Ricin. Molecular model of the toxic protein ricin. It comprises two entwined amino acid chains,termed A and B. The A-chain is toxic,inhibiting protein synthesis in cells. It is carried into cells by the non-toxic B-chain. Ricin is derived from the seeds of the castor oil plant (Ricinus communis),making it easy to be used as a toxin by bioterrorists. Less than a milligram is enough to kill an adult. Inhaling ricin causes coughing,pulmonary oedema and death. If ingested,it causes gastroenteritis,liver and kidney damage and death from circulatory failure. There is no antidote |