To bind or not to bind

Abstract

To bind two entities together, an attractive interaction is needed. In biological systems, such interactions are often between ligands and receptors. But this interaction constantly breaks and forms because it is (too) weak. To ensure a lasting bond, the system can form multiple weak bonds that form an overall strong bond – similar to velcro. An interesting feature of aweak multivalent systemis the sharp discrimination between surfaces based on receptor density. That means that when multivalent particles encounter surfaces with the specific receptor but different densities, they will most likely bind to the surface with the highest density, because it has the highest binding probability. This phenomenon is called superselectivity and emerges from the large entropic contribution in amultivalent system: The more ligands and receptors are involved in the binding, the more possibilities the system has to form a bond and hence a large entropy. In this thesis we investigate how the interaction strength and entropy influences superselective binding. In doing so, we study superselective binding of microparticleswith hundreds of interactions and, additionally, particles with only few interactions of the size of nanometers.