How to measure concentration of a peptide by tryptophan fluorescence? - (Oct/08/2013 )

excitation wavelength 280nm, emission wavelength 348 (see this webpage). you can also look at this webpage.

unless you need to use fluorescence, you can read absorbance at 215nm (or a little lower). this reads peptide bonds.

thank you so much. But it will give only tryptophan fluorescence. How can I measure concentration of the peptide? do I need to calculate from any equation? do I need to do standard curve? 

yes, you would use a standard curve (with absorbance you could use a specific extinction coefficient to calculate concentration, there may be a similar method with fluorescence but i'm not familiar with it).

optimally, a standard curve should be prepared with a purified sample of the peptide or protein of interest. it could be prepared with a similar peptide that has one tryptophan or another peptide with a known number of tryptophans (maybe with purified tryptophan?).

Thank you very much.

Do you know the formula with extinction coefficient ? Sorry to ask very silly stupid question, I know. 

Thank you 

you divide the reading by the extinction coefficient and then apply other factors (eg dilution).

extinction coefficient will be M^-1 cm^-1 for absorbance (see this wikipedia page).

Thank you very much, I solved the problem.