If you are using a biotinylated secondary, then you should use
avidin-biotin blocking. Most of your tissues will not show endogenous
biotin, but there is  evidence that antigen retrieval uncovers a lot
more endogenous biotin than is usually understood to be around.
Conventional knowledge says you only need it for certain tissues, but
you can see it in many tissues with AR treatment - especially in tumor
tissue.  The alternative is to 1) be very attentive to your negative
controls compared to your test tissue to rule out false positive due to
endogenous biotin (and document the results) or 2) use a biotin-free
detection kit.

See this article for some basic information:

http://www.propathlab.com/pdf/Focus_2004-01_endog_biotin.pdf 


Tim Morken
Technical Support Manager
Lab Vision Products
Anatomical Pathology
ThermoFisher Scientific

-----Original Message-----
From: histonet-bounces@lists.utsouthwestern.edu
[mailto:histonet-bounces@lists.utsouthwestern.edu] On Behalf Of
annrrob@aol.com
Sent: Tuesday, January 08, 2008 2:45 PM
To: histonet@lists.utsouthwestern.edu
Subject: [Histonet] (no subject)

Does anyone else use avidin biotin with the Biogenex QD200-OX kit.?
Biogenex tells me it is not necessary to use this block, but others tell
me avidin biotin must be used on all tissues regardless of biotin
activity.? Biogenex says the power block is universal and does not
require avidin biotin block unless there is biotin proven background
staining.? I am so confused.? Please help.
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