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Faillace MS, Dolgopolova EA, Ceballos NM, Ruiz Pereyra EN, Lanfri L, Argüello GA, Burgos Paci M, Shustova NB, Peláez WJ. GFP-related chromophores: photoisomerization, thermal reversion, and DNA labelling. Phys Chem Chem Phys 2023. [PMID: 37376968 DOI: 10.1039/d3cp01655b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/29/2023]
Abstract
Due to the pronounced effect of the confined environment on the photochemical properties of 4-hydroxybenzylidene imidazolinone (HBI), a GFP-related chromophore, imidazolidinone and imidazothiazolone analogues have been studied as fluorescent probes. Their photoisomerization and their thermal reversion were studied under 365-nm-irradiation, resulting in observation of an enthalpy-entropy compensation effect. Theoretical studies were carried out to shed light on the thermal reversion mechanism. Moreover, photophysical studies of benzylidene imidazothiazolone in the presence of dsDNA revealed fluorescence enhancement. The prepared compounds could be considered as a valuable tool for the detailed investigation of physicochemical, biochemical, or biological systems.
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Affiliation(s)
- Martin S Faillace
- INFIQC-CONICET-Dpto. de Fisicoquímica, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Ciudad Universitaria, Córdoba, X5000HUA, Argentina.
- Department of Chemistry and Biochemistry, University of South Carolina, Columbia, South Carolina 29208, USA
| | - Ekaterina A Dolgopolova
- Department of Chemistry and Biochemistry, University of South Carolina, Columbia, South Carolina 29208, USA
| | - Noelia M Ceballos
- INFIQC-CONICET-Dpto. de Fisicoquímica, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Ciudad Universitaria, Córdoba, X5000HUA, Argentina.
| | - E Nahir Ruiz Pereyra
- INFIQC-CONICET-Dpto. de Fisicoquímica, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Ciudad Universitaria, Córdoba, X5000HUA, Argentina.
| | - Lucia Lanfri
- INFIQC-CONICET-Dpto. de Fisicoquímica, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Ciudad Universitaria, Córdoba, X5000HUA, Argentina.
| | - Gustavo A Argüello
- INFIQC-CONICET-Dpto. de Fisicoquímica, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Ciudad Universitaria, Córdoba, X5000HUA, Argentina.
| | - Maximiliano Burgos Paci
- INFIQC-CONICET-Dpto. de Fisicoquímica, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Ciudad Universitaria, Córdoba, X5000HUA, Argentina.
| | - Natalia B Shustova
- Department of Chemistry and Biochemistry, University of South Carolina, Columbia, South Carolina 29208, USA
| | - Walter J Peláez
- INFIQC-CONICET-Dpto. de Fisicoquímica, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Ciudad Universitaria, Córdoba, X5000HUA, Argentina.
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Dalmau D, Crespo O, Matxain JM, Urriolabeitia EP. Fluorescence Amplification of Unsaturated Oxazolones Using Palladium: Photophysical and Computational Studies. Inorg Chem 2023. [PMID: 37315074 DOI: 10.1021/acs.inorgchem.3c00601] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
Weakly fluorescent (Z)-4-arylidene-5-(4H)-oxazolones (1), ΦPL < 0.1%, containing a variety of conjugated aromatic fragments and/or charged arylidene moieties, have been orthopalladated by reaction with Pd(OAc)2. The resulting dinuclear complexes (2) have the oxazolone ligands bonded as a C^N-chelate, restricting intramolecular motions involving the oxazolone. From 2, a variety of mononuclear derivatives, such as [Pd(C^N-oxazolone)(O2CCF3)(py)] (3), [Pd(C^N-oxazolone)(py)2](ClO4) (4), [Pd(C^N-oxazolone)(Cl)(py)] (5), and [Pd(C^N-oxazolone)(X)(NHC)] (6, 7), have been prepared and fully characterized. Most of complexes 3-6 are strongly fluorescent in solution in the range of wavelengths from green to yellow, with values of ΦPL up to 28% (4h), which are among the highest values of quantum yield ever reported for organometallic Pd complexes with bidentate ligands. This means that the introduction of the Pd in the oxazolone scaffold produces in some cases an amplification of the fluorescence of several orders of magnitude from the free ligand 1 to complexes 3-6. Systematic variations of the substituents of the oxazolones and the ancillary ligands show that the wavelength of emission is tuned by the nature of the oxazolone, while the quantum yield is deeply influenced by the change of ligands. TD-DFT studies of complexes 3-6 show a direct correlation between the participation of the Pd orbitals in the HOMO and the loss of emission through non-radiative pathways. This model allows the understanding of the amplification of the fluorescence and the future rational design of new organopalladium systems with improved properties.
