DNA Charge Transport Leading to Disulfide Bond Formation

Here, we show that DNA-mediated charge transport (CT) can lead to the oxidation of thiols to form disulfide bonds in DNA. DNA assemblies were prepared possessing anthraquinone (AQ) as a photooxidant spatially separated on the duplex from two SH groups incorporated into the DNA backbone. Upon AQ irradiation, HPLC analysis reveals DNA ligated through a disulfide. The reaction efficiency is seen to vary in assemblies containing intervening DNA mismatches, confirming that the reaction is DNA-mediated. Interestingly, one intervening mismatch near the thiols promotes an increase in efficiency, which we attribute to increased base dynamics. Hence, here, where the reaction is on the backbone rather than within the base stack, stacking perturbations do not necessarily lead to an inhibitory effect on DNA CT

“Signal-On” Detection of DNA Hole Transfer at the Single Molecule Level

“Signal-On” Detection of DNA Hole Transfer at the Single Molecule Leve

Observation of Hole Transfer through DNA by Monitoring the Transient Absorption of Pyrene Radical Cation

Observation of Hole Transfer through DNA by Monitoring the Transient Absorption of Pyrene Radical Catio

RNA-Mediated Electron Transfer: Double Exponential Distance Dependence

RNA-Mediated Electron Transfer: Double Exponential Distance Dependenc

Sequence Dependence of Excess Electron Transfer in DNA

DNA-mediated charge transfer has recently received a substantial attention because of its biological relevance in the DNA damage and DNA repair as well as the potential applications to nanoscale electronic devices. In contrast to the numerous mechanistic studies on oxidative hole transfer (HT) through DNA, our understanding of reductive electron transfer process still remains limited. In this article, we demonstrate the results of direct observation of the excess electron transfer (EET) through DNA, which conjugated with aminopyrene (APy) and diphenylacetylene (DPA) as a photosensitizing donor and an acceptor of excess electron, respectively. By inserting dihydrothymine as a spacer between APy and T or C, the yield of electron arrival to DPA was improved. It was indicated that EET through DNA completed within a few or a few tens nanosecond time scale even for EET over 34 Å for both consecutive T and C sequences. The various factors such as mismatch sequence and DNA length on the yield of electron arrival to DPA were examined

Observation of Hole Transfer through DNA by Monitoring the Transient Absorption of Pyrene Radical Cation

Observation of Hole Transfer through DNA by Monitoring the Transient Absorption of Pyrene Radical Catio

Photoresponsive DNA Monolayer Prepared by Primer Extension Reaction on the Electrode

We describe a simple and convenient method for the preparation of photoresponsive DNA-modified electrodes using primer extension (PEX) reactions. A naphthalimide derivative was used as the photosensitizer that was attached to the C5-position of 2′-deoxyuridine-5′-triphosphate (dUTP^NI). It has been found that dUTP^NI is a good substrate for the PEX reactions using KOD Dash and Vent (exo-) enzymes in solutions to incorporate naphthalimide (NI) moieties into the DNA sequences. On the electrode surface immobilized with the primer/template DNA, the PEX reactions to incorporate dUTP^NI molecules into the DNA sequence were found to efficiently proceed. With this solid-phase method, the DNA monolayers capable of generating photocurrent due to the photoresponsive NI molecule can be constructed. It was shown that the photocurrent generation was significantly suppressed by a single-nucleotide mismatch included in the primer/template DNA, which is applicable for the design of photoelectrochemical sensors to discriminate single-nucleotide sequences

Photocurrent Generation Enhanced by Charge Delocalization over Stacked Perylenediimide Chromophores Assembled within DNA

We now report the photocurrent generation and charge transfer dynamics of stacked perylenediimide (PDI) molecules within a π-stack array of DNA. The cofacially stacked PDI dimer and trimer were found to strongly enhance the photocurrent generation compared to an isolated PDI monomer. Femtosecond time-resolved transient absorption experiments revealed that the excitation of the stacked PDI dimer and trimer provided the broad transient absorption band, which was attributed to the charge delocalization of a negative charge over the PDI chromophores. The lifetime of the charge delocalization of the PDI dimer and trimer (nearly 1 ns) was much longer than that of the charge separated state of the PDI monomer. A comparison between the photocurrent measurements and time-resolved transient absorption measurements demonstrated that the cofacially stacked structure could possibly lead to the charge delocalization and increase the lifetime of the charge-separated state that is essential to enhancing the photocurrent generation