Re: molecular and radioactivity
Allan Jones
I would agree... GST pull downs just didn't work using the antibodies I
had...� a bit of 35S and it all went fine.
In our lab there is very little radioactive work and if you look at the
amounts used the risk is very low.
Take the 35S methionine i used for example: The ALI (annual limit on
intake)�for this isotope is 10 mCi. I used in total for all my experiments
less than 1 mCi. As I was not eating the stuff, worked with gloves and
tried to be reasonably careful, I assume not to have incorporated any
radiation, but even if I had 'eaten' the entire aliquot I�would still only
have doubled my annual background radiation, as it would not even amount to
10% ALI.
32P is of course a stronger source and actually requires adequate
shielding, but still you have a dosimeter monitoring whether or not you
have been overexposed.
In summary: I would set up a lab with radiation facilities, however
nevertheless try and reduce radioactive work where sensibly possible.
All The Best!
>
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Dr Engelbert Buxbaum
> Take the 35S methionine i used for example: The ALI (annual limit on
> intake)ï¿œfor this isotope is 10 mCi. I used in total for all my
> experiments
> less than 1 mCi. As I was not eating the stuff, worked with gloves and
> tried to be reasonably careful, I assume not to have incorporated any
> radiation, but even if I had 'eaten' the entire aliquot Iï¿œwould still
> only
> have doubled my annual background radiation, as it would not even amount
> to
> 10% ALI.
>
> 32P is of course a stronger source and actually requires adequate
> shielding, but still you have a dosimeter monitoring whether or not you
> have been overexposed.
And even that danger is overrated. Leukemia patients used to get 10 mCi
32P i.v., that is enough to run a major lab for a year or so. And nobody
worried about their wastes, while in the lab we carefully collect
everything!
It does make sense to replace 32P by 33P though, not only is the radiation
softer, but you get a longer half life too.
There are procedures where radioactivity is irreplaceble, I used to do
enzyme kinetics on ATPases which required measuring hydrolysis as function
of [ATP] down to 10 nM or so. Given that you need to work under initial
rate conditions you can have a maximum of 10% hydrolysis, that is 1 nM in
10 uL of sample, and you need a c.v. of less than 2% for meaningful
results. Measuring phosphate liberation from gamma-33P-ATP is actually
simple, I did up to 400 time-courses a day, each with 7 data points (by
hand, not with a robot!).
Nick Theodorakis
<engelbert_buxb...@hotmail.com> wrote:
>
> And even that danger is overrated. Leukemia patients used to get 10 mCi
> 32P i.v., that is enough to run a major lab for a year or so.
It depends on what you're doing. I used to be able to blow through one
or two mCi doing a nuclear run-off experiment, but if all you're doing
is blots and RPAs then that's true.
> And nobody
> worried about their wastes, while in the lab we carefully collect
> everything!
>
I once had a thallium perfusion scan heart test in which I was
injected with 5 mCi of radioactive thallium, and they just sent me
home to pee it away in the regular waste. Imagine the trouble you'd
have to take of you put that in a lab animal!
> It does make sense to replace 32P by 33P though, not only is the radiation
> softer, but you get a longer half life too.
>
There's often a cost issue which may not be so insignificant. If
you're using enough 32P that you're not wasting much by decay, then
you might find the cost saving to be worth it.
Nick
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