RE: 7-AAD

Flow Cytometry Mail Group (FLOWUSER@cyto.medsch.ucla.edu)
Wed, 05 Feb 97 11:55:00 PST

Dear Brent,
I make up 7-AAD using 1mg by first adding 50 microliters of absolute
methanol then adding 950 microliters of 1 x PBS. Originally, when I
started using 7-AAD for DNA staining in the late 1980s I was really
worried about stability and change of staining properties of 7-AAD. Since
then however,I have made the same observation as you did, that the
solution when kept at 4 degrees covered with foil protected from light it
can be used at least for dead cell discrimination and in our hands also
for DNA staining for much longer than one month. This has been also the
practice of the many users of our core facility who use 7-AAD for dead
cell discrimination.

Ingrid Schmid

----------
From:
owner-cyto-sendout[SMTP:owner-cyto-sendout@flowcyt.cyto.purdue.edu]
Sent: Friday, January 31, 1997 3:30 PM
To: Cytometry Mailing List
Subject: 7-AAD

Please excuse me for being a little behind the flow but I've had the
midwinter sniffles. I was just catching up on the recent live cell
discrimination dialog. In one of the replies was a reference to a
monograph
from the University of Washington about using 7-AAD. Included in it were
instructions for making a solution in DMSO, since it is not water soluble
and storing 1 month at 4 degrees C because of limited stability. This I
confirmed with a call to Calbiochem. All this came as something of a
surprise to me since I have been using ( perfectly successfully ) an
aqueous
solution of 7-AAD since I read Ingrid Schmid's Cytometry article in
1992.
In fact the last batch ( 50 ml made in PBS with azide @ 25 ug/ml and used
at
1 ug/ml ) was made in 1995 -- stored at 4=BAC in the dark has no
precipitate
and works just fine. Whenever some project calls for dead cell
discrimination in three color flow -- out comes the 7 AAD. Now don't get
me
wrong -- I'm not suggesting that I'm right and others are wrong. I'm just
reporting the facts I've observed. Since that batch was made there have
never been any observable shifts in fluorescence intensity or required
compensation. Maybe ignorance has just been bliss. At any rate I would be
interested in whether anyone else has used 7AAD from aqueous stock=
solutions.

Brent Dorsett
chief, flow cytometry facility
Lenox Hill Hospital, NYC =20


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