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. 2017 Feb 27;114(11):2819–2824. doi: 10.1073/pnas.1616019114

Fig. S4.

Fig. S4.

Fragmentation experiments to characterize dihydroxymagnesium carboxylates. (A–C) CID mass spectra of NWA 7325 of C16-dihydroxymagnesium carboxylate [C16H33MgO4]− complex are shown at collision energies of 10 eV, 15 eV, and 20 eV to identify the MgO4R− structures with R = hydrocarbon CxHy and x, y ∈ ℕ. Additionally, five precursor molecular ions, m/z = 285 for [C14H29MgO4]− (D), m/z = 299 for [C15H31MgO4]− (E), m/z = 327 for [C17H35MgO4]− (F), m/z = 341 for [C18H37MgO4]− (G), and m/z = 355 for [C19H39MgO4]− (H) show fairly congruent fragmentation patterns of dihydroxymagnesium carboxylates with the release of Mg(OH)2 out of the fragmented parent molecule. The collision energies used in these CID MS/MS experiments were high (15–20 eV) to ensure fragmentation of the complexes. The computed coordinates of the structures of C16-dihydroxymagnesium carboxylate ([C16H33MgO4]−) and its product ion (hexadecanoic acid) are presented in Table S2. (I) Exact masses of the fragmented molecules. (J) Negative ionization mode ESI-FT-ICR mass spectra of selected dihydroxymagnesium carboxylates [(OH)2MgO2CR]− in the NWA 7325 methanolic extract are shown, where the standard extract is labeled blue and the red signal is the extract in presence of formic acid (HCOOH). The complex is hydrolyzed in the presence of formic acid and Mg(OH)2 is precipitated. This indicates that the CHOMg anionic complexes possess Mg(OH)2 functional groups. The peaks were smoothed via the Gauss smoothing algorithm, as implemented in Bruker Compass DataAnalysis 4.2 SR1, with a smoothing width of 0.001 amu (2.1 points).