Investigate the interaction of cationic polymers with bacteria through ITC

• Main Author: Yip, Feng Kai
• Other Authors: Si Zhang Yong
• Format: Final Year Project
• Language: English
• Published: 2018
• Subjects: DRNTU::Engineering::Bioengineering
• Online Access: http://hdl.handle.net/10356/75601
• Institution: Nanyang Technological University

In order for cationic antimicrobial beta ( β) peptides to become a major force in tackling the problems of infectious disease that are caused by bacteria and virus, extensive studies and experiments have to be conducted to fully understand the working principle and working mechanism of it. As the structure of bacteria comprises of many complex materials, the experiments done on peptides and bacteria itself could lead to inaccurate results being acquired. Thus, simple bacteria model liposomes that resemble the structure of the bacteria itself are used in experiments with the cationic antimicrobial  peptides so that results of high precision and accuracy are obtained. This project reports the binding interaction between the cationic antimicrobial peptides 154-6 to the membrane of various bacteria model liposomes using Isothermal Titration Calorimetry (ITC). Cationic antimicrobial peptide 154-6 is a synthetic antimicrobial peptide designed to have better efficiency and selectivity as compared to naturally occurring antimicrobial peptides. Large unilamellar vesicles (LUVs) comprise of L-α-Phosphatidylcholine (POPC), 1-Palmitoyl-2-Oleoyl-sn-Glycero-3-[Phospho-rac-(1-glycerol)] (POPG) and Lipopolysaccharides (LPS) from Escherichia coli (E coil), were used as model system for the membrane of Gram-negative bacteria, Gram-positive bacteria and mammalian cell. It was illustrated that the binding reaction between the peptides and the membrane models were exothermic and the reactions occurred were spontaneous and favourable as the product that was produced during the reaction was stable. It was also discovered that the binding affinity between the different types of membrane models and the peptides were different which leads to the difference in binding strength between the peptides and the different types of membrane models. Ultimately, the binding of the peptides to the membrane models could cause inhibition of cell wall synthesis in bacteria and eventually result in cell death in bacteria.