35SMet, 35SCys or 35SCys/Met ?

fdaniels at BIOSCI.CBS.UMN.EDU fdaniels at BIOSCI.CBS.UMN.EDU
Fri Sep 29 08:51:22 EST 1995


imbeaud at wotan.ens.fr (Sandrine Imbeaud) wrote:

>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

The 35S Cys/Met mixtures are an economical option for general protein
labelling as they are hydrolysates of E. coli yeilding approximately
75% Met/25% Cys.  Purified amino acids simply cost more money.  Since
your goal is to label protein in vivo containing both Cys/Met it would
be to your advantage to use the mixtures as far as generating high
specific activity products at a low cost is concerned.  Although many
protocols require the pure amino acids it appears that yours does not.
Good luck.
Frank
Frank Daniels
Minneapolis Medical Research Foundation
Minneapolis MN 55404
Email: fdaniels at biosci.cbs.umn.edu
Voice: (612)-347-5834




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