| Method |
P.695 right column 3rd paragraph:"In this study, [investigators] used a custom-designed labeling chamber to carry out short-term 13CO2 labeling of intact Arabidopsis rosettes under ambient steady state conditions. Several complementary analytical platforms were applied, including GC-TOF-MS [gas-chromatography-time-of-flight-mass spectrometry] and two recently developed liquid chromatography–tandem mass spectrometry (LC-MS/MS) platforms (Lunn et al., 2006 Arrivault et al., 2009), allowing quantitative determination and 13C enrichment calculation of 40 metabolites from the CBC [Calvin-Benson cycle], Suc and starch synthesis, glycolysis, amino acid and organic acid metabolism, as well as trehalose-6-phosphate (Tre6P) metabolism." P.696 left column 3rd paragraph:"Samples were analyzed using three analytical platforms, namely, GC-TOF-MS, ion exchange LC-MS/MS, and reverse-phase LC-MS/MS. This allowed quantification of 40 metabolites from the CBC, starch and Suc biosynthesis, the photorespiratory pathway, amino acid metabolism, glycolysis, the tricarboxylic acid cycle (TCAC), and Tre6P metabolism. The mass distribution of all metabolites determined shifted to a higher mass-to-charge ratio with increasing labeling time, as illustrated for 3PGA, which is the first product of CO2 fixation (see Supplemental Figure 2 online). Labeling kinetics were reproducible between three biological replicates (e.g., average 13C enrichment and sd were 65.8 and 4.9% for RuBP isotopomer, corresponding to the fully labeled molecule after 1 h of labeling and 40.8 and 3.5% for Ala). The total content of the measured metabolites did not change significantly between different labeling times (see Supplemental Table 1 online)." |