Fig. 5.

Relevance of protein abundance x for the protein–protein interaction network studied in ref. 23. The statistical weight W(x,x′) describing the likelihood of links between proteins with concentrations x and x′ is first normalized to the analogous function WR(x,x′), which is obtained in the randomized dataset (with a random permutation of the abundance values x _i). The density plot reports the dependence of W(x,x′)/WR(x,x′) as a function of the protein abundance x, x′.