Excited State Intramolecular Proton Transfer in Schiff Bases. Decay of the Locally Excited Enol State Observed by Femtosecond Resolved Fluorescence

Rodríguez-Córdoba, William; Zugazagoitia, Jimena S.; Collado-Fregoso, Elisa; Peón, Jörge

doi:10.1021/jp072415d

Cited by 118 publications

(141 citation statements)

References 59 publications

(143 reference statements)

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“…Significantly, it is this feature of S65T/ H148D GFP photophysics which makes it suitable as a model system to study low-barrier or barrierless proton-transfer reactions in proteins. In intramolecular systems the proton transfer may occur on a subpicosecond time scale and be insensitive to hydrogen/deuterium exchange, 38 a situation mirrored for the intermolecular (in the sense of chromophore to D148) protontransfer reactions that occur in the GFP double mutants.…”

Section: Discussionmentioning

confidence: 99%

An Alternate Proton Acceptor for Excited-State Proton Transfer in Green Fluorescent Protein: Rewiring GFP

et al. 2008

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Abstract:The neutral form of the chromophore in wild-type green fluorescent protein (wtGFP) undergoes excited-state proton transfer (ESPT) upon excitation, resulting in characteristic green (508 nm) fluorescence. This ESPT reaction involves a proton relay from the phenol hydroxyl of the chromophore to the ionized side chain of E222, and results in formation of the anionic chromophore in a protein environment optimized for the neutral species (the I* state). Reorientation or replacement of E222, as occurs in the S65T and E222Q GFP mutants, disables the ESPT reaction and results in loss of green emission following excitation of the neutral chromophore. Previously, it has been shown that the introduction of a second mutation (H148D) into S65T GFP allows the recovery of green emission, implying that ESPT is again possible. A similar recovery of green fluorescence is also observed for the E222Q/H148D mutant, suggesting that D148 is the proton acceptor for the ESPT reaction in both double mutants. The mechanism of fluorescence emission following excitation of the neutral chromophore in S65T/H148D and E222Q/H148D has been explored through the use of steady state and ultrafast time-resolved fluorescence and vibrational spectroscopy. The data are contrasted with those of the single mutant S65T GFP. Time-resolved fluorescence studies indicate very rapid (<1 ps) formation of I* in the double mutants, followed by vibrational cooling on the picosecond time scale. The time-resolved IR difference spectra are markedly different to those of wtGFP or its anionic mutants. In particular, no spectral signatures are apparent in the picosecond IR difference spectra that would correspond to alteration in the ionization state of D148, leading to the proposal that a low-barrier hydrogen bond (LBHB) is present between the phenol hydroxyl of the chromophore and the side chain of D148, with different potential energy surfaces for the ground and excited states. This model is consistent with recent high-resolution structural data in which the distance between the donor and acceptor oxygen atoms is e2.4 Å. Importantly, these studies indicate that the hydrogen-bond network in wtGFP can be replaced by a single residue, an observation which, when fully explored, will add to our understanding of the various requirements for proton-transfer reactions within proteins.

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Section: Discussionmentioning

confidence: 99%

An Alternate Proton Acceptor for Excited-State Proton Transfer in Green Fluorescent Protein: Rewiring GFP

et al. 2008

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“…9,[14][15][16][17]22,24,28,29 Theory predicts a ground-state torsion angle of 36°about the anil twist angle α (C 7 NC 6 C 5 dihedral angle; see Figure 1c for a definition of the critical angles considered in this study) at the B3LYP/6-31G* level of theory 28 and 44°at the HF/6-31G* level. 29 An angle of 49°was found by X-ray diffraction of crystalline SA.…”

Section: Introductionmentioning

confidence: 91%

“…We note that this scheme does not contradict our interpretation of the initial steps in the proton transfer dynamics: Our second time constant could easily convolve torsional dynamics in both the enol and keto forms, as the two processes are thought to occur on similar time scales. 14,22 In addition to SA, ESIPT was studied in related species such as 2-(2′-hydroxyphenyl)benzothiazole (HBT) and 2-(2′-hydroxyphenyl)benzoxazole (HBO) in both the liquid 46−50 and gas 51 phases. However, in these molecules, the anilino group is fixed and cannot twist.…”

