Bacterial lipopolysaccharide (LPS) is a bioactive structural amphiphilic molecule which forms the outer leaflet of the outer membrane of the Gram negative cell envelope. During infection, LPS may be released from living or dead cells, and may cause over-stimulation of the immune system's inflammatory response (septic shock syndrome), which is the most common cause of death in hospital intensive care units. This bioactivity of LPS is thought to be related to its ability to form specific thermotropic/lyotropic aggregate structures whose toxicity may be neutralized following interaction with the body's own defensive peptides. The objective of this proposal is to determine the architecture of LPS-peptide aggregates and develop an in vivo screening method for testing novel anti-infective agents which are able to neutralize LPS toxicity.