NTFD--a stand-alone application for the non-targeted detection of stable isotope-labeled compounds in GC/MS data

Abstract

Summary: Most current stable isotope-based methodologies are targeted and focus only on the well-described aspects of metabolic networks. Here, we present NTFD (non-targeted tracer fate detection), a software for the non-targeted analysis of all detectable compounds derived from a stable isotope-labeled tracer present in a GC/MS dataset. In contrast to traditional metabolic flux analysis approaches, NTFD does not depend on any a priori knowledge or library information. To obtain dynamic information on metabolic pathway activity, NTFD determines mass isotopomer distributions for all detected and labeled compounds. These data provide information on relative fluxes in a metabolic network. The graphical user interface allows users to import GC/MS data in netCDF format and export all information into a tab-separated format.

Availability: NTFD is C++- and Qt4-based, and it is freely available under an open-source license. Pre-compiled packages for the installation on Debian- and Redhat-based Linux distributions, as well as Windows operating systems, along with example data, are provided for download at http://ntfd.mit.edu/.

Fig. 1.

To detect the metabolic fate of a stable isotope tracer, two experiments must be performed in parallel under identical conditions: for the first experiment, the biological system needs to be incubated with a mixture of stable isotope-labeled tracer and unlabeled compound. For the second experiment, the system needs to be incubated under the same conditions with only unlabeled tracer