1
|
Markovitsi D. Processes triggered in guanine quadruplexes by direct absorption of UV radiation: From fundamental studies toward optoelectronic biosensors. Photochem Photobiol 2024; 100:262-274. [PMID: 37365765 DOI: 10.1111/php.13826] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2023] [Revised: 05/29/2023] [Accepted: 05/30/2023] [Indexed: 06/28/2023]
Abstract
Guanine quadruplexes (GQs) are four-stranded DNA/RNA structures exhibiting an important polymorphism. During the past two decades, their study by time-resolved spectroscopy, from femtoseconds to milliseconds, associated to computational methods, shed light on the primary processes occurring when they absorb UV radiation. Quite recently, their utilization in label-free and dye-free biosensors was explored by a few groups. In view of such developments, this review discusses the outcomes of the fundamental studies that could contribute to the design of future optoelectronic biosensors using fluorescence or charge carriers stemming directly from GQs, without mediation of other molecules, as it is the currently the case. It explains how the excited state relaxation influences both the fluorescence intensity and the efficiency of low-energy photoionization, occurring via a complex mechanism. The corresponding quantum yields, determined with excitation at 266/267 nm, fall in the range of (3.0-9.5) × 10-4 and (3.2-9.2) × 10-3 , respectively. These values, significantly higher than the corresponding values found for duplexes, depend strongly on certain structural factors (molecularity, metal cations, peripheral bases, number of tetrads …) which intervene in the relaxation process. Accordingly, these features can be tuned to optimize the desired signal.
Collapse
Affiliation(s)
- Dimitra Markovitsi
- CNRS, Institut de Chimie Physique, UMR8000, Université Paris-Saclay, Orsay, France
| |
Collapse
|
2
|
Gustavsson T, Markovitsi D. The Ubiquity of High-Energy Nanosecond Fluorescence in DNA Duplexes. J Phys Chem Lett 2023; 14:2141-2147. [PMID: 36802626 DOI: 10.1021/acs.jpclett.2c03884] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/18/2023]
Abstract
During the past few years, several studies reported that a significant part of the intrinsic fluorescence of DNA duplexes decays with surprisingly long lifetimes (1-3 ns) at wavelengths shorter than the ππ* emission of their monomeric constituents. This high-energy nanosecond emission (HENE), hardly discernible in the steady-state fluorescence spectra of most duplexes, was investigated by time-correlated single-photon counting. The ubiquity of HENE contrasts with the paradigm that the longest-lived excited states correspond to low-energy excimers/exciplexes. Interestingly, the latter were found to decay faster than the HENE. So far, the excited states responsible for HENE remain elusive. In order to foster future studies for their characterization, this Perspective presents a critical summary of the experimental observations and the first theoretical approaches. Moreover, some new directions for further work are outlined. Finally, the obvious need for computations of the fluorescence anisotropy considering the dynamic conformational landscape of duplexes is stressed.
Collapse
Affiliation(s)
- Thomas Gustavsson
- Université Paris-Saclay, CEA, CNRS, LIDYL, 91191 Gif-sur-Yvette, France
| | - Dimitra Markovitsi
- Université Paris-Saclay, CNRS, Institut de Chimie Physique, UMR8000, 91405 Orsay, France
| |
Collapse
|
3
|
Milovanović B, Petković M, Popov I, Etinski M. Water-Mediated Interactions Enhance Alkaline Earth Cation Chelation in Neighboring Cavities of a Cytosine Quartet in the DNA Quadruplex. J Phys Chem B 2021; 125:11996-12005. [PMID: 34694801 DOI: 10.1021/acs.jpcb.1c05598] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Larger Coulombic repulsion between divalent cations compared to the monovalent counterparts dictates the cation-cation distance in the central ion channel of quadruplexes. In this work, density functional theory and a continuum solvation model were employed to study bond energies of alkaline earth cations in adjacent cavities of the central ion channel. Four crystallized tetramolecular quadruplexes with various geometric constraints and structural motifs available in the Protein Data Bank were examined in order to understand how the cation binding affinities could be increased in aqueous solution. A cytosine quartet sandwiched between guanine quartets has a larger bond energy of the second alkaline earth cation in comparison with guanine and uracil quartets. Four highly conserved hydrogen-bonded water molecules in the center of the cytosine quartet are responsible for a higher electrostatic interaction with the cations in comparison with guanines' carbonyl groups. The reported findings are valuable for the design of synthetic quadruplexes templated with divalent cations for optoelectronic applications.
