Blot Blocking Agent

Peter M. Muriana muriana at
Mon Jul 19 20:42:58 EST 1993

In article <1993Jul18.202300.2633 at>, mschweder at (Mark Schweder) writes:
>Folks in this lab for years used Salmon Sperm DNA (SIGMA PN# D1626) as a 
	Sorry to bust your new find, but Sigma #D1626 is DNA from "Salmon
	testes", not from Salmon sperm.  Everyone I know has used your new 
	found blocking DNA (i.e., from Salmon/Herring sperm) for years.

>blocking agent for Southern and Northern blots. The stuff costs about $200 
>for 10g. In addition it was quite difficult to prepare. 

>One day while looking through the SIGMA catalog, I ran across something 
>called DNA Degraded Free Acid From Herring Sperm (PN# D3159) which costs 
>about $10 for 10g. It sounded like what we had been spending lots of money 
>and time preparing. I ordered some and it easily dissolved in a basic 
>solution and works wonderfully as a blocking agent for Southern and Northern 
>blots. It costs 1/20 the Salmon Sperm DNA and is easily prepared. If you 
>have $10 to burn give it a try.
>   Mark Schweder           
>   Plant Science Laboratory

	You may now even save your $10 - there are a number of 
	hybridization procedures which don't even use sperm DNA as 
	a blocking agent - just uses casein and SDS. We've been using
	such a protocol for 2 years (i.e., Tropix chemiluminescent 
	detection protocol and others).

Regards, Peter

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