Protein-protein interaction (PPI) networks are emerging as valuable prototypes 
to study important problems in molecular cellular biology and systems 
biomedicine. An analysis of the topological properties of a PPI network is very 
helpful for understanding the function and structure of networks. In this study, 
we analyzed the topological patterns in the BioPlex network containing 
interactions among 10,961 proteins; most interactions were previously 
undocumented. The BioPlex network is a comprehensive map of human protein 
interactions and represents the first phase of a long-term effort to profile the 
entire human ORFEOME collection. Similar to other biological networks, we 
observed that the BioPlex network has several topological properties. We also 
quantified correlations profiles for the BioPlex network and compared them to 
randomized versions of the same network. We found that for the BioPlex network, 
edges between proteins with intermediate degrees were strongly suppressed, 
whereas edges between low-connected proteins were favored. Finally, the degrees 
of essential genes were compared with the degrees of non-essential genes and 
randomly selected proteins. There were no significant differences between the 
groups.