Optical Single Molecule Microscopy

Single molecule detection has become a widespread microscopy technique. The main reason for this is that the observation of single molecules which are spatially well separated, allows their localization with an accuracy which is not restricted by the diffraction limit. Typically, an accuracy better than 50 nm can be achieved for lager labeled proteins and organelles with integration times below 50 ms. From the recording of movies, trajectories of moving organelles can be constructed. The analysis of the data gives a detailed insight into the nature of the diffusion process. In biological cells this can either be driven by Brownian motion with or without restriction by cellular structures, or one observes directed motion by cellular motors. For the analysis of the three dimensional movement in the context of a living cell, we also develop new algorithms allowing automatized trajectory generation and segmentation.  The very same methods can be used for studies of samples of material scientific interest. In this case one commonly only observes diffusive motion which gives new insights into the structural dynamics.