Agilent Measurement Journal - Issue 3 - 2007 - (Page 63)

variance (ANOVA) for multiple pair-wise comparisons. The results of the ANOVA were overlaid in a Venn diagram using three pairs of comparisons. For example, in one instance we compared only the signiﬁcantly differential metabolites (p < 0.05) between TP309 (PXO99 vs. mock), TP309_Xa21 (PXO99 vs. mock) and TP309 mock vs. TP309_Xa21. From this we identiﬁed sets of feature ions that were speciﬁc to a particular class, speciﬁcally, TP309_Xa21/PXO99 features associated with resistance only and TP309/PXO99 features associated with susceptibility to infection. We then performed principle component analysis (PCA) of these feature sets to show how they visually discriminate the different treatment classes. We ﬁltered the mass lists further to select features with the highest abundance and largest fold-change ratios. The mass lists were searched against the METLIN metabolite database. For example, Table 2 lists the METLIN search results for the neutral masses (not charged ions) that were induced in the resistance-only (immunity) list. One of these masses, m/z 129.0414, with a single formula and six possible structures, was selected for further investigation by targeted MS/MS on the Q-TOF LC/MS system. Examination of the MS/MS spectrum for its precursor ion, 130.0532, is shown in Figure 9. Only two of the six possible metabolites could logically have produced the spectrum. However, because the two compounds are enantiomers, they were indistinguishable by mass spectrometry. Their precise identity could be determined on a chiral LC column. Clear differences between the two rice lines and infection states were detected. Identiﬁcation of putative biomarkers of infection is ongoing and shows that metabolomic proﬁling can be a compelling research tool. Table 2. This is a partial list of the induced (greater than two-fold change versus controls) feature ions from the TP309-Xa21/PXO99 condition, with their METLIN database search results. One of the highlighted neutral masses with six possible structures was subsequently analyzed by MS/MS. Retention time (min) 32.64 1.11 32.76 41.36 43.74 40.60 31.24 25.80 27.20 32.66 47.38 46.41 50.91 49.41 2.38 45.17 37.68 38.53 2.07 2.10 Mass (U) 771.4705 296.9389 710.4604 167.0575 401.3279 849.5386 295.2517 329.2925 453.2855 739.4514 934.5473 660.5333 565.8811 948.5989 221.0538 817.5082 608.2646 861.5044 129.0414 122.0383 Fold Change 2.4 2.8 4.2 6.1 9.7 10.7 11.5 11.9 12.4 12.9 18.6 20.3 20.7 23.2 24.8 25.0 27.8 28.0 35.5 36.2 Empirical formula C27H68N10013P C7HNO8F2S C38H60N706 C6H7N402 C24H41N40 C29H72N17010P C18H33N02 C19H39N03 C9H31N1903 C32H65N7010S C53H79N2010P C25H62N1902 C4HN6016F6PS C58H76N804 C6H7N503 C34H63N1903S C25H45N409PS C47H70N607P C5H7N03 C7H602 Number of formulas 93 13 71 3 9 100 2 2 20 85 100 32 32 100 4 100 75 100 1 2 METLIN search (number of hits) 0 0 0 3 0 0 0 0 0 0 0 0 0 0 0 0 Harderoporphyrin erythromycin ethylsuccinate 6 benzoic acid Agilent Measurement Journal 63

Table of Contents Feed for the Digital Edition of Agilent Measurement Journal - Issue 3 - 2007

Applying Ingenuity to the Measurement of Emerging Technologies Contents Emerging Innovations Department Delivering Bigger Benefits by Optimizing Customer Workflows Measuring Material Properties at the Nanoscale Utilizing In Situ Atomic Force Microscopy in Life Science, Pharmaceutical and other Bio-Related Applications WiMAX™: Plotting a New Path to Global Mobility Addressing the Triple Complexity of Triple-Play Networks What Next for Mobile Telephony? Exploring the Inner Workings of Tire-Pressure Monitoring Systems Developing, Assessing and Applying a High-Resolution Thin-Film Magnetic Probe Making Accurate Settling-Time Measurements Using a Vector Network Analyzer Applying Metabolomics Methods to the Study of Bacterial Leaf Blight in Rice Plants Measuring Stream Dynamics with Fiber Optics survey

Agilent Measurement Journal - Issue 3 - 2007

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