Additional file 3 of Identifying model error in metabolic flux analysis – a generalized least squares approach

SBML file. An SBML representation of the metabolic model. (XML 89 kb

Profiling Convoluted Single-Dimension Proton NMR Spectra: A Plackett–Burman Approach for Assessing Quantification Error of Metabolites in Complex Mixtures with Application to Cell Culture

Single-dimension hydrogen, or proton, nuclear magnetic resonance spectroscopy (1D-¹H NMR) has become an attractive option for characterizing the full range of components in complex mixtures of small molecular weight compounds due to its relative simplicity, speed, spectral reproducibility, and noninvasive sample preparation protocols compared to alternative methods. One challenge associated with this method is the overlap of NMR resonances leading to “convoluted” spectra. While this can be mitigated through “targeted profiling”, there is still the possibility of increased quantification error. This work presents the application of a Plackett–Burman experimental design for the robust estimation of precision and accuracy of 1D-¹H NMR compound quantification in synthetic mixtures, with application to mammalian cell culture supernatant. A single, 20 sample experiment was able to provide a sufficient estimate of bias and variability at different metabolite concentrations. Two major sources of bias were identified: incorrect interpretation of singlet resonances and the quantification of resonances from protons in close proximity to labile protons. Furthermore, decreases in measurement accuracy and precision could be observed with decreasing concentration for a small fraction of the components as a result of their particular convolution patterns. Finally, the importance of a priori concentration estimates is demonstrated through the example of interpreting acetate metabolite trends from a bioreactor cultivation of Chinese hamster ovary cells expressing a recombinant antibody