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conjugate stability

Bryan Kiehl b3748 at cts.com
Thu Aug 3 17:29:06 EST 1995

>We routinely make monoclonal AP conjugates by thiolation of the
>antibody followed by reaction with activated AP. We find that thge
>storage conditions for each conjugate is dependent on the Mab used.
>Some conjugates store well at 4C, some don't. All of them store well
>at -20C. We have also been looking at a Pierce product called 
>superfreeze which allows liquid storage of conjugates at -20C which
>should increase longevity. We find that some conjugates store better
>with it and some without. BTW in some cases conjugates stored with
>superfreeze had decreased activity compared to aliquots of the same
>batch stored at 4C without it!
>I think with Mab conjugates it all depends on the parent antibody.
>Anybody else got any conjugate stories?
I would agree with the above. Polyclonals have been consistent in my 
experience and can typically be stored in the refrigerator for extended 
periods if well preserved and start out sterile. Mabs are sometimes a 
different story. In fact I found that one Mab, a IgG3, usually precipitated 
out on repeated freeze thaw and was also unstable in the refrigerator.

My preservative of choice is sodium azide for alkaline phosphatase conjugates 
or any reagent if the azide doesn't interfer. You can't use azide with 
peroxidase conjugates and I recommend using ProClin.

Bryan Kiehl
15222-A Avenue of Science
San Diego, CA 92128
(619) 592-9300, ext 309
(619) 592-9400 [FAX]

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