Distance-Dependent Electron Transfer in DNA Hairpins

Lewis, Frederick D.; Wu, Taifeng; Zhang, Yifan; Letsinger, Robert L.; Greenfield, Scott R.; Wasielewski, Michael R.

doi:10.1126/science.277.5326.673

Cited by 580 publications

(559 citation statements)

References 18 publications

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“…This behavior follows the empirical relationship k(r) ϰ exp(Ϫ␤r), and from the slope we can obtain a distance range parameter of ␤ ϭ 0.6 Ϯ 0.1 Å Ϫ1 . It is interesting that this value is very close to that measured in DNA hairpins systems (13).…”

Section: Distance Dependence and Becomes Insignificant After Three Insupporting

confidence: 58%

See 1 more Smart Citation

Femtosecond direct observation of charge transfer between bases in DNA

Wan

Fiebig

Schiemann

et al. 2000

Proc. Natl. Acad. Sci. U.S.A.

364

332

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Charge transfer in supramolecular assemblies of DNA is unique because of the notion that the -stacked bases within the duplex may mediate the transport, possibly leading to damage and͞or repair. The phenomenon of transport through -stacked arrays over a long distance has an analogy to conduction in molecular electronics, but the mechanism still needs to be determined. To decipher the elementary steps and the mechanism, one has to directly measure the dynamics in real time and in suitably designed, structurally well characterized DNA assemblies. Here, we report our first observation of the femtosecond dynamics of charge transport processes occurring between bases within duplex DNA. By monitoring the population of an initially excited 2-aminopurine, an isomer of adenine, we can follow the charge transfer process and measure its rate. We then study the effect of different bases next to the donor (acceptor), the base sequence, and the distance dependence between the donor and acceptor. We find that the charge injection to a nearest neighbor base is crucial and the time scale is vastly different: 10 ps for guanine and up to 512 ps for inosine. Depending on the base sequence the transfer can be slowed down or inhibited, and the distance dependence is dramatic over the range of 14 Å. These observations provide the time scale, and the range and efficiency of the transfer. The results suggest the invalidity of an efficient wire-type behavior and indicate that long-range transport is a slow process of a different mechanism.S ince the first report on conductive (1) one-dimensional DNA crystals more than 30 years ago (2, 3) different methods have been used for the study of conductivity, the latest of which is the measurement of conductance on the mesoscopic scale, which suggests a large band-gap semiconductor behavior (4). Charge transfer by photoinduced reactions between donors and acceptors has provided a useful methodology for exploring the mechanism in DNA (5, 6); the donor and acceptor were either noncovalently (7-10) or covalently (11-15) bound to DNA. Evidence for long-range oxidative damage was also demonstrated (16-19). However, results for different systems have shown different values for the distance range over which the transfer is efficient, in part because of measurements of the yield in most cases.Recently, we have studied DNA with covalently tethered ethidium (hole donor) and a base-like acceptor (7-deazaguanine, Z; ref. 20); the rates and yields reflect the different processes involved. Even though these systems have a covalently tethered hole donor, a careful study of the effects of stacking and distance on charge transfer requires DNA assemblies unperturbed by donor͞acceptor probes. Here, we report such studies in DNA assemblies with the donor and acceptor being nucleic acid bases (Fig. 1). These systems are unique because (i) there are only minor structural perturbations arising; (ii) no ambiguities occur with respect to distance separating donors and acceptors; (iii) the assemblies are structurally wel...

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Section: Distance Dependence and Becomes Insignificant After Three Insupporting

confidence: 58%

“…Charge transfer by photoinduced reactions between donors and acceptors has provided a useful methodology for exploring the mechanism in DNA (5,6); the donor and acceptor were either noncovalently (7)(8)(9)(10) or covalently (11)(12)(13)(14)(15) bound to DNA. Evidence for long-range oxidative damage was also demonstrated (16)(17)(18)(19).…”

mentioning

confidence: 99%

Femtosecond direct observation of charge transfer between bases in DNA

Wan

Fiebig

Schiemann

et al. 2000

Proc. Natl. Acad. Sci. U.S.A.

