methanol in formaldehyde

[David L. Haviland, Ph.D.]

At 08:16 7/18/97 -0700, Namik Kaya wrote:
>Hi,
>we just found a note on the ordered formaldehyde bottle, that it contains 
>10% methanol. The technical support gave us the information that all 
>formaldehyde solution contains methanol to prevent paraformaldehyde 
>precipitation, even if it is not indicated (?). Will this methanol 
>content have negative effect on RNA in formaldehyde/agarose gels, and we 
>should find "real" 37% formaldehyde in water, with that nice white pellet 
>in it?
>Thanks,
>Namik Kaya

Namik:

Funny  you should ask...  I've been using formaldehyde (w/ methanol) in RNA
gels for years without a problem.   

The issue of the methanol for stabilization was a current topic in the
flow-cytometry listserv as folks wondered if it would affect FITC, PE, and
GFP - and the consenses is that it doesn't affect the first two, the jury
is still out for GFP.   I have used it for flow and it works well without
detectable loss of signal when compared to "paraformaldehyde".    You can
get a aqueous solution of formaldehyde by dissolving paraformaldehyde at
the desired concentration but that takes a while.  Your technical
information is correct,  in a formaldehyde solution, written or unwritten,
it is usually stabilized with methanol (10-15%).  Paraformaldehyde is but
poly-formaldehyde.   Technically, a solution of paraformaldehyde is a
mis-nomer as is fetal calf serum (you can't be both a fetus and a calf!),
but they are "conventions" that have been with us for all time.

As of today I'm testing formaldehyde as the fixative for b-gal assays in a
side by side with "parformaldehyde" fixation.

Hope this helps,
David

=============================
 David L. Haviland, Ph.D.
 Asst. Prof. Immunology 
 University of Texas - Houston, H.S.C.
 Institute of Molecular Medicine  
 2121 W. Holcombe Blvd.  
 Houston, TX  77030 
 Internet:"dhavilan at imm2.imm.uth.tmc.edu" 
 Voice: 713.500.2413  FAX: 713.500.2424
 ------------------------------------------------------  
Never take life seriously. Nobody gets out alive anyway.
=============================