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Propidium Iodide (A rare derivative)

By moleculeoftheday on June 18, 2008.

Chemistry spans orders of magnitude in terms of polarity. Many of the organic guys who read this work on stuff that never would dissolve in water (which becomes something of a pain when you try and make that something into a drug for aqueous things like people). And the biologists work on stuff that would just maybe dissolve in DMSO, but not even methanol, otherwise. Polarity defines chemistry. I know techniques that will help me isolate gobs of biomolecules out of water, and gobs of organic molecules out of ether. It's that intermediate, medium solubility stuff that's a pain!

i-168b4930340c003995cdc388d7bcef41-propidium.png

Propidium is a derivative of ethidium.

i-7e91952fc5759f4144eb9d1bca4197d8-ethidium.gif

Ethidium's medium-soluble in everything and super-soluble in nothing, making preparation of derivatives a pain. Propidium is one of those rare ducks.

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One technique I use for low-solubility compound manipulations is Soxleth solid-liquid extraction. Example: LiAlH4 reduction of acid, difficult to dissolve in ether or THF. Put the solids in the extractor, the LiAlH4 in the ether and boil away. Gradually the acid dissolves and each portion reacts nicely with the reduction agent.
I have also used it for recrystallization/reprecipitation of sticky stuff on many occasions.