Dispersed Fluorescence and Delayed Ionization of Jet‐Cooled 2‐Aminopurine: Relaxation to a Dark State Causes Weak Fluorescence

Ke, Feng; Engler, Gernot; Seefeld, Kai; Kleinermanns, Karl

doi:10.1002/cphc.200800816

Cited by 16 publications

(18 citation statements)

References 16 publications

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“…This led to reiteration of the proposal that the fluorescence quantum yield is high in polar solvents because the 1 nπ* state is shifted to higher energy, and a re-examination of the computational predictions. As discussed in detail by Lobsiger et al, the predicted relative energies of the 1 ππ* and 1 nπ* states depend on the computational method used (Feng et al, 2009;Lobsiger et al, 2011); by adopting a method different from those used in previous studies, they achieved good agreement between the calculated and experimental excited state energies for the isolated molecule. Definitive experimental evidence for the effect of solvation on the relative energies of 1 ππ* and 1 nπ* states can be obtained, in principle, from high resolution spectroscopy of 2APsolvent complexes in supersonic molecular beams.…”

Section: Intrinsic Properties Of the Fluorophorementioning

confidence: 78%

“…The important influence of solvation on the fluorescence of 2AP was emphatically demonstrated by the recent revelation that 2AP is barely fluorescent in the gas phase (Feng et al, 2009;Lobsiger et al, 2011). These high-resolution spectroscopic studies of 2AP molecules, free from collisions and cooled to a few Kelvin in supersonic molecular beams, showed the fluorescence lifetime of the isolated molecule to be 77 ps, corresponding to a quantum yield of about 0.005.…”

Section: Intrinsic Properties Of the Fluorophorementioning

confidence: 98%

Section: Fluorescence Properties and Photophysics Of 2-aminopurinementioning

confidence: 99%

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2-aminopurine as a fluorescent probe of DNA conformation and the DNA–enzyme interface

Jones

Neely

2015

Quart. Rev. Biophys.

120

130

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Nearly 50 years since its potential as a fluorescent base analogue was first recognized, 2-aminopurine (2AP) continues to be the most widely used fluorescent probe of DNA structure and the perturbation of that structure by interaction with enzymes and other molecules. In this review, we begin by considering the origin of the dramatic and intriguing difference in photophysical properties between 2AP and its structural isomer, adenine; although 2AP differs from the natural base only in the position of the exocyclic amine group, its fluorescence intensity is one thousand times greater. We then discuss the mechanism of interbase quenching of 2AP fluorescence in DNA, which is the basis of its use as a conformational probe but remains imperfectly understood. There are hundreds of examples in the literature of the use of changes in the fluorescence intensity of 2AP as the basis of assays of conformational change; however, in this review we will consider in detail only a few intensity-based studies. Our primary aim is to highlight the use of time-resolved fluorescence measurements, and the interpretation of fluorescence decay parameters, to explore the structure and dynamics of DNA. We discuss the salient features of the fluorescence decay of 2AP when incorporated in DNA and review the use of decay measurements in studying duplexes, single strands and other structures. We survey the use of 2AP as a probe of DNA-enzyme interaction and enzyme-induced distortion, focusing particularly on its use to study base flipping and the enhanced mechanistic insights that can be gained by a detailed analysis of the decay parameters, rather than merely monitoring changes in fluorescence intensity. Finally we reflect on the merits and shortcomings of 2AP and the prospects for its wider adoption as a fluorescence-decay-based probe.

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Section: Intrinsic Properties Of the Fluorophorementioning

confidence: 78%

Section: Intrinsic Properties Of the Fluorophorementioning

confidence: 98%

See 1 more Smart Citation

2-aminopurine as a fluorescent probe of DNA conformation and the DNA–enzyme interface

Jones

Neely

2015

Quart. Rev. Biophys.

