Mechanisms of Photoinitiated Cleavage of DNA by 1,8-Naphthalimide Derivatives¶

Abstract

Using water-soluble 1,8-naphthalimide derivatives, the mechanisms of photosensitized DNA damage have been elucidated. Specifically, a comparison of rate constants for the photoinduced relaxation of supercoiled to circular DNA, as a function of dissolved halide, oxygen and naphthalimide concentration, has been carried out. The singlet excited states of the naphthalimide derivatives were quenched by chloride, bromide and iodide. In all cases the quenching products were naphthalimide triplet states, produced by induced intersystem crossing within the collision complex. Similarly, the halides were found to quench the triplet excited state of the 1,8-naphthalimide derivatives by an electron transfer mechanism. Bimolecular rate constants were Ͻ10 5 M Ϫ1 s Ϫ1 for quenching by bromide and chloride. As expected from thermodynamic considerations quenching by iodide was 6.7 ؋ 10 9 and 8.8 ؋ 10 9 M Ϫ1 s Ϫ1 for the two 1,8-naphthalimide derivatives employed. At sufficiently high ground-state concentration self-quenching of the naphthalimide triplet excited state also occurs. The photosensitized conversion of supercoiled to circular DNA is fastest when selfquenching reactions are favored. The results suggest that, in the case of 1,8-naphthalimide derivatives, radicals derived from quenching of the triplet state by ground-state chromophores are more effective in cleaving DNA than reactive oxygen species or radicals derived from halogen atoms.

Comparative studies of photocatalytic and photoelectrocatalytic inactivation of E. coli in presence of halides

“…In this work, the bactericidal performance under photocatalytic and photoelectrocatalytic conditions in presence of low concentration of Cl − and Br − were investigated. Other halides such as F − and I − were excluded because the illuminated TiO 2 is incapable to oxidize [35] and the insufficient oxidation power of [36] for high bactericidal effect. The bactericidal performance with the TiO 2 and the halides without illumination was carried out as a control.…”

“…This work extends the investigation to include Cl − . F − and I − are unsuitable for photocatalysis-based bactericidal applications because F − (E 0 [F • /F − ] = +3.6 V) [35] cannot be photocatalytically oxidized to F • by the illuminated TiO 2 while I • (E 0 [I • /I − ] = +1.33 V) [36] possesses insufficient oxidation power for inactivation. Detailed investigations were carried out to understand the effect of halides presence on the bactericidal performance of photocatalytic (PC-X) and photoelectrocatalytic (PEC-X) inactivation efficiency.…”

Enzyme Modification and Oxidative Cross‐linking Using Carboxylate‐, Phenol‐ and Catechol‐Conjugated 1,8‐Naphthalimides

“…N-(2-Ethanoic Acid)-1,8-Naphthalene Imide (NI-Ala). UV (10 mM phosphate buffer pH 7.0) k max (e): 344 nm (14 600 AE 100 M À1 cm À1 ), 234 nm (42 200 AE 300 M À1 cm À1 ) and 214 nm (23 000 AE 400 M À1 cm À1 ) (28). 1 N-(3,4-Dihydroxyphenyl)-1-carboxyethyl-1,8-Naphthalene Imide (NI-Dopa).…”

Sequence‐dependent Interactions of Cationic Naphthalimides and Polynucleotides

“…The site-selectivity is governed by the substitution pattern of the naphthalimide ring (13,14). Several reports, including work from our own laboratory, have demonstrated the photonuclease activity of variety of 1,8-naphthalimide derivatives (15)(16)(17)(18).…”