On the use of antibodies to detect GFP....A lot depends on your construct
- what you have the FP hooked up with. I've used several of the anti-FP
antibodies, from several different vendors, and had some success. But with the
same fixation, same cells/tissue, same GFP vector, same antibody, some
constructs will label and others won't. I know this is a pain, but the
best advice I can give is to try the antibody on your sample and see what
happens! 

Oh, and anyone who tells you, "But it works on Westerns",  should be
taken out and shot :)

Good luck!

Tamara Howard
CSHL