Related Experiment Video
Updated: Jun 28, 2026

Developing Photosensitizer-Cobaloxime Hybrids for Solar-Driven H2 Production in Aqueous Aerobic Conditions
Published on: October 5, 2019
Synthesis and DNA interactions of a bis-phenothiazinium photosensitizer
Beth Wilson1, María-José Fernández, Antonio Lorente
1Department of Chemistry, Georgia State University, P.O. Box 4098, Atlanta, GA 30302-4098, USA.
Abstract:
We report the synthesis and characterization of N,N-bis[(7-dimethylamino)phenothiazin-5-ium-3-yl]-4,4-ethylenedipiperidine diiodide (3), consisting of two photosensitizing phenothiazinium rings attached to a central ethylenedipiperidine linker. At all time points (10, 30, 60 min) and all wavelengths (676, 700, 710 nm) tested, photocleavage of pUC19 plasmid DNA (22 degrees C and pH 7.0) was markedly enhanced by 1 microM of 3 in comparison to 1 microM of the parent phenothiazine methylene blue (MB). At concentrations of phenothiazine ranging from 5 to 0.5 microM, the photocleavage levels produced by compound 3 were consistently higher than the cleavage produced using approximately twice the amount of MB (e.g., 710 nm irradiation of 5 microM of 3 and 10 microM of MB cleaved the plasmid DNA in 93% and 71% yields, respectively). Scavenger assays provided evidence for the involvement of singlet oxygen and, to a lesser extent, hydroxyl radicals in DNA damage. Analysis of photocleavage products at nucleotide resolution revealed that direct strand breaks and alkaline-labile lesions occurred predominantly at guanine bases. While compound 3 and MB were both shown to stabilize duplex DNA, the DeltaTm values of calf thymus (CT) and C. perfringens DNAs were approximately three fold higher in the presence of compound 3. Finally, viscometric data indicated that CT DNA interacts with compound 3 and MB by a combination of groove binding and monofunctional intercalation, and with compound 3 by a third, bisintercalative binding mode.
Related Concept Videos
Aryldiazonium Salts to Azo Dyes: Diazo Coupling
Photochemical Electrocyclic Reactions: Stereochemistry
Selection Rules: Photochemical Activation
Cycloaddition Reactions: MO Requirements for Photochemical Activation
Hydrolysis of Chlorobenzene to Phenol: Dow Process
Thermal and Photochemical Electrocyclic Reactions: Overview
ortho–para-Directing Activators: –CH3, –OH, –⁠NH2, –OCH3

