Catching Proteins in the Act of Folding (IMAGE)
Caption
To analyze a protein as it folds, a cold solution of an unfolded protein (the thread in the top image), and hydrogen peroxide (paired red dots) is injected into a capillary. The solution is hit with a laser at an infrared wavelength (second image), which heats the protein enough to encourage it to start folding (the blue coil is an alpha helix, a common protein "fold"). In the third step, the solution is exposed to an ultraviolet pulse that breaks the hydrogen peroxide into two parts that attach oxygen atoms (red dots) to portions of the protein that are still outside the folding structure and exposed to the solution. The protein is later cut up and the parts "weighed" to see if they are carrying additional oxygen atoms. The pathway by which the protein folds can be deduced by repeatedly "painting" it with oxygen in this way.
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