protein radioiodination

D.K. DK at no.valid.address
Thu Jun 19 07:24:26 EST 2003

In article <43733e0a.0306182130.73883db3 at posting.google.com>, immunoq at sbcglobal.net (Kiley) wrote:
>I need to radioiodinate a protein to use in immunoprecipitation assays
>for screening hybridomas producing MAbs specific to this protein of
>interest. I will be purchasing recombinant, carrier-free protein for
>this purpose and intend to have it commercially labeled.
>I have never worked with radioiodinated proteins and therefore have
>some basic questions, such as: (i) will the structure and/or stability
>of the protein be affected by this process (and if so to what
>degree...what properties of the protein could predispose to structural
>changes/instability following radioiodination)?; 

You cannot know it a priori. It depends on your iodination method 
(Bolton-Hunter reagent coupling or direct iodination of tyrosines) and 
properties of your protein. Generally however iodination is mild 
enough to keep most of any protein active. 

>(ii) given the
>half-life of I-125 (60 days?), at what point in time following
>labeling should I expect to see a decline in radioactivity to the
>point that sensitivity for the purposes of immunoprecipitation would
>be "lost"?

Assuming radiolysis is not a problem (also impossible to know
before hand), it will decay 8X in a year. Thus, it depends on
the original specific radioactivity of your protein and whether 
you can afford exposing for ~ 10X longer. 


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