Flourescent fading GFP

[Eric Robb Siegel]

On 17 Aug 1996, claude selitrennikoff wrote:

> 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

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?