We employed the random graph theory approach
to analyze the protein-protein interacting database
DIP (Oct. 7 and Nov. 25, 2003), for six different
species (S. cerevisiae, H. pylori, E. coli, H. sapiens, M.
musculus and D. melanogaster). Two global
topological parameters (node connectivity, average
diameter) were used to characterize these
protein-protein interaction networks (PINs). The
logarithm of the connectivity distribution vs. the
logarithm of connectivity plot indicates that it follows
a power law behavior quite well for the six species.
We also demonstrated that the interaction networks are
quite robust when subject to random perturbation.
Node degree correlation study supports the earlier
results that nodes of low connectivity are correlated,
whereas nodes of high connectivity are not directly
linked. These results provided some evidence
suggesting such correlation relations might be a
general feature of the PINs across different species.