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Maillard J, Klehs K, Rumble C, Vauthey E, Heilemann M, Fürstenberg A. Universal quenching of common fluorescent probes by water and alcohols. Chem Sci 2020; 12:1352-1362. [PMID: 34163898 PMCID: PMC8179231 DOI: 10.1039/d0sc05431c] [Citation(s) in RCA: 77] [Impact Index Per Article: 19.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2020] [Accepted: 11/18/2020] [Indexed: 12/13/2022] Open
Abstract
Although biological imaging is mostly performed in aqueous media, it is hardly ever considered that water acts as a classic fluorescence quencher for organic fluorophores. By investigating the fluorescence properties of 42 common organic fluorophores recommended for biological labelling, we demonstrate that H2O reduces their fluorescence quantum yield and lifetime by up to threefold and uncover the underlying fluorescence quenching mechanism. We show that the quenching efficiency is significantly larger for red-emitting probes and follows an energy gap law. The fluorescence quenching finds its origin in high-energy vibrations of the solvent (OH groups), as methanol and other linear alcohols are also found to quench the emission, whereas it is restored in deuterated solvents. Our observations are consistent with a mechanism by which the electronic excitation of the fluorophore is resonantly transferred to overtones and combination transitions of high-frequency vibrational stretching modes of the solvent through space and not through hydrogen bonds. Insight into this solvent-assisted quenching mechanism opens the door to the rational design of brighter fluorescent probes by offering a justification for protecting organic fluorophores from the solvent via encapsulation.
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Affiliation(s)
- Jimmy Maillard
- Department of Physical Chemistry, University of Geneva 1211 Geneva Switzerland
- Department of Inorganic and Analytical Chemistry, University of Geneva 1211 Geneva Switzerland
| | - Kathrin Klehs
- Institute for Physical and Theoretical Chemistry, Goethe University Frankfurt 60438 Frankfurt am Main Germany
| | - Christopher Rumble
- Department of Physical Chemistry, University of Geneva 1211 Geneva Switzerland
| | - Eric Vauthey
- Department of Physical Chemistry, University of Geneva 1211 Geneva Switzerland
| | - Mike Heilemann
- Institute for Physical and Theoretical Chemistry, Goethe University Frankfurt 60438 Frankfurt am Main Germany
| | - Alexandre Fürstenberg
- Department of Physical Chemistry, University of Geneva 1211 Geneva Switzerland
- Department of Inorganic and Analytical Chemistry, University of Geneva 1211 Geneva Switzerland
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2
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Miomandre F, Audebert P. 1,2,4,5-Tetrazines: An intriguing heterocycles family with outstanding characteristics in the field of luminescence and electrochemistry. JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY C-PHOTOCHEMISTRY REVIEWS 2020. [DOI: 10.1016/j.jphotochemrev.2020.100372] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
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3
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Jacob MH, Ghosh I, D'Souza RN, Nau WM. Two Orders of Magnitude Variation of Diffusion-Enhanced Förster Resonance Energy Transfer in Polypeptide Chains. Polymers (Basel) 2018; 10:E1079. [PMID: 30961004 PMCID: PMC6403563 DOI: 10.3390/polym10101079] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2018] [Revised: 09/20/2018] [Accepted: 09/26/2018] [Indexed: 11/17/2022] Open
Abstract
A flexible peptide chain displays structural and dynamic properties that correspond to its folding and biological activity. These properties are mirrored in intrachain site-to-site distances and diffusion coefficients of mutual site-to-site motion. Both distance distribution and diffusion determine the extent of Förster resonance energy transfer (FRET) between two sites labeled with a FRET donor and acceptor. The relatively large Förster radii of traditional FRET methods (R₀ > 20 Å) lead to a fairly low contribution of diffusion. We introduced short-distance FRET (sdFRET) where Dbo, an asparagine residue conjugated to 2,3-diazabicyclo[2.2.2]octane, acts as acceptor paired with donors, such as naphtylalanine (NAla), tryptophan, 5-l-fluorotryptophan, or tyrosine. The Förster radii are always close to 10 Å, which makes sdFRET highly sensitive to diffusional motion. We recently found indications that the FRET enhancement caused by diffusion depends symmetrically on the product of the radiative fluorescence lifetime of the donor and the diffusion coefficient. In this study, we varied this product by two orders of magnitude, using both donors of different lifetime, NAla and FTrp, as well as a varying viscogen concentration, to corroborate this statement. We demonstrate the consequences of this relationship in evaluating the impact of viscogenic coadditives on peptide dimensions.
