Terry,

The following treatment is used after a PBS rinse and is followed by PBS
rinses prior to the application of a blocking serum or primary Ab step.

immerse slides in fresh 0.3% H2O2 prepared in 0.1% Sodium Azide(aq)  for
10-15 minutes

prepare fresh and place in coplin jar
3% H2O2 	5ml
0.1% NaAzide	45 ml

Dispose of Na azide solution in accordance with local and other regulations.

Reference:
Title 
     Use of azide and hydrogen peroxide as an inhibitor for endogenous
peroxidase
     in the immunoperoxidase method.
Source 
     J HISTOCHEM CYTOCHEM 35:1457-1460,
     DECEMBER, 1987.

This works very well,
Tim



	-----Original Message-----
	From:	t.hacker@har.mrc.ac.uk [SMTP:T.Hacker@har.mrc.ac.uk]
	Sent:	Thursday, May 31, 2001 10:31 AM
	To:	'Histonet'endogenous peroxidase


	Subject:	What are you using for blocking endogenous
peroxidase in acetone 
	fixed frozen sections?
	I have used a weak solution of H202 which is not always effective, 
	too strong and I get excessive "bubbling" of the tissue. Yes, I 
	know, try a strength in between, but I was wondering if there is 
	something more appropriate and less aggressive.
	I look forward to a wealth of knowledge and experience, preferably 
	by 9am GMT tomorrow.
	Many thanks,
	Terry.
	Terry Hacker,r
	Medical Research Council,
	Harwell,
	Didcot,
	Oxfordshire, OX11 ORD
	01235 834393 x360