Collapse
Affiliation(s)
- Branislav Milovanović
- Faculty of Physical Chemistry, University of Belgrade, Studentski trg 12-16 11000 Belgrade, Serbia
| | - Milena Petković
- Faculty of Physical Chemistry, University of Belgrade, Studentski trg 12-16 11000 Belgrade, Serbia
| | - Igor Popov
- Institute for Multidisciplinary Research, University of Belgrade, Kneza Višeslava 1, 11030 Belgrade, Serbia.,Institut of Physics, University of Belgrade, Pregrevica 118, 11080 Belgrade, Serbia
| | - Mihajlo Etinski
- Faculty of Physical Chemistry, University of Belgrade, Studentski trg 12-16 11000 Belgrade, Serbia
| |
Collapse
|
4
|
Abstract
The intrinsic fluorescence of nucleic acids is extremely weak compared to that of the fluorescent labels used to probe their structural and functional behavior. Thus, for technical reasons, the investigation of the intrinsic DNA fluorescence was limited for a long time. But with the improvement in spectroscopic techniques, the situation started to change around the turn of the century. During the past two decades, various factors modulating the static and dynamic properties of the DNA fluorescence have been determined; it was shown that, under certain conditions, quantum yields may be up 100 times higher than what was known so far. The ensemble of these studies opened up new paths for the development of label-free DNA fluorescence for biochemical applications. In parallel, these studies have shed new light on the primary processes leading to photoreactions that damage DNA when it absorbs UV radiation.We have been studying a variety of DNA systems, ranging from the monomeric nucleobases to double-stranded and four-stranded structures using fluorescence spectroscopy. The specificity of our work resides in the quantitative association of the steady-state fluorescence spectra with time-resolved data recorded from the femtosecond to the nanosecond timescales, made possible by the development of specific methodologies.Among others, our fluorescence studies provide information on the energy and the polarization of electronic transitions. These are valuable indicators for the evolution of electronic excitations in complex systems, where the electronic coupling between chromophores plays a key role. Highlighting collective effects that originate from electronic interactions in DNA multimers is the objective of the present Account.In contrast to the monomeric chromophores, whose fluorescence decays within a few picoseconds, that of DNA multimers persists on the nanosecond timescale. Even if long-lived states represent only a small fraction of electronic excitations, they may be crucial to the DNA photoreactivity because the probability to reach reactive conformations increases over time, owing to the incessant structural dynamics of nucleic acids.Our femtosecond studies have revealed that an ultrafast excitation energy transfer takes place among the nucleobases within duplexes and G-quadruplexes. Such an ultrafast process is possible when collective states are populated directly upon photon absorption. At much longer times, we discovered an unexpected long-lived high-energy emission stemming from what was coined "HELM excitons". These collective states, whose emission increases with the duplex size, could be responsible for the delayed fluorescence of ππ* states observed for genomic DNA.Most studies dealing with excited-state relaxation in DNA were carried out with excitation in the absorption band peaking at around 260 nm. We went beyond this and also performed the first time-resolved study with excitation in the UVA spectral range, where a very weak absorption tail is present. The resulting fluorescence decays are much slower and the fluorescence quantum yields are much higher than for UVC excitation. We showed that the base pairing of DNA strands enhances the UVA fluorescence and, in parallel, increases the photoreactivity because it modifies the nature of the involved collective excited states.
Collapse
Affiliation(s)
- Thomas Gustavsson
- Université Paris-Saclay, CEA, CNRS, LIDYL, F-91191 Gif-sur-Yvette, France
| | - Dimitra Markovitsi
- Université Paris-Saclay, CEA, CNRS, LIDYL, F-91191 Gif-sur-Yvette, France
| |
Collapse
|
5
|
Avagliano D, Tkaczyk S, Sánchez-Murcia PA, González L. Enhanced Rigidity Changes Ultraviolet Absorption: Effect of a Merocyanine Binder on G-Quadruplex Photophysics. J Phys Chem Lett 2020; 11:10212-10218. [PMID: 33206544 PMCID: PMC7735745 DOI: 10.1021/acs.jpclett.0c03070] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2020] [Accepted: 11/11/2020] [Indexed: 05/10/2023]
Abstract
The urge to discover selective fluorescent binders to G-quadruplexes (G4s) for rapid diagnosis must be linked to understand the effect that those have on the DNA photophysics. Herein, we report on the electronic excited states of a bound merocyanine dye to c-Myc G4 using extensive multiscale quantum mechanics/molecular mechanics calculations. We find that the absorption spectra of c-Myc G4, both without and with the intercalated dye, are mainly composed of exciton states and mixed local/charge-transfer states. The presence of merocyanine hardly affects the energy range of the guanine absorption or the number of guanines excited. However, it triggers a substantial amount (16%) of detrimental pure charge-transfer states involving oxidized guanines. We identify the rigidity introduced by the probe in G4, reducing the overlap among guanines, as the one responsible for the changes in the exciton and charge-transfer states, ultimately leading to a redshift of the absorption maximum.
Collapse
Affiliation(s)
- Davide Avagliano
- Institute
of Theoretical Chemistry, Faculty of Chemistry, University of Vienna, Währinger Straße 17, A-1180 Vienna, Austria
| | - Sara Tkaczyk
- Institute
of Theoretical Chemistry, Faculty of Chemistry, University of Vienna, Währinger Straße 17, A-1180 Vienna, Austria
| | - Pedro A. Sánchez-Murcia
- Institute
of Theoretical Chemistry, Faculty of Chemistry, University of Vienna, Währinger Straße 17, A-1180 Vienna, Austria
| | - Leticia González
- Institute
of Theoretical Chemistry, Faculty of Chemistry, University of Vienna, Währinger Straße 17, A-1180 Vienna, Austria
- Vienna
Research Platform on Accelerating Photoreaction Discovery, University of Vienna, Währinger Straße 17, A-1180 Vienna, Austria
| |
Collapse
|
6
|
Milovanović B, Stanković IM, Petković M, Etinski M. Modulating Excited Charge-Transfer States of G-Quartet Self-Assemblies by Earth Alkaline Cations and Hydration. J Phys Chem A 2020; 124:8101-8111. [DOI: 10.1021/acs.jpca.0c05022] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Affiliation(s)
- Branislav Milovanović
- Faculty of Physical Chemistry, University of Belgrade, Studentski trg 12-16, Belgrade 11000, Serbia
| | - Ivana M. Stanković
- Institute of Chemistry, Technology and Metallurgy, University of Belgrade, Njegoševa 12, Belgrade 11000, Serbia
| | - Milena Petković
- Faculty of Physical Chemistry, University of Belgrade, Studentski trg 12-16, Belgrade 11000, Serbia
| | - Mihajlo Etinski
- Faculty of Physical Chemistry, University of Belgrade, Studentski trg 12-16, Belgrade 11000, Serbia
| |
Collapse
|
7
|
Martínez-Fernández L, Esposito L, Improta R. Studying the excited electronic states of guanine rich DNA quadruplexes by quantum mechanical methods: main achievements and perspectives. Photochem Photobiol Sci 2020; 19:436-444. [DOI: 10.1039/d0pp00065e] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Calculations are providing more and more useful insights into the interaction between light and DNA quadruplexes.
