Native ambient mass spectrometry of membrane proteins directly from bacterial colonies

Native ambient mass spectrometry (NAMS) enables analysis of protein structure directly from biological substrates by use of liquid junction sampling techniques together with sampling solvents which mimic the proteins' natural environment. Here, we demonstrate detection of membrane and membrane-associated proteins directly from E. coli by combining liquid extraction surface analysis (LESA) with a straightforward washing protocol, which attenuates soluble proteins and enables detection of membrane proteins.