Intramolecular excited-state proton transfer in 3-hydroxyflavone. Hydrogen-bonding solvent perturbations

1984 ◽  
Vol 88 (11) ◽  
pp. 2235-2243 ◽  
Author(s):  
Dale McMorrow ◽  
Michael Kasha
Keyword(s):  
Hydrogen Bonding ◽  
Excited State ◽  
Proton Transfer ◽  
Excited State Proton Transfer

Excited-State Proton Transfer in Fluorescent Photoactive Yellow Protein Containing 7-Hydroxycoumarin

2014 ◽  
Vol 896 ◽  
pp. 85-88
Author(s):  
Dian Novitasari ◽  
Hironari Kamikubo ◽  
Yoichi Yamazaki ◽  
Mariko Yamaguchi ◽  
Mikio Kataoka
Keyword(s):  
Hydrogen Bonding ◽  
Excited State ◽  
Proton Transfer ◽  
Fluorescent Protein ◽  
Stokes Shift ◽  
Spectroscopic Studies ◽  
Photoactive Yellow Protein ◽  
Excited State Proton Transfer ◽  
Hydrogen Bonding Network ◽  
Green Fluorescent

Green fluorescent protein (GFP) has been used as an effective tool in various biological fields. The large Stokes shift resulting from an excited-state proton transfer (ESPT) is the basis for the application of GFP in such techniques as ratiometric GFP biosensors. The chromophore of GFP is known to be involved in a hydrogen-bonding network. Previous X-ray crystallographic and FTIR studies suggest that a proton wire along the hydrogen-bonding network plays a role in the ESPT. In order to examine the relationship between the ESPT and hydrogen-bonding network within proteins, we prepared an artificial fluorescent protein using a light-sensor protein, photoactive yellow protein (PYP). The native chromophore of p-coumaric acid (pCA) of PYP undergoes trans-cis isomerization after absorbing a photon, which triggers proton transfers within the hydrogen-bonding network comprised of pCA and proximal amino acid residues. Although PYP emits little fluorescence, we succeeded to reconstitute an artificial fluorescent PYP (PYP-coumarin) by substituting the pCA with its trans-lock analog 7-hydroxycoumarin. Spectroscopic studies with PYP-coumarin revealed that the chromophore takes an anionic form at neutral pH, but is protonated by lowering pH. Both the protonated and deprotonated forms of PYP-coumarin emit intense fluorescence, as compared with the native PYP. In addition, both the deprotonated and protonated forms show identical λmax values in their fluorescence spectra, indicating that ESPT occurs in the artificial fluorescent protein.

Effects of intermolecular hydrogen bonding on the excited-state proton transfer properties of the cinnamonitrile–methanol complex

2013 ◽  
Vol 91 (3) ◽  
pp. 229-234 ◽  
Author(s):  
Dapeng Yang ◽  
Ruiquan Qi
Keyword(s):  
Hydrogen Bonding ◽  
Excited State ◽  
Charge Transfer ◽  
Proton Transfer ◽  
Density Functional ◽  
Dft Method ◽  
Electronic Energy ◽  
Intermolecular Hydrogen Bonding ◽  
Excited State Proton Transfer ◽  
Hydrogen Bonded

The time-dependent density functional theory (TD-DFT) method was used to study the excited-state proton transfer (ESPT) properties of the hydrogen-bonded cinnamonitrile (3TPAN)–methanol (MeOH) complex (3TPAN–MeOH). The intermolecular hydrogen bonds N1···H11 in both the ground state S0 and the excited state S1 were demonstrated by the optimized geometric structures of the hydrogen-bonded 3TPAN–MeOH complex. While in the excited state S3, a new hydrogen bond H11···O1 was formed after the ESPT took place from the hydrogen-bonded MeOH molecule to the 3TPAN moiety. It was demonstrated that the electronic transitions of the S1 states for both the 3TPAN monomer (including the S3 state) and the hydrogen-bonded 3TPAN–MeOH complex should be of a localized-excited (LE) nature on the 3TPAN molecule, while the S3 state of the hydrogen-bonded 3TPAN–MeOH complex should be of charge transfer (CT) character from the hydrogen-bonded MeOH molecule (through O1···H11) to the 3TPAN moiety. The S3-state proton transfer and charge transfer due to the intermolecular hydrogen-bonding interaction should be the reasons for the remarkable redshift (0.91 eV) of the S3-state electronic energy for the hydrogen-bonded 3TPAN–MeOH complex compared with that of the 3TPAN monomer.

scholarly journals Effect of Water Microsolvation on the Excited-State Proton Transfer of 3-Hydroxyflavone Enclosed in γ-Cyclodextrin

Molecules ◽  
2021 ◽  
Vol 26 (4) ◽  
pp. 843
Author(s):  
Khanittha Kerdpol ◽  
Rathawat Daengngern ◽  
Chanchai Sattayanon ◽  
Supawadee Namuangruk ◽  
Thanyada Rungrotmongkol ◽  
...  
Keyword(s):  
Hydrogen Bonding ◽  
Excited State ◽  
Proton Transfer ◽  
Density Functional ◽  
Photophysical Properties ◽  
Intramolecular Hydrogen Bonding ◽  
Keto Form ◽  
Ring Form ◽  
Hydrophobic Cavity ◽  
Excited State Proton Transfer

The effect of microsolvation on excited-state proton transfer (ESPT) reaction of 3-hydroxyflavone (3HF) and its inclusion complex with γ-cyclodextrin (γ-CD) was studied using computational approaches. From molecular dynamics simulations, two possible inclusion complexes formed by the chromone ring (C-ring, Form I) and the phenyl ring (P-ring, Form II) of 3HF insertion to γ-CD were observed. Form II is likely more stable because of lower fluctuation of 3HF inside the hydrophobic cavity and lower water accessibility to the encapsulated 3HF. Next, the conformation analysis of these models in the ground (S0) and the first excited (S1) states was carried out by density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations, respectively, to reveal the photophysical properties of 3HF influenced by the γ-CD. The results show that the intermolecular hydrogen bonding (interHB) between 3HF and γ-CD, and intramolecular hydrogen bonding (intraHB) within 3HF are strengthened in the S1 state confirmed by the shorter interHB and intraHB distances and the red-shift of O–H vibrational modes involving in the ESPT process. The simulated absorption and emission spectra are in good agreement with the experimental data. Significantly, in the S1 state, the keto form of 3HF is stabilized by γ-CD, explaining the increased quantum yield of keto emission of 3HF when complexing with γ-CD in the experiment. In the other word, ESPT of 3HF is more favorable in the γ-CD hydrophobic cavity than in aqueous solution.

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