Wavelength-resolved lifetime measurements of emissions from DNA components and poly rA at room temperature excited with synchrotron radiation

Ballini, Jean‐Pierre; Daniels, Malcolm; Vigny, Paul

doi:10.1016/0022-2313(82)90039-4

Cited by 37 publications

(46 citation statements)

References 6 publications

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“…Nanosecond emission components like the ones in Figures – were first detected in the 1980 s. Ballini et al . measured lifetimes of 0.31 ns (69 %) and 4.6 ns (31 %) for poly(A) emission at 406 nm upon excitation at 271 nm.…”

Section: Discussionmentioning

confidence: 95%

“…The time-integrated spectra shown in Figure 8a lso agree reasonably well with steady-statee mission spectra from the literature for all three DNA compounds. As an added check, we comparet he time-integrated spectrum for a( dA) 18 oligomer with the steady-state spectrum in Figure S10 (SI). Markovitsi and co-workers observed am aximum at 370 nm and aw eak shouldern ear 425 nm for both poly(dA) and (dA) 20 with excitation at 265 nm, in good agreement with our results.…”

Section: Emission Spectramentioning

confidence: 99%

“…On the other hand, the sensitive time‐correlated single‐photon counting (TCSPC) technique excels at detecting even very weak emission on timescales longer than about 50 ps. The exquisite sensitivity of single‐photon counting detection has revealed emission on the many ns timescale where it is typically difficult to detect signals in fs‐TA experiments . Consequently, literature descriptions of long‐lived excited states do not always refer to the same states .…”

Section: Introductionmentioning

confidence: 99%

“…The exquisite sensitivity of single-photon countingd etection has revealed emission on the many ns timescale where it is typically difficult to detect signals in fs-TAe xperiments. [7,18] Consequently,l iterature descriptions of long-lived excited states do not alwaysr efer to the same states. [19] Instead, "long-lived excited states" are often the states with the longest lifetimest hat can be detected by ag iven technique-nanosecondi nt he case of TCSPC studies [8] and subnanosecond for fs-TAe xperiments.A si se vident from their very differentl ifetimes, these states may have little in common.…”

Section: Introductionmentioning

confidence: 99%

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Subnanosecond Emission Dynamics of AT DNA Oligonucleotides

et al. 2016

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UV radiation creates excited electronic states in DNA that can decay to mutagenic photoproducts. When excited states return to the electronic ground state, photochemical injury is avoided. Understanding of the available relaxation pathways has advanced rapidly during the past decade, but there has been persistent uncertainty, and even controversy, over how to compare results from transient absorption and time-resolved emission experiments. Here, emission from single- and double-stranded AT DNA compounds excited at 265 nm was studied in aqueous solution using the time-correlated single photon counting technique. There is quantitative agreement between the emission lifetimes ranging from 50 to 200 ps and ones measured in transient absorption experiments, demonstrating that both techniques probe the same excited states. The results indicate that excitations with lifetimes of more than a few picoseconds are weakly emissive excimer and charge transfer states. Only a minute fraction of excitations persist beyond 1 ns in AT DNA strands at room temperature.

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Section: Discussionmentioning

confidence: 95%

Section: Emission Spectramentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Subnanosecond Emission Dynamics of AT DNA Oligonucleotides

et al. 2016

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“…[6±8] Although this reduces the accessible velocity range and limits the cluster size selection possibilities, it allows the investigation of processes in molecular clusters that are unperturbed by the presence of additional ions. [9] Here, we show that charged cluster fragments can indeed be observed upon the low-energy surface collision of a neutral molecular cluster containing preexisting charge carriers. Experiments performed at different collision velocities, using clusters seeded in He and H 2 carrier gases, indicate the conservative nature of the cluster fragmentation with respect to the chemical identity of the cluster constituents within a certain impact velocity range.…”

Section: Methodsmentioning

confidence: 94%

The Potential of the Xenon “Spin‐Spy” Methodology for the Study of Configurational Equilibria in Solution

