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Dear List,

I have a technical questions: 
When we live image cells (in buffered saline, pH7.4) expressing GFP- and
mCherry-labeled proteins, respectively, on our confocal and we add a drug
(dissolved in DMSO) we rapidly (within seconds) lose fluorescence of both
dyes. After a very sharp drop down to 50% of intensity within the first 2
minutes, we reach a plateau (2-5minutes), followed by another less sharp,
though steady, decrease in fluorescence for another 2 minutes.
This is the effect we see with an end concentration of 1% DMSO, which is
completely absent when are scaling down the DMSO concentration to 0,1% !
We have already ruled out that it's simple bleaching due to lightning
conditions.
My understanding was that the OH-radical scavenging properties of DMSO
should more stabilize fluorescence!?
Anyone an idea how DMSO can act like that?

thx
Josef