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Fluorescent derivatives of the GFP chromophore give a new insight into the GFP fluorescence process.

ABSTRACT: The photophysical properties of synthetic compounds derived from the imidazolidinone chromophore of the green fluorescent protein were determined. Various electron-withdrawing or electron-donating substituents were introduced to mimic the effect of the chromophore surroundings in the protein. The absorption and emission spectra as well as the fluorescence quantum yields in dioxane and glycerol were shown to be highly dependent on the electronic properties of the substituents. We propose a kinetic scheme that takes into account the temperature-dependent twisting of the excited molecule. If the activation energy is low, the molecule most often undergoes an excited-state intramolecular twisting that leads it to the ground state through an avoided crossing between the S(1) and S(0) energy surfaces. For a high activation energy, the torsional motion within the compounds is limited and the ground-state recovery will occur preferentially by fluorescence emission. The excellent correlation between the fluorescence quantum yields and the calculated activation energies to torsion points to the above-mentioned avoided crossing as the main nonradiative deactivation channel in these compounds. Finally, our results are discussed with regard to the chromophore in green fluorescent protein and some of its mutants.

SUBMITTER: Follenius-Wund A

PROVIDER: S-EPMC1303356 | biostudies-literature | 2003 Sep

REPOSITORIES: biostudies-literature

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Fluorescent derivatives of the GFP chromophore give a new insight into the GFP fluorescence process.

Follenius-Wund Anny A Bourotte Maryline M Schmitt Martine M Iyice Fatih F Lami Hans H Bourguignon Jean-Jacques JJ Haiech Jacques J Pigault Claire C

Biophysical journal 20030901 3

The photophysical properties of synthetic compounds derived from the imidazolidinone chromophore of the green fluorescent protein were determined. Various electron-withdrawing or electron-donating substituents were introduced to mimic the effect of the chromophore surroundings in the protein. The absorption and emission spectra as well as the fluorescence quantum yields in dioxane and glycerol were shown to be highly dependent on the electronic properties of the substituents. We propose a kineti ...[more]

PMID: 12944297

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Project description:The dark-colored viologen radical cations are unstable in air and easily fade, thus greatly limiting their applications. If a suitable substituent is introduced into the structure, it will have the dual function of chromism and luminescence, which will broaden its application field. Here, Vio1·2Cl and Vio2·2Br were synthesized by introducing aromatic acetophenone and naphthophenone substituents into the viologen structure. The keto group (-CH2CO-) on the substituents is prone to isomerize into the enol structure (-CH[double bond, length as m-dash]COH-) in organic solvents, especially in DMSO, resulting in a larger conjugated system to stabilize the molecular structure and enhance fluorescence. The time-dependent fluorescence spectrum shows obvious keto-to-enol isomerization-induced fluorescence enhancement. The quantum yield also increased significantly (T = 1 day, ΦVio1 = 25.81%, ΦVio2 = 41.44%; T = 7 days, ΦVio1 = 31.48%, and ΦVio2 = 54.40%) in DMSO. The NMR and ESI-MS data at different times further confirmed that the fluorescence enhancement was caused by isomerization, and no other fluorescent impurities were produced in solution. DFT calculations show that the enol form is almost coplanar throughout the molecular structure, which is conducive to stabilizing the structure and enhancing fluorescence. The fluorescence emission peaks of the keto and enol structures of Vio12+ and Vio22+ were at 416-417 nm and 563-582 nm, respectively. The fluorescence relative oscillator strength of Vio12+ and Vio22+ enol structures is significantly higher than that of keto structures (f value changes from 1.53 to 2.63 for Vio12+ and from 1.62 to 2.81 for Vio22+), indicating stronger fluorescence emission of the enol structure. The calculated results are in good agreement with the experimental results. Vio1·2Cl and Vio2·2Br are the first examples of isomerization-induced fluorescence enhancement of viologen derivatives, which shows strong solvatofluorochromism under UV light, making up for the disadvantage that it is easy for a viologen radical to fade in air, and providing a new strategy for designing and synthesizing viologen materials with strong fluorescence.

Dataset Information

Fluorescent derivatives of the GFP chromophore give a new insight into the GFP fluorescence process.

Publications

Fluorescent derivatives of the GFP chromophore give a new insight into the GFP fluorescence process.

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