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Unformatted text preview: 09/18/2006 08:42 PM Biological Chemistry Page 1 of 10 http://courses.chem.psu.edu/chem497a/ Science & Technology September 4, 2006 Volume 84, Number 36 pp. 49-52 Squint Busters Tool builders are pushing optical microscope vision to single-molecule sharpness Ivan Amato To see something that no one has ever seen before is one of science's most fulfilling rewards. It's a home run, a trophy, a gift of knowledge. It's a CV highlight, a string of research papers, a story to tell over and over. Courtesy of Eric Betzig SEEING MOLECULES At high resolutions, conventional fluorescence 09/18/2006 08:42 PM Biological Chemistry Page 2 of 10 http://courses.chem.psu.edu/chem497a/ microscopy of a small mitochondrial region yields blurry information (top) from a fluorescently tagged protein. Electron microscopy of the same region (bottom) reveals structure but not molecular identity. A new fluorescence technique called PALM resolves signals from individual tagged molecules (red dots), yielding optical images with nearly molecular-scale resolution (second from top). PALM and EM also can be combined into more telling composites (second from bottom). Late last year, a pair of then-unemployed Bell Labs expatriates, Eric Betzig and Harald Hess, shipped a prototype microscope they had designed, financed in part with $50,000 of their own money, and built in Hess's living room to collaborators at the National Institute of Child Health & Human Development (NICHD), in Bethesda, Md. They all knew from the first test runs in January that they had in their hands a new window on the biological world. With PALM, the soothing acronym for photoactivated localization microscopy, Betzig, Hess, and collaborators have been able to discern the precise cellular locations of thousands of individual protein molecules. With conventional fluorescence microscopy techniques, particularly at high magnifications, these molecular multitudes appear as smeared fields of luminous blur. But PALM focuses those blurs, which have served biologists mightily despite their lack of clarity, into subcellular "star fields," each point of light due to the here-I-am beacon of a single cleverly labeled protein. "It's amazing," says Jennifer Lippincott-Schwartz , cell biologist at NICHD, who, with labmate George Patterson, designed the fluorescent "optical highlighters," a type of photoactivatable light- emitting tag for cellular studies that Betzig and Hess needed to make PALM work. Lippincott- Schwartz is especially excited about combining PALM, which produces images that identify the locations of specific individual molecules in a sample, with electron microscopy (EM), which gives images with fine structural detail but usually without clearly specifying the molecules involved in the structures....
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