Native mass spectrometry-based metabolomics identifies metal-binding compounds

Although metals are essential for the molecular machineries of life, systematic methods for discovering metal–small molecule complexes from biological samples are limited. Here, we describe a two-step native electrospray ionization–mass spectrometry method, in which post-column pH adjustment and metal infusion are combined with ion identity molecular networking, a rule-based data analysis workflow. This method enabled the identification of metal-binding compounds in complex samples based on defined mass (m/z) offsets of ion species with the same chromatographic profiles. As this native electrospray metabolomics approach is suited to the use of any liquid chromatography–mass spectrometry system to explore the binding of any metal, this method has the potential to become an essential strategy for elucidating metal-binding molecules in biology. The systemic discovery of metal–small-molecule complexes from biological samples is a difficult challenge. Now, a method based on liquid chromatography and native electrospray ionization mass spectrometry has been developed. The approach uses post-column pH adjustment and metal infusion combined with ion identity molecular networking, and a rule-based informatics workflow, to interrogate small-molecule–metal binding.