The Langmuir Monolayer technique was used to investigate the antibacterial properties of the alpha and beta acids found naturally in hops.  The surface pressure and molecular area of the amphiphilic molecules that make up Langmuir monolayers, in this case phospholipids, are monitored at an air-water interface upon introducing another molecule, hop acids, to the system.  Langmuir monolayers are often used as model cell membranes because the change in molecular area or surface pressure of these phospholipid monolayers is an indication of an increase or decrease in the fluidity of the membrane. In this research, the monolayer was varied based on the electrostatic nature and hydrogen bonding capability of the phospholipid used.  Phospholipids used included dipalmitoylphosphatidylcholine (DPPC), dipalmitoylphosphatidylethanolamine (DPPE), and dipalmitoylphosphatidylserine (DPPS).  For a more physiological situation for representing gram negative bacteria, Langmuir monolayers of an E. coli lipid extract and lipopolysaccharide were also investigated.  Preliminary data shows that hop acids have some surface activity and that co-spreading the lipid monolayer and the hop acid solution leads to a more fluid monolayer in all lipid cases which may be indicative of the antibacterial activity of the hop acids thereby breaking down the lipid film. Future experiments will involve the use of dipalmitoylphosphatidylglycerol (DPPG) as a model membrane for gram positive bacterial cells.<br/><br/>

Mechanism behind the antibacterial properties of hop acid investigated with model cell membranes

249th National Meeting (2015)

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