What happens to 32P-labelled compounds?

[Tom Schneider]

In article <1992Jul30.085812.18345 at polaris.utu.fi>
eepee at polaris.utu.fi (Esa-Pekka P{lvim{ki) writes:

>I understand that a S atom in ATP is replaced with a 32P atom to produce a
>radioactive ATP molecule. When the 32P decays to 32S, the ATP molecule 
>continues to exist as a "real" ATP with a 32S where it should be. 
>I might be wrong, though.

There is no S in ATP.  ATP = Adenosine triphosphate.  It contains 3 phosphate
groups.  One of these is replaced by 32P to make the radioactive molecule.  The
chemistry of the ATP is (presumably almost) identical to that of one without
the ATP.  One can label DNA or whatever with it.  When it decays, a near by
film is exposed.  The molecule may or may not be destroyed (so this thread is
an interesting one) but molecular biologists in general don't care because
having seen that a decay occured, they don't care about the smoldering ruin (?)
left behind.  (That is, they are able to read the DNA sequence, so what if the
actual DNA was destroyed in the process?)

(You can also label ATP by replacing the P with 35S.)

An interesting question on these lines is:

Suppose one labeled some DNA with 32P.  Then look under an STM.  Watch again.
Watch again.   POOF!  Look again and there is a little crater there or what?
This experiment is easy to do and one would be (I think) the first person
to observe the radioactive decay of a single molecule.  If someone does
the experiment I'd like to know the result.  (I ran some calculations on this
a while back, and it seems like one would not need to wait very long to see
some molecules decay if one watched a large enough set of them.  Half life
of 32P is only 2 weeks.)

  Tom Schneider
  National Cancer Institute
  Laboratory of Mathematical Biology
  Frederick, Maryland  21702-1201
  toms at ncifcrf.gov