Collapse
Affiliation(s)
- Lara Martínez-Fernández
- Departamento de Química
- Facultad de Ciencias
- Modulo 13 Universidad Autónoma de Madrid
- Campus de Excelencia UAM-CSIC Cantoblanco
- 28049 Madrid
| | | | - Roberto Improta
- Istituto di Biostrutture e Bioimmagini
- CNR
- I-80134 Napoli
- Italy
| |
Collapse
|
8
|
Ma C, Chan RCT, Chan CTL, Wong AKW, Kwok WM. Real-time Monitoring Excitation Dynamics of Human Telomeric Guanine Quadruplexes: Effect of Folding Topology, Metal Cation, and Confinement by Nanocavity Water Pool. J Phys Chem Lett 2019; 10:7577-7585. [PMID: 31769690 DOI: 10.1021/acs.jpclett.9b02932] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
Guanine(G)-rich human telomeric (HT) DNA repeats, crucial to maintenance of genome stability, readily form G-quadruplexes (GQs) with various folding topologies. Research on excitation dynamics of HT-GQs is, however, scarce. Herein, we report a femtosecond time-resolved fluorescence coupled with transient absorption investigation on HT-GQ with the basket-type structure in Na+ solution. The result unveils an unusual multichannel nonradiative mechanism dominated by states with varying character of charge transfer lasting ten and hundreds of picoseconds, accounting altogether for an overwhelming ∼85% of the overall deactivation involving proton transfer. Our comparative study shows that encapsulating the GQ in nanocavity water pool or changing it into hydrid-type topologies with the presence of K+ ions alter differently energies and lifetimes of these states, yet without affecting the nature of the electronic excitation involved. The finding of this work underscores a leading role of structural rigidity in regulating the interplay with the microenvironment of photoexcited monomolecularly folded HT-GQs.
Collapse
Affiliation(s)
- Chensheng Ma
- College of Chemistry and Environmental Engineering , Shenzhen University , Shenzhen , Guangdong P. R. China
| | - Ruth C-T Chan
- College of Chemistry and Environmental Engineering , Shenzhen University , Shenzhen , Guangdong P. R. China
| | - Chris T-L Chan
- College of Chemistry and Environmental Engineering , Shenzhen University , Shenzhen , Guangdong P. R. China
| | - Allen K-W Wong
- Department of Applied Biology and Chemical Technology , The Hong Kong Polytechnic University , Hung Hom, Kowloon , Hong Kong , P. R. China
| | - Wai-Ming Kwok
- Department of Applied Biology and Chemical Technology , The Hong Kong Polytechnic University , Hung Hom, Kowloon , Hong Kong , P. R. China
| |
Collapse
|
9
|
Martinez-Fernandez L, Changenet P, Banyasz A, Gustavsson T, Markovitsi D, Improta R. Comprehensive Study of Guanine Excited State Relaxation and Photoreactivity in G-quadruplexes. J Phys Chem Lett 2019; 10:6873-6877. [PMID: 31613628 DOI: 10.1021/acs.jpclett.9b02740] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
G-quadruplexes (G4) are four-stranded DNA/RNA structures playing a key role in many biological functions and promising for nanotechnology applications. Here, combining theoretical calculations and multiscale time-resolved fluorescence, we describe, for the first time, an ensemble of photoactivated processes involving the guanines of the G4 core. We use as showcase the G4 formed by the human telomeric sequence GGG(TTAGGG)3 in the presence of Na+ ions. According to quantum mechanical/molecular mechanics calculations, the hyperchromism at the red part of the absorption spectrum, typical of G4 structures, arises mainly from the inner Na+ ions. Various relaxation pathways, leading to excited states localized on individual bases, neutral excimers, and excited charge transfer states between two guanines or a guanine and a thymine in the loop, are mapped. Their fingerprints are detected in the fluorescence anisotropies and the fluorescence decays, spanning five decades of time. Finally, a reaction funnel leading to guanine dimerization is identified.
Collapse
Affiliation(s)
| | - Pascale Changenet
- LIDYL, CEA, CNRS, Université Paris-Saclay , F-91191 Gif-sur-Yvette , France
- Laboratoire d'Optique et Biosciences, Institut Polytechnique de Paris , CNRS, INSERM, Université Paris-Saclay , 91128 Palaiseau cedex , France
| | - Akos Banyasz
- LIDYL, CEA, CNRS, Université Paris-Saclay , F-91191 Gif-sur-Yvette , France
| | - Thomas Gustavsson
- LIDYL, CEA, CNRS, Université Paris-Saclay , F-91191 Gif-sur-Yvette , France
| | - Dimitra Markovitsi
- LIDYL, CEA, CNRS, Université Paris-Saclay , F-91191 Gif-sur-Yvette , France
| | - Roberto Improta
- LIDYL, CEA, CNRS, Université Paris-Saclay , F-91191 Gif-sur-Yvette , France
- Istituto Biostrutture e Bioimmagini-Consiglio Nazionale delle Ricerche , Via Mezzocannone 16 , I-80134 Napoli , Italy
| |
Collapse
|
10
|
Tan J, Li R, Jiang ZT, Tang SH, Wang Y. Rapid and non-destructive prediction of methylxanthine and cocoa solid contents in dark chocolate by synchronous front-face fluorescence spectroscopy and PLSR. J Food Compost Anal 2019. [DOI: 10.1016/j.jfca.2019.01.001] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
|
11
|
Majerová T, Streckerová T, Bednárová L, Curtis EA. Sequence Requirements of Intrinsically Fluorescent G-Quadruplexes. Biochemistry 2018; 57:4052-4062. [PMID: 29898365 DOI: 10.1021/acs.biochem.8b00252] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
G-Quadruplexes are four-stranded nucleic acid structures typically stabilized by GGGG tetrads. These structures are intrinsically fluorescent, which expands the known scope of nucleic acid function and raises the possibility that they could eventually be used as signaling components in label-free sensors constructed from DNA or RNA. In this study, we systematically investigated the effects of mutations in tetrads, loops, and overhanging nucleotides on the fluorescence intensity and maximum emission wavelength of >500 sequence variants of a reference DNA G-quadruplex. Some of these mutations modestly increased the fluorescence intensity of this G-quadruplex, while others shifted its maximum emission wavelength. Mutations that increased the fluorescence intensity were distinct from those that increased the maximum emission wavelength, suggesting a trade-off between these two biochemical properties. The fluorescence intensity and maximum emission wavelength were also correlated with multimeric state: the most fluorescent G-quadruplexes were monomers, while those with the highest maximum emission wavelengths typically formed dimeric structures. Oligonucleotides containing multiple G-quadruplexes were in some cases more fluorescent than those containing a single G-quadruplex, although this depended on the length and sequence of the spacer linking the G-quadruplexes. These experiments provide new insights into the properties of fluorescent G-quadruplexes and should aid in the development of improved label-free nucleic acid sensors.
