Bacterial LPS (endotoxin) is a key determinant of host/pathogen interactions. We propose to investigate the role of membrane lateral phase separation on LPS insertion into model membranes and the effects of target membrane structure and composition on LPS insertion. LPS from different classes of gram negative bacteria show strikingly different behaviour both biologically, and in preliminary fluorescence and ssNMR data on their interaction with model membranes. We propose to exploit the availability of LPS from a range of symbiotic (Escherichia coli), opportunistic pathogens (Klebsiella and Salmonella spp), and obligate pathogens of human and cattle (Brucella melitensis and Brucella abortis) to investigate how the distinct biological activity of these LPS is related to their binding to model membranes.