We have recently created and published a model of the Gram negative bacterial Outer membrane (OM) which recreates many aspects of its behaviour and will improve our ability to develop new antibiotics. The next stage is to increase the complexity to match the natural membrane more closely. This involves using more complex lipids, so called smooth LPS, and proteins. Both these bring new challenges since they will require us to change the way we assemble the layers of the OM model. In this proposal we wish to compare three ways to add LPS to membrane protein free and protein containing layers. Only neutrons can measure the density and structure of these complex layers. The results will enable us to choose the correct methods for future development of the outer membrane models.