scholarly journals A Novel Dialkylamino GFP Chromophore as an Environment-Polarity Sensor Reveals the Role of Twisted Intramolecular Charge Transfer

Chemosensors ◽  
2021 ◽  
Vol 9 (8) ◽  
pp. 234
Author(s):  
Cheng Chen ◽  
Sean A. Boulanger ◽  
Anatolii I. Sokolov ◽  
Mikhail S. Baranov ◽  
Chong Fang
Keyword(s):  
Charge Transfer ◽  
Transient Absorption ◽  
Fluorescent Protein ◽  
Intramolecular Charge Transfer ◽  
Multivariable Analysis ◽  
Solvent Polarity ◽  
Dimethylamino Group ◽  
Twisted Intramolecular Charge Transfer

We discovered a novel fluorophore by incorporating a dimethylamino group (–NMe2) into the conformationally locked green fluorescent protein (GFP) scaffold. It exhibited a marked solvent-polarity-dependent fluorogenic behavior and can potentially find broad applications as an environment-polarity sensor in vitro and in vivo. The ultrafast femtosecond transient absorption (fs-TA) spectroscopy in combination with quantum calculations revealed the presence of a twisted intramolecular charge transfer (TICT) state, which is formed by rotation of the –NMe2 group in the electronic excited state. In contrast to the bright fluorescent state (FS), the TICT state is dark and effectively quenches fluorescence upon formation. We employed a newly developed multivariable analysis approach to the FS lifetime in various solvents and showed that the FS → TICT reaction barrier is mainly modulated by H-bonding capability instead of viscosity of the solvent, accounting for the observed polarity dependence. These deep mechanistic insights are further corroborated by the dramatic loss of fluorogenicity for two similar GFP-derived chromophores in which the rotation of the –NMe2 group is inhibited by structural locking.

Direct evidence of solvent polarity governing the intramolecular charge and energy transfer: ultrafast relaxation dynamics of push–pull fluorene derivatives

2019 ◽  
Vol 21 (21) ◽  
pp. 11087-11102 ◽  
Author(s):  
Afeefah U. Neelambra ◽  
Chinju Govind ◽  
Tessy T. Devassia ◽  
Guruprasad M. Somashekharappa ◽  
Venugopal Karunakaran
Keyword(s):  
Energy Transfer ◽  
Charge Transfer ◽  
Emission Spectroscopy ◽  
Direct Evidence ◽  
Transient Absorption ◽  
Intramolecular Charge Transfer ◽  
Solvent Polarity ◽  
Relaxation Dynamics ◽  
Ultrafast Relaxation ◽  
Absorption And Emission Spectroscopy

The occurrence of intramolecular charge transfer along with energy transfer controlled by the polarity of solvent is revealed by femtosecond and nanosecond transient absorption and emission spectroscopy.

Effect of bulky meso-substituents on photoinduced twisted intramolecular charge transfer processes in meso-diarylamino subporphyrins

2016 ◽  
Vol 20 (06) ◽  
pp. 663-669 ◽  
Author(s):  
Seung-Kyu Lee ◽  
Jun Oh Kim ◽  
Daiki Shimizu ◽  
Atsuhiro Osuka ◽  
Dongho Kim
Keyword(s):  
Charge Transfer ◽  
Intramolecular Charge Transfer ◽  
Solvent Polarity ◽  
Intramolecular Electron Transfer ◽  
Separation Processes ◽  
Time Resolved ◽  
Twisted Intramolecular Charge Transfer ◽  
Transfer Processes ◽  
Steady State Time ◽  
Photoexcited State

Photoexcited-state dynamics of meso-diarylamino subporphyrins 4–6 in cyclohexane, toluene, and acetonitrile have been studied by steady-state/time-resolved absorption and fluorescence experiments and quantum calculations. While 4 emits fluorescence from the locally excited state regardless of solvent polarity, the fluorescence of 5 and 6 are solvent-polarity dependent. The observed efficient fluorescent quenching of 5 and 6 has been ascribed to twisted intramolecular charge transfer (TICT), in which the two N–C[Formula: see text] bonds in 5 and the C[Formula: see text]–N bond in 6 are twisted to facilitate the intramolecular electron transfer. In 2-methyltetrahydrofuran (2-MeTHF), the fluorescence of 5 and 6 are both almost completely quenched at 297 K, but restored at 77 K (below the melting point of 2-MeTHF) because of the frozen molecular twisting. Furthermore, electrochemical studies also revealed the charge separation processes of 4–6 are thermally unfavorable in nonpolar toluene and cyclohexane unless their structures change contrary to the observed efficient fluorescence quenching. These observations support the TICT mechanism. In addition, the formation of TICT state is affected by steric effect as the size of the meso-substituents increases.

Fluorescence Spectroscopic Investigation of the Effect of α-Cyclodextrin on the Twisted Intramolecular Charge Transfer of p-Dimethylaminobenzoic Acid in Aqueous Media

1994 ◽  
Vol 48 (9) ◽  
pp. 1169-1173 ◽  
Author(s):  
Yun-Bao Jiang
Keyword(s):  
Charge Transfer ◽  
Inclusion Complex ◽  
Intramolecular Charge Transfer ◽  
Aqueous Media ◽  
Normal Band ◽  
Guest Molecules ◽  
Dimethylamino Group ◽  
Twisted Intramolecular Charge Transfer ◽  
The Difference ◽  
Dimethylaminobenzoic Acid

The effect of α-cyclodextrin (α-CD) on the twisted intramolecular charge transfer (TICT) of p-dimethylaminobenzoic acid (DMABOA) in aqueous media is investigated with the use of TICT-typical dual fluorescence. With the increase of α-CD concentration in aqueous DMABOA solution, the LE fluorescence is slightly quenched and is not shifted in position, while the TICT fluorescence is strongly enhanced and shifted to blue. The correlation of the intensity ratio of the TICT band to the normal band, Ia/ Ib, of DMABOA with medium polarity in aqueous α-CD media is opposite to that in pure organic solvent, which is explained in terms of the different TICT behavior in aqueous solution. The p Ka of DMABOA is not affected by the presence of α-CD, and the orientation of the DMABOA molecule in the DMABOA/α-CD inclusion complex is determined to be with the dimethylamino group in the cavity. The stoichiometry and association constant of the DMABOA/α-CD inclusion complex are investigated by monitoring the Ib/ Ia of DMABOA as a function of α-CD concentration. The Ia/ Ib value of DMABOA in α-CD media is generally much lower than that of DMABN in the same media, which is interpreted by the difference in the energy barrier from the locally excited (LE) to the TICT state and in the orientation of the guest molecules in the α-CD cavity. The effect of the cyclodextrin cavity is clearly demonstrated to be a micro-environmental effect.

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