Flux analysis

Metabolic Flux Analysis and Metabolic Control Analysis... 

Iwatani, S., Yamada, Y. andUsuda, Y. (2008) Metabolic flux analysis in biotechnology processes. Biotechnology Letters, 30, 791-799. 

Bushell, M.E., Kirk, S., Zhao, H.-J. and Avignone-Rossa, C.A. (2006) Manipulation of the physiology of clavulanic acid biosynthesis with the aid of metabolic flux analysis. Enzyme and Microbial Technology, 39, 149-157. 

Similar models using a multi-flux analysis of particle absorption and scattering are reported by Radauer, Glatzer and Linzer (1996). 

Abstract. Coronal abundances have been a subject of debate in the last years due to the availability of high-quality X-ray spectra of many cool stars. Coronal abundance determinations have generally been compared to solar photospheric abundances from this a number of general properties have been inferred, such as the presence of a coronal metal depletion with an inverse First Ionization Potential dependence, with a functional form dependent on the activity level. We report a detailed analysis of the coronal abundance of 4 stars with various levels of activity and with accurately known photospheric abundances. The coronal abundance is determined using a line flux analysis and a full determination of the differential emission measure. We show that, when coronal abundances are compared with real photospheric values for the individual stars, the resulting pattern can be very different some active stars with apparent Metal Abundance Deficiency in the corona have coronal abundances that are actually consistent with their photospheric counterparts. 

Flux Analysis for Calculating Reaction Probabilities with Real Wave Packets. 

Figure 14. Principle for measuring bidirectional fluxes by 13C metabolic flux analysis. In a carbon labeling experiment, 1 13C glucose is provided in the medium, and the culture is grown until a steady state is reached. Glucose can either go directly via the hexose phosphate pool (Glu 6P and Fru 6P) into starch, resulting in labeling hexose units of starch only at the Cj position, or it can be cleaved to triose phosphates (DHAP and GAP), from which hexose phosphates can be resynthesized, which will result in 50% labeling at both the Ci and the C6 position (assuming equilibration of label by scrambling at the level of triose phosphates). From the label in the hexose units of starch, the steady state fluxes at the hexose phosphate branchpoint can be calculated for example, if we observe 75% label at the Ci and 25% at the C6 position, the ratio of vs to V7 must have been 1 to 1. All other fluxes can be derived if two of the fluxes of Vi, V6, and V7 are known (e.g., V2 vi V3 V5 + v6).

The first example of a dynamic flux analysis was a study performed in the 1960s [269]. In the yeast Candida utilis, the authors determined metabolic fluxes via the amino acid synthesis network by applying a pulse with 15N-labeled ammonia and chasing the label with unlabeled ammonia. Differential equations were then used to calculate the isotope abundance of intermediates in these pathways, with unknown rate values fitted to experimental data. In this way, the authors could show that only glutamic acid and glutamine-amide receive their nitrogen atoms directly from ammonia, to then pass it on to the other amino acids. 

Huege et al. [271] cultivated Arabidopsis plants in 13C02 atmosphere, transferred the plants to normal atmosphere, and monitored the dilution of isotopes in several metabolite pools. Through evaluation of the mass isotopomer distribution, metabolite partitioning processes could be monitored. However, due to the lack of absolute metabolite concentrations, no absolute fluxes could be calculated. Nevertheless, building upon this method, suitable approaches for flux analysis in autotrophic tissue might be derived in the future. 

U. Sauer, Metabolic networks in motion 13C based flux analysis. Mol. Syst. Biol. 2, 62 (2006) doi 10.1038/msb4100109. 

K. Raman and N. Chandra, Pathwayanalyser A systems biology tool for flux analysis of metabolic pathways. Nature Precedings, 2008. 

U. Sauer, N. Zamboni, and E. Fischer, FiatFlux a software for metabolic flux analysis from 13C glucose experiments. BMC Bioinform. 6, e209 (2005). 

I. G. L. Libourel and Y. Shachar Hill, Metabolic flux analysis in plants From intelligent design to rational engineering. Annu. Rev. Plant Biol. 59, 625 650 (2008). 

Kronzucker HJ, Siddiqi MY, Glass ADM, Kirk GJD. 1999. Nitrate-ammonium synergism in rice. A subcellular flux analysis. Plant Physiology 119 1041-1045. 

Metabolic Flux Analysis Using Mass Spectrometry... 

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