"We have discovered that tert-butoxyl radicals are even more reactive than we thought and thus a terrible model for reactive oxygen species in biological systems," says Jim Tanko, professor of chemistry at Virginia Tech. Robert A. Friedline of Mars, Pa., a Ph.D. student in chemistry at Virginia Tech, will present his research findings at the 225th America Chemical Society national meeting March 23-27 in New Orleans.
Oxygen free-radicals are "hungry" molecular species that can damage living tissue by grabbing hydrogen atoms off of other molecules, interfering with normal chemistry necessary to processes ranging from thinking clearly to tissue repair or removal of toxins from the blood. Oxygen free-radicals have an extra electron on their oxygen atom, which results in the molecule plucking hydrogen atoms from nearby molecules.
However, in biological systems, oxygen free-radicals do their work in complex environments that are difficult to observe. Many of the compounds which generate oxygen radicals are too unstable to use in a laboratory. "You look at them wrong and they will blow up in your hand," says Tanko. So, years ago, chemists started using a specific oxygen-centered radical-- t-butoxyl radical – which is easily produced from a stable and safe source, as a model. The t-butoxyl radical was then subjected to various tests within organic solutions to observe its behavior and characteristics. "It seemed like a good approximation of a 'generic' oxygen-centered radical," says Tanko.
Even though it is easy to make, the t-butoxyl radical only exists for a fraction of a second before it grabs a hydrogen atom from something, or decomposes. "Its behavior is recorded in a period of a few hundred nanoseconds using light so we can study the resulting spectrum to determine what happened and how fast. We try to understand the molecule's chemistry in a chemical system first," Tanko explains. "In the course of our studies, we soon realized that chemists have been missing something that limits its use in a biological model."
The Virginia Tech researchers began to explore the properties of t-butoxyl radical when the department acquired a new laser system and the researchers wanted to study chemistry that had been well studied and reported in the literature so they could learn how to use the system.
"We began to realize there were aspects of t-butoxyl radical that no one had realized. Oxygen free-radicals pluck hydrogen atoms from sites where there is a weak carbon-hydrogen bond; but, we were seeing a major breakdown in that pattern. The t-butoxyl radical was plucking tightly bound hydrogens as well as those where the bond was weak," says Tanko.
But before he could accept the new results, he asked Friedline to repeat his experiments several times. "That's what you do when the findings aren't consistent with the hypothesis. I had a mental block, until, finally, I realized this must be the right answer.
"There had been a hint of that in the literature," he says. "We are now trying to figure out why. But, in the meantime, we do know that t-butoxyl radical is a poor model for other oxygen free- radicals."
The paper, "Oxidation of tertiary amines by tert-butoxyl radical: Model studies for radical reactions in biological systems (Medi 28)," by Friedline, Tanko, student Christopher Wohl, and professor Neal Castagnoli, all of Virgnia Tech, and N. Kamrudin Suleman of the University of Guam, will be presented on Sunday, March 23, at 4:10 p.m. in room 353 of the Morial Convention Center in New Orleans.
Friedline earned his B.A. from Washington and Jefferson College in 1999.
Contact Jim Tanko at jtanko@vt.edu of 540-231-6687 or Robert Friedline at r_friedline@hotmail.com
PR CONTACT: Susan Trulove 540-231-5646 strulove@vt.edu