(536a) Metabolic Flux Analysis in E. Coli Using Tandem Mass Spectrometry

We recently developed a new technique for metabolic flux analysis based on stable isotope labeling and tandem mass spectrometry (MS/MS). In the paper we demonstrate the first application of our tandem MS methodology for metabolic flux analysis in E. coli. We show that tandem MS offers considerable advantages for in vivo flux analysis compared to conventional mass spectrometry (GC/MS and LC/MS). The number of independent measurements is greatly increased with tandem MS, as is the information content of the labeling measurements. As a result, metabolic fluxes are determined with much higher precision and accuracy. The application of tandem MS allowed us, for the first time, to accurately quantify a number of pathways in E. coli that were previously unobservable with conventional MS techniques. In summary, our new tandem MS technique allows us to trace isotopic labeling in complex metabolic networks with much higher resolution and ultimately measure metabolic fluxes with a much higher degree of confidence.