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. Author manuscript; available in PMC: 2013 Jan 3.
Published in final edited form as: Nat Rev Microbiol. 2012 Feb 27;10(4):291–305. doi: 10.1038/nrmicro2737

Figure 5. Refining thermodynamic constraints.

Figure 5

Thermodynamic constraints in COBRA models can be refined. (a) For example, when a metabolic network is not adequately constrained, metabolites can cycle infinitely in loops. Akin to Kirchhoff’s loop law for electrical circuits, this property is thermodynamically infeasible. (b) Thus, methods like ll-FVA, which uses the loopless-COBRA96 constraints on flux variability analysis, are able to systematically remove these loops by adding a constraint that limits flux to the solution space regions that are not involved in these loops.