Gram negative bacteria cause a wide range of diseases including meningitis, bubonic plague, gonorrhoea, diarrhoea, Legionnaires' disease and cholera. Their outer membrane provides them with their characteristic impermeable outer shell. This structure is being resolved by electron microscopy, AFM plus X-ray structures of individual proteins. However the structures of the large membrane protein complexes are very difficult resolve. We are interested in resolving these by SANS and one complex, between an outer membrane protein receptor OmpF and a toxin which kills E coli, has has already been resolved by the use of deuterated detergents and hydrogenous/deuterated protein components. In this proposal we wish to build on preliminary data obtained from SANS 2D (RB910498) to resolve the structure of OmpF bound to the TolA protein which is required to maintain outer membrane integrity.