Saxitoxins, also known as Paralytic Shelfish Poisons (PSPs), are neurotoxic alkaloids that block the entrance of sodium ions into nerve cells and cause the paralysis characteristic of saxitoxin poisoning. Saxitoxins naturally gather in marine and freshwater microalgae, especially Anabaena circinalis in freshwater and Alexandrium catenella, Alexandrium minutum, Alexandrium ostenfeldii, Alexandrium tamarense, Gymnodinium catenatum and Pyrodinium bahamense var. compressum in saltwater. The Saxitoxins are passed on to marine life that ingests the microalgae. Saxitoxin was named after the mollusk Saxidomus giganteus in which it was first recognized. Due to its selective blockage of only the sodium channels but not affecting the potassium or calcium channels or the chloride ions count, saxitoxins have become biomedical tools in the study of nerve disorders.
Consisting of polar molecules, saxitoxins dissolve easily in water and low level alcohols. The toxins are stable in neutrals and acids even at high temperatures but are inactivated by strong alkalines. The threat of saxitoxin poisoning increases during red tide algae blooms, especially for shellfish eaters. Pufferfish poisoning results from saxitoxins. The most lethal non-protein toxin, 0.2 milligrams of saxitoxins can kill a human of average bodyweight.
Saxitoxins as a Biological Weapons Agent
1,000 times more toxic than sarin, saxitoxins have been explored by the United States biological and chemical weapons programs. Reportedly, the CIA used saxitoxins for suicide capsules and other covert uses in the 1950s. It was reported that Francis Gary Powers carried saxitoxins on the tip of a hidden drill bit inside a silver dollar. Named Agent TZ, saxitoxins were designated Schedule 1 chemical agent and stockpiled. In biochemical form, saxitoxins are easily dissolved into water and can be ingested or inhaled.
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