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Affiliation(s)
- David Dalmau
- Instituto de Síntesis Química y Catálisis Homogénea, ISQCH (CSIC-Universidad de Zaragoza), Pedro Cerbuna 12, 50009 Zaragoza, Spain
| | - Olga Crespo
- Instituto de Síntesis Química y Catálisis Homogénea, ISQCH (CSIC-Universidad de Zaragoza), Pedro Cerbuna 12, 50009 Zaragoza, Spain
| | - Jon M Matxain
- Polimero eta Material Aurreratuak: Fisika, Kimika eta Teknologia Saila, Kimika Fakultatea, Euskal Herriko Unibertsitatea UPV/EHU and Donostia International Physics Center (DIPC) PK 1072, 20080 Donostia, Euskadi, Spain
| | - Esteban P Urriolabeitia
- Instituto de Síntesis Química y Catálisis Homogénea, ISQCH (CSIC-Universidad de Zaragoza), Pedro Cerbuna 12, 50009 Zaragoza, Spain
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Ke HW, Sung K. 7-membered-ring effect on fluorescence quantum yield: does metal-complexation-induced twisting-inhibition of an amino GFP chromophore derivative enhance fluorescence? Phys Chem Chem Phys 2023; 25:14627-14634. [PMID: 37194347 DOI: 10.1039/d3cp00467h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
To investigate two aspects, namely, (1) the 7-membered-ring effect on fluorescence quantum yield and (2) whether metal-complexation-induced twisting-inhibition of an amino green fluorescent protein (GFP) chromophore derivative is bound to enhance fluorescence, a novel GFP-chromophore-based triamine ligand, (Z)-o-PABDI, is designed and synthesized. Before complexation with metal ions, the S1 excited state of (Z)-o-PABDI undergoes τ-torsion relaxation (Z/E photoisomerization) with a Z/E photoisomerization quantum yield of 0.28, forming both ground-state (Z)- and (E)-o-PABDI isomers. Since (E)-o-PABDI is less stable than (Z)-o-PABDI, it is thermo-isomerized back to (Z)-o-PABDI at room temperature in acetonitrile with a first-order rate constant of (1.366 ± 0.082) × 10-6 s-1. After complexation with a Zn2+ ion, (Z)-o-PABDI as a tridentate ligand forms a 1 : 1 complex with the Zn2+ ion in acetonitrile and in the solid state, resulting in complete inhibition of the φ-torsion and τ-torsion relaxations, which does not enhance fluorescence but causes fluorescence quenching. (Z)-o-PABDI also forms complexes with other first-row transition metal ions Mn2+, Fe3+, Co2+, Ni2+ and Cu2+, generating almost the same fluorescence quenching effect. By comparison with the 2/Zn2+ complex, in which a 6-membered ring of Zn2+-complexation enhances fluorescence significantly (a positive 6-membered-ring effect on fluorescence quantum yield), we find that the flexible 7-membered rings of the (Z)-o-PABDI/Mn+ complexes trigger their S1 excited states to relax through internal conversion at a rate much faster than fluorescence (a negative 7-membered-ring effect on fluorescence quantum yield), leading to fluorescence quenching regardless of the type of transition metal that complexes with (Z)-o-PABDI.
