Title page for ETD etd-10162005-200707

Type of Document Master's Thesis
Author Narayanan, Shivaram
Author's Email Address shivaram@vt.edu
URN etd-10162005-200707
Title The Betweenness Centrality Of Biological Networks.
Degree Master of Science
Department Computer Science
Advisory Committee
Advisor Name Title
Murali, T. M. Committee Chair
Marathe, Madhav V. Committee Member
Vullikanti, Anil Kumar S. Committee Member
  • Betweenness centrality
  • Vertex Betweenness
  • Edge Betweenness
  • Power law
  • Biological networks
Date of Defense 2005-09-16
Availability unrestricted
In the last few years, large-scale experiments have generated genome-wide protein interaction networks for many organisms including Saccharomyces cerevisiae (baker's yeast), Caenorhabditis elegans (worm) and Drosophila melanogaster (fruit fly). In this thesis, we examine the vertex and edge betweenness centrality measures of these graphs. These measures capture how "central" a vertex or an edge is in the graph by considering the fraction of shortest paths that pass through that vertex or edge. Our primary observation is that the distribution of the vertex betweenness centrality follows a power law, but the distribution of the edge betweenness centrality has a Poisson-like distribution with a very sharp spike. To investigate this phenomenon, we generated random networks with degree distribution identical to those of the protein interaction networks. To our surprise, we found out that the random networks and the protein interaction networks had almost identical distribution of edge betweenness. We conjecture that the "Poisson-like" distribution of the edge betweenness centrality is the property of any graph whose degree distribution satisfies power law.
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