# Where do 35S and 32P come from?

Hi all,

I remember a long time ago in highschool our bio teacher mentioned that radiotracers used in biology back in the 40s-50s came out of the Manhattan project.

But searching through google, i haven't really been able to find which radiotracers that we commonly use in biology come from decaying uranium/plutonium etc.

2 of the big radiotracers we use are $$^{35}S$$ and $$^{32}P$$. Normally sulfur is used to label proteins and phosphorus is used to label DNA (although $$^{32}P$$ is useful for phosphorylation states of proteins too)

There are also others used such as $$^{123}I$$ and $$^{125}I$$.

Many of these (particularly $$^{32}P$$) have incredibly short half-lives so I'd imagine if they weren't being made from something with a much longer 1/2 life they'd have burned out of the universe long ago. So where do they come from and how are they made?

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