Proton-Coupled Photoinduced Electron Transfer, Deuterium Isotope Effects, and Fluorescence Quenching in Noncovalent Benzo[a]pyrenetetraol-Nucleoside Complexes in Aqueous Solutions

Shafirovich, Vladimir; Courtney, S. H.; Ya, Naiqi; Geacintov, Nicholas E.

doi:10.1021/ja00122a024

Cited by 145 publications

(130 citation statements)

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“…32,34,42 We have shown previously that BPT •+ radical cations selectively oxidize guanine but not any of the other DNA bases, A, C or T. 32,34,42 The photoionization of BPT is accompanied by the ejection of electrons into the aqueous environment thus generating hydrated electrons (Table 1). In the absence of any DNA, the decay of BPT •+ radical cations and the hydrated electrons are detected by their characteristic absorption bands with maxima at 455 and near 720 nm, respectively ( Figure 1A).…”

Section: Heterogeneous Kinetics Of Guanine Oxidation By Bpt •+ Radicamentioning

confidence: 99%

“…These short lifetimes are attributed to BPT molecules in complexes with double-stranded DNA molecules, and the sum of amplitudes I 1 and I 2 are assumed to be equal to the fractions of BPT molecules (ϕ) bound to the DNA. [41][42][43] The values of ϕ monotonously increase with increasing concentrations of DNA duplexes (see, Figure S2 in Supporting Information); at a duplex concentration ([duplex]) of 100 μM, practically all BPT molecules are bound to DNA and the ϕ values are in the range of 0.8 to 0.9 for a series of six oligonucleotide duplexes (Table S2, Supporting Information). The binding constants, K = (1.4±0.3)× 10 5 M −1 were obtained by fitting the following equation (12) to the experimental data points ( Figure S2).…”

Section: Fractions Of Bpt Molecules Bound To the Dnamentioning

confidence: 99%

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Oxidation of Guanine in G, GG, and GGG Sequence Contexts by Aromatic Pyrenyl Radical Cations and Carbonate Radical Anions: Relationship between Kinetics and Distribution of Alkali-Labile Lesions

et al. 2008

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Oxidatively generated DNA damage induced by the aromatic radical cation of the pyrene derivative 7,8,9,10-tetrahydroxytetrahydrobenzo[a]pyrene (BPT), and by carbonate radicals anions, was monitored from the initial one-electron transfer, or hole injection step, to the formation of hot alkali-labile chemical end-products monitored by gel electrophoresis. The fractions of BPT molecules bound to double-stranded 20-35-mer oligonucleotdes with noncontiguous guanines G, and grouped as contiguous GG and GGG sequences, were determined by a fluorescence quenching method. Utilizing intense nanosecond 355 nm Nd: Yag laser pulses, the DNA-bound BPT molecules were photoionized to BPT •+ radicals by a consecutive two-photon ionization mechanism. The BPT •+ radicals thus generated within the duplexes selectively oxidize guanine by intraduplex electron transfer reactions, and the rate constants of these reactions follow the trend 5′-..GGG.. > 5′-..GG.. > 5′-..G… In the case of CO 3 •− radicals, the oxidation of guanine occurs by intermolecular collision pathways and the bimolecular rate constants are independent of base sequence context. However, the distributions of the end-products generated by CO 3 •− radicals, as well as by BPT •+ , is base sequence context-dependent and is greater than in isolated guanines at the 5′-G in 5′-…GG… sequences, and the first two 5′-guanines in the 5′-..GGG sequences. These results help to clarify the conditions that lead to a similar or different base sequence dependence of the initial hole injection step and the final distribution of oxidized, alkalilabile guanine products. In the case of the intermolecular one-electron oxidant CO 3 •− , the rate constant of hole injection is similar for contiguous and isolated guanines, but the subsequent equilibration of holes by hopping favors trapping and product formation at contiguous guanines, and the sequence dependence of these two phenomena are not correlated. In contrast, in the case of the DNA bound oxidant BPT •+ , the hole injection rate constants, as well as hole equilibration, exhibit a similar dependence on base sequence context, and are thus correlated to one another.

