Mechanism of toxicity
Cyanide is an irreversible enzyme inhibitor. Cyanide ions bind to the iron atom of the enzyme cytochrome c oxidase (also known as aa3) in the fourth complex in the mitochondrial membrane in the mitochondria of cells. This denatures the enzyme, and the final transport of electrons from cytochrome c oxidase to oxygen cannot be completed. As a result, the electron transport chain is disrupted, meaning that the cell can no longer aerobically produce ATP for energy.
Tissues that mainly depend on aerobic respiration, such as the central nervous system and the heart, are particularly affected.
Plants contain an alternative pathway for respiration in their mitochondria. The alternate oxidase is not as efficient as the normal pathway, but immune to cyanide. As a result, plants are insensitive to concentrations of cyanide that are lethal to animals, and a few species (e.g. the Giant Bamboo in its shoots) are known to contain cyanides.[4] Interestingly, the Greater Bamboo Lemur is able to consume lethal doses of the Giant Bamboo shoots with no effect. The reason for its immunity is not yet understood.
Clinical symptoms
It is difficult to give dose figures in this section due to the rapid metabolism of cyanide in the human body. Animal studies are of little help, as different species have widely different sensitivities to cyanide: it is quite possible that there is also a considerable range of sensitivity among human individuals. The Regulatory information section below may give some guidance.
Suicide
Cyanide salts are sometimes used as fast-acting suicide devices. Cyanide is reputed to work faster on an empty stomach, possibly because the anion is protonated by stomach acids to give HCN. Famous cyanide salt suicides include:
* Erwin Rommel
* Adolf Hitler (likely, see article on Hitler's death)
* Eva Braun
* Wallace Carothers
* Joseph Goebbels
* Hermann Göring
* Heinrich Himmler
* Alan Turing
* Odilo Globocnik
* Martin Bormann
* A North-Korean agent identified as Kim Sung Il, who along with a female accomplice in police custody in Bahrain bit into cyanide tablets hidden in cigarettes after having left a bomb onboard Korean Air Flight 858 which subsequently exploded over the Indian Ocean on November 29, 1987. The woman's life was saved by a quick-thinking police officer who knocked the cigarette away at the last second.
* Ramón Sampedro
* Gavrilo Princip attempted suicide, but failed
* Nedeljko Čabrinović attempted suicide, but failed
* Behzad Nabavi attempted suicide, but failed
Some espionage agents also carried glasses with cyanide in the frames. If they were caught by the enemy they could 'casually' chew the frame, releasing the cyanide, and die before having information extracted from them.[citation needed] Members of the Liberation Tigers of Tamil Eelam which operate in north-eastern Sri Lanka are probably the most reported to use capsules made out of cyanide compound/compounds, where each member of the militia wears a capsule round their neck, which is used to commit suicide when they are about to be captured by the security forces of Sri Lanka.
War
Cyanides were stockpiled in both the Soviet and the United States chemical weapons arsenals in the 1950s and 1960s.[citation needed] During the Cold War, the Soviet Union was thought to be planning to use hydrogen cyanide as a "blitzkrieg" weapon to clear a path through the opposing front line, knowing that the hydrogen cyanide would dissipate and allow unprotected access to the captured zone[citation needed]. However, as a military agent, hydrogen cyanide was not considered very effective, since it is lighter than air and need a significant dose to incapacitate or kill.
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