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. Author manuscript; available in PMC: 2020 Dec 17.
Published in final edited form as: Anal Chem. 2019 Dec 3;91(24):15686–15693. doi: 10.1021/acs.analchem.9b03849

Figure 3.

Figure 3.

Identification of L-alanyl-L-valine metabolite in mouse bile extracts. Panels a and b: 2D 13C-1H HSQC and 2D 1H-1H TOCSY of the unknown spin system A. Panels c and d: overlay of 2D NMR spectra of L-alanyl-L-valine (blue peaks) and bile extracts (gray peaks). Chemical shift agreement confirms the presence of L-alanyl-L-valine in the mouse bile mixture. Panel e: the chemical structure of L-alanyl-L-valine. Panel f: partial FT-ICR spectrum of the mouse bile extracts. The red peak with m/z 189.12337 of the [M+H]+ adduct is consistent with molecular formula C8H17N2O3 of L-alanyl-L-valine (mass error: 16 ppb).