CE-TOFMS Analysis of Metabolites

CE-TOFMS was performed using an Agilent capillary electrophoresis system equipped with an Agilent 6210 time-of-flight mass spectrometer, Agilent 1100 isocratic high-performance liquid chromatography pump, Agilent G1603A CE-MS adapter kit, and Agilent G1607A CE-ESI-MS sprayer kit (Agilent Technologies, Waldbronn, Germany). The analytical conditions were identical to those used in a previous study [21 (link)].
Raw data were processed using MasterHands, as described previously [21 (link)]. Briefly, among the detected compounds, those annotated in the Human Metabolome Database (ver. 4.0, http://www.hmdb.ca/, accessed on 27 January 2022) or KEGG database (http://www.genome.jp/kegg/, accessed on 27 January 2022) were further analyzed. The relative contents of the annotated compounds were determined by comparing the peaks of compounds with the same MS properties. To compare the relative content of the compounds between the LN and HN groups, the peak areas were normalized to those of the internal standards and sample weights. The abundance of each compound used for comparative analysis was set to zero when the level of the compound was not detected. The file conversion of raw MS data, peak picking, reduction of noise, and alignment of data for multiple samples was conducted as previously described [21 (link)].