The determination of tryptophan and tyrosine in native proteins on the basis of inner filter effect in spectrofluorimetry.

Determination of tryptophan content in proteins, or tyrosine in proteins not containing tryptophan, is described. The method was applied to five proteins containing from 2 to 8 tryptophan residues per molecule. It was found that the simultaneous presence of a large amount of tyrosine in the protein has no influence on the accuracy of tryptophan determination.