Laser Flash Photokinetic Studies of Rose Bengal Sensitized Photodynamic Interactions of Nucleotides and Dna

Laser flash photolysis studies of the production of the triplet state of the xanthene dye, rose bengal (RB), have been carried out. The reactions of this state with oxygen to form singlet oxygen and the superoxide anion radical have been observed and yields measured. Quenching of RB(T 1 ) by oxygen leads to approximately 75% singlet oxygen and 20% superoxide. The reactivity of these species‐RB(T 1 ), O 2 ( 1 Δ g ) and O 2 ‐ —with four nucleotides and DNA have been determined. Only guanine residues showed any noticeable reaction at neutral pH. At higher pH guanine rate constants increased. The consequences to biological photodynamic processes are discussed.