The outer membrane (OM) of Gram-Negative bacteria (GNB) is an asymmetric structure which contains complex lipids known as lipopolysaccharides (LPSs) on the outer surface. LPSs comprise the membrane anchoring Lipid-A, the anionic core oligosaccharides and the very large, solution facing O-antigen which acts as a hydrophilic barrier to antibiotics. We intend to deposit LPS on OTS coated silicon surfaces as a model OM. Using this system we will be able to deposit smooth LPS, a more complete form of the molecule than deposited previously as it contains the O-antigen. We the aim to examine the interactions of two antimicrobial agents which interact with the core of the OM in their killing activity with the OM model containing smooth LPS and compare this to a model containing the O-antigen free rough LPS to determine the role of the O-antigen in bacterial defence against antimicrobial agents.