Tryptophan λmax when buried inside protein is:
Tryptophan fluorescence quantum yield and wavelength are exquisitely sensitive to local polarity and hydrogen bonding. Fully solvent-exposed indole in water emits near 350-355 nm because excited state dipole stabilized by reorientation of surrounding water dipoles, lowering emission energy. When buried inside hydrophobic interior of proteins such as azurin, ribonuclease or lysozyme, nonpolar surroundings restrict solvent relaxation, destabilize excited state and reduce dipole stabilization. Consequently emission blue shifts to about 308-335 nm, commonly centered near 325 nm. This shift serves
Ref: NCERT Biology Class XII Principles on Klenow fill-in labeling, Lehninger Chapter 9 DNA cloning techniques, and Molecular Cloning by Sambrook Chapter 10 documenting end-labeling of cohesive termini.
