RE: [Histonet] (para)formaldehyde

From:Rene J Buesa

Probably, because the "masking" of DNA/mRNA is due to the cross linking action of methanal (formaldehyde) over the proteins that exist in their close proximity and both "formalin" and formaldehyde solution prepared from paraformaldehyde act in the same way (via methanal).
René J.

--- On Wed, 8/27/08, Jacqui Detmar  wrote:

From: Jacqui Detmar 
Subject: RE: [Histonet] (para)formaldehyde
To: "Monfils, Paul" ,
Date: Wednesday, August 27, 2008, 7:50 PM

I thought I heard something about 10% formalin causing more DNA/RNA
breaks than 4% paraformaldehyde.  Have I been having strange dreams

The lowly post-doc ,


Jacqui Detmar, Post-doctoral Fellow
Samuel Lunenfeld Research Institute, 
Mount Sinai Hospital
25 Orde Street, room 6-1001 AJ,
Toronto, ON, Canada
M5T 3H7
phone:   416-586-4800 x5607
fax:        416-586-8588
-----Original Message-----
[] On Behalf Of Monfils,
Sent: Wednesday, August 27, 2008 5:26 PM
Subject: RE: [Histonet] (para)formaldehyde

10% formalin and 4% paraformaldehyde are interchangeable for most
purposes (in histology at least).  However there are a couple of minor
differences.  First, commercial formaldehyde solution contains 37% to
38% formaldehyde.  Therefore diluting it 1:9 results in a solution
containing 3.7% to 3.8% formaldehyde, while a 4% solution of
paraformaldehyde in water contains a full 4% formaldehyde.  Secondly,
commercial formaldehyde solution contains 10% to 15% methanol as a
preservative.  Therefore diluting it 1:9 results in a solution
containing 1.0% to 1.5% methanol.  This is not a problem for most
histological applications, but it could be a problem in a procedure
where sources of methylation have to be avoided.  4% paraformaldehyde
solution contains no methanol - nothing but water and formaldehyde.

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