Metabolite profiling and identification in living cells by coupling stable isotope tracing and induced electrospray mass spectrometry

Direct observation of metabolites in living cells by mass spectrometry offers a bright future for biological studies but also suffers a severe challenge to untargeted peak assignment to tentative metabolite candidates. In this study, we developed a method combining stable isotope tracing and induced electrospray mass spectrometry for living-cells metabolite measurement and identification. By using 13C6-glucose and ammonium chloride-15N as the sole carbon and nitrogen sources for cell culture, Escherichia coli synthesized metabolites with 15N and 13C elements. Tracing the number of carbon and nitrogen atoms could offer a complementary dimension for candidate peak searching. As a result, the identification confidence of metabolites achieved a universal improvement based on carbon/nitrogen labelling and filtration.

Automated summary

Direct observation of metabolites in living cells by mass spectrometry offers great potential for biological studies, but there is a challenge in identifying untargeted metabolites. In this study, a method combining stable isotope tracing and induced electrospray mass spectrometry was developed. By using specific isotopes as carbon and nitrogen sources, metabolites with labeled carbon and nitrogen atoms were synthesized in Escherichia coli. Tracking the number of labeled atoms improved the confidence in metabolite identification.