Glenn, 
I agree with Gayle's comments, and for those of you out there still
using anything besides Alexa Fluors, please switch! It will save you so
much headache, they are superior to anything I've tried thus far. The
Molecular Probes website and handbook are excellent. 
I still use Vectashield Hardset most of the time however, just because I
have not personally observed an improvement over using ProLong Gold
mounting media. 
I also have not seen any amplification in signal by using Streptavidin
conjugates of Alexa's, so I usually don't bother with those. 
But everyone's situation is different, so I never rule anything out. 
The next thing on my list to try are Qdots, but I've heard mixed
reviews. 
Good luck!

Melissa

Melissa A. Gonzalez
R&D Histology
Cell Genesys 
South San Francisco, CA
ph(650) 266-3168
fx(650) 266-3080



Glenn,  You wrote:

I am using H2DCFDA for the detection of cellular reactive oxygen species

following treatment with various agents. Cells are subsequently mounted
in 
anti-fadent with DAPI (Slow Fade Gold with DAPI).

   The green fluorescence appears awfully weak. I have noticed this in
past 
experiments looking at cytochrome c release with FITC detection.  Could
the 
antifadent be the culprit? Don't some antifadent products quench 
fluorescein right-off-the-bat? Would it be best to just do a standard 
aqueous mount and be extra careful with light exposure?

Reply:

What you are experiencing is NOT quenching but photobleaching.  FITC is
far 
easier to photobleach when exposed to UV excitation and not performing
the 
staining in the dark (under cover!) The mounting media helps prevent 
photobleaching but not 100%, however if you use Alexa 488 from Molecular

Probes instead of FITC as the fluorophore, you will probably have far 
better retention of fluorescnce with the Alexa's.  It definitely will be

brighter and you can look at it longer with UV light.

It is not only mounting media but also the choice of fluorophore. There
are 
several mounting medias that Molecular Probes did a comparison on  and 
showed(results available online)which mounting medias worked better for 
fluoresecence.

You can learn a great deal about fluorsceinated fluorophores (FITC,
TRITC, 
Texas Red) versus Alexa dyes that are sulfonated with the latter be 
superior.  These are more more resistant to photobleaching and
definitely 
worth a try.  Molecular Probes Handbook explains this, although it is a 
rather "physical chemistry" oriented subject.  The original publication
in 
J HIstochem Cytochem by the Hauglands who developed the use of Alexa
dyes 
is a good read.

Microscopy Today just had a wonderful comparison of mounting medias for
IFA 
by Collins, go back in Histonet Archives to access the website for this 
free article.

I have never had a mounting media fade FITC immediately, but I do enjoy 
good fluroescent signal retention with this after using Molecular Probes

hard set Prolong Gold ready to use with or without DAPI. I have use 
AquaMount, but examination of slide is same day - photobleaching
generally 
occurs more at time of UV light excitation so we take photos at time of 
viewing sections.

There are some ways to increase the signal - we use Strepavidin-Alex
dyes 
with biotinylated secondary or a biotinylated primary to amplify more -

Hope this helps.



Gayle Callis
MT,HT,HTL(ASCP)
Research Histopathology Supervisor
Veterinary Molecular Biology
Montana State University - Bozeman
PO Box 173610
Bozeman MT 59717-3610
406 994-6367
406 994-4303 (FAX)


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