Global Challenges/Chemistry Solutions

Promoting Personal Safety & National Security: Targeting ricin Analytical Chemistry

June 16, 2009


Ricin structure. The A chain is shown
in blue and the B chain in orange.
Credit: Wikimedia Commons
(High-resolution version)

  Summary

Today’s topic is research on new ways to detect
and possibly treat poisoning from ricin, a potential
bioterrorist agent. Since there’s no known antidote
for the poison, detecting it quickly in the food supply
is a matter of life and death.

 

The September 11 attacks terrorized America and put the defense industry on high-alert. In the wake of this incident, one much-feared scenario involves the possibility of a bioterrorist attack on the food supply using ricin, a plant toxin found in castor beans. There’s enough ricin in eight castor beans to kill the average person. Since there’s no known antidote for the poison, detecting it quickly in the food supply is a matter of life and death. Unfortunately, current methods for ricin detection are generally slow, cumbersome, and inaccurate. Researchers say that a better way to detect the poison is needed.

One of the researchers making progress toward this goal is Dr. Vern Schramm, a professor of biochemistry at the Albert Einstein College of Medicine in New York. Dr. Schramm and his team developed a faster, more sensitive test for detecting ricin. They reported their work in the ACS journal Analytical Chemistry. Here now is Dr. Schramm:

“This test can detect a nanogram, about one billionth of a gram, of ricin in just a few minutes. So that’s faster and it’s more sensitive than any of the current methods for detecting the poison.”

He says that ricin attacks the ribosomes, tiny organs found in cells that are responsible for making proteins that are essential for life. In particular, the poison causes the ribosomes to release of a chemical called adenine, which is normally found in the genetic machinery of the ribosomes. When that happens, it stops protein production, causing illness and eventually death.

By studying the poison’s mechanism of action, Dr. Schramm found a clever way to easily detect this process in any sample that contains ricin. The new test does this using luciferase, the same chemical that gives lightning bugs their characteristic glow. The luciferase “lights up” areas in the body where adenine is being released in dangerous levels. Here again is Dr. Schramm:

“By doing that, we can visualize the presence of ricin by the simple
detection of light. This makes the assay portable, highly detective,
and extremely sensitive.”

In the future, the testing device could be crafted into a small hand-held box that technicians could carry into the field to test suspicious food samples. The technician would place a food sample into the box and special sensors would read the amount of light produced. Then, a digital or analog display would show how much ricin is present. This would make detection of ricin almost as easy as using a microwave oven.

But Schramm’s research involves more than just detecting the presence of ricin. He says that insights learned from the study could potentially allow researchers to cure ricin poisoning for the first time.

“It turns out with this test that what we have is also a fantastic laboratory tool. …   We can use this assay just to look for light and then screen libraries or design specific inhibitors to try to block the action of ricin, thereby finding an antidote or rescue agent for ricin poisoning.”

In a related study, Dr. John Barr of the Centers for Disease Control and Prevention used a different approach for detecting ricin poisoning in food. Dr. Barr and his colleagues developed a highly selective, three-part test. His new test involves capturing the ricin protein using special antibodies that specifically target the protein. Next, he evaluates the activity of the ricin protein and identifies its presence using a mass spectrometer, an instrument that analyzes unknown chemical substances based on molecules emitted in the presence of a powerful light beam. While seemingly more complex than Dr. Schramm’s test, it gets the job done. Here is Dr. Barr:

“In laboratory tests using small amounts of ricin spiked into food and body fluids, including milk, apple juice, serum, and saliva, we found that the test was highly specific and accurate in comparison to current tests. This test could go a long way toward protecting the food supply against bioterrorism involving ricin.”

Thanks to clever chemistry, the public will have at least some measure of assurance that the food supply will be protected against ricin poisoning through its quick and timely detection. But if the dreadful event happens, a cure is also in the works.

Smart Chemists/Innovative Thinking

Smart chemists. Innovative thinking. That’s the key to solving global challenges of the 21st Century. Please check our full-length podcasts on Promoting Personal Safety & National Security. For the American Chemical Society, I’m Adam Dylewski in Washington.

Further reading:
Analytical Chemistry

“Detecting Ricin: Sensitive Luminescent Assay for Ricin A-Chain Ribosome Depurination Kinetics”

Vern L. Schramm, Ph.D.
Image courtesy of
the Albert Einstein
College of Medicine.