Direct observation of mobility state transitions in RNA trajectories by sensitive single molecule feedback tracking.

Observation and tracking of fluorescently labeled molecules and particles in living cells reveals detailed information about intracellular processes on the molecular level. Whereas light microscopic particle observation is usually limited to two-dimensional projections of short trajectory segments, we report here image-based real-time three-dimensional single particle tracking in an active feedback loop with single molecule sensitivity. We tracked particles carrying only 1-3 fluorophores deep inside living tissue with high spatio-temporal resolution.

Light-inducible molecular beacons for spatio-temporally highly defined activation.

We have developed a new molecular beacon design that requires an additional UV pulse for fluorescence activation. This improves the signal-to-noise ratio tremendously compared to previous approaches and allows for a precise control of the time point and location of RNA labelling.