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. Author manuscript; available in PMC: 2021 Aug 18.
Published in final edited form as: Anal Chem. 2020 Jul 31;92(16):11242–11249. doi: 10.1021/acs.analchem.0c01826

Figure 1.

Figure 1.

Natural compounds are potent charge-reducing molecules. (A–C) Representative mass spectra of AmtB in C8E4 doped with 100 mM of (A) TMAO, (B) histamine, or (C) spermidine. Data was acquired on an ultrahigh mass range (UHMR) Orbitrap mass spectrometer under gentle instrument conditions. Structures of molecules are shown in the inset. (D) Total number of charge states for AmtB in the presence of compounds at different concentrations. (E) Plot of average charge states (Zavg, dots) as a function of concentration of charge-reducing molecules. A modified form of Hill equation was fit to the data (solid lines) to determine the half maximal effective concentration (EC50). (F) Mass spectra of AmtB doped with different concentrations of spermine ranging from 0 to 250 mM.