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Section: Heterogeneous Kinetics Of Guanine Oxidation By Bpt •+ Radicamentioning

confidence: 99%

Section: Fractions Of Bpt Molecules Bound To the Dnamentioning

confidence: 99%

Oxidation of Guanine in G, GG, and GGG Sequence Contexts by Aromatic Pyrenyl Radical Cations and Carbonate Radical Anions: Relationship between Kinetics and Distribution of Alkali-Labile Lesions

et al. 2008

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“…4,6,8,9,12 The dependency of fluorescence quenching on the distance between a dye and a guanine has been studied intensively by using fluorescent dyes, acridine, 9 stilbene, 13,14 pyrene, 15 and oxazine dyes. 16 Photoinduced electron transfer occurring in the fluorescence-quenching process has been ascertained by detailed investigations of the photophysical and photochemical behavior of free dyes of coumarin derivatives, 12 rhodamine derivatives, [17][18][19] [25][26][27][28] in the presence of a guanine. In these cases, the quenchable dyes acted as electron acceptors in their excited state and a guanine base acted as an electron donor.…”

Section: Introductionmentioning

confidence: 99%

Fluorescence-Quenching Phenomenon by Photoinduced Electron Transfer between a Fluorescent Dye and a Nucleotide Base

Takasu¹,

Kurata

Yamada³

et al. 2001

ANAL. SCI.

330

267

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“…[21] Shafirovich proposed a PCET mechanism for complexes between nucleic acids in DNA and aromatic fluorophores exhibiting strong fluorescence quenching of the fluorophores by photoinduced electron transfer. [22] Zahavy and Fox have observed enhanced quenching of pyrene attached to nucleosides due to hydrogen-bond interactions. [23] Atherton and Harriman proposed a quenching mechanism for methylene blue in DNA which involves hydrogen abstraction and thus a combined electron/ proton transfer.…”

Section: Introductionmentioning

confidence: 99%

Ultrafast Proton‐Coupled Electron‐Transfer Dynamics in Pyrene‐Modified Pyrimidine Nucleosides: Model Studies towards an Understanding of Reductive Electron Transport in DNA

et al. 2004

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5-(Pyren-1-yl)-2'-deoxyuridine (PydU) and 5-(Pyren-1-yl)-2'-deoxycytidine (PydC) were used as model nucleosides for DNA-mediated reductive electron transport (ET) in steady-state fluorescence and femtosecond time-resolved transient absorption spectroscopy studies. Excitation of the pyrene moiety in PydU and PydC leads to an intramolecular electron transfer that yields the pyrenyl radical cation and the corresponding pyrimidine radical anion (dU.- and dC.-. By comparing the excited state dynamics of PydC and PydU, we derived information about the energy difference between the two pyrimidine radical anion states. To determine the influence of protonation on the rates of photoinduced intramolecular ET, the spectroscopic investigations were performed in acetonitrile, MeCN, and in water at different pH values. The results show a significant difference in the basicity of the generated pyrimidine radical anions and imply an involvement of proton transfer during electron hopping in DNA. Our studies revealed that the radical anion dC.- is being protonated even in basic aqueous solution on a picosecond time scale (or faster). These results suggest that protonation of dC.- may also occur in DNA. In contrast, efficient ET in PydU could only be observed at low pH values (< 5). In conclusion, we propose--based on the free energy differences and the different basicities--that only dT.- but not dC.- can participate as an intermediate charge carrier for excess electron migration in DNA.

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Proton-Coupled Photoinduced Electron Transfer, Deuterium Isotope Effects, and Fluorescence Quenching in Noncovalent Benzo[a]pyrenetetraol-Nucleoside Complexes in Aqueous Solutions

Cited by 145 publications

References 0 publications

Oxidation of Guanine in G, GG, and GGG Sequence Contexts by Aromatic Pyrenyl Radical Cations and Carbonate Radical Anions: Relationship between Kinetics and Distribution of Alkali-Labile Lesions

Oxidation of Guanine in G, GG, and GGG Sequence Contexts by Aromatic Pyrenyl Radical Cations and Carbonate Radical Anions: Relationship between Kinetics and Distribution of Alkali-Labile Lesions

Fluorescence-Quenching Phenomenon by Photoinduced Electron Transfer between a Fluorescent Dye and a Nucleotide Base

Ultrafast Proton‐Coupled Electron‐Transfer Dynamics in Pyrene‐Modified Pyrimidine Nucleosides: Model Studies towards an Understanding of Reductive Electron Transport in DNA

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