Reactions of Photoexcited Aromatic Radical Cations with Polar Solvents

Shkrob, Ilya A.; Sauer, Myran C.; Liu, An Dong; Crowell, and Robert A.; Trifunac, A. D.

doi:10.1021/jp981065f

Cited by 36 publications

(63 citation statements)

References 78 publications

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“…[54] Furthermore, the other band coincides well with the absorption spectrum of TrpC + generated by twophoton ionisation in water. [55] These two bands decay within a few tens of picoseconds and the subsequent TA spectra are similar to those measured with LY13b alone. Figure 7 A shows the time profile of the TA signal intensity at 440 nm in the LY13bC À band.…”

Section: Transient Absorption and Fluorescence Quenchingsupporting

confidence: 69%

Site‐Dependent Excited‐State Dynamics of a Fluorescent Probe Bound to Avidin and Streptavidin

et al. 2009

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Sensing protein environment: The femtosecond fluorescence dynamics of a molecular probe attached to avidin and streptavidin (see figure) depends markedly on the location of the probe and on the protein. These differences reflect not only the protein primary and tertiary structures but also the effect of the surrounding water molecules. The excited‐state dynamics of biotin–spacer–Lucifer‐Yellow (LY) constructs bound to avidin (Avi) and streptavidin (Sav) was investigated using femtosecond spectroscopy. Two different locations in the proteins, identified by molecular dynamics simulations of Sav, namely the entrance of the binding pocket and the protein surface, were probed by varying the length of the spacer. A reduction of the excited‐state lifetime, stronger in Sav than in Avi, was observed with the long spacer construct. Transient absorption measurements show that this effect originates from an electron transfer quenching of LY, most probably by a nearby tryptophan residue. The local environment of the LY chromophore could be probed by measuring the time‐dependent polarisation anisotropy and Stokes shift of the fluorescence. Substantial differences in both dynamics were observed. The fluorescence anisotropy decays analysed by using the wobbling‐in‐a‐cone model reveal a much more constrained environment of the chromophore with the short spacer. Moreover, the dynamic Stokes shift is multiphasic in all cases, with a ∼1 ps component that can be ascribed to diffusive motion of bulk‐like water molecules, and with slower components with time constants varying not only with the spacer, but with the protein as well. These slow components, which depend strongly on the local environment of the probe, are ascribed to the motion of the hydration layer coupled to the conformational dynamics of the protein.

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Section: Transient Absorption and Fluorescence Quenchingsupporting

confidence: 69%

Site‐Dependent Excited‐State Dynamics of a Fluorescent Probe Bound to Avidin and Streptavidin

et al. 2009

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“…9). 68 Apart from the positive and negative spikes around time zero, which are due to the non-resonant response of the solvent, the time profile can be well reproduced using a biexponential function with a rise time of 800 fs and a decay time of 2.6 ps. This rise time is consistent with the quenching time of LYen determined by fluorescence up-conversion.…”

Section: Intermolecular Quenching Studiesmentioning

confidence: 87%

Excited-state dynamics of the fluorescent probe Lucifer Yellow in liquid solutions and in heterogeneous media

Fürstenberg

Vauthey

2005

Photochem Photobiol Sci

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The photophysics of the dye Lucifer Yellow ethylenediamine (LYen) has been investigated in various polar solvents. The main deactivation pathways of its first singlet excited state are the fluorescence and the intersystem crossing. In water, non-radiative decay by intermolecular proton transfer becomes a significant deactivation channel. The early fluorescence dynamics, which was investigated in liquids and in reverse micelles, was found to depend substantially on the environment. An important static quenching of LYen by tryptophan and indole occurring in the subpicosecond timescale was observed. The use of the fluorescence dynamics of LYen as a local probe is illustrated by preliminary results obtained with a biotinylated Lucifer Yellow derivative complexed with avidin.

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“…S2, ESIw), pointing to a mechanism that includes biphotonic ionization of the solvent at this excitation wavelength and subsequent trapping of the solvated electron by galvinoxyl in accord with the pulse radiolysis studies by Capellos and Allen. 55 Such a scheme explains why the highest galvinoxylate anion yield is observed in toluene and alcohol solutions, the solvents with the lowest liquid ionization potentials, 56 whereas no ionization takes place in MeCN which has a high ionization potential (Table 2).…”

Section: Downloaded By Universite De Geneve On 18 April 2012mentioning

confidence: 99%

Photophysics of the galvinoxyl free radical revisited

Grilj

Zonca

Daku

et al. 2012

Phys. Chem. Chem. Phys.

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The photophysical properties of the free neutral radical galvinoxyl were studied by a combination of femtosecond time-resolved spectroscopy and quantum chemical calculations. The electronic absorption spectrum is dominated by an intense band at 430 nm that is ascribed to the D 9,10 ' D 0 transitions. Upon photoexcitation at 400 nm, the population of the D 9,10 states decays within less than 200 fs to the electronic ground state. This ultrafast internal conversion does not involve intramolecular modes with large amplitude motion as the measured dynamics does not show any significant dependence on the environment, but is most probably facilitated by a high density of electronic states of different character. Depending on the solvent, a weak transient band due to the galvinoxylate anion is also observed. This closed-shell species, which is fluorescent although its deactivation is also dominated by non-radiative decay, is generated upon biphotonic ionization of the solvent and electron capture. The ultrashort excited-state lifetime of the galvinoxyl radical precludes photoinduced disproportionation previously claimed to be at the origin of the formation of both anion and cation.

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Reactions of Photoexcited Aromatic Radical Cations with Polar Solvents

Cited by 36 publications

References 78 publications

Site‐Dependent Excited‐State Dynamics of a Fluorescent Probe Bound to Avidin and Streptavidin

Site‐Dependent Excited‐State Dynamics of a Fluorescent Probe Bound to Avidin and Streptavidin

Excited-state dynamics of the fluorescent probe Lucifer Yellow in liquid solutions and in heterogeneous media

Photophysics of the galvinoxyl free radical revisited

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