This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. Three programs have been developed by the Resource and are used on a daily basis. tcaSIM allows the simulation of complex metabolic networks including the citric acid cycle, glycolysis, gluconeogenesis and anaplerosis. The operator controls all aspects of 13C labeling and fluxes in all pathways. The program generates 13C NMR and HMQC-TOCSY spectra, as well as mass and tandem mass spectra, of numerous metabolites such as amino acids, ketones and glucose. The companion program tcaCALC is used to analyze experimental data, determining the same metabolic parameters as used in tcaSIM from observed NMR or mass spectra. Both these rograms examine the relative flux through pathways, while tcaFLUX determines absolute fluxes from time series of 13C NMR and HMQC-TOCSY spectra. The details of tcaSIM, tcaCALC, and tcaFLUX have been described in previous progress reports.