Intramolecular fluorescence quenching of tyrosine by the peptide alpha-carbonyl group revisited

The environment-dependent multiexponential behavior of N-acetyltyrosinamide (NAYA) and other tyrosine derivatives are revisited. It is demonstrated that observations of double exponential-decays with NAYA is exceptional and restricted to narrow ranges of solvent polarity and viscosity which in turn determine the electron-transfer and the interconversion rate constants, respectively.