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salmon sperm blocker

Tracy Aquilla aquilla at salus.med.uvm.edu
Wed Jul 27 17:36:00 EST 1994

In Article <30p4q9$gvp at server.st.usm.edu>, sywang at whale.st.usm.edu (Shiao Y.
Wang) wrote:
>Robert Burns (burns at sasa.gov.uk) wrote:
>:  We are trying to develop an avidin-biotin based ELISA assay for
>: the detection of a biotinylated LCR product.There have been reports
>: in the literature that the addition of 100ug/ml of salmon sperm 
>: to the blocking buffer reduces the background. At current Sigma
>: prices this would make any assay fairly expensive. Does anyone
>: know of an alternative to or a cheaper source of salmon sperm.
>The U.S. catalog says $28.11/g. That's enough for 10 liters. Seems pretty
>reasonable to me. Are things that expensive in the U.K.? Perhaps someone
>in the U.S. can purchase some for you and send it by mail.
>Shiao Wang 
>University of Southern Mississippi

    I presume you are referring to salmon sperm *DNA*, as opposed to the
salmon sperm itself. If not, ignore the rest of this posting. I also presume
that this blocker is meant to decrease signals obtained from non-specidfic
hybridizations. In this case, DNA from many other creatures is probably just
as good as DNA from salmon sperm (please let me know if this is not true!).
There are various qualities of this type of DNA available. The cheapest is
the highly polymerized, high molecular weight form, which looks like string
in the bottle (i.e. calf thymus DNA). The expensive type is already prepared
for you; it comes pre-sonicated into approximately 500-800 base fragments
and is single stranded to boot (i.e. calf thymus DNA, salmon testes DNA,
etc.). I have used both for Southerns and Northerns and have not noticed a
difference. If you can not afford prepared non-specific DNA, you can prepare
your own by sonicating and then boiling to denature it. Not a trivial
procedure, but not that bad either, considering the price of the prepared
stuff. Both are available from Sigma.

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