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Affiliation(s)
- Maik H Jacob
- Department of Life Sciences and Chemistry, Jacobs University Bremen, 28759 Bremen, Germany.
| | - Indrajit Ghosh
- Department of Life Sciences and Chemistry, Jacobs University Bremen, 28759 Bremen, Germany.
| | - Roy N D'Souza
- Department of Life Sciences and Chemistry, Jacobs University Bremen, 28759 Bremen, Germany.
| | - Werner M Nau
- Department of Life Sciences and Chemistry, Jacobs University Bremen, 28759 Bremen, Germany.
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4
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Marefat Khah A, Karbalaei Khani S, Hättig C. Analytic Excited State Gradients for the QM/MM Polarizable Embedded Second-Order Algebraic Diagrammatic Construction for the Polarization Propagator PE-ADC(2). J Chem Theory Comput 2018; 14:4640-4650. [PMID: 30040882 DOI: 10.1021/acs.jctc.8b00396] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
An implementation of a QM/MM embedding in a polarizable environment is presented for second-order Møller-Plesset perturbation theory, MP2, for ground state energies and molecular gradients and for the second-order Algebraic Diagrammatic Construction, ADC(2), for excitation energies and excited state molecular gradients. In this implementation of PE-MP2 and PE-ADC(2), the polarizable embedded Hartree-Fock wave function is used as uncorrelated reference state. The polarization-correlation cross terms for the ground and excited states are included in this model via an approximate coupling density. A Lagrangian formulation is used to derive the relaxed electron densities and molecular gradients. The resolution-of-the-identity approximation speeds up the calculation of four-index electron repulsion integrals in the molecular orbital basis. As a first application, the method is used to study the photophysical properties of host-guest complexes where the accuracy and weaknesses of the model are also critically examined. It is demonstrated that the ground state geometries of the full quantum mechanical calculation for the supermolecule can be well reproduced. For excited state geometries, the deviations from the supermolecular calculation are slightly larger, but still the environment effects are captured qualitatively correctly, and energy gaps between the ground and excited states are obtained with sufficient accuracy.
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Affiliation(s)
- Alireza Marefat Khah
- Arbeitsgruppe Quantenchemie , Ruhr-Universität Bochum , Bochum D-44801 , Germany
| | | | - Christof Hättig
- Arbeitsgruppe Quantenchemie , Ruhr-Universität Bochum , Bochum D-44801 , Germany
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5
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Jacob MH, D'Souza RN, Schwarzlose T, Wang X, Huang F, Haas E, Nau WM. Method-Unifying View of Loop-Formation Kinetics in Peptide and Protein Folding. J Phys Chem B 2018; 122:4445-4456. [PMID: 29617564 DOI: 10.1021/acs.jpcb.8b00879] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Protein folding can be described as a probabilistic succession of events in which the peptide chain forms loops closed by specific amino acid residue contacts, herein referred to as loop nodes. To measure loop rates, several photophysical methods have been introduced where a pair of optically active probes is incorporated at selected chain positions and the excited probe undergoes contact quenching (CQ) upon collision with the second probe. The quenching mechanisms involved triplet-triplet energy transfer, photoinduced electron transfer, and collision-induced fluorescence quenching, where the fluorescence of Dbo, an asparagine residue conjugated to 2,3-diazabicyclo[2.2.2]octane, is quenched by tryptophan. The discrepancy between the loop rates afforded from these three CQ techniques has, however, remained unresolved. In analyzing this discrepancy, we now report two short-distance FRET methods where Dbo acts as an energy acceptor in combination with tryptophan and naphtylalanine, two donors with largely different fluorescence lifetimes of 1.3 and 33 ns, respectively. Despite the different quenching mechanisms, the rates from FRET and CQ methods were, surprisingly, of comparable magnitude. This combination of FRET and CQ data led to a unifying physical model and to the conclusion that the rate of loop formation in folding reactions varies not only with the kind and number of residues that constitute the chain but also in particular with the size and properties of the residues that constitute the loop node.
