super-resolution imaging in living cells
Saturday 22 October 2011
In 1873, Ernst Abbe discovered that features closer than approximately 200 nm cannot be resolved by lens-based light microscopy.
In recent years, however, several new far-field super-resolution imaging techniques have broken this diffraction limit, producing, for example, video-rate movies of synaptic vesicles in living neurons with 62 nm spatial resolution.
Current research is focused on further improving spatial resolution in an effort to reach the goal of video-rate imaging of live cells with molecular (1-5 nm) resolution.
Photoactivatable fluorescent proteins (PA-FPs) are molecules that switch to a new fluorescent state in response to activation to generate a high level of contrast.
Over the past eight years, several types of PA-FPs have been developed. The PA-FPs fluoresce green or red, or convert from green to red in response to activating light.
Others reversibly switch between ’off’ and ’on’ in response to light.
The optical "highlighting" capability of PA-FPs has led to the rise of novel imaging techniques providing important new biological insights.
These range from in cellulo pulse-chase labeling for tracking subpopulations of cells, organelles or proteins under physiological settings, to super-resolution imaging of single molecules for determining intracellular protein distributions at nanometer precision.