Collapse
Affiliation(s)
- Tat'ána Majerová
- The Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences , Prague 166 10 , Czech Republic
| | - Tereza Streckerová
- The Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences , Prague 166 10 , Czech Republic.,Department of Biochemistry and Microbiology , University of Chemistry and Technology , Prague 166 10 , Czech Republic
| | - Lucie Bednárová
- The Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences , Prague 166 10 , Czech Republic
| | - Edward A Curtis
- The Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences , Prague 166 10 , Czech Republic
| |
Collapse
|
12
|
Sha R, Xiang L, Liu C, Balaeff A, Zhang Y, Zhang P, Li Y, Beratan DN, Tao N, Seeman NC. Charge splitters and charge transport junctions based on guanine quadruplexes. NATURE NANOTECHNOLOGY 2018; 13:316-321. [PMID: 29483600 DOI: 10.1038/s41565-018-0070-x] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/10/2016] [Accepted: 01/18/2018] [Indexed: 06/08/2023]
Abstract
Self-assembling circuit elements, such as current splitters or combiners at the molecular scale, require the design of building blocks with three or more terminals. A promising material for such building blocks is DNA, wherein multiple strands can self-assemble into multi-ended junctions, and nucleobase stacks can transport charge over long distances. However, nucleobase stacking is often disrupted at junction points, hindering electric charge transport between the two terminals of the junction. Here, we show that a guanine-quadruplex (G4) motif can be used as a connector element for a multi-ended DNA junction. By attaching specific terminal groups to the motif, we demonstrate that charges can enter the structure from one terminal at one end of a three-way G4 motif, and can exit from one of two terminals at the other end with minimal carrier transport attenuation. Moreover, we study four-way G4 junction structures by performing theoretical calculations to assist in the design and optimization of these connectors.
Collapse
Affiliation(s)
- Ruojie Sha
- Department of Chemistry, New York University, New York, NY, USA
| | - Limin Xiang
- Biodesign Center for Biosensors and Bioelectronics, Biodesign Institute, Arizona State University, Tempe, AZ, USA
- School of Molecular Sciences, Arizona State University, Tempe, AZ, USA
| | - Chaoren Liu
- Departments of Chemistry, Duke University, Durham, NC, USA
| | - Alexander Balaeff
- Departments of Chemistry, Duke University, Durham, NC, USA
- Nanoscience Technology Center & Department of Physics, University of Central Florida, Orlando, FL, USA
| | - Yuqi Zhang
- Departments of Chemistry, Duke University, Durham, NC, USA
| | - Peng Zhang
- Departments of Chemistry, Duke University, Durham, NC, USA
| | - Yueqi Li
- Biodesign Center for Biosensors and Bioelectronics, Biodesign Institute, Arizona State University, Tempe, AZ, USA
- School of Molecular Sciences, Arizona State University, Tempe, AZ, USA
| | - David N Beratan
- Departments of Chemistry, Duke University, Durham, NC, USA.
- Department of Biochemistry, Duke University, Durham, NC, USA.
- Department of Physics, Duke University, Durham, NC, USA.
| | - Nongjian Tao
- Biodesign Center for Biosensors and Bioelectronics, Biodesign Institute, Arizona State University, Tempe, AZ, USA.
| | - Nadrian C Seeman
- Department of Chemistry, New York University, New York, NY, USA.
| |
Collapse
|
13
|
Lee W, Matsika S. Conformational and electronic effects on the formation of anti cyclobutane pyrimidine dimers in G-quadruplex structures. Phys Chem Chem Phys 2018; 19:3325-3336. [PMID: 28091673 DOI: 10.1039/c6cp05604k] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Cyclobutane pyrimidine dimers (CPDs) are the most commonly formed photochemical products when nucleic acids interact with UV radiation. In duplex DNA, the relative inflexible structure allows for only the cis, syn CPD isomer to be formed. G-quadruplex structures, however, have loops that are more flexible and allow for different orientations of the bases to interact. As a result, the highly unusual formation of an anti CPD has been observed in these structures. Due to the close proximity between two opposing loops containing the TTA sequence in two G-quadruplex structures (called "form-3" and "basket"), a high yield of anti CPD formation was expected in these structures. However, while significant yields of anti CPDs are observed in form-3, the anti CPD is hardly observed in the basket structure. To account for this inconsistency, we examine the process of anti CPD formation in form-3 and basket structures using simulations at the atomistic level. Here, we consider the conformational effect using MD simulations, which show whether the formation of the anti CPD is structurally feasible. Quantum mechanical/molecular mechanical (QM/MM) calculations of excited states are also used to consider the electronic effect by an adjacent guanine base which can quench the formation of the anti CPD through charge transfer (CT). Our results are in qualitative agreement with the experimental results, predicting a significant yield of the anti CPD in the form-3 structure and a negligible yield in the basket structure, while they also predict the formation of the cis, syn CPD between two opposing loops in form-3. Most importantly, our simulation results show that the yields of the anti CPD in the G-quadruplex are affected significantly by both conformational and electronic effects.