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Affiliation(s)
- Maik H Jacob
- Department of Life Sciences and Chemistry , Jacobs University Bremen , Bremen 28759 , Germany
| | - Roy N D'Souza
- Department of Life Sciences and Chemistry , Jacobs University Bremen , Bremen 28759 , Germany
| | - Thomas Schwarzlose
- Department of Life Sciences and Chemistry , Jacobs University Bremen , Bremen 28759 , Germany
| | - Xiaojuan Wang
- Center for Biotechnology and Bioengineering , China University of Petroleum , Qingdao , Shandong , China 266580
| | - Fang Huang
- Center for Biotechnology and Bioengineering , China University of Petroleum , Qingdao , Shandong , China 266580
| | - Elisha Haas
- Department of Life Science , Bar Ilan University , Ramat Gan 5290002 , Israel
| | - Werner M Nau
- Department of Life Sciences and Chemistry , Jacobs University Bremen , Bremen 28759 , Germany.,Center for Biotechnology and Bioengineering , China University of Petroleum , Qingdao , Shandong , China 266580
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BECERRA-HERRERA MERCEDES, SAYAGO ANA, BELTRÁN RAFAEL. Exploring antioxidant reactivity and molecular structure of phenols by means of two coupled assays using fluorescence probe (2,3-diazabicyclo[2.2.2]oct-2-ene, DBO) and free radical (2,2-diphenyl-1-picrylhydrazyl, $$\hbox {DPPH}^{\cdot }$$ DPPH · ). J CHEM SCI 2017. [DOI: 10.1007/s12039-017-1331-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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7
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Chen C, Li Y, Jia X, Li F, Chen F, Liu L. Wavelength-focusing organic molecular materials with diazoacetate or fumarate as a monofluorophore. NEW J CHEM 2017. [DOI: 10.1039/c6nj03952a] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Wavelength-focusing molecular materials can focus the shorter and longer wavelengths of simulated solar radiation into an identical wavelength in between.
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Affiliation(s)
- Cheng Chen
- Key Laboratory of Biomedical Polymers
- Ministry of Education
- College of Chemistry and Molecular Sciences
- Wuhan University
- Wuhan
| | - Yan Li
- Key Laboratory of Biomedical Polymers
- Ministry of Education
- College of Chemistry and Molecular Sciences
- Wuhan University
- Wuhan
| | - Xiangxiang Jia
- Key Laboratory of Biomedical Polymers
- Ministry of Education
- College of Chemistry and Molecular Sciences
- Wuhan University
- Wuhan
| | - Feifei Li
- Key Laboratory of Biomedical Polymers
- Ministry of Education
- College of Chemistry and Molecular Sciences
- Wuhan University
- Wuhan
| | - Fangjuan Chen
- Key Laboratory of Biomedical Polymers
- Ministry of Education
- College of Chemistry and Molecular Sciences
- Wuhan University
- Wuhan
| | - Lijian Liu
- Key Laboratory of Biomedical Polymers
- Ministry of Education
- College of Chemistry and Molecular Sciences
- Wuhan University
- Wuhan
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8
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Chen C, Li Y, Liu L. A high quantum yield two-way conversion luminescent oligomer: 1,4-butanediol-bis(5-carbonyl-3-carbethoxy-2-pyrazoline). RSC Adv 2016. [DOI: 10.1039/c6ra15007a] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Oligomers as fluorescent macromolecules exhibit excellent efficiency of a two-way conversion fluorescence process which makes them potentially attractive for biological applications.
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Affiliation(s)
- Cheng Chen
- Key Laboratory of Biomedical Polymers
- Ministry of Education
- College of Chemistry and Molecular Sciences
- Wuhan University
- Wuhan
| | - Yan Li
- Key Laboratory of Biomedical Polymers
- Ministry of Education
- College of Chemistry and Molecular Sciences
- Wuhan University
- Wuhan
| | - Lijian Liu
- Key Laboratory of Biomedical Polymers
- Ministry of Education
- College of Chemistry and Molecular Sciences
- Wuhan University
- Wuhan
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Xiao LQ, Jia XX, Liao LQ, Liu LJ. Synthesis of azo-incorporated copolymers by C1/N2C1 copolymerization under microwave irradiation. CHINESE CHEM LETT 2014. [DOI: 10.1016/j.cclet.2014.09.009] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
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10
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Zheng J, Meana-Pañeda R, Truhlar DG. Including Tunneling in Non-Born-Oppenheimer Simulations. J Phys Chem Lett 2014; 5:2039-43. [PMID: 26273892 DOI: 10.1021/jz500653m] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
For electronically nonadiabatic processes in all but the simplest systems, the most practical multidimensional simulation method is a semiclassical approximation in which a trajectory or the center of a wave packet follows a classical path governed by an effective potential energy function. Here, we show how such simulations can be made more realistic by including tunneling by the army ants tunneling method. We illustrate the theory by calculations with model potential energy surfaces; one model study is in the adiabatic limit, and the other one has nonadiabatic transitions between two electronic states during the tunneling event. The army ants tunneling algorithm is used to efficiently sample tunneling events in the trajectories in both cases. This work makes it possible to simulate complex nonadiabatic chemical processes by efficiently including the important quantum effect of tunneling.
