Synchrotron Takes Aim at Live Cells

By Paul Preuss

A bright, tightly focused beam of infrared light from the ALS's beamline 1.4.3 allows researchers to follow subtle chemical and molecular changes in individual human cells, without killing the cells or using intrusive probes.

Traditional methods of biomedical research require killing cells (fixing them), averaging results from many cells, or introducing dyes, tagged proteins, or other agents that can affect cell chemistry--methods that involve tedious preparation and long delays between experiment and result.

Hoi-Ying Holman is the principal investigator in the study of living human cells using the ALS's infrared beamline, designed and built by Michael Martin (center) and Wayne McKinney. Photo by Roy Kaltschmidt

"Now we can study individual cells in real time without introducing extraneous factors," says Hoi-Ying Holman of the Earth Sciences Division, the principal investigator in developing the new technique.

Holman and her colleague Michael Martin of the ALS described the technique, known as Synchrotron Radiation-Based Fourier Transform Infrared spectromicroscopy, at recent meetings of the American Chemical Society and the American Physical Society.

Despite the jawbreaking name, the principle of SR-FTIR spectromicroscopy is straightforward. Different molecular and physical states of a cell absorb different wavelengths of infrared light, yielding unique spectra that can distinguish different cell types, different phases in the cell cycle, and different chemical reactions and physical changes inside the cell.

Light from the infrared beamline is hundreds of times as intense as conventional infrared sources and can be focused to a spot less than 10 micrometers in diameter, smaller than the dimensions of a typical mammalian cell.

"We can position the spot on a sample within one micrometer," says Wayne McKinney, who developed the beam line with Martin. He adds that "because the synchrotron light comes in pulses two nanoseconds apart, we can record very fast changes in cells." Although this capacity has not been applied to work done so far, it promises to open new insights into cellular processes.

So far, Holman and her collaborators have concentrated on the response of cultured human cells to low doses of environmental agents. In lung cells, they have shown that different oxidizers and x-rays produce different kinds of damage marked by distinct spectral changes. In liver cells, their work indicates that dioxin's influence is related to its interaction with a specific binding site.

They have also recorded distinctive spectra from lung cells going through different stages of the cell cycle. With other researchers, they plan to study radiation and drug therapies for brain tumors and oxidative stress in such diseases as atherosclerosis, diabetes, and rheumatoid arthritis.

SR-FTIR spectromicroscopy allows studies of live cells impossible or impractical by any other method, enabling basic studies of the life, death, damage, and self-repair of tissues and cells at the subcellular level.