Acidity of cyanophenols in the S1 and T1 states. The influence of substituent orientation

Vincent, William R.; Underberg, W.J.M.

doi:10.1021/j150626a023

Cited by 36 publications

(25 citation statements)

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“…The GFP Cro appears to follow the same principles (Scharnagl et al, 1999). The high RO ÿ quantum yield in GFP contrasts with the denatured protein or the isolated Cro which, like para-phenols (Schulman et al, 1981), do not fluoresce (Tsien, 1998;Zimmer, 2002). The x-ray data of the wild-type (wt) protein (Ö rmo et al, 1996;Yang et al, 1996) show that GFPs possess a unique barrel geometry, consisting of 11 tightly packed b-sheets, with a a-helix carrying the Cro traversing its center.…”

Section: Introductionmentioning

confidence: 82%

Proton Pathways in Green Fluorescence Protein

Agmon

2005

Biophysical Journal

107

154

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Proton pathways in green fluorescent protein (GFP) are more extended than previously reported. In the x-ray data of wild-type GFP, a two-step exit pathway exists from the active site to the protein surface, controlled by a threonine switch. A proton entry pathway begins at a glutamate-lysine cluster around Glu-5, and extends all the way to the buried Glu-222 near the active site. This structural evidence suggests that GFP may function as a portable light-driven proton-pump, with proton emitted in the excited state through the switchable exit pathway, and replenished from Glu-222 and the Glu-5 entry pathway in the ground state.

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Section: Introductionmentioning

confidence: 82%

Proton Pathways in Green Fluorescence Protein

Agmon

2005

Biophysical Journal

107

154

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“…The good UV-absorption along with their well-known electronic properties makes them well suited to investigate the important ESPT parameters, such as the nature of substituents and their positions. 8,[23][24][25][26][27][28][29] Another paradigmatic photoacid is 8-hydroxypyrene-1,3,6-trisulfonate (HPTS, pyranine), which exhibits absorption and emission in the visible part of the electromagnetic spectrum and a high water solubility. 13,[30][31][32][33][34][35][36] ESPT of these photoacids to bases 32,37 or the solvent [38][39][40] has been reported.…”

Section: Introductionmentioning

confidence: 99%

Solvatochromism of pyranine-derived photoacids

Spies

Finkler

Açar

et al. 2013

Phys. Chem. Chem. Phys.

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Photoacidity is frequently found in aromatic alcohols where the equilibrium dissociation constant increases by some orders of magnitude upon electronic excitation. In this study we investigated the solvatochromism of a family of recently synthesized super-photoacids and their methylated counterparts based on pyrene. The chemical similarity of these molecules on the one hand and their differing photoacidity with pKa* values between -0.8 and -3.9 on the other allow for gaining insights into the mechanisms contributing to excited-state proton transfer. Three different solvent scales, namely Lippert-Mataga, Kamlet-Taft and Catalán, were independently employed in this study and gave consistent results. We found the strongest correlation of the excited-state acidity with the dipolarity of the excited state, pem ranging from -1775 cm(-1) to -2500 cm(-1), and a concomitant change in the permanent dipole moment of roughly 14 Debye. Spectral changes due to varying basicity of the solvent, which probes the conjugated property of the solute, are found to be less indicative of the graduation of excited-state acidity, i.e. bem values between -700 and -1200 cm(-1). The solvent acidity is the only parameter with a distinct influence on the electronic spectra of the deprotonated species. The low values of aem ~ 400 cm(-1), which are 3-4× smaller than aabs and aexc, indicate the low basicity of these species in the excited state. Triggered by semiempirical theoretical calculations, the energetic splitting between the two lowest excited states could be related to the excited-state acidity and points to alterations in the electronic mixing of locally excited and charge-transfer states, caused by the substituents. Differences between the threefold negatively charged pyranine and the new neutral photoacids are also discussed.

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“…They found a unusually large influence of meta substitution on the pK a value of phenols in the S 1 state. Schulman et al [13] studied the influence of substituent orientation on acidity of cyanophenols in the excited state by fluorimetric titrimetry. They reported that the acidity of o-, m-, and p-cyanophenols in the S 1 state decreased in that order.…”

Section: Introductionmentioning

confidence: 99%