Done by:
Kwa Jie Si (S10095886B)
Clara Chen Si Jia (S1009648E)
T01
Ricin
Ricin is a naturally toxic protein molecule found in germinating castor beans. It is a stable substance and is not affected by extreme conditions. Once the seed has germinated, the toxin is destroyed. Ricin is part of the waste “mash” produced when castor oil is made (CDC.gov, 2008.).
Chemical Formula
Image 1: Crystal Structure of Ricin showing the A Chain and the B Chain (John Wiley & Sons Publishers, 2012).
A-Chain (RTA) is a 267-amino acid globular protein which consists of 8 alpha helices and 8 beta sheets.
B-Chain (RTB) is a 262-amino acid protein shaped like a barbell and has a binding site for galactose at each end. The two sites allow hydrogen bonding to specific membrane sugars, galactose and N-acetyl galactosamine (Cornell University Department, 2013).
Lethal Dosage
The lethal dosage depends on the route of administration. If injected or inhaled, doses as low as 3-5 μg/kg body weight may be lethal. This is equivalent to 240-400 mg for a 175 lb individual. If ingested, the lethal dosage is much higher as Ricin is not well absorbed in the gastrointestinal tract (Shea, D. A. and Gottron, F., 2010).
Profile of chemical analysis
Image 2: SDS-PAGE analysis of Ricin, PEG-Ricin and mPEG-Ricin (Hu et al., 2002).
Pegylation of Ricin was done to investigate whether it would inhibit the activity of Ricin.
Proteins (∼5g) were subjected to analysis by SDS-PAGE (12%). Protein bands were stained and visualized with Coomassie Brilliant Blue. Lane M represents the molecular weight marker and their molecular masses (in kDa) are indicated at the right. Lane 1 shows the molecular weight of A-chain and B-chain of Ricin to be approximately 32 kDa and 34 kDa respectively. Lane 2 and 3 represents PEG-Ricin and mPEG-Ricin respectively.
The results have shown that pegylated Ricin have larger molecular sizes which prolongs their half lives. This could be due pegylation changing Ricin’s ability to interact with its receptors in cell membrane and their entry into the cell, thus affecting the cytokinetics (Hu et al., 2002).
Pharmacokinetics and pharmacodynamics
Ricin contains two long chains, A-chain and B-Chain. B-Chain, which holds the key to toxicity, binds to a range of cell surface glycolipids or glycoproteins having β-1,4-linked galactose residues. The toxic action occurs when A-Chain, aided by B-Chain, penetrates the membrane and goes into the cytosol. A-Chain will then seek out the site where the essential enzymes are made and catalyze the depurination of the ribosomes, halting protein synthesis. Without this supply of enzyme, the cell eventually dies (Cornell University Department, 2013).
When Ricin is ingested, the initial symptoms of Ricin poisoning will appear within 6 hours. If it’s a deadly dosage, the symptoms consists of nausea, vomiting, difficulty breathing, high temperature, coughing, tightness in the chest and abdominal pain and they are most likely to affect the gastrointestinal system. As fluid builds up in the lungs, difficulty of breathing is increased and the skin takes on a bluish colour as the blood becomes deoxygenated and death ensues. If it’s a toxic dose, the person will vomit, suffer from diarrhoea, internal bleeding, be severely dehydrated and have a reduced blood pressure. Within a day or two of exposure, organ failure will occur. If ricin is injected, death could ensue within 36 to 72 hours of exposure depending on the dosage. If the dosage is in minute amounts and the victim has survived five days, it is possible that he/she might recover (John, E., 2008).
