Nucleic Acid Oxidation Mediated by Naphthalene and Benzophenone Imide and Diimide Derivatives:  Consequences for DNA Redox Chemistry

Abstract

The rate constants for electron transfer from guanosine 5‘-monophosphate (GMP), adenosine 5‘-monophosphate (AMP), cytidine 5‘-monophosphate (CMP), and thymidine 5‘-monophosphate (TMP) to the triplet excited states of N-(3-propanol)-1,8-naphthalimide (NI), N,N ‘-(3-propanol)-1,4,5,8-naphthaldiimide (NDI), and N,N ‘-(3-propanol)-3,3‘,4,4‘-benzophenonediimide (BPDI) have been determined in 1:1 H2O/CH3CN solution. Upon 355-nm (8 ns) laser flash excitation of each of the imide or diimides in solution, the triplet states decayed by first-order kinetics under conditions of low excitation energy. Photoinduced electron transfer to the lowest electronically excited triplet state of N-(3-propanol)-1,8-naphthalimide from GMP occurred with a rate constant of 2.0 × 107 M-1 s-1. Electron-transfer quenching by the other nucleotides was almost 2 orders of magnitude slower. In the case of BPDI, photooxidation rate constants ranged from 2.3 × 108 M-1 s-1 for quenching by CMP to 1.1 × 109 M-1 s-1 by GMP. In all cases, the imide radical anion was observed by laser flash photolysis, and the yields were quantified. From these investigations, nucleotide oxidation by the triplet state of a series of redox-active photosensitizers has been demonstrated. The results represent a systematic study of nucleotide oxidation by the triplet states of a series of structurally related organic photosensitizers in which the reduction potential can be tuned by ca. 800 mV. The greater than 100-fold variation in bimolecular rate constants for oxidation of base monophosphates by these photosensitizers offers the prospect of kinetic “selectivity” of oxidative damage in random-sequence DNA.

Direct observation of hole transfer through double-helical DNA over 100 Å

“…Photophysical and redox properties for NI, PTZ, and nucleobases have been established (39)(40)(41)(42). From the reduction potential of Ϫ1.0 V (vs. normal hydrogen electrode) for NI and the excitation energy of 3.4 eV for NI in the singlet excited state ( 1 NI*), reduction potential of 1 NI* is calculated to be 2.4 eV.…”

Ultrafast charge transfer dynamics in supramolecular Pt(ii) donor–bridge–acceptor assemblies: the effect of vibronic coupling

“…50,51,[53][54][55] A range of additional, overlapping, higher energy transitions observed for * ), especially two prominent features centred at 327 and 341 nm but not in ( allows their assignment to intra$ ligand transitions associated with the Pt(II)$centred / $acetylide bridging unit. An additional absorption band at >400 nm, with the extinction coefficient of an order of 100 dm 3 mol $1 cm $1 observed in *$) implies a presence of a charge$transfer transition. '…”

Photosensitized one-electron oxidation of DNA

“…NDI was selected as a Sens since 1 NDI * can oxidize A to promote hole transfer by the A-hopping to eventually yield G ؒ+ [18,19,25,34,35]. Several ODNs with different distances between the NDI and Gs with intervening A n sequences (NDn) were synthesized, and the effect of the hole transfer on the DNA damage was investigated ( Table 2).…”

“…7). In this study, NDI was used as a Sens that can be excited with a first laser at a wavelength of 355 nm [17,19,34,50,51]. First, to assess the feasibility of electron ejection from Sens bound to DNA, a pulse radiolysis-laser flash photolysis of NDI-conjugated ODN (NDI-ODN) was performed ( Fig.…”