Researchers Develop Molecular Claw To Grab Arsenic

By Stephanie Cartier

It's been used in rat poisons and insecticides and causes cancer in humans, but now, one of the world's most notorious deadly poisons may meet its match. In early lab tests, Northwest researchers may have discovered a way to render arsenic harmless.

Darren Johnson, an assistant professor of chemistry at the University of Oregon in Eugene, says his research looks promising. "We have designed a simple organic molecule that can assemble with arsenic atoms to form a remarkably stable structure,” Johnson says.

The molecule forms when the arsenic atoms and the organic molecules interact and create a new molecule, which essentially traps the deadly poison in a molecular "claw.” The claw, or chelator–derived from the Greek word for crab claw–consists of sulfur-based molecules which were chosen for their known attraction to arsenic. "We are optimistic that by using this strategy, we have created a compound that is more stable than the sum of its parts,” Johnson says.

According to the Centers for Disease Control, people can be exposed to the deadly poison by consuming food and drinks contaminated by arsenic; the substance also can be found in the air. It is a naturally-occurring chemical, but once an individual is poisoned, the potential exists for a variety of health problems. Arsenic can cause damage to blood vessels, nausea, vomiting, and even cancer.

Arsenic contamination is an issue that hits close to home for many in this region. "There are activities that occurred in the twentieth century that spread arsenic over large areas of land in the Northwest,” says Jim White, a toxicologist with the Washington State Department of Health. Two of the problems were a smelter in Tacoma that spread emissions over 1,000 square miles of land, and widespread pesticide use in the central and eastern parts of the state. While groups are working to clean up the man-made mess, arsenic does occur naturally as well. Most of the risk to health from environmental arsenic exposure typically comes from contaminated water, which usually contains highly toxic chemical forms. White says 10 percent of new private wells that have been tested have higher arsenic levels than federal standards–and about a million people in the state rely on private wells for drinking water. "If you have a private well, get it tested for arsenic,” he advises.

Johnson and graduate student Jake Vickaryous have had success extracting arsenic from small amounts of water using chelators. While large-scale water treatment plans may not be practical yet, the team will continue research. Eventually, their discoveries may lead to medical remedies for poisoned individuals, large-scale water treatments, and arsenic detection advances.

If that work looks promising, Johnson and Vickaryous will begin testing to make sure the molecules are non-toxic. "The long-term goal of that aspect of the project would be to develop an organic molecule that is water soluble, binds specifically and powerfully to arsenic, is non-toxic, and can effectively remove arsenic from poisoned individuals.”

Johnson's research group has teamed up with Crystal Clear Technologies, Inc. (CCT) to create a filtration system to remove arsenic from contaminated water. CCT has offices in Portland and the San Francisco Bay Area and recently received a National Science Foundation Small Business Innovation Research grant to study contamination problems. While Johnson says the research will take more time, and results are still very preliminary, he is optimistic about future findings and hopes to find applications that would be welcome developments in the fight against a deadly poison.

Stephanie Cartier is pursuing a master's degree in Technical Communications at the University of Washington.

Images:

Top: This model shows the structure of the chelator at work. The arsenic atoms, shown in purple, are trapped by molecules of carbon, sulfur and hydrogen atoms, which are shown in gray, yellow, and white. The chelator grabs the arsenic atom and prevents it from forming bonds with other types of molecules. Image: Darren Johnson

Bottom: Graduate student Jake Vickaryous (left) and Professor Darren Johnson use this instrument to study molecular structure. Photo: Melody Ward Leslie