Time-Dependent Blue Shift of the Fluorescence Origin Band of Benzo[a]Pyrene (BP)-Derived BP-6-N7ADE Adducts in Glasses

Abstract

We report unusual spectroscopic properties of the benzo-[a]pyrene (BP)-derived one-electron oxidation DNA adduct. BP-6-N7Ade. in glasses at low temperatures. Time-resolved fluorescence emission and fluorescence excitation spectra showed that the position of the origin bands shift to higher energies with longer delay time of the observation window. A non-linear and time-dependent Stokes shift has been revealed. This effect has not been observed for any BP-derived diol-epoxide adduct. Such a blue-shift, in opposite direction to the shift expected from solvation dynamics, has not been previously reported. The experimental data are interpreted in terms of a distribution of conformers and a matrix-induced frequency dependent dipole moment change across the inhomogeneously broadened absorption band.

Key Words:

• benzo[a]pyrene
• one-electron oxidation adduct
• BP-6-N7Ade adduct
• fluorescence spectroscopy
• Stokes shift.