Gas-phase structure of the E. coli OmpA dimer

In this issue of Structure, Marcoux and colleagues use gas-phase collisional cross section (CCS) measured by ion-mobility mass spectrometry to analyze the CCS of oligomeric states of E. coli outer membrane OmpA. CCS of the dimer supports a model of paired periplasmic C-terminal domains projecting away from the transmembrane porins.