[Histonet] RE: Fresh vs. frozen paraformaldehyde

[mrl0627 <@t> mail.ecu.edu]

Hello, Gillian!
My understanding is that repeated freeze-thaw hastens oxidation (per Bridget Hogan and several other texts). I freeze freshly-made 4% para in aliquots so that I thaw only once. Of course, since it has to be kept in glass, it takes up a bit of space in the freezer! Otherwise, our lab keeps fresh-made at 4 degrees for no longer than one week. No problems in last 2 years.  Hope this helps.
Maureen Loomer, MS candidate in Cell Biology, East Carolina U.  

-----Original Message-----
From: &quot;Barlow, Gillian&quot; &lt;Gillian.Barlow <@t> cshs.org&gt;
To: 'Histonet' &lt;histonet <@t> lists.utsouthwestern.edu&gt;
Sent: Fri, 17 Oct 2003 17:38:13 -0400
Subject: Fresh vs. frozen paraformaldehyde

Dear Histonetters

Please solve an ongoing debate for our perfusions!  I was always told
that 4% paraformaldehyde should be made fresh each time before using, at
max made the evening before and stored at 4 degrees to use the following
morning.  However, somebody from another lab says they make theirs in
bulk and freeze what they dont use, thawing and refreezing as necessary.
Is this ok to do?  They also say they use 10% neutral buffered formalin
for their perfusions if they dont have 4% PFA. 

Many thanks 
Gillian
Gillian Barlow, PhD
Postdoctoral Fellow
Laboratory of Julie Korenberg, PhD, MD
Cedars-Sinai Medical Center
Davis Bldg, Lab 2007
110 George Burns Rd
Los Angeles, CA 90048

Phone: (310) 423 7650
Fax: (310) 423 0302