Collapse
Affiliation(s)
- Wook Lee
- Department of Chemistry, Temple University, Philadelphia, PA 19122, USA.
| | - Spiridoula Matsika
- Department of Chemistry, Temple University, Philadelphia, PA 19122, USA.
| |
Collapse
|
14
|
Banyasz A, Martínez-Fernández L, Balty C, Perron M, Douki T, Improta R, Markovitsi D. Absorption of Low-Energy UV Radiation by Human Telomere G-Quadruplexes Generates Long-Lived Guanine Radical Cations. J Am Chem Soc 2017; 139:10561-10568. [PMID: 28737902 DOI: 10.1021/jacs.7b05931] [Citation(s) in RCA: 55] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Telomeres, which are involved in cell division, carcinogenesis, and aging and constitute important therapeutic targets, are prone to oxidative damage. This propensity has been correlated with the presence of guanine-rich sequences, capable of forming four-stranded DNA structures (G-quadruplexes). Here, we present the first study on oxidative damage of human telomere G-quadruplexes without mediation of external molecules. Our investigation has been performed for G-quadruplexes formed by folding of GGG(TTAGGG)3 single strands in buffered solutions containing Na+ cations (TEL21/Na+). Associating nanosecond time-resolved spectroscopy and quantum mechanical calculations (TD-DFT), it focuses on the primary species, ejected electrons and guanine radicals, generated upon absorption of UV radiation directly by TEL21/Na+. We show that, at 266 nm, corresponding to an energy significantly lower than the guanine ionization potential, the one-photon ionization quantum yield is 4.5 × 10-3. This value is comparable to that of cyclobutane thymine dimers (the major UV-induced lesions) in genomic DNA; the quantum yield of these dimers in TEL21/Na+ is found to be (1.1 ± 0.1) × 10-3. The fate of guanine radicals, generated in equivalent concentration with that of ejected electrons, is followed over 5 orders of magnitude of time. Such a quantitative approach reveals that an important part of radical cation population survives up to a few milliseconds, whereas radical cations produced by chemical oxidants in various DNA systems are known to deprotonate, at most, within a few microseconds. Under the same experimental conditions, neither one-photon ionization nor long-lived radical cations are detected for the telomere repeat TTAGGG in single-stranded configuration, showing that secondary structure plays a key role in these processes. Finally, two types of deprotonated radicals are identified: on the one hand, (G-H2)• radicals, stable at early times, and on the other hand, (G-H1)• radicals, appearing within a few milliseconds and decaying with a time constant of ∼50 ms.
Collapse
Affiliation(s)
- Akos Banyasz
- LIDYL, CEA, CNRS, Université Paris-Saclay , F-91191 Gif-sur-Yvette, France
| | - Lara Martínez-Fernández
- Istituto Biostrutture e Bioimmagini, Consiglio Nazionale delle Ricerche , Via Mezzocannone 16, I-80134 Napoli, Italy
| | - Clémence Balty
- LIDYL, CEA, CNRS, Université Paris-Saclay , F-91191 Gif-sur-Yvette, France
| | - Marion Perron
- LIDYL, CEA, CNRS, Université Paris-Saclay , F-91191 Gif-sur-Yvette, France
| | - Thierry Douki
- CEA, INAC-SyMMES Laboratoire des Lésions des Acides Nucléiques, F-38000 Grenoble, France
| | - Roberto Improta
- LIDYL, CEA, CNRS, Université Paris-Saclay , F-91191 Gif-sur-Yvette, France.,Istituto Biostrutture e Bioimmagini, Consiglio Nazionale delle Ricerche , Via Mezzocannone 16, I-80134 Napoli, Italy
| | - Dimitra Markovitsi
- LIDYL, CEA, CNRS, Université Paris-Saclay , F-91191 Gif-sur-Yvette, France
| |
Collapse
|
15
|
Martinez-Fernandez L, Banyasz A, Esposito L, Markovitsi D, Improta R. UV-induced damage to DNA: effect of cytosine methylation on pyrimidine dimerization. Signal Transduct Target Ther 2017; 2:17021. [PMID: 29263920 PMCID: PMC5661629 DOI: 10.1038/sigtrans.2017.21] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2016] [Revised: 01/24/2017] [Accepted: 03/30/2017] [Indexed: 11/09/2022] Open
Abstract
Methylation/demethylation of cytosine plays an important role in epigenetic signaling, the reversibility of epigenetic modifications offering important opportunities for targeted therapies. Actually, methylated sites have been correlated with mutational hotspots detected in skin cancers. The present brief review discusses the physicochemical parameters underlying the specific ultraviolet-induced reactivity of methylated cytosine. It focuses on dimerization reactions giving rise to cyclobutane pyrimidine dimers and pyrimidine (6–4) pyrimidone adducts. According to recent studies, four conformational and electronic factors that are affected by cytosine methylation may control these reactions: the red-shift of the absorption spectrum, the lengthening of the excited state lifetime, changes in the sugar puckering modifying the stacking between reactive pyrimidines and an increase in the rigidity of duplexes favoring excitation energy transfer toward methylated pyrimidines.
