Synchrotron beam makes cells tell all.

Nothing makes a cell more willing to confess its secrets than the bright light of a synchrotron. An international team of scientists reports that it has ' used that intense glare to grill a few suspects and has obtained some of the first images of the chemical components of intact, living cells.

The researchers, working with the National Synchrotron Light Source at Brookhaven National Laboratory in Upton, N.Y., shone bright infrared light onto cells and used a combination of spectroscopy and microscopy to create images. The technique revealed more than the shape and structural features of cells, which microscopy can uncover.

"We were able to monitor the location of lipids, proteins, and nucleic acids inside," says Paul Dumas of the Applied Electromagnetic Radiation Laboratory (LURE) in Orsay, France.

The method, known as infrared spectromicroscopy, could open up "a new investigation domain," allowing researchers to trace the chemical changes in living cells as they undergo processes such as cell division or programmed death, says Dumas. "We were able to image, for the first time, the role played by lipids" during cell division.

Lipids, molecules that form cell membranes, appear to concentrate in the region where a dividing cell pinches into two. Dumas and his colleagues noticed the appearance in dying cells of a chemical feature not present in living cells.

The researchers report their findings in the April 28 Proceedings of the National Academy of Sciences.

Infrared light is commonly used to identify organic compounds. By determining what wavelengths of light a sample absorbs, scientists can deduce some of the compounds it contains. The bonds between elements such as carbon, hydrogen, oxygen, and nitrogen absorb infrared radiation of characteristic energies.

Combining an infrared spectrometer with a microscope gives researchers a way to both identify and map the location of a cell's organic compounds. Ordinary infrared light sources don't deliver enough photons to reveal the chemical details of cells, says Dumas. Synchrotron radiation, created as electrons whirl around in a particle accelerator, is 1,000 times brighter.

Infrared spectromicroscopy takes about an hour to scan a cell completely. Dumas predicts that improved detectors, could cut the time down to less than a minute, making movies of cell processes possible.

Although the synchrotron infrared images reveal considerable detail, images taken with synchrotron X rays show even more, says physicist Gelsomina De Stasio of the Italian National Research Council in Rome and the Swiss Institute of Technology in Lausanne.

X-ray spectromicroscopic images she has obtained at the University of Wisconsin's Synchrotron Radiation Center in Stoughton display cellular details just 23 nanometers across, one-thousandth the size of the smallest structures in the infrared images. Moreover, instead of probing mainly carbon bonds, X rays can detect individual nuclei of most elements, she explains.

However, the "great advantage" of infrared light is that it works at normal atmospheric pressure, De Stasio notes. So far, X-ray spectromicroscopy can't image living cells because the samples must be dehydrated and placed in a vacuum chamber.

"The vacuum doesn't kill the cell, but the cell kills the vacuum," releasing substances that must be pumped out, she explains. De Stasio is working on ways to isolate the cells in a pocket of water inside the chamber.