You were taught correctly. And the socalled "degradation" is re-polymerization as you wrote. The only thing is that you should add buffer salts bettwen than PBS. René J.
--- On Sat, 12/6/08, [EMAIL PROTECTED] <[EMAIL PROTECTED]> wrote: From: [EMAIL PROTECTED] <[EMAIL PROTECTED]> Subject: [Histonet] PFA preparation To: histonet@lists.utsouthwestern.edu Date: Saturday, December 6, 2008, 3:30 PM Hi, So then what is the best way to prepare formaldehyde fixative from PFA? The way I have been taught, which differs from what I have read, is to dissolve 4% into ddH2O at room temperature. After that one could add PBS or buffer. I've also been taught that too much heat during preparation "degrades" PFA, and that PFA (or formaldehyde solution, rather) stored too long will lose freshness because it "degrades." What I read is different. Texts suggest to dissolve the PFA in warm water, and that aging of the fix is due to repolymerization, not through degradation. What should i do? Eric Schmidt University of Calgary Medical Sciences _______________________________________________ Histonet mailing list Histonet@lists.utsouthwestern.edu http://lists.utsouthwestern.edu/mailman/listinfo/histonet _______________________________________________ Histonet mailing list Histonet@lists.utsouthwestern.edu http://lists.utsouthwestern.edu/mailman/listinfo/histonet