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Affiliation(s)
- Jingjing Zheng
- Department of Chemistry, Chemical Theory Center, and Supercomputing Institute, University of Minnesota, Minneapolis, Minnesota 55455-0431, United States
| | - Rubén Meana-Pañeda
- Department of Chemistry, Chemical Theory Center, and Supercomputing Institute, University of Minnesota, Minneapolis, Minnesota 55455-0431, United States
| | - Donald G Truhlar
- Department of Chemistry, Chemical Theory Center, and Supercomputing Institute, University of Minnesota, Minneapolis, Minnesota 55455-0431, United States
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12
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Dsouza RN, Pischel U, Nau WM. Fluorescent dyes and their supramolecular host/guest complexes with macrocycles in aqueous solution. Chem Rev 2011; 111:7941-80. [PMID: 21981343 DOI: 10.1021/cr200213s] [Citation(s) in RCA: 805] [Impact Index Per Article: 61.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Affiliation(s)
- Roy N Dsouza
- School of Engineering and Science, Jacobs University Bremen, Campus Ring 1, D-28759 Bremen, Germany
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Meyer R, Sonnen AFP, Nau WM. Phase-dependent lateral diffusion of α-tocopherol in DPPC liposomes monitored by fluorescence quenching. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2010; 26:14723-14729. [PMID: 20722430 DOI: 10.1021/la101915x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
The temperature-dependent fluorescence quenching of an amphiphilic palmitoyl derivative of 2,3-diazabicyclo[2.2.2]oct-2-ene (Fluorazophore-L) by α-tocopherol (α-Toc) has been determined in liposomes composed of a saturated lipid, 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC). The mutual lateral diffusion coefficients (D(L)) were extracted according to a laterally diffusion-controlled dynamic quenching model. Three distinct temperature regimes were identified: one between 65 and 39 °C, where the lateral diffusion coefficients were in the range of 10(-7) cm(2) s(-1) and the lifetime of the probe was monoexponential in the absence of α-Toc, a second one between 39 and 30 °C, where the lateral diffusion coefficients were in the range of 10(-8) cm(2) s(-1) and the lifetime of the probe was biexponential in the absence of α-Toc, and a third one below 30 °C, in which no diffusion was detectable, suggesting D(L) < 10(-9) cm(2)s (-1). These temperature domains were assigned, supported by differential scanning calorimetry (DSC) measurements, to the liquid-crystalline, ripple, and solid-gel phases of DPPC liposomes in the presence of the two additives. The absolute values of the individual lateral diffusion coefficients (taken as (1)/(2) of the D(L) values) of the Fluorazophore-L/α-Toc (ca. 2.5 × 10(-7) cm(2) s(-1) at 52 °C) couple demonstrates that α-Toc does not diffuse at an unexpectedly high rate in comparison to the self-diffusion of DPPC (1.5 × 10(-7) cm(2) s(-1) at 52 °C). However, diffusion in DPPC liposomes is distinctly slower than that in POPC ones (e.g., D(L) = 4.9 × 10(-7) cm(2) s(-1) versus 6.4 × 10(-7) cm(2) s(-1) at 50 °C), with an activation energy of 49 ± 5 kJ mol(-1) (value for POPC: 47 ± 5 kJ mol(-1)), in the temperature range of the liquid-crystalline phase. Diffusion in the ripple phase, that is, below the main phase transition temperature, was found to be non-negligible, with an apparent activation energy of 175 ± 50 kJ mol(-1).