Section: Comparison With Previousmentioning

confidence: 99%

Initial Processes of Proton Transfer in Salicylideneaniline Studied by Time-Resolved Photoelectron Spectroscopy

Sekikawa

Schalk

et al. 2013

J. Phys. Chem. A

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Excited-state intramolecular proton transfer (ESIPT) in salicylideneaniline (SA) and selected derivatives substituted in the para position of the anilino group have been investigated by femtosecond time-resolved photoelectron spectroscopy (TRPES) and time-dependent density functional theory (TDDFT). SA has a twisted structure at the energetic minimum of the ground state, but ESIPT is assumed to take place through a planar structure, although this has not been fully established. The TRPES studies revealed that the excited-state dynamics within the S 1 band varied significantly with excitation wavelength. At finite temperatures, the ground state was found to sample a broad range of torsional angles, from planar to twisted. At lower photon energies (370 nm), only the planar groundstate molecules were excited, and the excited-state reaction took place within 50 fs. At higher energies (350 and 330 nm), predominantly twisted ground-state molecules were excited: they had to planarize before ESIPT could occur. This process was found to be slower in methylated SA but did not change significantly in the brominated and nitrated SAs. These substitution effects on the decay dynamics can be explained by modifications of the potential barriers, as predicted by the TDDFT calculations, and support the mechanism of a twisting motion of the anilino ring prior to ESIPT. The contribution of another pathway leading to internal conversion within the enol form was found to be minor at the excitation wavelengths considered here.

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“…The spectrokinetic data sets D 1 -D 5 were artificially constructed in general agreement with the previously published results on SA photodynamics (transient absorption spectra and kinetic profiles) [29,30,33]. They contain 400 spectra of 1340 difference optical density (DOD) values each.…”

Section: Simulated Time-resolved Spectroscopic Datamentioning

confidence: 99%

“…The photo-reaction is based on an excitedstate intramolecular proton transfer (ESIPT) between an enol and a keto form of the molecule (Figure 1), which then creates the photoproduct. The detailed mechanism is still controversial but the ESIPT usually occurs in less than 50 fs in solution [29][30][31][32][33][34]. In the previous analysis [7], new insights into the photo-reaction were obtained but as deconvolution was not considered, the kinetic analysis had to be considered very carefully at ultrashort time scale.…”

Section: Introductionmentioning

confidence: 99%

Deconvolution of femtosecond time‐resolved spectroscopy data in multivariate curve resolution. Application to the characterization of ultrafast photo‐induced intramolecular proton transfer

Mouton

Sliwa

Buntinx

et al. 2010

Journal of Chemometrics

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In femtosecond absorption spectroscopy, deconvolution of the measured kinetic traces is still an important issue as photochemical processes that may possess shorter characteristic times than the time resolution of the experiment are usually considered. In this work, we propose to perform deconvolution of the time-dependent concentration profiles extracted from multivariate curve resolution (MCR) applied to spectrokinetic data. The profiles are fitted with a model function including a description of the instrumental response function (IRF) of the experiment. The method combines the potential benefits of soft-modeling data analysis with the ones of hard-modeling for parameter estimation. The potential of the method is demonstrated first analyzing five synthetic data sets for which IRF of different widths are simulated. It is then successfully applied to resolve femtosecond UV-visible transient absorption spectroscopy data investigating the photodynamics of salicylidene aniline, a photochromic molecule of wide interest. Considering a time resolution of 150 fs for the IRF, a characteristic time of 45 fs is recovered for the first step of the photo-induced process which consists of an ultrafast intramolecular proton transfer. Our results also confirm the existence of an intermediate species with a characteristic time of 240 fs.

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Excited State Intramolecular Proton Transfer in Schiff Bases. Decay of the Locally Excited Enol State Observed by Femtosecond Resolved Fluorescence

Cited by 118 publications

References 59 publications

An Alternate Proton Acceptor for Excited-State Proton Transfer in Green Fluorescent Protein: Rewiring GFP

An Alternate Proton Acceptor for Excited-State Proton Transfer in Green Fluorescent Protein: Rewiring GFP

Initial Processes of Proton Transfer in Salicylideneaniline Studied by Time-Resolved Photoelectron Spectroscopy

Deconvolution of femtosecond time‐resolved spectroscopy data in multivariate curve resolution. Application to the characterization of ultrafast photo‐induced intramolecular proton transfer

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