An extremely toxic protein present in the castor bean (Ricinus communis) of the family Euphorbiaceae, which has been used as a deadly poison in political assassinations. It has been proposed as a chemical warfare agent.
Ricin can be extracted from castor beans and is known to have an average lethal dose in humans of 0.2 milligrams (1/5,000th of a gram), though some sources give higher figures.Toxicity and manufacture
Ricin is poisonous if inhaled, injected, or ingested, acting as a toxin by the inhibition of protein synthesis. In small doses, such as the typical dose contained in a measure of castor oil, ricin causes digestive tract cramps.
Although the castor bean plant has long been noted for its toxicity, ricin was first isolated and named in 1888 by Hermann Stillmark. Modern feed-making techniques break down the ricin in castor beans by heating at 140 degrees Celsius for 20 minutes, although some studies suggest that residual toxic effects may linger. Although one seed contains enough ricin to kill an adult human, they may pass harmlessly through the digestive system if swallowed whole..
Ricin consists of two distinct protein chains (almost 30kDa each) that are linked to each other by disulfide bond:
Ricin A is toxic to the cell by interfering with ribosomes, responsible for protein synthesis Ricin B is important in assisting ricin A's entry into a cell by binding with a cell surface component. Since people do not get sick from eating large amounts of such products, ricin A is of extremely low toxicity as long as the B chain is not present.Ricin is easily purified from castor-oil manufacturing waste. The seed-pulp left over from pressing for castor oil contains on average about 5% by weight of ricin. Since 0.2 mg of purified Ricin constitutes a fatal dose, this is a considerable amount of ricin.
In the United States, a person caught manufacturing or possessing ricin may be sentenced up to 30 years in prison.
Potential medicinal use
Ricin may have therapeutic use in the treatment of cancer. Genetic modification of ricin is believed to be possible to lessen its toxicity to humans, but not to the cancer cells.
Use as a chemical/biological warfare agent
The United States investigated ricin for its military potential during the First World War.
During the Second World War the United States and Canada undertook studying ricin in cluster bombs. This conclusion was based on comparison of the final weapons rather than ricin's toxicity (LD50 <30 mg.min.m–3).
The best-known documented use of ricin as an agent of biological warfare was by the Soviet Union's KGB during the Cold War. In 1978, the Bulgarian dissident Georgi Markov was assassinated by Bulgarian secret police who surreptitiously 'shot' him on a London street with a modified umbrella using compressed gas to fire a tiny pellet contaminated with ricin into his leg.
Despite ricin's extreme toxicity and utility as an agent of chemical/biological warfare, it is extremely difficult to limit the production of the toxin. Under both the 1972 Biological Weapons Convention and the 1997 Chemical Weapons Convention, ricin is listed as a schedule 1 controlled substance. Despite this, more than 1 million metric tonnes of castor beans are processed each year, and approximately 5% of the total is rendered into a waste containing high concentrations of ricin toxin.
In August of 2002, US officials asserted that the Islamic militant group Ansar al-Islam tested ricin, along with other chemical and biological agents, in northern Iraq.
To put ricin used as weapon into perspective, it is worth noting that as a biological weapon or chemical weapon, ricin may be considered as not very powerful, if only in comparison with other poisons such as botulinum or anthrax. Ricin is easy to produce, but is not as practical nor likely to cause as high casualties as other agents. (Jan van Aken, an expert on biological weapons explained in an interview with the German magazine Der Spiegel that he judges it rather reassuring that Al Qaeda experimented with ricin as it suggests their inability to produce botulin or anthrax.)
Pure ricin could be dispersed through the air, but ozone, nitrogen oxides, and other pollutants would oxidize it within a few hours, rendering it harmless. Ricin is actually several orders of magnitude less toxic than botulinum or tetanus toxin, but those are more difficult to obtain.
Patent
The process for creating ricin is well-known, in part because a patent was granted for it in 1952. The inventors named in U.S. Patent 3,060,165 (granted October 23, 1962) "Preparation of Toxic Ricin", assigned to the U.S. Secretary of the Army, are Harry L. Modern extraction plants might use membrane filtration to make highly purified ricin isolates.
Ricin is initially extracted from defatted castor beans by aqueous extraction at pH 3.8 to yield a leachate containing solubilized ricin. After precipitation, the crude ricin cake is washed with a 16.7% solution of sodium sulfate to remove extraneous nitrogenous substances.
The final ricin precipitate is dried and then purified by floatation in carbon tetrachloride. An aerosol powder may be prepared by spray drying or air grinding the purified ricin using cold air.
Detected ricin incidents
Assassination of Bulgarian Dissident Georgi Markov, London 1978
On September 7, 1978 the Bulgarian dissident Georgi Markov was shot in the leg in public on Waterloo Bridge in the middle of London by a man using a weapon built into an umbrella. The weapon embedded a small pellet in Markov's leg which contained ricin.
Related arrests in Britain in 2003
On 5 January 2003 the Metropolitan Police raided a flat in north London and arrested six Algerian men whom they claimed were manufacturing ricin as part of a plot for a poison attack on the London Underground.
Ricin was detected in the mail at the White House in Washington, D.C. The letter contained a fine powdery substance that later tested positive for ricin. This information was not made public until February 3, 2004, when preliminary tests showed the presence of ricin in an office mailroom of U.S. Senate Majority Leader Bill Frist's office.
In Richmond, VA
In January 2006, ricin was found in a home in the suburbs of Richmond, VA. Although the suspect, Chetanand Sewraz, was allegedly isolating the toxin to kill his estranged wife, and not for some form of bioterrorism, it nonetheless highlighted the ease with which ricin toxin can be made.
In Austin, Texas
Wikinews has news related to: FBI confirms that ricin was not found at the University of TexasOn 23 February 2006, a student in the Moore-Hill dormitory at the University of Texas at Austin found a strange powder in a roll of quarters she was using to do laundry. News reports on 25 February report that further testing has indicated that the substance found is not, in fact, ricin. Ricin was used as the poison of choice of the murderer in the 1962 comedy film Kill or Cure. Ricin was the poison used in Agatha Raisin and the Wizard of Evesham by M.C.Beaton, published in 1999. Ricin was mentioned in the "call me the prankster" comic at toothpaste for dinner The Penn and Teller book How To Play With Your Food (ISBN 0-679-74311-1) includes a "gimmicks envelope" of small objects related to the tricks inside the book. The book explains that ricin is a poison. Dieke, and Charlotte Karel, US Patent 3,060,165, "Preparation of Toxic Ricin", granted October 23, 1962 ^ http://www.globalsecurity.org/org/nsn/nsn-040723.htm ^ http://wtvr.com/Global/story.asp?S=4457615 ^ http://wtvr.com/Global/story.asp?S=4457626 ^ "Ricin discovered in dormitory", Austin-American Statesman, 25 February 2006 ^ "Powdered substance reported by student in Moore-Hill Dormitory", Official UT Austin Press Release, 24 February 2006 ^ "Tests: No ricin in UT student from Pearland", Houston Chronicle, 25 February 2006 ^ "call me the prankster" ^ toothpaste for dinner ^ CSI Series 2 Episode 7
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