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Affiliation(s)
- Roland Meyer
- School of Engineering and Science, Jacobs University Bremen, Campus Ring 1, D-28759 Bremen, Germany
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Mu L, He Z, Kong X, Hui G, Xu M, Liang C, Jing X, Danel A, Kulig E. Exploring Reversible Quenching of Fluorescence from a Pyrazolo[3,4-b]quinoline Derivative by Protonation. Chemphyschem 2010; 11:2623-9. [DOI: 10.1002/cphc.201000152] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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Meyer R, Zhang X, Nau WM. Effect of bridgehead substitution on the fluorescence quenching of 2,3-diazabicyclo[2.2.2]oct-2-enes by solvents and antioxidants. Photochem Photobiol Sci 2009; 8:1694-700. [PMID: 20024166 DOI: 10.1039/b9pp00081j] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Azoalkanes of the 2,3-diazabicyclo[2.2.2]-oct-2-ene type have been introduced as probes for antioxidants in homogeneous solution as well as in liposomes and micelles. The bimolecular fluorescence quenching of the bridgehead dichloro-substituted 1,4-dichloro-2,3-diazabicyclo[2.2.2]-oct-2-ene (3) was compared with that of the parent compound 2,3-diazabicyclo[2.2.2]-oct-2-ene (1) and the bridgehead-dialkylated compound 4-methyl-1-isopropyl-2,3-diazabicyclo[2.2.2]-oct-2-ene (2). Compound 3 showed a more efficient fluorescence quenching in C-H containing solvents (e.g., in n-hexane: 30 ns for 3 versus 340 ns for 1 and 770 ns for 2), but a less efficient quenching in aqueous solution (e.g., in deaerated H(2)O: 485 ns for 3 versus 420 ns for 1 and 340 ns for 2), and also by molecular oxygen (k(q)/10(9) M(-1) s(-1) = 0.32 for versus 2.5 for 1 and 1.9 for 2). Towards low-molecular weight antioxidants, compound 3 showed a significantly higher reactivity (e.g., for reduced glutathione: k(q)/10(9) M(-1) s(-1) = 1.8 for 3 versus 0.82 for 1 and 0.39 for 2), at the expense of a lower differentiation between the investigated antioxidants (lower selectivity). The increased reactivity of 3 and lower, as well as qualitatively different, selectivity is attributed to a combination of factors, most importantly the slightly increased excitation energy of 3 and its lower excited-state nucleophilicity. The latter was independently corroborated, besides its longer fluorescence lifetime in aqueous solution, through the trends in quenching rate constants of the azoalkanes 1-3 towards electron-deficient versus electron-rich lactone antioxidants of the benzofuranone type. While common inorganic buffer constituents caused no fluorescence quenching, significant quenching was observed, as a curiosity, for hydrogencarbonate (k(q)/10(6) M(-1) s(-1) = 1.7 for 3 versus 2.4 for 1 and 0.45 for 2), with a fully manifested kinetic deuterium isotope effect (k(q)(H(2)O)/k(q)(D(2)O) = 12) for 3.
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Affiliation(s)
- Roland Meyer
- School of Engineering and Science, Jacobs University Bremen, Campus Ring 1, D-28759, Bremen, Germany
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16
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Physical and chemical problems of the creation of photostable converters of light energy on the basis of dyed polymers. THEOR EXP CHEM+ 2009. [DOI: 10.1007/s11237-009-9078-5] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Anbazhagan V, Kandavelu V, Kathiravan A, Renganathan R. Investigation on the fluorescence quenching of 2,3-diazabicyclo[2.2.2]oct-2-ene (DBO) by certain estrogens and catechols. J Photochem Photobiol A Chem 2008. [DOI: 10.1016/j.jphotochem.2007.06.026] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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18
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Zhang X, Erb C, Flammer J, Nau WM. Absolute Rate Constants for the Quenching of Reactive Excited States by Melanin and Related 5,6-Dihydroxyindole Metabolites: Implications for Their Antioxidant Activity. Photochem Photobiol 2007. [DOI: 10.1562/0031-8655(2000)0710524arcftq2.0.co2] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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19
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Pischel U, Patra D, Koner AL, Nau WM. Investigation of Polar and Stereoelectronic Effects on Pure Excited-state Hydrogen Atom Abstractions from Phenols and Alkylbenzenes†. Photochem Photobiol 2006; 82:310-7. [PMID: 15882091 DOI: 10.1562/2005-02-07-ra-434] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The fluorescence quenching of singlet-excited 2,3-diazabicyclo[2.2.2]oct-2-ene (DBO) by 22 phenols and 12 alkylbenzenes has been investigated. Quenching rate constants in acetonitrile are in the range of 10(8)-10(9) M(-1)s(-1) for phenols and 10(5)-10(6) M(-1)s(-1) for alkylbenzenes. In contrast to the quenching of triplet-excited benzophenone, no exciplexes are involved, so that a pure hydrogen atom transfer is proposed as quenching mechanism. This is supported by (1) pronounced deuterium isotope effects (kH/kD ca 4-6), which were observed for phenols and alkylbenzenes, and (2) a strongly endergonic thermodynamics for charge transfer processes (electron transfer, exciplex formation). In the case of phenols, linear free energy relationships applied, which led to a reaction constant of rho = -0.40, suggesting a lower electrophilicity of singlet-excited DBO than that of triplet-excited ketones and alkoxyl radicals. The reactivity of singlet-excited DBO exposes statistical, steric, polar and stereoelectronic effects on the hydrogen atom abstraction process in the absence of complications because of competitive exciplex formation.
