Discovery of "weak links" may yield future measures to prevent radiation damage.
UPTON, NY -- While attempting to "photograph" the chemical reactions of an important enzyme of the nervous system, an international team of scientists found that the "flash" they were using -- a high-intensity X-ray beam -- was systematically destroying their target. The resulting "movie" of molecular images is the first-ever direct observation of how proteins break apart when exposed to high-energy X-rays.
"The observation was stunning," said collaborator Joel Sussman, formerly on the staff and now a visiting biologist at the U.S. Department of Energy's Brookhaven National Laboratory, where some of this research took place. Stunning because, previously, scientists believed radiation damage was nonspecific, or random. But the Brookhaven work and studies with other enzymes elsewhere confirm that the X-rays selectively break particular chemical bonds.
"It looks like we are seeing 'weak points' in protein structures that are particularly sensitive to ionizing radiation," says Sussman, who is now principally affiliated with the Weizmann Institute of Science in Israel. Certain disulfide bonds, which often bridge protein chains, and carboxyl acids, such as those found at an enzyme's "active site" where reactions take place, seem particularly vulnerable. Understanding these weak links may lead to improved methods of preventing high-dose radiation damage.
Organisms are constantly exposed to radiation, mainly from natural sources, such as sunlight and cosmic rays, as well as man-made sources such as diagnostic X-rays. "The ability to visualize the specific damage caused by radiation at a test-tube' level offers an important diagnostic tool for developing pharmacological means to protect against radiation damage," says Israel Silman, also a guest scientist at BNL's Biology Department. The Weizmann team and European collaborators, together w
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Contact: Karen McNulty
kmcnulty@bnl.gov
631-344-8350
DOE/Brookhaven National Laboratory
14-Feb-2000