35SMet, 35SCys or 35SCys/Met ?

Sandrine Imbeaud imbeaud at wotan.ens.fr
Thu Sep 28 04:55:02 EST 1995

I would like to evaluate the stability of a recombinant protein expressed
in CHO cells, and measure rates of secretion. So, I need to process pulse
and pulse-chase protocols. 
What radioactive amino acid is more frequently used in these experiments.
My protein only contains 3 Methionine and 12 Cysteine. Is 35SCys the best
choice or 35SMet, is it necessary to use simply a mix 35SCys/Met ? I know
that some firms prepare ready mix of 35SCys/Met : Amersham (ProMix (35S)),
ICN (Tran35S-label) and NEN (Expre35S35S (35S) Protein Labelling Mix).
Have you already test them ? Somebody told me that the background of
ProMix (35S) was more important than Tran35S-label one. Is that true ?
What would be the advantages to use a mix rather than a radioactive amino
acid ? 


Sandrine Imbeaud - 
e-mail : imbeau at wotan.ens.fr
Ecole Normale Superieure (Paris)
"every cloud has a silver lining"

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