Figure 3From: Including metabolite concentrations into flux balance analysis: thermodynamic realizability as a constraint on flux distributions in metabolic networksImpact of random perturbations of observed metabolite concentrations on calculated flux distributions for the erythrocyte network. Each bar shows the relative frequency of alternative flux distributions (y-axis) in dependence on the standard deviation of the perturbation (x-axis) of the set-point concentration values. The perturbationanalysis is based on random numbers generated with the Cliff random number generator [45] transformed to normal distribution by theBox-Muller method [46] where the expectation value is fixed to zero and for each series (1000 runs) the standard deviation is fixed to a specified value (given in the figures). For the perturbation of the concentrations each concentration value is multiplied with eXwhere X is a newly generated pseudo-random number. Each concentration value is modified independently from the perturbation of the other concentration values. The standard deviation value s can be translated to a 'deviation factor' as es. For the perturbation of the equilibrium constants each value is also multiplied with eXwhere X is a newly generated pseudo-random number. After the perturbation the values are modified again to ensure well-formedness by the algorithm described in the text. The standard deviation value s can be translated into deviations of Gibb's free energy change as 2.58·s kJ/mol.Back to article page