As seen for the brainbow mouse, microscopic imaging of molecules that have different hues, reveals their spatial correlation. But diffraction hampers standard microscopy and implies that biomolecules cannot be located more precisely than within ~200 nm. Different approaches (as reviewed last month) tried to broke the Abbé limit, and another one (Resonance Energy Transfer) leads to explore tight proximities (~5 nm). Bates et al. claims now on Science, the possibility to probe 25 nm fluorescence microscopy (nanoscopy!) in a modular system that can accomodate also nine color channels. Such thunderclap introduces STORM (STOchastic Reconstruction Microscopy) that is based on activation and deactivation of isolated molecules. Each probe consists of a photo-switchable "reporter" fluorophore that can be cycled between fluorescent and dark states, and an "activator" that facilitates photo-activation of the reporter. This on/off cycle produce tiny focal spots so sparsely that they coordinates can be easily tracked by the camera, and the cycle is repeated until the tick-marcks form an image. Using this approach, authors showed multicolor imaging of DNA model samples and mammalian cells with 20- to 30-nanometer resolution. This technique will facilitate direct visualization of molecular interactions at the nanometer scale.
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Bates, M., Huang, B., Dempsey, G., & Zhuang, X. (2007). Multicolor Super-Resolution Imaging with Photo-Switchable Fluorescent Probes Science, 317 (5845), 1749-1753 DOI: 10.1126/science.1146598
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