364

332

View full text Add to dashboard Cite

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“…It is currently accepted that the value of is mostly sensitive to the structure of the bridging media, 8 with highly conjugated organic bridges having the smallest values (0.2-0.6 Å -1 ) 7,9-18 and with free space being characterized by a value of ∼2.0 A -1 . 3 Lying between these two regimes are many motifs, both synthetic and natural, including cytochromes and docked proteins, [19][20][21][22][23][24] DNA, [25][26][27][28][29][30][31][32] and saturated organic molecules. [33][34][35][36][37] Each displays its own characteristic range of values and, hence, its own time scales and distance dependencies of ET.…”

Section: Introductionmentioning

confidence: 99%

Electron Transfer Rates in Bridged Molecular Systems 2. A Steady-State Analysis of Coherent Tunneling and Thermal Transitions

Segal¹,

Nitzan²,

Davis³

et al. 2000

J. Phys. Chem. B

Self Cite

317

371

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The effect of dephasing and relaxation on electron transfer in bridged molecular systems is investigated using a simple molecular model. The interaction between the molecular system and the thermal environment is described on the level of the Redfield theory, modified when needed for the description of steady-state situations. Noting that transient as well as steady-state measurements are possible in such system, we discuss the relationship between the rates obtained from these different types of experiments and, in particular, the conditions under which these rates are the same. Also, a formal relation between the steady-state rate for electron transfer across a molecular bridge and the conductance of this bridge when placed between two metal contacts is established. The effect of dephasing and relaxation on the electron transfer is investigated, and new observations are made with regard to the transition from the superexchange to the thermal (hopping through bridge) regime of the transfer process. In particular, the rate is temperature-independent in the superexchange regime, and its dependence on the bridge length (N) is exponential, exp(-N). The rate behaves like (R 1 + R 2 N) -1 exp(-∆E/k B T) beyond a crossover value of N, where ∆E is the energy gap between the donor/acceptor and the bridge levels, and where R 1 and R 2 are characteristic times for activation onto the bridge and diffusion in the bridge, respectively. We find that, in typical cases, R 1 . R 2 , and therefore, a region of very weak N dependence is expected before the Ohmic behavior, N -1 , is established for large enough N. In addition, a relatively weak exponential dependence, exp(-RN), is expected for long bridges if competing processes capture electrons away from the bridge sites. Finally, we consider ways to distinguish experimentally between the thermal and the tunneling routes.

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“…[1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] The DNA π-stack is capable of mediating oxidative DNA damage over long molecular distances in a reaction that is sensitive to DNA sequence-dependent conformation and dynamics. [14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31] A mixture of tunneling and hopping mechanisms has been proposed to account for this long-range chemistry, which is gated by dynamical variations within the stack.…”

Section: Introductionmentioning

confidence: 99%

Intercalative Stacking: A Critical Feature of DNA Charge-Transport Electrochemistry

et al. 2003

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In electrochemistry experiments on DNA-modified electrodes, features of the redox probe that determine efficient charge transport through DNA-modified surfaces have been explored using methylene blue (MB + ) and Ru(NH 3 ) 6 3+ as DNA-binding redox probes. The electrochemistry of these molecules is studied as a function of ionic strength to determine the necessity of tight binding to DNA and the number of electrons involved in the redox reaction; on the DNA surface, MB + displays 2e -/1H + electrochemistry (pH 7) and Ru(NH 3 ) 6 3+ displays 1e -electrochemistry. We examine also the effect of electrode surface passivation and the effect of the mode (intercalation or electrostatic) of MB + and Ru(NH 3 ) 6 3+ binding to DNA to highlight the importance of intercalation for reduction by a DNA-mediated charge-transport pathway. Furthermore, in experiments in which MB + is covalently linked to the DNA through a σ-bonded tether and the ionic strength is varied, it is demonstrated that intercalative stacking rather than covalent σ-bonding is essential for efficient reduction of MB + . The results presented here therefore establish that efficient charge transport to the DNA-binding moiety in DNA films requires intercalative stacking and is mediated by the DNA base pair array.

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Distance-Dependent Electron Transfer in DNA Hairpins

Cited by 580 publications

References 18 publications

Femtosecond direct observation of charge transfer between bases in DNA

Femtosecond direct observation of charge transfer between bases in DNA

Electron Transfer Rates in Bridged Molecular Systems 2. A Steady-State Analysis of Coherent Tunneling and Thermal Transitions

Intercalative Stacking: A Critical Feature of DNA Charge-Transport Electrochemistry

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