Subject: Flourescent fading GFP

From: claude selitrennikoff <[email-masked]>
Date: 17 Aug 1996 16:26:09 GMT

Has anyone ever observed GFP bleaching in certain organisms?
I am expressing GFP in a fungus and I have noticed that the GFP is
fading under extended UV exposure.  This occurs very quickly when I put
on a microscope slide, which I presume is due to lack of oxygen.
However, it occurs more slowly when I leave the microscope slide off.
As far as I can tell, the bleaching is irreversible.

My guess is that the chromophore formation is slightly altered in this
fungus, and the result is a lower stability.
Any suggestions?
Dr. S. Canada

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From: [email-masked] (Eric Robb Siegel)
Date: 18 Aug 1996 16:13:43 -0700

> fungus, and the result is a lower stability.

While I don't know if GFP is known for photobleaching, I do know that 
most fluorescent dyes used in epifluorescence microscopy are subject to 
photobleaching.  I have found that putting sodium azide in my samples 
makes them take longer to photobleach.  I am told that N-ethyl maleimide 
also protects against photobleaching.  However, both are toxic to the 
cells.  I believe that Molecular Probes, Inc. sells non-toxic anti-fade 
reagents, but I doubt if they are cheap.

Eric Siegel

P.S.:  While writing this, I was struck by the question, Has anyone ever 
tried sodium ascorbate an an anti-photobleaching reagent for 
epifluorescence microscopy?