  We study the problem of computing outer bounds for the region of steady
states of biochemical reaction networks modelled by ordinary differential
equations, with respect to parameters that are allowed to vary within a
predefined region. Using a relaxed version of the corresponding feasibility
problem and its Lagrangian dual, we show how to compute certificates for
regions in state space not containing any steady states. Based on these
results, we develop an algorithm to compute outer bounds for the region of all
feasible steady states. We apply our algorithm to the sensitivity analysis of a
Goldbeter--Koshland enzymatic cycle, which is a frequent motif in reaction
networks for regulation of metabolism and signal transduction.
