Photophysical study on daunorubicin by fluorescence spectroscopy

Steady-state fluorescence and time-resolved fluorescence intensity decays of daunorubicin have been studied in polar solvents and in aqueous solution by a time-correlated single-photon counting technique. Daunorubicin, quinizarin, and 2,3-dimethylquinizarin show bi-exponential decay. The decay of daunorubicin becomes tri-exponential in the presence of adenosine 5′ monophosphate. The quenching of the fluorescence of daunorubicin by adenosine 5′ monophosphate exhibits downward deviation from the Stern–Volmer linearity, suggesting the existence of fluorophore in two conformers in the ground state differing only in the extent of hydrogen bonding.