a natural born killer

Ricin is a naturally occurring protein found in beans of Ricinus communis, the castor plant. Squeeze the bean to release castor oil, and you are left with an aqueous extract that contains between 5% and 10% ricin. A little rudimentary chemistry and chromatography is all that anyone needs to separate it.

If inhaled, ingested, injected or absorbed through the skin with the aid of a solvent like DMSO, the protein can kill or make you seriously ill. The lethal dose required to kill 50% of people exposed (LD₅₀) depends on the route of entry, but ranges from 30mcg/kg for ingestion to 3mcg/kg for inhalation. It is unlikely that exposure to unbroken skin could ever achieve a toxic dose.

The protein consists of 2 haemaglutins and 2 toxins. The toxins are 66kD dimers RCL III and RCL IV. Each one consists of two chains joined by a disulphide bond.

When in ...