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Affiliation(s)
- Hao-Wei Ke
- Department of Chemistry, National Cheng Kung University, Tainan, Taiwan.
| | - Kuangsen Sung
- Department of Chemistry, National Cheng Kung University, Tainan, Taiwan.
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Liao JW, Sung R, Sung K. Against the NEER principle: the third type of photochromism for GFP chromophore derivatives. Phys Chem Chem Phys 2021; 24:295-304. [PMID: 34889318 DOI: 10.1039/d1cp03581a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Photochromism is the heart of photochromic fluorescent proteins. Excited-state proton transfer (ESPT) is the major cause of photochromism for the green fluorescent protein (GFP) and Z-E photoisomerization through τ-torsion is the major cause of photochromism for Dronpa (a GFP mutant). In this article, s-E-1 opens a third type of photochromism for GFP chromophore derivatives, which involves light-driven φ-torsion with no τ-torsion, followed by excited-state intramolecular proton transfer (ESIPT), and is gated by environmental polarity. Since s-E-1 does not follow Z-E photoisomerization through τ-torsion but undergoes light-driven φ-torsion, which involves equilibration of the excited-state rotamers, it is clearly against the NEER (Non-Equilibration of Excited-state Rotamers) principle.
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Affiliation(s)
- Jun-Wei Liao
- Department of Chemistry, National Cheng Kung University, Tainan, Taiwan.
| | - Robert Sung
- Department of Chemistry, National Cheng Kung University, Tainan, Taiwan.
| | - Kuangsen Sung
- Department of Chemistry, National Cheng Kung University, Tainan, Taiwan.
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Li MJ, Lin YH, Sung R, Sung K. E- Z Isomerization Mechanism of the Green Fluorescent Protein Chromophore: Remote Regulation by Proton Dissociation of the Phenol Group. J Phys Chem A 2021; 125:3614-3621. [PMID: 33885302 DOI: 10.1021/acs.jpca.1c01371] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Dronpa, a GFP (green fluorescent protein)-like fluorescent protein, allows its fluorescent and nonfluorescent states to be switched to each other reversibly by light or heat through E-Z isomerization of the GFP chromophore. In this article, a GFP chromophore (p-HBDI) in water is used as a model to explore this E-Z isomerization mechanism. Based on the experimental solvent isotope effect (kH2O/kD2O = 2.30), the E-Z isomerization of p-HBDI in water is suggested to go through the remote-proton-dissociation-regulated direct mechanism with a proton transfer in the rate-determining step. The fractionation factor (ϕ) of the water-associated phenol proton of p-HBDI in the transition state is found to be 0.43, which is exactly in the range of 0.1-0.6 for the fractionation factor (ϕ) of the transferring proton in the transition state of R2O···H···O+H2 in water. This means that the phenol proton of E-p-HBDI in the transition state is on the way to the associated water oxygen during the E-Z isomerization. The proton dissociation from the phenol group of p-HBDI remotely regulates its E-Z isomerization. Less proton dissociation from the phenol group (pKa = 8.0) at pH = 1-4 results in a modest reduction in the E-Z isomerization rate of p-HBDI, while complete proton dissociation from the phenol group at pH = 11-12 also reduces its E-Z isomerization rate by one order of magnitude because of the larger charge separation in the transition state of the p-HBDI anion. All of these results are consistent with the remote-proton-dissociation-regulated direct mechanism but against the water-assisted addition/elimination mechanism.
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Affiliation(s)
- Ming-Ju Li
- Department of Chemistry, National Cheng Kung University, Tainan 701401, Taiwan
| | - Yen-Hsun Lin
- Department of Chemistry, National Cheng Kung University, Tainan 701401, Taiwan
| | - Robert Sung
- Faculty of Family Medicine, Northern Ontario School of Medicine, Sudbury, Ontario P3E 2C6, Canada
| | - Kuangsen Sung
- Department of Chemistry, National Cheng Kung University, Tainan 701401, Taiwan
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