The toxic gas of ricin is a biological toxin derived from the coat of a castor bean. The toxic gas kills by inhibiting the human body's ability to synthesize protein.

蓖麻毒气是种生物药剂，取自于蓖麻子的外皮，这种毒气的致命原因是会抑制人体合成蛋白质的能力。

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Three of four field tests conducted on the powder inside the envelope addressed to Wicker tested positive for a protein that later tests determined to be ricin, a lethal toxin, it says.

CNN: FBI confirms letters to Obama, others contained ricin