Where do 35S and 32P come from?

[Mr.V.]

Hi all,

I remember a long time ago in high school 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?

 

[mgb_phys]

They aren't made from heavy metal decay but from neutron irradiation of smaller atoms -
for which you need a reactor.
Today they are generally made in small specialised reactors or as a side product in a few powerstations.
Very short lived isotopes you have to make on-site in an accelarator and then inject them directly into the patient - often involving a frantic sprint across the hospital.

 

[quicknote]

Thank you for your question. ^{35}S and ^{32}P are both radioactive isotopes of naturally occurring elements sulfur and phosphorus, respectively. These isotopes are produced through the process of nuclear reactions, specifically neutron bombardment.

In the case of ^{35}S, it is produced by irradiating ^{34}S with neutrons in a nuclear reactor. This process converts some of the stable ^{34}S atoms into radioactive ^{35}S atoms. Similarly, ^{32}P is produced by irradiating ^{31}P with neutrons.

These radioactive isotopes have short half-lives because they are not naturally abundant in the environment and are constantly decaying into stable isotopes. This is why they need to be continuously produced in nuclear reactors in order to be used as radiotracers in biology.

I hope this helps to answer your question. Let me know if you have any further inquiries.