Table 2. The general characteristics of eight protein-protein interaction networks. For each network we indicate the number of nodes, the number of edges, the average degree, the diameter, the clustering coefficient and the average path length.

Species	Number of nodes	Number of edges	Average degree	Diameter	Clustering coefficient	Average path length
H. pylori	714	1,393	3.90	9	0.016	4.139
R. norvegicus	758	691	1.82	9	0.001	3.651
M. musculus	1,868	1,895	2.03	20	0.006	6.280
E. coli	2,997	12,348	8.24	12	0.115	3.986
C. elegans	3,183	5,068	3.18	13	0.012	4.803
S. cerevisiae	5,213	25,073	9.62	10	0.058	3.860
H. sapiens	5,940	14,144	4.76	17	0.017	4.755
D. melanogaster	7,931	23,386	5.90	12	0.012	4.468