If the protein is concentrated enough and if the GFP is correctly folded and its fluorophore matured, you may be able to detect it by its fluorescence in solution. However, this may be difficult to do because of phenol red in the medium. If you want to try this, I suggest taking some of the medium, concentrating it 10X with a centrifugal or pressurized ultrafiltration unit, and dialyzing it or passing it through a desalting spin column to remove the phenol red. Then find a spectrofluorometer or monochromator-type fluorescence plate reader and see if you can detect the characteristic fluorescence emission spectrum of GFP. As a blank for this whole procedure, use the same medium that doesn't have the protein expressed in it.

Hi, Rahelen,

I agree with Adam, you can try to detect the GFP emission with a spectrofluorometer or the GFP absorbance with a spectrophotometer. It might also be helpful to  grow your cells in a type of DMEM media that does not contain phenol red, like FluoroBrite™ DMEM which should have a low background flourescence (comparable to the one of PBS buffer). Good luck!

It depends on the size of your protein, you most likely won't be able to just measure the fluorescence in the media due to the high background, you would need to isolate your protein of interest (A GFP IP could work, Filtration could do the trick if it a large protein as you can find a lot of centrifugation based filtration system for protein of different sizes) alternatively you can perform a Acetone based concentration (TCA-Acetone should work) then wash with PBS and resuspended in a buffer with low or no background. If you have access to a confocal microscope you could separate the Phenol signal from your GFP fused protein and quantify that using Image-J.

Best,

Gal.

Thank you all for your kind contributions.

Best regard