Proton-Coupled Electron Transfer in DNA on Formation of Radiation-Produced Ion Radicals

Kumar, Anil; Sevilla, Michael D.

doi:10.1021/cr100023g

Cited by 186 publications

(202 citation statements)

References 277 publications

(788 reference statements)

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“…For relative scaling of measurements at different wavelengths and absolute quantum yield determinations, we developed a method using the long-lived absorption changes of a ruthenium complex as a standard. Apart from applications in photorepair of DNA [including repair of pyrimidine (6-4) pyrimidone photoproducts] (15), the setup and methods presented here could be used for time-resolved studies of electron and hole transfer within DNA and from type I photosensitizers to DNA (16).…”

Section: Discussionmentioning

confidence: 99%

Kinetics of cyclobutane thymine dimer splitting by DNA photolyase directly monitored in the UV

Thiagarajan

Byrdin

Eker³

et al. 2011

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

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CPD photolyase uses light to repair cyclobutane pyrimidine dimers (CPDs) formed between adjacent pyrimidines in UV-irradiated DNA. The enzyme harbors an FAD cofactor in fully reduced state (FADH − ). The CPD repair mechanism involves electron transfer from photoexcited FADH − to the CPD, splitting of its intradimer bonds, and electron return to restore catalytically active FADH − . The two electron transfer processes occur on time scales of 10 −10 and 10 −9 s, respectively. Until now, CPD splitting itself has only been poorly characterized by experiments. Using a previously unreported transient absorption setup, we succeeded in monitoring cyclobutane thymine dimer repair in the main UV absorption band of intact thymine at 266 nm. Flavin transitions that overlay DNA-based absorption changes at 266 nm were monitored independently in the visible and subtracted to obtain the true repair kinetics. Restoration of intact thymine showed a short lag and a biexponential rise with time constants of 0.2 and 1.5 ns. We assign these two time constants to splitting of the intradimer bonds (creating one intact thymine and one thymine anion radical T ∘− ) and electron return from T ∘− to the FAD cofactor with recovery of the second thymine, respectively. Previous model studies and computer simulations yielded various CPD splitting times between <1 ps and <100 ns. Our experimental results should serve as a benchmark for future efforts to model enzymatic photorepair. The technique and methods developed here may be applied to monitor other photoreactions involving DNA.DNA repair | flavin adenine dinucleotide | transient absorption spectroscopy | UV damage E xposure of living organisms to UV light from the sun induces harmful lesions in DNA. To overcome this threat, specific repair enzymes have evolved, probably the most ancient and widespread one being CPD photolyase (1, 2). It uses light to repair cis-syn cyclobutane pyrimidine dimer (CPD) lesions, formed by a UV-induced [2 þ 2] cycloaddition of two adjacent pyrimidines (mostly thymines) in the same strand (Fig. 1). CPD photolyase has been found in organisms from all kingdoms of life, except placental mammals (including humans) that rely on nucleotide excision repair for CPD lesions. Among the various DNA repair mechanisms known, that of CPD photolyase is considered the most "cost-efficient" and least error-prone (3, 4). Note, however, that for CPDs containing cytosine, deamination of the cytosine may occur prior to repair. Uracil containing CPD cleavage by photolyase would then result in harmful cytosine-to-uracil mutations (5).Photolyase is a globular single chain protein of approximately 60 kDa that harbors two buried cofactors: flavin adenine dinucleotide (FAD) in its fully reduced state (FADH − ), which is the essential catalytic cofactor, and an antenna pigment, either a folate or a flavin derivative that absorbs blue or near UV light much stronger than FADH − does and efficiently transfers the excitation energy to FADH − .It is widely accepted (1, 2) that CPD repair by phot...

