Ricin - Molecule of the Month - Jan 2003
Ricin is a protein toxin, which acts as a cellular poison and is readily produced from castor beans (Ricinus communis), which are found throughout the world. Making it easy to be used as a toxin by bioterrorists.
Naturally occurring cases of ricin involve ingestion of castor beans, by either animals or humans, and are marked by severe gastrointestinal symptoms, vascular collapse, and death.
As ricin is toxic by numerous exposure routes, however, its use by bioterrorists might involve poisoning of water or foodstuffs, inoculation via ricin-laced projectiles, or aerosolization of liquid ricin or lyophilized powder.
Ricin was the toxin used in the assignation of Georgi Markov in 1969 in London by KGB agents. .Read more here.
When poisoned ricin would likely produce symptoms within 8 hours. Fever, cough, dyspnea, nausea, and chest tightness are followed by profuse sweating, the development of pulmonary edema, cyanosis, hypotension, and finally respiratory failure and circulatory collapse. Time to death would likely be 36-72 hours, depending on the dose received.
Useful links:
Cornell University Animal Science Web site - mechanism of action and toxicity studies
Background on Ricin and Protein Structure
Structure from research paper: Rutenber, E., Katzin, B. J., Ernst, S., Collins, E. J., Mlsna, D., Ready, M. P., Robertus, J. D.: Crystallographic refinement of ricin to 2.5 A. Proteins 10 pp. 240 (1991)