The Heart of Protein-Protein Interaction Networks
  Recent developments in complex networks have paved the way to a series of important biological insights, such as the fact that many of the essential proteins of S. cerevisae corresponds to the so-called hubs of the respective protein-protein interaction networks. Despite the special importance of hubs, other types of nodes such as those corresponding to the network border, as well as the innermost nodes, also deserve special attention. This work reports on how the application of the concept of distance transform to networks showed that a great deal of the innermost nodes correspond to essential proteins, with interesting biological implications. 
Luciano da Fontoura Costa