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Cobalt Hexamine (We call it cobalt, but it's actually orange)

By moleculeoftheday on December 11, 2007.

Most metal ions will coordinate some electron-rich species in solution - water is a common suspect. Many other things can be hung off of certain metals, however, and an entire field and fame and fortune are available to those who manage to make something useful involving a metal. "Inorganic chemistry" is really a field unto itself - organic and biochemists make use of it, but we don't really understand it.

To that end, here's something we use to condense DNA. Cobalt (III) hexamine, or Co(NH3)63+. It actually hangs onto six molecules of ammonia, and they're "exchange inert" - you can put the stuff in water all day long and they won't go anywhere.

In DNA condensation, it's useful because it's just a small, highly charged widget. Lots of other stuff can do the job, but each in slightly different ways...

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you forgot the 6 in the subscript, it is HEXamine after all!

Love MotD!!

Organiker

By organiker (not verified) on 11 Dec 2007 #permalink

Molecular biologists will also recognize cobalt hexamine as "hexammine(III)cobalt chloride," a component of Doug Hanahan's 'brown buffer' used to coax E. coli to take up plasmid DNA. Legend has it that he didn't recall the exact composition so his advisor made him do a series of empirical experiments to determine the components that were key to increasing the frequency of bacterial transformation, resulting in this classic 1983 paper.

Subsequent analysis has questioned the need for this form of cobalt, or cobalt at all, but it has always worked well for me.

Go for the gusto with cobalt: Co(sepulchrate) and Co(sarcophagate). Now you've got permanent resolved chirality regardless of oxidation state. Substitution-labile Co(II) or substitution-inert Co(III) makes no difference.

A real man... well, like this. Bottom, +6 charge. If anybody can do that structure -6, like [Co(en)3](+3) versus [Co(ox)3]-3), Uncle Al would like to hear about it.