2003

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For many years, monatomic xenon has been used to probe cavities in systems ranging from zeolites to proteins. [1,2] A few examples of the use of monatomic xenon to probe molecules which do not possess specific xenon binding sites have also been published. [2, 3] The xenon atom is an excellent probe because it is ™inert∫ in the sense that its presence does not affect the structure of the system being probed. Indeed, xenon interacts with other molecules through London dispersion energy interactions, which are much less directional than other interactions, such as hydrogen bonds or multipole ± multipole methods have shown that the lowest excited state of (dA) 20 ¥ (dT) 20 is delocalised over the whole double helix.[15] These calculations were performed assuming an ideal regular geometry. Consequently, before making any comparison with the experimental results, the structural disorder, naturally occurring in double strands, [16] as well as excited-state relaxation have to be taken into account.To summarise, we present here the first, time-resolved fluorescence investigation of DNA oligomers performed with femtosecond resolution. The main conclusion is that the organisation of nucleotides into single strands, and further into double strands, does make the fluorescence decays slower and slower. Such an observation is important because a longer lifetime increases the reactivity of the excited states and, thus, the probability of inducing damage to the double helix. In order to go beyond the present phenomenological description and get a deeper understanding of the nature of the excited states and the related deactivation processes, time-resolved fluorescence spectra and anisotropies have to be recorded and compared with steady-state photophysical properties. Only then will it be possible to address the issues tackled in this study correctly, and develop appropriate theoretical models. We are currently working in this direction. Experimental SectionThe nucleotides were purchased from Sigma Aldrich. Single and double-stranded oligomers were obtained from Eurogentec. The double strands were purified by polyacrylamide gel electrophoresis (PAGE). All measurements were carried out in phosphate buffer (pH 6.8; 0.1 M NaH 2 PO 4 , 0.1 M Na 2 HPO 4 , 0.25 M NaCl) at room temperature (20 AE 1 8C) under aerated conditions.The fluorescence upconversion setup is described in detail elsewhere.[6±8] Briefly, the third harmonic of a mode-locked Ti-sapphire laser (50 mW at 267 nm) was used for excitation. Temporal scans were made in 8 or 15 ps time-windows with 33.3 fs steps in both parallel (I par ) and perpendicular (I perp ) mode by controlling the polarisation of the exciting beam with a half-wave plate. The total fluorescence decays shown in Figures 1 ± 3 were calculated according to:The apparatus function was 450 fs (full width at half maximum; fwhm) and we judged the time-resolution to be 100 fs after deconvolution.About 20 mL of solution were kept flowing through a 0.4 mm quartz cell (optical densities at 267 nm: 0.15 ± 0.25), w...

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The Effect of Molecular Organisation in DNA Oligomers Studied by Femtosecond Fluorescence Spectroscopy

et al. 2003

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It is known that carcinogenic mutations may be caused by chemical reactions triggered by the absorption of ultraviolet light by DNA. [1,2] One of the main factors determining the efficiency of these reactions is evidently the lifetime of the excited states involved. The longer the lifetime, the higher the probability for the excitation energy to be transferred from base to base and reach a reactive site, as happens in photosynthesis. Furthermore, bimolecular reactions involving the excited bases and other nonexcited species become more probable, because the reactants have the time to reach the appropriate configuration by molecular diffusion or other local motions. However, the extremely short lifetimes ( 1 ps) of the lowest excited singlet states of the DNA units (adenine, cytosine, guanine and thymine nucleosides and nucleotides), [3±8] are thought to function as an intrinsic protection against DNA degradation by sunlight. Nevertheless, one would expect that the nature of the excited states and/or the deactivation pathways to be modified when going from individual units to organised multichromophoric systems. In particular, exciton states may be formed, delocalised over several molecular units. Consequently, the lifetime of the excited state of the organised system may be drastically altered.Previous fluorescence measurements performed for single and double-stranded oligonucleotides and polynucleotides have indeed revealed the existence of long-lived components decaying on the nanosecond timescale. [9±12] The major part of the fluorescence could not be resolved because of the limited time resolution.Herein, we report the first fluorescence measurements of DNA oligonucleotides obtained with femtosecond resolution using the upconversion technique. They concern a double-stranded oligomer (dA) 20 ¥ (dT) 20 consisting of twenty adenosine (dA) ± thymidine (dT) base pairs and its constitutive single-stranded oligomers (dA) 20 and (dT) 20 . The choice of this particular system was motivated from the fact that the photophysical properties of double-stranded oligomers, in which adenosine units are located on one single strand and thymidine on the other, have been the subject of several studies. [11±15] Fluorescence decays were recorded at 330 nm, corresponding to the emission maximum of (dA) 20 ¥ (dT) 20 , after excitation at 267 nm. All oligomer fluorescence disappeared more slowly than that of the monomers and, in addition, showed a weak tail persisting at times longer than the studied time window. This long tail was difficult to characterise due to the limited signal-tonoise ratio of our setup for such weak signals. In order to describe the decays in a quantitative way and make some phenomenological comparisons, we fitted the fluorescence decays by biexponential functions to which we added, when necessary, a constant c to account for the persisting long tail: a ¥ exp(À t/t 1 ) b ¥ exp(À t/t 2 ) c. The results of the fits of the decays are shown in Table 1. We have also determined an [17] M. Table 1. Characteristic...

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Wavelength-resolved lifetime measurements of emissions from DNA components and poly rA at room temperature excited with synchrotron radiation

Cited by 37 publications

References 6 publications

Subnanosecond Emission Dynamics of AT DNA Oligonucleotides

Subnanosecond Emission Dynamics of AT DNA Oligonucleotides

The Potential of the Xenon “Spin‐Spy” Methodology for the Study of Configurational Equilibria in Solution

The Effect of Molecular Organisation in DNA Oligomers Studied by Femtosecond Fluorescence Spectroscopy

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