X-ray crystallography generate selegant, yet static, portraits for biologists' ever-growing gallery of protein structures. To reveal protein motion, bio-physicists have developed site-directed spin labeling (SDSL), which uses electron paramagnetic resonance (EPR) spectroscopy to probe protein dynamics. The technique, performed using an EPR spectrometer, is complementary to nuclear magnetic resonance (NMR) but also offers some distinct advantages, including higher sensitivity, applicability to larger proteins, and the potential for real-time measurements.
With SDSL, scientists can observe proteins in motion, "like watching a movie," says Wayne Hubbell of the University of California, Los Angeles, who originated the method in the 1980s. Since that time, SDSL has become "mature to the point where it is usable as routine standard technology," he says. Sunil Saxena, who explores new SDSL methodologies at the University of Pittsburgh, concurs. "It's backed by very solid theory," he says, which means that the software and instrumentation can now be "packaged ...
