Physical principles of membrane reshaping: A theoretical study of self organization on membrane surfaces through membrane-mediated interactions

The research described in this doctoral thesis was part of the BaSyC consortium, which aims to build synthetic cells from bottom up. My small role in this large collaboration was to study the theoretical basis for cell division. This is a very complex process in living organisms, involves many components and can be accomplished in a variety of ways. To successfully replicate cell division in synthetic organisms it will be important to identify the simplest mechanisms and understand the basic components of the cell division machinery, that come together to reshape membranes and divide one compartment into two. The theoretical framework used to study these self-assembly processes, that lead to membrane deformations and division, is the framework of membrane mediated interactions. Let me use an example to explain this framework.
Imagine you sit down on a couch, while holding a saucer with a coffee cup on it. The coffee is too hot, so you set it down next to you ont the couch and while you wait you get lost in your thoughts. . .You feel like getting up and walking around in the room. While you are still lifting your body up from the sitting position, you hear the clinking of the cup against the saucer, and you see from the corner of your eye that the coffee cup is shaking. Without having touched the cup you managed to spill the coffee. The surface of the couchwas deformed and pulled tight because youwere sitting on it. When you got up the surface relaxed back to its original shape. This movement of the surface caused the cup to shake and spill its contents (see fig. 1 for an artist’s impression). Membrane mediated interactions are just like that! When something deforms a membrane in one place, that deformation is felt at a distance by other objects that inhabit the membrane. Exactly how far and how strongly such signals are felt depends on how floppy or tense a membrane is. When we study membrane mediated interactions, our main goal is to quantify the effects membrane deforming objects can have on each other.