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Section: Discussionmentioning

confidence: 99%

Kinetics of cyclobutane thymine dimer splitting by DNA photolyase directly monitored in the UV

Thiagarajan

Byrdin

Eker³

et al. 2011

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

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“…These findings indicate that the corresponding TM1-enolate is most likely obtained through electron-coupled proton transfer, 43,44 in which radical anions of nitro and carbonyl groups serve as the 'electro-base' 26,28 to extract the proton from the methylene unit of TM1 to induce its enolization.…”

Section: Design and Synthesis Of The Switchable Moleculementioning

confidence: 94%

A single-molecule multicolor electrochromic device generated through medium engineering

et al. 2015

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Multicolor organic electrochromic materials are important for the generation of full-color devices. However, achieving multiple colors using a single-molecule material has proved challenging. In this study, a multicolor electrochromic prototype device is generated by integrating medium engineering/in situ 'electro base'/laminated electrode technologies with the simple flying fish-shaped methyl ketone TM1. This multicolor electrochromic (green, blue and magenta) device is durable and has a high coloration efficiency (350 cm 2 C 21 ), a fast switching time (50 ms) and superior reversibility. This study is a successful attempt to integrate solvatochromism and basochromism in an electronic display. This integration not only introduces a new avenue for color tuning, in addition to the structural design of the colorant, but will also inspire further developments in the tuning of many other properties by this medium engineering approach, such as conductance and the redox property, and thereby accelerate versatile applications in data recording, ultrathin flexible displays, and optical communication and sensing. Keywords: electrochromic materials; laminated electrodes; microenvironment; multicolor devices; solvatochromic materials INTRODUCTION Owing to the increasing demand for low-power, ultrathin, flexible electronic displays, organic electrochromic materials 1-3 have become a research focus because of their distinct merits: low weight, high contrast, wide viewing angle, flexibility and the potential for low power consumption. Because the realization of a multicolor switch is preferred in the majority of their applications in displays, 4-10 various electrochromic materials including polymers, 11,12 small organic molecules 13,14 and metal-organic complexes, 15 and technologies aimed at multicolor switches have been intensively explored. Transition metals based on metal-organic complex multicolor electrochromic materials exhibit attractive properties, such as high stability and chemiluminescence. 16 However, the expense and scarcity of the precious metals, such as ruthenium, 15,16 osmium 17 and iridium, 18 limit their practical applications. Polymeric multicolor electrochromic materials with different electrochromic activation units [19][20][21] possess the advantages of easy processing, diverse resources and facile color tunability. However, some intrinsic problems, such as the lack of colorless states, poor transparency, poor color purity and complicated synthesis procedures, hinder their applications. Compared with electrochromic polymers, small organic color switches possess the advantages of low cost, good color purity, distinct transition from colorless to colored states and fine tunability of their photoelectronic properties via easy structure modifications. The lack of multicolor abilities is their intrinsic

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“…11 In particular, dissociative electron attachment (DEA) 12 and intermolecular charge transfer 13 play key roles in radiation damage to DNA. These results have stimulated extensive experimental and theoretical research into low-energy electron interactions with gas-phase DNA/RNA constituents, revealing detailed understanding of their transient negative ion states.…”

Section: Introductionmentioning

confidence: 99%

Communication: Site-selective bond excision of adenine upon electron transfer

Cunha

Mendes

Silva

et al. 2018

The Journal of Chemical Physics

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This work demonstrates that selective excision of hydrogen atoms at a particular site of the DNA base adenine can be achieved in collisions with electronegative atoms by controlling the impact energy. The result is based on analysing the time-of-flight mass spectra yields of potassium collisions with a series of labeled adenine derivatives. The production of dehydrogenated parent anions is consistent with neutral H loss either from selective breaking of C-H or N-H bonds.

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Proton-Coupled Electron Transfer in DNA on Formation of Radiation-Produced Ion Radicals

Cited by 186 publications

References 277 publications

Kinetics of cyclobutane thymine dimer splitting by DNA photolyase directly monitored in the UV

Kinetics of cyclobutane thymine dimer splitting by DNA photolyase directly monitored in the UV

A single-molecule multicolor electrochromic device generated through medium engineering

Communication: Site-selective bond excision of adenine upon electron transfer

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