120

130

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“…17 Jet-cooled 2AP examined via laser induced fluorescence (LIF) and resonance enhanced two photon ionization (R2PI) show that 9H-2AP tautomer exhibits only weak fluorescence in the gas phase. 18,19 …”

Section: Introductionmentioning

confidence: 99%

Exciplexes and conical intersections lead to fluorescence quenching in π-stacked dimers of 2-aminopurine with natural purine nucleobases

Liang

Nguyen

Matsika

2013

Photochem Photobiol Sci

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Fluorescent analogues of the natural DNA bases are useful in the study of nucleic acids’ structure and dynamics. 2-Aminopurine (2AP) is a widely used analogue with environmentally sensitive fluorescence behavior. The quantum yield of 2AP has been found to be significantly decreased when engaged in π-stacking interactions with the native bases. We present a theoretical study on fluorescence quenching mechanisms in dimers of 2AP π-stacked with adenine or guanine as in natural DNA. Relaxation pathways on the potential energy surfaces of the first excited states have been computed and reveal the importance of exciplexes and conical intersections in the fluorescence quenching process.

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“…[8][9][10] On the other hand, the ∼80 ps lifetime agrees with recent observations that jet-cooled 9H-2AP shows weak gas-phase fluorescence and rapidly relaxes to a dark state. 12 9-methyl-2-aminopurine (9M-2AP) is substituted at the N 9 position, like the biologically relevant derivatives of adenine and 2AP, see Figure 1. It is important to investigate if and how the 9-methylation influences the photophysical properties of 2AP, e.g., by increasing its fluorescence lifetime.…”

Section: Introductionmentioning

confidence: 99%

Low-lying excited states and nonradiative processes of 9-methyl-2-aminopurine

Trachsel

Lobsiger

Schär

et al. 2014

The Journal of Chemical Physics

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The UV spectrum of the adenine analogue 9-methyl-2-aminopurine (9M-2AP) is investigated with one- and two-color resonant two-photon ionization spectroscopy at 0.3 and 0.05 cm(-1) resolution in a supersonic jet. The electronic origin at 32,252 cm(-1) exhibits methyl torsional subbands that originate from the 0A1'' (l = 0) and 1E(″) (l = ±1) torsional levels. These and further torsional bands that appear up to 00 (0)+230 cm(-1) allow to fit the threefold (V3) barriers of the torsional potentials as |V3''|=50 cm(-1) in the S0 and |V3'|=126 cm(-1) in the S1 state. Using the B3LYP density functional and correlated approximate second-order coupled cluster CC2 methods, the methyl orientation is calculated to be symmetric relative to the 2AP plane in both states, with barriers of V3''=20 cm(-1) and V3'=115 cm(-1). The 00 (0) rotational band contour is 75% in-plane (a/b) polarized, characteristic for a dominantly long-axis (1)ππ(*) excitation. The residual 25% c-axis polarization may indicate coupling of the (1)ππ(*) to the close-lying (1)nπ(*) state, calculated at 4.00 and 4.01 eV with the CC2 method. However, the CC2 calculated (1)nπ oscillator strength is only 6% of that of the (1)ππ(*) transition. The (1)ππ(*) vibronic spectrum is very complex, showing about 40 bands within the lowest 500 cm(-1). The methyl torsion and the low-frequency out-of-plane ν1' and ν2' vibrations are strongly coupled in the (1)ππ(*) state. This gives rise to many torsion-vibration combination bands built on out-of-plane fundamentals, which are without precedence in the (1)ππ(*) spectrum of 9H-2-aminopurine [S. Lobsiger, R. K. Sinha, M. Trachsel, and S. Leutwyler, J. Chem. Phys. 134, 114307 (2011)]. From the Lorentzian broadening needed to fit the 00 (0) contour of 9M-2AP, the (1)ππ(*) lifetime is τ ⩾ 120 ps, reflecting a rapid nonradiative transition.

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Dispersed Fluorescence and Delayed Ionization of Jet‐Cooled 2‐Aminopurine: Relaxation to a Dark State Causes Weak Fluorescence

Cited by 16 publications

References 16 publications

2-aminopurine as a fluorescent probe of DNA conformation and the DNA–enzyme interface

2-aminopurine as a fluorescent probe of DNA conformation and the DNA–enzyme interface

Exciplexes and conical intersections lead to fluorescence quenching in π-stacked dimers of 2-aminopurine with natural purine nucleobases

Low-lying excited states and nonradiative processes of 9-methyl-2-aminopurine

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