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Processing of GC-TOF/MS data<br />&l … Processing of GC-TOF/MS data<br /><br />
Nonprocessed MS data from GC-TOF/MS analysis were exported in NetCDF format to MATLAB 6.5 (Mathworks, Natick, MA, USA), where all data-pretreatment procedures, such as smoothing, alignment, time-window setting, and H-MCR, were carried out (Jonsson et al. 2006). The resolved MS spectra were matched against reference mass spectra using the NIST mass spectral search program for the NIST/EPA/NIH mass spectral library (version 2.0) and our custom software for peak annotation written in JAVA. Peaks were identified or annotated based on retention indices (RIs) and the reference mass spectra comparison to the Golm Metabolome Database (GMD) (Kopka et al. 2005) and our in-house spectral library. The metabolites were identified by comparison with RIs from the library databases (GMD and our own library) and with those of authentic standards, and the metabolites were defined as annotated metabolites on comparison with mass spectra and RIs from these two libraries. The amount of S-adenosyl-methionine was calculated by the sum of the mass numbers at m/z 188 and 236 using Leco ChromaTOF software version 2.32 (LECO, St. Joseph, MI, USA) since this compound was not adequately detected by H-MCR. ound was not adequately detected by H-MCR.
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