gentle raidioiodination protocols

[KBHATNAG at CCMAIL.SUNYSB.EDU]

>What is the best protocol around these days for radioiodinating a protein 
>_without_ disrupting its function too much (chloramine T, for instance, seems 
>too aggressive for this purpose)?

We use the Enzymobeads Reagent from Pierce extensively for radioidinating our
peptides and also making radioiodinated photoactivable analogs with much 
success and retention of activity. Loss of function can be attributed to "over"
radioiodination, which can be reduced by controlling the reaction time and 
molar excess of 125I. Also, you could label an aromatic residue or a 
photoactivable group during peptide synthesis or modification for better
selectivty in radioiodination. Other advantage is that the work up is easy. 

Another poster was curious about the Iodobeads reagent. Again, its a very clean
method for radioiodination. We have not used it for peptides but for 
photolabels.

Chloramine T method is very harsh indeed, and we have used it only in organic
synthesis.  
      
Kavish 

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Kavish Bhatnagar
Dept. of Chemistry                           Fax: 516 632 7962
SUNY @ Stony Brook                           Phone: 516 632 7935
Stony Brook, NY 11794-3400                   Email:kbhatnag at ccmail.sunysb.edu   
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