Collapse
Affiliation(s)
| | - Akos Banyasz
- LIDYL, CEA, CNRS, Université Paris-Saclay, Gif-sur-Yvette, France
| | | | | | | |
Collapse
|
16
|
Thazhathveetil AK, Harris MA, Young RM, Wasielewski MR, Lewis FD. Efficient Charge Transport via DNA G-Quadruplexes. J Am Chem Soc 2017; 139:1730-1733. [DOI: 10.1021/jacs.6b10265] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Affiliation(s)
- Arun K. Thazhathveetil
- Department of Chemistry and
Argonne-Northwestern Solar Energy Research (ANSER) Center, Northwestern University, Evanston, Illinois 60208-3113, United States
| | - Michelle A. Harris
- Department of Chemistry and
Argonne-Northwestern Solar Energy Research (ANSER) Center, Northwestern University, Evanston, Illinois 60208-3113, United States
| | - Ryan M. Young
- Department of Chemistry and
Argonne-Northwestern Solar Energy Research (ANSER) Center, Northwestern University, Evanston, Illinois 60208-3113, United States
| | - Michael R. Wasielewski
- Department of Chemistry and
Argonne-Northwestern Solar Energy Research (ANSER) Center, Northwestern University, Evanston, Illinois 60208-3113, United States
| | - Frederick D. Lewis
- Department of Chemistry and
Argonne-Northwestern Solar Energy Research (ANSER) Center, Northwestern University, Evanston, Illinois 60208-3113, United States
| |
Collapse
|
17
|
Yashchuk VM, Kudrya VY. The spectral properties of DNA and RNA macromolecules at low temperatures: fundamental and applied aspects. Methods Appl Fluoresc 2017; 5:014001. [PMID: 28099165 DOI: 10.1088/2050-6120/aa50c9] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
This paper summarizes the results of studies of the spectral properties-optical absorption, fluorescence and phosphorescence-of DNA and RNA macromolecules and synthetic poly-, oligo- and mono-nucleotides, which have been carried out in our laboratory. The system of first excited singlet and triplet energy levels for DNA and RNA is evaluated using low-temperature (4.2 K-77 K) luminescent measurements. The traps of the singlet and triplet electronic excitations in these compounds are identified. An important self-protection mechanism against photo-damage of DNA and RNA by UV photons or penetrative radiation based on the capture of triplet electronic-energy excitations by the most photostable centers-in DNA, the complex formed by neighboring adenosine (A) and thymidine (T) links; in RNA, the adenosine links-is described. It is confirmed that despite similarities in the chemical and partly energy structures DNA is more stable than RNA. The spectral manifestation of the telomeres (the important functional system) in DNA macromolecules is examined. The results obtained on telomere fragments provide the possibility of finding the configuration peculiarities of the triplet excitations traps in DNA macromolecules. The resulting spreading length of the migrating singlet (l s) and triplet (l t) excitations for DNA and RNA macromolecules are evaluated.
Collapse
Affiliation(s)
- Valeriy M Yashchuk
- Physics Faculty, Kyiv National Taras Shevchenko University, prosp. Glushkova, 4, Kyiv 03022, Ukraine
| | | |
Collapse
|
18
|
Xanthines Studied via Femtosecond Fluorescence Spectroscopy. Molecules 2016; 21:molecules21121668. [PMID: 27918492 PMCID: PMC6274292 DOI: 10.3390/molecules21121668] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2016] [Revised: 11/25/2016] [Accepted: 11/29/2016] [Indexed: 11/30/2022] Open
Abstract
Xanthines represent a wide class of compounds closely related to the DNA bases adenine and guanine. Ubiquitous in the human body, they are capable of replacing natural bases in double helices and give rise to four-stranded structures. Although the use of their fluorescence for analytical purposes was proposed, their fluorescence properties have not been properly characterized so far. The present paper reports the first fluorescence study of xanthine solutions relying on femtosecond spectroscopy. Initially, we focus on 3-methylxanthine, showing that this compound exhibits non-exponential fluorescence decays with no significant dependence on the emission wavelength. The fluorescence quantum yield (3 × 10−4) and average decay time (0.9 ps) are slightly larger than those found for the DNA bases. Subsequently, we compare the dynamical fluorescence properties of seven mono-, di- and tri-methylated derivatives. Both the fluorescence decays and fluorescence anisotropies vary only weakly with the site and the degree of methylation. These findings are in line with theoretical predictions suggesting the involvement of several conical intersections in the relaxation of the lowest singlet excited state.
Collapse
|
19
|
Vayá I, Brazard J, Huix-Rotllant M, Thazhathveetil AK, Lewis FD, Gustavsson T, Burghardt I, Improta R, Markovitsi D. High-Energy Long-Lived Mixed Frenkel-Charge-Transfer Excitons: From Double Stranded (AT)n to Natural DNA. Chemistry 2016; 22:4904-14. [PMID: 26928984 DOI: 10.1002/chem.201504007] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2015] [Indexed: 01/07/2023]
Abstract
The electronic excited states populated upon absorption of UV photons by DNA are extensively studied in relation to the UV-induced damage to the genetic code. Here, we report a new unexpected relaxation pathway in adenine-thymine double-stranded structures (AT)n . Fluorescence measurements on (AT)n hairpins (six and ten base pairs) and duplexes (20 and 2000 base pairs) reveal the existence of an emission band peaking at approximately 320 nm and decaying on the nanosecond time scale. Time-dependent (TD)-DFT calculations, performed for two base pairs and exploring various relaxation pathways, allow the assignment of this emission band to excited states resulting from mixing between Frenkel excitons and adenine-to-thymine charge-transfer states. Emission from such high-energy long-lived mixed (HELM) states is in agreement with their fluorescence anisotropy (0.03), which is lower than that expected for π-π* states (≥0.1). An increase in the size of the system quenches π-π* fluorescence while enhancing HELM fluorescence. The latter process varies linearly with the hypochromism of the absorption spectra, both depending on the coupling between π-π* and charge-transfer states. Subsequently, we identify the common features between the HELM states of (AT)n structures with those reported previously for alternating (GC)n : high emission energy, low fluorescence anisotropy, nanosecond lifetimes, and sensitivity to conformational disorder. These features are also detected for calf thymus DNA in which HELM states could evolve toward reactive π-π* states, giving rise to delayed fluorescence.
