GFP will most likely be larger than your peptide, GFP is a ~240 amino acid protein after all. It is up to you to decide if this will affect your experiment. I would just tag a peptide with a smaller fluorescent label like fluorescein.

GFP will most likely be larger than your peptide, GFP is a ~240 amino acid protein after all. It is up to you to decide if this will affect your experiment. I would just tag a peptide with a smaller fluorescent label like fluorescein.

Thanks

Henrik is absolutely right, GFP will most probably kill the properties of your peptide.

You could implement an additional cystein to your peptide, e.g. GGCG at the N or C-terminus (depends, if your peptide has an active site either on C or N term). The thiol group can be used for Michael-type addition ("Click" chemistry) with e.g. Fluorescein maleimide or Atto maleimide (different dyes from Sigma Aldrich). The reaction takes place at pH 7-8 and room temperature.

If you do not want to add Cys, try Lys (e.g. GGKG) and react it with NHS ester of the dye (check Sigma Aldrich). Be careful - this reaction is way more unselective towards amino groups (depends on the sequence). Lys usually reacts faster than the N-terminus at e.g. 4°C and slighly basic pH (you could acetylate the N term during solid phase peptide synthesis - if you do SPPS).

Third possibility: Use EDC/NHS chemistry to activate a COOH group (e.g. GGEG) of your peptide to react with the amino substituent of the dye (check Sigma Aldrich). Problem here is of course the reaction of free amino groups of the peptide with itself/the activated COOH group, if there are some.

I personally would prefer the Cys, the reaction is much more reliable, simpler and selective.

Both abswers are right. It does not make much sense to use GFP with a peptide. I would do the labeling during the solid phase synthesis. There are a bunch of fluorophores that you can use. We particularly like Rhodamine-NHS to tag the N-terminal amine (usually we put a spacer such aminopentanoic)