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Affiliation(s)
- Uwe Pischel
- REQUIMTE/Department of Chemistry, University of Porto, Porto, Portugal.
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Bucher G, Lu C, Sander W. The Photochemistry of Lipoic Acid: Photoionization and Observation of a Triplet Excited State of a Disulfide. Chemphyschem 2005; 6:2607-18. [PMID: 16331730 DOI: 10.1002/cphc.200500211] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
Under short-wavelength UV irradiation, lipoic acid (LipSS) and its reduced form, dihydrolipoic acid (DHLA), undergo photoionization processes through a bi- or monophotonic pathway. After ionization, the LipSS radical cation (LipSS*+) and radical anion (LipSS*-) are generated. LipSS*- can be converted to equimolar amounts of LipSS and DHLA through second-order decay. Triplet acetone can be quenched by LipSS and DHLA with a rate close to the diffusion-controlled limit. The mechanism was further confirmed by continuous irradiation experiments. When LipSS is directly irradiated with UVA light, the first excited triplet state of LipSS is observed, with a lifetime tau=75 ns. Characteristic reactions include triplet energy transfer to oxygen and beta-carotene and addition to isoprene. The lifetime of triplet LipSS is also shortened by addition of water and methanol.
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Affiliation(s)
- Götz Bucher
- Lehrstuhl für Organische Chemie II, Ruhr-Universität, 44780 Bochum, Germany.
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Chen H, Li S. Theoretical Study on the Photolysis Mechanism of 2,3-Diazabicyclo[2.2.2]oct-2-ene. J Am Chem Soc 2005; 127:13190-9. [PMID: 16173746 DOI: 10.1021/ja050002p] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
A CASPT2/CASSCF study has been carried out to investigate the mechanism of the photolysis of 2,3-diazabicyclo[2.2.2]oct-2-ene (DBO) under direct and triplet-sensitized irradiation. By exploring the detailed potential energy surfaces including intermediates, transition states, conical intersections, and singlet/triplet crossing points, for the first excited singlet (S(1)) and the low-lying triplet states (T(1), T(2), and T(3)), we provide satisfactory explanations of many experimental findings associated with the photophysical and photochemical processes of DBO. A key finding of this work is the existence of a significantly twisted S(1) minimum, which can satisfactorily explain the envelope of the broad emission band of DBO. It is demonstrated that the S(1) (n-pi*) intermediate can decay to the T(1) (n-pi*) state by undergoing intersystem crossing (rather inefficient) to the T(2) (pi-pi*) state followed by internal conversion to the T(1) state. The high fluorescence yield and the extraordinarily long lifetime of the singlet excited DBO are due to the presence of relatively high barriers, both for intersystem crossing and for C-N cleavage. The short lifetime of the triplet DBO is caused by fast radiationless decay to the ground state.
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Affiliation(s)
- Hui Chen
- Lab of Mesoscopic Chemistry, Institute of Theoretical and Computational Chemistry, Nanjing University, Nanjing 210093, People's Republic of China
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Marquez C, Pischel U, Nau WM. Selective fluorescence quenching of 2,3-diazabicyclo[2.2.2]oct-2-ene by nucleotides. Org Lett 2004; 5:3911-4. [PMID: 14535741 DOI: 10.1021/ol035454q] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
[reaction: see text] The fluorescence quenching of 2,3-diazabicyclo[2.2.2]oct-2-ene (DBO) by nucleotides has been studied. The quenching mechanism was analyzed on the basis of deuterium isotope effects, tendencies for exciplex formation, and the quenching efficiency in the presence of a molecular container (cucurbit[7]uril). Exciplex-induced quenching appears to prevail for adenosine, cytidine, and uridine, while hydrogen abstraction becomes competitive for thymidine and guanosine. Compared to other fluorescent probes, DBO responds very selectively to the type of nucleotide.
