Protocols have been established to enable hydrogen/deuterium exchange mass spectrometry (HDX-MS) analysis of membrane proteins within lipid vesicles , liposomes , nanodiscs and so-called 'native nanodiscs', which allow membrane proteins to stay in contact with the native lipid milieu . In HDX-MS, a protein is diluted into a deuterated buffer enabling H/D exchange of its labile backbone amide hydrogens. This reaction is quenched at different time intervals by dropping pH and temperature to 2.5 and 0 °C, respectively. The quenched protein sample is then digested by an acid-labile protease (e.g. pepsin) into peptides and the incorporation of deuterium measured by liquid chromatography (LC)-MS analysis.