Figure 4
From: A methodology for the structural and functional analysis of signaling and regulatory networks
Computation of all signaling paths between two species (here: between I1 and O1). (a) via the incorporation of a "simplified" input and output arc; (b) with explicit introduction of an ENV („environment") node. Computing the elementary modes from the respective incidence matrix for (a) and (b) yields basically the same result, namely all paths between I1 and O1, as well as the two feedback circuits in the intermediate layer.