Re: Iodinated Proteins

["Martha Kupcho" <martha@maroon.tc.umn.edu>]

Kristin, I am wondering if I may copy your response for my labelers.  You have 
clearly written what I have been teaching.  I think it would be invaluable to 
the labelers to read safety precautions from someone outside this institution.  
Please let me know if you are okay with this.  I would copy the entire response,
crediting you, but will remove your address if you would prefer.  Please let me 
know if you are okay with this.  Thanks in advance, Martha  
address: martha@maroon.tc.umn.edu    


In message <ac2c4d860302100452cb@[35.8.104.89]>  writes:
> Hello, Radsafers:
> 
> In response to the iodinated protein discussion, there are a few
> considerations that have not been mentioned.  I do have  personal
> experience, having been in research before health physics.
> 
> Once the iodine is bound to protein, it is stable for a period of time, at
> most a few weeks, depending on the particular protein.  It is related to
> molecular weight of the protein, among other factors.  However, after a
> period of time, the protein is broken down by the radiation, liberating
> free iodine once again.  For this reason, workers should be cautious in
> handling old iodinated compounds.  We require workers to handle wastes from
> iodinations in the fume hoods.
> 
> Another factor to consider with these iodinated proteins is the efficiency
> of the chromatography separation.  Some chromatography columns are better
> than others, some proteins separated better than others, etc.  Indeed, if
> making their own columns, as most  iodination labs do, the pouring of the
> column, the protein coating agent, the proper mixing of the buffers, and
> the speed of coating the column all affect the efficiency of separating
> free from bound iodine. Obviously, a less efficient separation is an
> increased amount of free iodine in the bound fractions.
> 
> One of our radiation safety committee members used to do 100 millicurie
> iodinations, where this efficiency was a significant factor in risk of
> intake.  He actually measured free iodine release from capped 12 x 75 test
> tubes containing fractions of 125I-bound proteins.  There is some amount of
> free iodine in even the very best of separations.
> 
> In typical uses, though, this is not a problem.  We conduct thyroid scans
> on all workers iodinating or observing iodinations.  We seldom see any
> uptake, and when we do, it is typically a new worker who did not follow the
> iodination precautions.  Only if the users are iodinating the very high
> quantities would this be a problem.
> 
> The more common problems in intakes are due to
> 
>  -Not handling waste in the fume hood
>  -Not capping the fraction tubes before moving from the hood
>  -Disposing of waste in containers outside the hood
>  -Having a very cluttered hood; blocks the air flow
>  -Not venting the stock Na125I vial prior to withdrawing the aliquot for
> iodination (a 16 gauge cannula adaptor needle makes an excellent
> conduit for venting and then allowing the very tiny Hamilton syringe needle
> to enter the vial)
>   -Last, but not least, carelessness
> 
> 
> Hope this helps.  Just some pointers learned over the years.
> 
> Have a great weekend!  We are steaming like clams here in Michigan!
> 
> Kristin
> 
> All comments herein contained are my own opinions and/or experiences and
> are not necessarily those of my employer or institution.
> 
> ************************************************************************
> Kristin Erickson, Radiation Safety Officer
> Office of Radiation, Chemical and Biological Safety
> C124 Research Complex-Eng.
> Michigan State University
> East Lansing, Michigan 48824
> Telephone: (517) 355-5008   Fax: (517)353-4871   Email: 10525kfb@msu.edu
> ************************************************************************
> 
> 
> 
> 
> 


________________________________
Martha Kupcho
Department of Environmental Health & Safety
University of Minnesota
(612) 625-1664
martha@maroon.tc.umn.edu