes (on the right) and a number of small isolated clusters. Figure reproduced with permission from Wiley-VCH (Yook et al., 2004).