Is it possible that the quantum yield of a protein can be calculated by methods other than fluorescence quenching studies?
Quantum yields are calculated by comparison to a fluorophore of known quantum yield with a similar spectrum. In the case of the tryptophan fluorescence of a protein, you could use N-acetyl-tryptophanamide as the standard.
Here are some references:
https://www.ncbi.nlm.nih.gov/pubmed/18672928
http://www.jbc.org/content/274/35/24539.full.pdf
Thank you Dr. Shapiro. Would it be alright if I perform this experiment using L-tryptophan as the standard? Also is it necessary to correct for tyrosine absorption at the exciting wavelength?
I think it is OK to use L-tryptophan. You can avoid significant absorption by tyrosine by using a slightly longer excitation wavelength (https://www3.nd.edu/~aseriann/CHAP9B.html/sld013.htm), or by making sure the tyrosine concentration is too low to have an effect. Alternatively, you could include the same amount of tyrosine with the tryptophan as is found in the protein.
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