[Protein-analysis] Re: Help with calculations for specific activity

Dr Engelbert Buxbaum via proteins%40net.bio.net (by engelbert_buxbaum from hotmail.com)
Tue Oct 14 15:19:14 EST 2008

Am 30.09.2008, 16:55 Uhr, schrieb Fasulo, Lisa M  
<lisa.m.fasulo from pfizer.com>:

> I am trying to calculate the specific activity of my [3H]-ligand but
> don't know how to do it.  The package insert for my radioligand states
> that the Specific Activity is 200 mCi/g but I need to know what the
> Specific Activity is in Ci/mmol.  How do I calculate this?  The
> molecular weight of the radioligand is 463.6 g/mol.  Can anyone walk me
> through the calculations to give the specific activity in Ci/mmol?  The
> only other info I have is the concentration of the radioligand which is
> 1mCi/mL.

You use the rule of proportions (also known as rule of 3) for such  
calculations, i.e. if 463.6 g equals 1 mol (1000 mmol), how many mmol is 1  

If 1 g has the activity of 200 mCi, and 1 ml contains 1 mCi, how many g  
are there in a ml (and by similar argument, how many mmol)?

Btw, the Curie (Ci) as unit of radioactivity is outdated by some 50 years,  
we use the Bequerel (Bq) now.

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