Collapse
Affiliation(s)
- Ignacio Vayá
- LIDYL, CEA, CNRS, Université Paris Saclay, 91191, Gif-sur-Yvette, France
| | - Johanna Brazard
- LIDYL, CEA, CNRS, Université Paris Saclay, 91191, Gif-sur-Yvette, France
| | - Miquel Huix-Rotllant
- LIDYL, CEA, CNRS, Université Paris Saclay, 91191, Gif-sur-Yvette, France.,Institut für Physikalische und Theoretische Chemie, Goethe-Universität, Max-von-Laue-Str. 7, 60438, Frankfurt am Main, Germany
| | | | - Frederick D Lewis
- Department of Chemistry, Northwestern University, Evanston, Illinois, 60208, USA.
| | - Thomas Gustavsson
- LIDYL, CEA, CNRS, Université Paris Saclay, 91191, Gif-sur-Yvette, France
| | - Irene Burghardt
- Institut für Physikalische und Theoretische Chemie, Goethe-Universität, Max-von-Laue-Str. 7, 60438, Frankfurt am Main, Germany
| | - Roberto Improta
- Istituto Biostrutture e Bioimmagini-Consiglio Nazionale delle Ricerche, Via mezzocannone 16, 80136, Napoli, Italy.
| | - Dimitra Markovitsi
- LIDYL, CEA, CNRS, Université Paris Saclay, 91191, Gif-sur-Yvette, France.
| |
Collapse
|
20
|
Improta R, Santoro F, Blancafort L. Quantum Mechanical Studies on the Photophysics and the Photochemistry of Nucleic Acids and Nucleobases. Chem Rev 2016; 116:3540-93. [PMID: 26928320 DOI: 10.1021/acs.chemrev.5b00444] [Citation(s) in RCA: 332] [Impact Index Per Article: 41.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
The photophysics and photochemistry of DNA is of great importance due to the potential damage of the genetic code by UV light. Quantum mechanical studies have played a key role in interpretating the results of modern time-resolved pump-probe spectroscopy, and in elucidating the main photoactivated reactive paths. This review provides a concise, complete picture of the computational studies carried out, approximately, in the past decade. We start with an overview of the photophysics of the nucleobases in the gas phase and in solution. We discuss the proposed mechanisms for ultrafast decay to the ground state, that involve conical intersections, consider the role of triplet states, and analyze how the solvent modulates the photophysics. Then we move to larger systems, from dinucleotides to single- and double-stranded oligonucleotides. We focus on the possible role of charge transfer and delocalized or excitonic states in the photophysics of these systems and discuss the main photochemical paths. We finish with an outlook on the current challenges in the field and future directions of research.
Collapse
Affiliation(s)
- Roberto Improta
- Istituto di Biostrutture Biommagini (IBB-CNR), CNR-Consiglio Nazionale delle Ricerche , Via Mezzocannone 16, I-80134, Napoli, Italy
| | - Fabrizio Santoro
- Area della Ricerca di Pisa, Istituto di Chimica dei Composti Organo Metallici (ICCOM-CNR), CNR-Consiglio Nazionale delle Ricerche , Via G. Moruzzi 1, I-56124 Pisa, Italy
| | - Lluís Blancafort
- Institut de Química Computacional i Catàlisi and Departament de Química, Universitat de Girona, Campus de Montilivi , 17071 Girona, Spain
| |
Collapse
|
21
|
Markovitsi D. UV-induced DNA Damage: The Role of Electronic Excited States. Photochem Photobiol 2015; 92:45-51. [PMID: 26436855 DOI: 10.1111/php.12533] [Citation(s) in RCA: 69] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2015] [Accepted: 08/27/2015] [Indexed: 01/23/2023]
Abstract
The knowledge of the fundamental processes induced by the direct absorption of UV radiation by DNA allows extrapolating conclusions drawn from in vitro studies to the in-vivo DNA photoreactivity. In this respect, the characterization of the DNA electronic excited states plays a key role. For a long time, the mechanisms of DNA lesion formation were discussed in terms of generic "singlet" and "triplet" excited state reactivity. However, since the beginning of the 21(st) century, both experimental and theoretical studies revealed the existence of "collective" excited states, i.e. excited states delocalized over at least two bases. Two limiting cases are distinguished: Frenkel excitons (delocalized ππ* states) and charge-transfer states in which positive and negative charges are located on different bases. The importance of collective excited states in photon absorption (in particular in the UVA spectral domain), the redistribution of the excitation energy within DNA, and the formation of dimeric pyrimidine photoproducts is discussed. The dependence of the behavior of the collective excited states on conformational motions of the nucleic acids is highlighted.
Collapse
Affiliation(s)
- Dimitra Markovitsi
- CNRS, IRAMIS, LIDYL, Laboratoire Francis Perrin, URA 2453, F-91191 Gif-sur-Yvette, France
| |
Collapse
|
22
|
Huix-Rotllant M, Brazard J, Improta R, Burghardt I, Markovitsi D. Stabilization of Mixed Frenkel-Charge Transfer Excitons Extended Across Both Strands of Guanine-Cytosine DNA Duplexes. J Phys Chem Lett 2015; 6:2247-2251. [PMID: 26266599 DOI: 10.1021/acs.jpclett.5b00813] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
The photoreactive pathways that may lead to DNA damage depend crucially upon the nature of the excited electronic states. The study of alternating guanine-cytosine duplexes by fluorescence spectroscopy and quantum mechanical calculations identifies a novel type of excited states that can be populated following UVB excitation. These states, denoted High-energy Emitting Long-lived Mixed (HELM) states, extend across both strands and arise from mixing between cytosine Frenkel excitons and guanine-to-cytosine charge transfer states. They emit at energies higher than ππ* states localized on single bases, survive for several nanoseconds, are sensitive to the ionic strength of the solution, and are strongly affected by the structural transition from the B form to the Z form. Their impact on the formation of lesions of the genetic code needs to be assessed.
