It will be another few months before the Canadian Light Source (CLS) in Saskatoon zaps a sample of matter with light, but when it does, the $174-million facility will be yet another option for scientists at the university who use radiation in their research. The CLS is Canada’s first synchrotron, an accelerator that speeds particles around in circles with electrical and magnetic fields.

Professor Emil Pai of the department of medical biophysics uses a technique called x-ray crystallography, which was famously used by Watson and Crick to uncover the shape of DNA. Pai uses it to determine the shapes of large molecules, such as proteins, which are the key actors inside living cells. Pairs of proteins fit together like keys in a lock, and a protein’s shape is like the zig-zag pattern of grooves on a key-unique to each protein. So knowing the shapes of proteins can be incredibly important for understanding biological processes-many deadly diseases are caused simply by the body’s inability to produce an antibody protein of the right fit.

To determine a protein’s structure, Pai grows a crystal out of it and zaps it with a burst of x-rays. “Access to a synchrotron has become a necessity for a protein-structure lab,” he said. “The radiation it generates is much more intense than what we produce in our labs.” The CLS will offer another venue in which Pai can test his samples. “Most of the time we go to the Advanced Photon Source at Argonne National Labs in Chicago. But crossing borders with samples is really a pain.”

The CLS opened to great fanfare in October 2004. There are about 40 synchrotrons worldwide, seven of them in the United States. Only three synchrotrons produce radiation more intense than the CLS, according to Jeffrey Cutler, co-director of research at the facility. “But they are all billion-dollar facilities,” Cutler said in a telephone interview.

The centre piece of any synchrotron is a hollow metal ring shaped like a doughnut. Inside it a beam of electrons careens around in a vacuum at nearly the speed of light, spun around by powerful magnetic fields. “At those speeds, an electron accelerated through a magnetic field emits light,” said Cutler. Electrons emit photons (particles of light) with wavelengths ranging from the innocuous infrared (invisible, but felt as heat) to powerful, penetrating x-rays.

The photons exit the storage ring through a series of experimental stations, or beamlines. These cost about $5 million apiece. Each is designed to admit photons with a narrow range of wavelengths, because in their experiments scientists only need radiation with a very specific wavelength.

Pai zaps protein crystals with x-rays. The crystal splits the x-ray beam much like a prism splits white light. But instead of a rainbow of colours, it produces a distinct pattern of rings and dots. Scientists then work backward to deduce the shape of the molecule that produced that pattern.

Though the storage ring was first powered up last fall, Cutler said that only two of the initial seven beamlines are complete. “Users will start coming in within the next two to three months to do actual experiments,” he said, adding that crystallographers will have to wait until the second or third quarter of 2005.

But that does not necessarily mean Canadian crystallographers will be flocking to Saskatoon to use the synchrotron. “We can do our experiments anywhere in the world. Saskatchewan is just another option,” said Professor Alan Edwards of the Banting and Best department of medical research. “I’ve already got a collaboration at the synchrotron in Chicago-it’s a cheaper flight there,” he explained. “If it had been closer, we’d have used it.”

Cutler explained that the University of Saskatchewan had been the site of a nuclear physics lab. “They had the expertise to build a synchrotron,” he said. Government support also helped: jointly, the university and the provincial government funded 22 per cent of the project. “The university and the province realized that having this facility might not pay off from day one. But in 10 or 15 years it will impact science in Canada and internationally,” said Cutler.

“It will make Saskatchewan a have province, not a have-not province,” he said.