Single Particle and Polymer Tracking in Two-Dimensional Energy Landscapes

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Membranes of biological cells exemplify a complex film for diffusive transport of proteins and lipids (i.e. nano-sized objects) and can teach us how to control diffusive two-dimensional transport from the nano- to micro-scale. In inhomogeneous lipid membranes a wide variety of interactions from simple steric repulsion to complex viscous or electrostatic interactions can locally influence the motion of a probe particle. Here, we focus on the impact of the interplay between steric repulsion of rigid domains and attractive dipole-dipole/charge interactions on local diffusion. Our previous results indicate that changes in the domain structure in Langmuir monolayers, supported bilayers, and giant vesicles can switch between one- and two-dimensional diffusion as well as Brownian and subdiffusion. First, we will track the motions of point-like probes (latex spheres, quantum dots, quantum dots coupled to lipids) in changing energy landscapes modulated by domain-size and shape. We will not only learn how to switch in a controlled fashion between one- and two dimensional as well as Brownian and subdiffusive transport, but we will also catalogue the complex energy landscapes in these complex films. Secondly, we analyze the diffusive behavior of polymers in such an energy landscape. Polymers as connected chain of point diffusors (DNA, actin filaments) have internal degrees of freedom. Their behavior can be better understood knowing first what a single point diffusor does. For many biological processes nature prefers two-dimensional diffusive over directed molecular motorbased transport. Understanding how diffusion in membranes can be modulated will help to comprehend why evolution has frequendy chosen this route.