Collapse
Affiliation(s)
- Miquel Huix-Rotllant
- †CNRS, IRAMIS, LIDYL, Laboratoire Francis Perrin, URA 2453, F-91191 Gif-sur-Yvette, France
- §Institut für Physikalische u. Theoretische Chemie, Goethe-Universität, Max-von-Laue-Strasse 7, 60438 Frankfurt am Main, Germany
| | - Johanna Brazard
- †CNRS, IRAMIS, LIDYL, Laboratoire Francis Perrin, URA 2453, F-91191 Gif-sur-Yvette, France
| | - Roberto Improta
- ‡Istituto Biostrutture e Bioimmagini- Consiglio Nazionale delle Ricerche, Via Mezzocannone 16, I-80136 Napoli, Italy
| | - Irene Burghardt
- §Institut für Physikalische u. Theoretische Chemie, Goethe-Universität, Max-von-Laue-Strasse 7, 60438 Frankfurt am Main, Germany
| | - Dimitra Markovitsi
- †CNRS, IRAMIS, LIDYL, Laboratoire Francis Perrin, URA 2453, F-91191 Gif-sur-Yvette, France
| |
Collapse
|
23
|
Solar UV radiation-induced DNA Bipyrimidine photoproducts: formation and mechanistic insights. Top Curr Chem (Cham) 2015; 356:249-75. [PMID: 25370518 DOI: 10.1007/128_2014_553] [Citation(s) in RCA: 74] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
This review chapter presents a critical survey of the main available information on the UVB and UVA bipyrimidine photoproducts which constitute the predominant recipient classes of photo-induced DNA damage. Evidence is provided that UVB irradiation of isolated DNA in aqueous solutions and in cells gives rise to the predominant generation of cis-syn cyclobutane pyrimidine dimers (CPDs) and, to a lesser extent, of pyrimidine (6-4) pyrimidone photoproducts (6-4PPs), the importance of which is strongly primary sequence dependent. A notable change in the photoproduct distribution is observed when DNA either in the dry or in desiccated microorganisms is exposed to UVC or UVB photons with an overwhelming formation of 5-(α-thymidyl)-5,6-dihydrothymidine, also called spore photoproduct (dSP), at the expense of CPDs and 6-4PPs. UVA irradiation of isolated and cellular DNA gives rise predominantly to bipyrimidine photoproducts with the overwhelming formation of thymine-containing cyclobutane pyrimidine dimers at the exclusion of 6-4PPs. UVA photons have been shown to modulate the distribution of UVB dimeric pyrimidine photoproducts by triggering isomerization of the 6-4PPs into related Dewar valence isomers. Mechanistic aspects of the formation of bipyrimidine photoproducts are discussed in the light of recent photophysical and theoretical studies.
Collapse
|
24
|
Lech CJ, Phan AT, Michel-Beyerle ME, Voityuk AA. Influence of base stacking geometry on the nature of excited states in G-quadruplexes: a time-dependent DFT study. J Phys Chem B 2015; 119:3697-705. [PMID: 25654765 DOI: 10.1021/jp512767j] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
G-quadruplexes are four-stranded structures of nucleic acids that are formed from the association of guanine nucleobases into cyclical arrangements known as tetrads. G-quadruplexes are involved in a host of biological processes and are of interest in nanomaterial applications. However, not much is known about their electronic properties. In this paper, we analyze electronic excited states of G-quadruplexes using a combination of time-dependent DFT calculations and molecular dynamics simulations. We systematically consider experimentally observed arrangements of stacked guanine tetrads. The effects of structural features on exciton delocalization and photoinduced charge separation are explored using a quantitative analysis of the transition electron density. It is shown that collective coherent excitations shared between two guanine nucleobases dominate in the absorption spectrum of stacked G-tetrads. These excitations may also include a significant contribution of charge transfer states. Large variation in exciton localization is also observed between different structures with a general propensity toward localization between two bases. We reveal large differences in how charge separation occurs within different nucleobase arrangements, with some geometries favoring separation within a single tetrad and others favoring separation between tetrads. We also investigate the effects of the coordinating K(+) ion located in the central cavity of G-quadruplexes on the relative excited state properties of such systems. Our results demonstrate how the nature of excited states in G-quadruplexes depends on the nucleobase stacking geometry resulting from the mutual arrangement of guanine tetrads.
Collapse
Affiliation(s)
- Christopher J Lech
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University , 637371, Singapore
| | | | | | | |
Collapse
|
25
|
Abstract
Photoinduced processes in nucleic acids are phenomena of fundamental interest in diverse fields, from prebiotic studies, through medical research on carcinogenesis, to the development of bioorganic photodevices. In this contribution we survey many aspects of the research across the boundaries. Starting from a historical background, where the main milestones are identified, we review the main findings of the physical-chemical research of photoinduced processes on several types of nucleic-acid fragments, from monomers to duplexes. We also discuss a number of different issues which are still under debate.
Collapse
Affiliation(s)
- Mario Barbatti
- Max-Planck-Institut für Kohlenforschung, Kaiser-Wilhelm-Platz 1, 45470, Mülheim an der Ruhr, Germany,
| | | | | |
Collapse
|