Detergent-free mass spectrometry of membrane protein complexes

Amphipols, bicelles and nanodiscs are used to study intact membrane protein complexes by mass spectrometry, with better preservation of oligomeric complexes than traditional detergent micelles. We developed a method that allows release of intact membrane protein complexes from amphipols, bicelles and nanodiscs in the gas phase for observation by mass spectrometry (MS). Current methods involve release of membrane protein complexes from detergent micelles, which reveals subunit composition and lipid binding. We demonstrated that oligomeric complexes or proteins requiring defined lipid environments are stabilized to a greater extent in the absence of detergent.