Measure Intrinsic Tryptophan Fluorescence on the SpectraMax iD3 Microplate Reader

The intrinsic fluorescence of proteins is due to the aromatic amino acids tryptophan, tyrosine, and phenylalanine. Tryptophan, which excites maximally around 270-280 nm and has an emission peak near 350 nm in water, dominates the emission of proteins and is the most sensitive to solvent polarity and the local environment. Exposure of tryptophan residues to water, which occurs when a protein is denatured, leads to a shift to longer emission wavelengths. This shift in peak emission can be used to monitor protein unfolding.