By outrunning a laser's path of destruction, an international research team has created 3D images of fragile but biologically important molecules inside protein nanocrystals. Using the Linac Coherence Light Source (LCLS), a powerful X-ray laser at the SLAC National Accelerator Laboratory in Menlo Park, Calif., the scientists fired femtosecond (one quadrillionth of a second) bursts of light at a stream of tumbling molecules, obliterating them as they pass, but not before capturing otherwise illusive images of their crystalline structures.
An overview and early results of this new imaging technique will be presented at the 2012 meeting of the American Crystallographic Association (ACA), which takes place July 28 Aug. 1 in Boston, Mass.
"These laser pulses are so brief that we are able to outrun the radiation's damaging effects," said John C.H. Spence of Arizona State University, one of more than 70 international researchers from institutions including SLAC; DESY, the German Electron Synchrotron; and the Max-Planck Institute in Heidelberg, Germany.
"Using this so-called 'diffract-then-destroy' approach, our research team recorded about a hundred scattering patterns per second from protein nanocrystals," said Spence. "This is an important step toward the making of movies of biomolecules at work."
In traditional crystallography, a beam of X-rays first interacts with a crystal and then appears on a photo-detector as diffraction spots of greater and lesser intensity. These patterns encode the density of electrons in the crystal, enabling scientists to determine the three-dimensional position of atoms, chemical bonds, and other information. To obtain this information, the crystal is frozen, to reduce radiation damage, and placed on a rotating mount and bombarded with X-rays as its orientation is changed. A scattering pattern is slowly built up and the 3D structure can eventually be deduced.
This traditional method of using
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American Institute of Physics