Characterization of Lipopolysaccharide -containing supported lipid bilayers

Abstract

Bacteria have played a huge role over the course of human history. Some bacterial strains have wrought havoc and others have proved hugely beneficial and exist in a symbiotic relationship with humans. Regardless of the type of bacteria, a better understanding of how they communicate and interact with their environment is of great value, for example when developing new types of drugs targeting bacteria. However, the complexity of bacterial membranes and the myriad of surface active molecules and proteins found on it, makes the analysis of specific biomolecular interactions occurring at bacterial membranes a challenging task. This project has therefore focused on developing sensing platforms. The first sensing platform mimics bacterial surfaces by presenting specific biomolecules in a native but wellcontrolled manner. It therefore comes in the form of a supported lipid bilayer (SLB) consisting of mainly 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) and lipopolysaccharides (LPS). The second approach used in this thesis was to extract native membranes directly from bacteria and use these to form an SLB. The SLBs were characterized in order to verify their composition, as well as to determine their physiochemical properties and biological activity. The potential platform was also demonstrated in binding experiments using the LPS-binding molecule human lactoferrin. The outcome was analyzed using quartz crystal microbalance with dissipation monitoring (QCM-D) or total internal reflection microscopy (TIRFM). It was determined that LPS have successfully been incorporated into the SLB and that vesicles created using native membranes extracted from bacteria could also be used to form SLBs. It was also determined that these sensing platforms could be used to study a variety of biomolecular interactions involving LPS.