  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.