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Affiliation(s)
- Cesar Marquez
- School of Engineering and Science, International University Bremen, Campus Ring 1, D-28759 Bremen, Germany
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Marquez C, Huang F, Nau WM. Cucurbiturils: Molecular Nanocapsules for Time-Resolved Fluorescence-Based Assays. IEEE Trans Nanobioscience 2004; 3:39-45. [PMID: 15382642 DOI: 10.1109/tnb.2004.824269] [Citation(s) in RCA: 132] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
A new fluorescent host-guest system based on the inclusion of the fluorophore 2,3-diazabicyclo[2.2.2]oct-2-ene (DBO) into the cavity of the molecular container compound cucurbit[7]uril (CB7) has been designed which possesses an exceedingly long-lived emission (690 ns in aerated water). The large binding constant of (4 +/- 1) x 10(5) M(-1) along with the resistance of the CB7.DBO complex toward external fluorescence quenchers allow the use of CB7 as an enhancer in time-resolved fluorescence-based assays, e.g., to screen enzyme activity or inhibition by using DBO-labeled peptides as substrates. The response of CB7.DBO to different environmental conditions and possible quenchers are described.
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Affiliation(s)
- Cesar Marquez
- School of Engineering and Science, International University Bremen, Bremen D-28759, Germany.
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Burdzinski G, Maciejewski A, Buntinx G, Poizat O, Lefumeux C. Ultrafast quenching of the excited S2 state of benzopyranthione by acetonitrile. Chem Phys Lett 2004. [DOI: 10.1016/j.cplett.2003.12.029] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Pischel U, Huang F, Nau WM. Intramolecular singlet–singlet energy transfer in antenna-substituted azoalkanes. Photochem Photobiol Sci 2004; 3:305-10. [PMID: 14993948 DOI: 10.1039/b311416c] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Two novel azoalkane bichromophores and related model compounds have been synthesised and photophysically characterised. Dimethylphenylsiloxy (DPSO) or dimethylnaphthylsiloxy (DNSO) serve as aromatic donor groups (antenna) and the azoalkane 2,3-diazabicyclo[2.2.2]oct-2-ene (DBO) as the acceptor. The UV spectral window of DBO (250-300 nm) allows selective excitation of the donor. Intramolecular singlet-singlet energy transfer to DBO is highly efficient and proceeds with quantum yields of 0.76 with DPSO and 0.99 with DNSO. The photophysical and spectral properties of the bichromophoric systems suggest that energy transfer occurs through diffusional approach of the donor and acceptor within a van der Waals contact at which the exchange mechanism is presumed to dominate. Furthermore, akin to the behaviour of electron-transfer systems in the Marcus inverted region, a rate of energy transfer 2.5 times slower was observed for the system with the more favourable energetics, i.e. singlet-singlet energy transfer from DPSO proceeded slower than from DNSO, although the process is more exergonic for DPSO (-142 kJ mol(-1) for DPSO versus-67 kJ mol(-1) for DNSO).
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Affiliation(s)
- Uwe Pischel
- REQUIMTE/Department of Chemistry, Faculty of Sciences, University of Porto, R. Campo Alegre, 4169-007 Porto, Portugal
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Nature of the S2-state quenching process of benzopyranthione by hydrocarbon solvents measured by pico- and femtosecond laser spectroscopy. Chem Phys Lett 2003. [DOI: 10.1016/s0009-2614(02)01926-7] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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Sinicropi A, Nau WM, Olivucci M. Excited state quenching via "unsuccessful" chemical reactions. Photochem Photobiol Sci 2002; 1:537-46. [PMID: 12659494 DOI: 10.1039/b202653h] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
We discuss the results of recent photochemical reaction path computations on 1n,pi* azoalkanes interacting with a single quencher molecule. We provide computational and experimental evidence that there are two basic mechanisms for the true quenching of 1n,pi* states both based on unsuccessful chemical reactions. The first mechanism is based upon an unsuccessful hydrogen atom transfer and may occur through two different (direct and stepwise) routes. The second mechanism is based on an unsuccessful charge transfer reaction that occurs exclusively in a direct fashion. We show that the efficiency of the two quenching mechanisms is substantially due to the existence of two different types of conical intersections between the excited and ground state potential energy surfaces of the reacting bimolecular system.
