Fig. 2.

A hybrid ¹³C-MFA approach. Intracellular metabolites were assumed to turnover rapidly and thus achieve steady state enrichments, whereas large extracellular metabolite pools (lactate and pyruvate) accumulate over time and have transient enrichments. The forward (explicit) Euler method was used to perform the numerical integration using 1- and 2-min time steps to fit the HEK293 and PANC-1 data, respectively. Weighted least-square optimization was used to generate new flux and initial concentration estimates based on the difference between measured and simulated values