X-ray vision

Scientists use X-rays to peer into a person’s body, and a new X-ray imaging technique does the same for individual cells.

“You should be able to image most macromolecular assemblies inside the cell”, such as proteins and DNA, says Pierre Thibault, a physicist at the Paul Scherrer Institute in Villigen, Switzerland who leads the team that reports the new technique in the July 18 Science.

Also, “it’s certainly a very important tool for nanotechnology,” Thibault says. The best light microscopes can’t distinguish features smaller than 200 nanometers. But images made with the new technique, called scanning X-ray diffraction microscopy, reveal features as small as 10 nanometers.

Electron microscopes can “see” details as small as 0.2 nanometers, but since electrons don’t penetrate far into most materials, only the surface gets imaged. X-rays penetrate materials much better, allowing the new technique to peer into objects tens of thousands of nanometers thick — about the size of most plant or animal cells.

“It’s an important development,” comments Jianwei Miao, a physicist at the University of California, Los Angeles who helped pioneer a related X-ray imaging technique. “The image is much better quality compared to previous ones.”

To make an image, Thibault and his colleagues scanned a specimen with an X-ray beam focused into a spot 300 nanometers across. For each point in the specimen, a high-speed photon detector recorded the X-rays that had passed through the specimen and spread out into a diffraction pattern — akin to the rainbow produced by a prism. Using the series of diffraction patterns, the scientists could mathematically reconstruct the image. “Our method should be easy to apply for 3-D imaging also,” Thibault adds.