Body Text (Summary of story)
A communist defector working for the BBC World Service, Markov is believed to have been stabbed with the poisoned tip of an umbrella filled with the toxin ricin in September 1978. On 7 September 1978, Markov parked his car near Waterloo Station and was waiting for a bus to take him over the River Thames to Bush House. Suddenly he felt a sharp jab in his thigh, and turned to find a man behind him with an umbrella which he had dropped onto the pavement (CNN World, 2008). Although Markov did not know it, the umbrella had fired a tiny metal pellet into his thigh. By the time Markov reached his home that evening he was already feeling very ill. He began vomiting and was running a high fever. He died in agony four days later despite being in intensive care.
Image 3: Ricin ‘bullet’ fired by an umbrella into BBC broadcaster Georgi Markov (Gardner, T., 2012).
Markov’s the pathologist, Dr Rufus Crompton, deduced that Markov had died of acute toxaemia. Although he could not deduce what poison or toxin had caused it, it was linked to the metallic sphere which he extracted from the back of Markov’s right thigh. A post-mortem examination, conducted with the help of UK germ warfare scientists, established he had been killed by a tiny pellet containing a 0.2mg dose of ricin (CNN World, 2008). When a pig was injected with a dose of the size that would have fitted within the pellet the animal suffered in the same way that Markov had, and with almost identical symptoms. Although Ricin antibodies could not be detected in Markov’s remains, they were detectable in the sample provided by Kostov which had been sent to Porton Down. Tests on the pellets showed them to be an alloy of platinum (90%) and iridium (10%), which is one the human body is known not to reject. This alloy is also inert to ricin. Forensic inspection of Markov’s jeans revealed no trace of a firearm powder, nor evidence that they had been pierced by a hypodermic needle. It was subsequently deduced that it had been fired from a gas or air gun.
The person responsible for ordering this assassination was the Bulgarian Interior Minister, Dimiter Stoyanov, while the plan was put in operation by his deputy, General Stoyan Savov, helped by the KGB (John, E., 2008).
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References (Scientific Articles) * Hu, R. G., Zhai, Q. W., He, W. J., Mei, L. and Liu, W. Y. 2002. Bioactivities of ricin retained and its immunoreactivity to anti-ricin polyclonal antibodies alleviated through pegylation. The International Journal of Biochemistry & Cell Biology, 34, 396-402.
References (Electronic or Web-based References) * CDC.gov. 2008. Facts about Ricin. Centers for Disease Control and Prevention. [Online] Available at: <http://www.bt.cdc.gov/agent/ricin/facts.asp> [Accessed 30th January 2013] * CNN World. 2008. Police in fresh 'umbrella assassination' probe. Cable News Network. [Online] Available at: <http://articles.cnn.com/2008-06-20/world/umbrella.markov_1_bulgarian-law-british-police-georgi-markov?_s=PM:WORLD> [Accessed 30th January 2013] * Cornell University Department. 2013. Ricin Toxin from Castor Bean Plant, Ricinus communis. [Online] Avalable at: <http://www.ansci.cornell.edu/plants/toxicagents/ricin.html> [Accessed 30th January 2013] * John Wiley & Sons Publishers. 2012. Molecular Recognition. Wiley. [Online] Available at: <http://www.wiley.com/college/boyer/0470003790/cutting_edge/molecular_recognition/molecular_recognition.htm> [Accessed 30th January 2013] * Shea, D. A. and Gottron, F. 2010. Ricin: Technical Background and Potential Role in Terrorism. Congressional Research Service. [Online] Available at: <http://www.fas.org/sgp/crs/terror/RS21383.pdf> [Accessed 30th January 2013] * Gardner, T. 2012. German man stabbed with poison umbrella dies a year after attack which has chilling echoes of infamous Markov assassination. Mail Online. [Online] Available at: <http://www.dailymail.co.uk/news/article-2143522/German-man-stabbed-poison-umbrella-dies-year-attack-chilling-echoes-infamous-Markov-assassination.html#axzz2K0UHz5Ky> [Accessed 30th January 2013]
References (Books) * John, E. 2008. Molecules of Murder: Criminal Molecules and Classic Cases. Cambridge, UK: The Royal Society of Chemistry.
