Cell membranes, their structure, behavior and composition, are among the poorest-understood biological constructs. A few years ago, Simon and Ikonen have introduced lipid rafts, cholesterol rich regions, as part of the bilayer organization. Jacobson and Anderson have described lipid clustering as chaperoning lipid around proteins. Over the last ~10y, the composition, the lifetime function, signaling and other behaviors of the lipid rafts or lipid shell clusters have been hotly debated. As a key component to cell function, the membrane represents a veritable “black-box” where we understand parts of it but not whole.
When we separate the various components of the membrane, isolate the lipids and form model systems, the complexity decreases. Vesicles, or a cell without the inner workings, and supported bilayers on glass or other substrates allow us to control lipid composition and phase-state of the system. We then are able to probe the lipid behavior and to understand its contributions to the overall cell membrane. In the field of biophysics, understanding lipid and lipid-cholesterol behavior has begun to shed light onto the membrane black-box. Our research combines cell and lipid vesicle behavior to open the hinges on the black-box.
In our system, we have mimicked the well-known red blood cell dimpled shape with vesicles. We trap vesicles between two interfaces and analyze the energetics of the lipid-water, lipid-glass and lipid-air interactions. Our initial study has been conducted on a simple system of lipids in the disordered liquid phase-state.