The outer membrane of gram negative bacteria is an asymmetrical structure containing complex lipids known as lipopolysaccharides (LPS¿s) on the outer surface. LPS¿s are anchored to the membrane but contain a very large hydrophilic oligosaccharide chains which is anionic in nature due to high phosphorylation. Part of the role of this region is to protect the bacteria from hydrophobic antibiotics by creating a large hydrophilic barrier. Divalent cations are thought to help stabilize this structure by bridging the phosphate groups leading to a dense barrier. Here we wish to build on our work on understanding how surface cationic and hydrophobic affect the ability of antimicrobial to disrupt model pathogenic membranes by examining how the divalent cations and protein hydrophobicity affect the ability of antimicrobial proteins to penetrate and disrupt model gram negative bacterial membranes.