Resolution and characterization of tryptophyl fluorescence of hen egg-white lysozyme by quenching- and time-resolved spectroscopy

The fluorescence spectral distributions of four tryptophan residues of hen egg-white lysozyme were analyzed using time-resolved and quenching-resolved fluorescence spectroscopy. Trp62 and Trp108 gave the fluorescence maxima a t 352 nm and 342 nm, respectively. The fluorescence of Trp28 and Trp111 occ urred only at 300-360 nm and they were observed as an unresolved emission b and with a maximum and shoulder at 320 nm and 330 nm. The fluorescence quen ching and decay parameters of each tryptophan residue reconfirmed that Trp6 2 was fully exposed to the solvent but Trp108 was sealed in the cage of the peptide chains and furthermore showed that Trp28 and Trp111 are under the influence of the larger fluctuational motion at the hydrophobic matrix box. The fluorescence responses of each tryptophan residue to the lysozyme-ligan d interaction suggested that the internal fluctuation was reduced by the bi nding of ligand to give a distorted conformation to the hydrophobic matrix box region.