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CocktailChemist t1_j92bzxl wrote

Reply to comment by grumble11 in Why does the thyroid use iodine ? by geistererscheinung

To add to this, it’s also why you’re mostly likely to find halogen-containing biomolecules in aquatic species, especially marine mollusks. The dye Tyrian purple would be a classic example.

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Y_m_l t1_j92uv6z wrote

It's wild to me that that molecule and it's derivatives are so localized to certain species. For folks information, Tyrian purple is indigo that has been substituted on both ends with bromine groups (6,6'-dibromoindigo). Indigo itself is only found in a couple species (indigo and woad are the most prevalent). Also Tyrian purple was harvested by "milking" a certain snail for minute amounts of the dye.

I went to a farm near me to buy some madder (the roots of which contains the anthraquinoidal dye alizarin) and one of the farmers, an older man, told me all of that above and I asked him if he was a chemist? Non chemists don't use words like "substituents."

"In a past life," he said.

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