A combination of advanced techniques at Oak Ridge National Laboratory helped researchers gain a better understanding of how some proteins attack bacteria. Colicins, a family of protein toxins, kill E. coli by crossing the bacterial membrane to exert their toxic effects. One family member, Colicin N, utilizes outer membrane protein F, or OmpF, to penetrate the bacterial membrane. Since neutron scattering alone cannot differentiate between the complex formed between Colicin N and OmpF in membranes, University of Newcastle scientists collaborated with Kevin Weiss in the Center for Structural Molecular Biology's Bio-Deuteration Laboratory to label OmpF with deuterium. This allowed the individual proteins to be selectively highlighted in neutron scattering experiments, a critical step in determining how colicins cross the membrane barrier. Results from these experiments support the hypothesis that Colicin N penetrates the E. coli membrane at the perimeter of OmpF and reveal possible new routes for antibiotics to enter bacteria. —Emma Macmillan