Application of Linear Free Energy Relations to Electronically Excited States of Monosubstituted Phenols

Wehry, Ε. L.; Rogers, L. B.

doi:10.1021/ja00947a003

Cited by 112 publications

(55 citation statements)

References 3 publications

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“…35 Upon electronic excitation, the pK a of the chromophore is reduced. 39,40 In the case of wtGFP the effect is to make the anionic I* form more stable. However, the proton transfer proceeds from A* to I* through a barrier, leading to the observed picosecond lifetime of the A* and its sensitivity to isotopic exchange.…”

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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“…Similar effects are also found for phenol derivatives. Wehry and Rogers [12] reported excited-state pK a values of a series of substituted phenols evaluated using the F€ o orster cycle method. They found a unusually large influence of meta substitution on the pK a value of phenols in the S 1 state.…”

Section: Introductionmentioning

confidence: 99%

Substituent effects on ultrafast excited-state proton transfer of protonated aniline derivatives in aqueous solution

Shiobara¹,

Tajima²,

Tobita³

2003

Chemical Physics Letters

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“…The entropy term can be calculated for the change of the dipole moment in a polar medium. Applications to acid-base equilibria Numerous examples of the proton transfer processes in excited states have been critically reported in several excellent reviews [4,13,[19][20][21][22]. (8) of ref.…”

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confidence: 99%

The Förster Cycle Reconsidered

Grabowski¹,

Grabowska²

1976

Zeitschrift Für Physikalische Chemie

108

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The Förster cycle is reconsidered, with emphasis on the thermodynamic approximations and on the necessary experimental precautions. Some examples of acid-base equilibria in excited states are discussed along with new possible applications of the cycle. Der Förster-Zyklus wird neu diskutiert unter Berücksichtigung thormodynamischer Näherungen und möglicher Meßfehler. Einige Beispiele von Säure-Base Gleichgewichten in angeregten Zuständen und neue mögliche Anwendungen des Zyklus werden diskutiert.

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Application of Linear Free Energy Relations to Electronically Excited States of Monosubstituted Phenols

Cited by 112 publications

References 3 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

Substituent effects on ultrafast excited-state proton transfer of protonated aniline derivatives in aqueous solution

The Förster Cycle Reconsidered

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