Some protein interaction data do not exhibit power law statistics

Tanaka, Reiko; Yi, Tau-Mu; Doyle, John

Some protein interaction data do not exhibit power law statistics

Authors

Tanaka, Reiko

Yi, Tau-Mu

Doyle, John

Description

It has been claimed that protein-protein interaction (PPI) networks are scale-free based on the observation that the node degree sequence follows a power law. Here we argue that these claims are likely to be based on erroneous statistical analysis. Typically, the supporting data are presented using frequency-degree plots. We show that such plots can be misleading, and should correctly be replaced by rank-degree plots. We provide two PPI network examples in which the frequency-degree plots appear linear on a log-log scale, but the rank-degree plots demonstrate that the node degree sequence is far from a power law. We conclude that at least these PPI networks are not scale-free.
4 pages, 2 figures