In a development that could help safeguard people against potential acts of terrorism involving ricin, two groups of scientists in Georgia and New York are reporting the development of faster, more sensitive tests for detecting the deadly poison. One can detect one billionth of a gram of toxin in a single droplet of fluid in just five minutes, the scientists say. This is the most sensitive test to date for detecting ricin.
The scientists note in the new studies that ricin, a ribosomal inactivating protein found in castor beans, is one of the agents most likely to be used in acts of aerosol or food-related bioterrorism. Ricin can be obtained easily and quickly causes death when inhaled or eaten in small amounts. There is no known antidote. Quantitation of ricin also has medical applications, since ricin immunoconjugates have been used as anticancer agents. Although earlier researchers have developed tests capable of identifying ricin by protein recognition methods, existing tests are generally slow, cumbersome, and inaccurate.
In one study, Vern Schramm and Matthew Sturm describe a new test that detects the presence of active ricin in any sample by measuring the release of adenine from specific ricin substrates. Ricin-catalyzed adenine release from ribosomes stops protein synthesis and is the mechanism of action of this deadly toxin. By coupling adenine release to light formation by firefly luciferase, scientists can visualize the presence of ricin by the simple detection of light. The test can detect nanogram (one-billionth of a gram) amounts of ricin in minutes, they note.
In the other, John Barr and Suzanne Kalb describe development of a highly selective three-part test that involves capturing the ricin protein using special antibodies, evaluating the enzymatic activity of the ricin protein by mass spectrometry, and identifying the ricin protein by its amino acid sequence through mass spectrometry. In laboratory tests using small amounts of ricin spiked into food and body fluids, including milk, apple juice, serum, and saliva, the scientists found that the test was highly specific and accurate in comparison to current tests.
- Sturm et al. Detecting Ricin: Sensitive Luminescent Assay for Ricin A-Chain Ribosome Depurination Kinetics. Analytical Chemistry, 2009; 090320161057080 DOI: 10.1021/ac8026433
- Kalb et al. Mass Spectrometric Detection of Ricin and its Activity in Food and Clinical Samples. Analytical Chemistry, 2009; 81 (6): 2037 DOI: 10.1021/ac802769s
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