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Affiliation(s)
- Adalgisa Sinicropi
- Dipartimento di Chimica, Università di Siena, Via Aldo Moro, Siena, Italy.
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Pischel U, Galletero MS, Garcı́a H, Miranda MA, Nau WM. Photophysical properties and fluorescence quenching of 2,3-diazabicyclo[2.2.2]oct-2-ene in zeolites. Chem Phys Lett 2002. [DOI: 10.1016/s0009-2614(02)00711-x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Pischel U, Nau WM. Structure-reactivity relationships in the photoreduction of n,pi*-excited ketones and azoalkanes: the effect of reaction thermodynamics, excited-state electrophilicity, and antibonding character in the transition state. Photochem Photobiol Sci 2002; 1:141-7. [PMID: 12659131 DOI: 10.1039/b110108k] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The reaction enthalpies for the photoreduction of n,pi*-excited states (acetone, benzophenone, 2.3-diazabicyclo[2.2.2]oct-2-ene, and a 2,3-diazabicyclo[2.2.1]hept-2-ene derivative) by model hydrogen donors (methanol and dimethylamine) were calculated on the basis of a critically evaluated data set of bond dissociation energies for donors and reduced acceptors. These were compared with the observed photoreactivity, which can be assessed through quenching rate constants of the excited states by hydrogen donors. The intriguing observation of a preferential attack at electrophilic hydrogen atoms, i.e., N-H or O-H, by n,pi*-excited azoalkanes is rationalised on the basis of the calculated thermochemical data, differences in electrophilicity, and varying contributions of antibonding character in the transition state. Singlet-excited azoalkanes act as nucleophilic species, while excited ketones display an electrophilic reactivity. This is in line with the pictorial description of the electron distribution in these excited states.
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Affiliation(s)
- Uwe Pischel
- Departement Chemie, Universität Basel, Klingelbergstrasse 80, CH-4056 Basel, Switzerland
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Sinicropi A, Pogni R, Basosi R, Robb MA, Gramlich G, Nau WM, Olivucci M. Fluoreszenzlöschung über stufenweisen Wasserstoff-, Elektronen- und Protonentransfer in der Nähe einer konischen Durchdringung. Angew Chem Int Ed Engl 2001. [DOI: 10.1002/1521-3757(20011119)113:22<4313::aid-ange4313>3.0.co;2-l] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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Sinicropi A, Pogni R, Basosi R, Robb MA, Gramlich G, Nau WM, Olivucci M. Fluorescence Quenching by Sequential Hydrogen, Electron, and Proton Transfer in the Proximity of a Conical Intersection. Angew Chem Int Ed Engl 2001; 40:4185-4189. [DOI: 10.1002/1521-3773(20011119)40:22<4185::aid-anie4185>3.0.co;2-y] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2001] [Indexed: 11/12/2022]
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Gramlich G, Zhang J, Winterhalter M, Nau WM. A long-lived amphiphilic fluorescent probe studied in POPC air-water monolayer and solution bilayer systems. Chem Phys Lipids 2001; 113:1-9. [PMID: 11687222 DOI: 10.1016/s0009-3084(01)00133-5] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
A novel amphiphilic fluorescent probe (Fluorazophore-L) with a strongly dipolar, nonionic azoalkane as headgroup and a palmitoyl tail has been synthesized and characterized. Pure Fluorazophore-L was found to be sufficiently amphiphilic to form stable air-water monolayers. An analysis of the surface pressure versus area suggests an area per molecule of about 34+/-2 A(2) at 29 mN m(-1). The partitioning into a lipid membrane model was quantified at the air-water interface by spreading 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) monolayers. Measurements with different molar fractions of Fluorazophore-L revealed a small but significant reduction of the mean area in the mixed monolayer. The excess free energy of mixing (-0.5+/-0.1 kT) indicated a weakly attractive interaction slightly above thermal energy, suggesting a good miscibility of the fluorescent probe within the lipid monolayer without major structural modifications. Spectroscopic measurements confirmed the incorporation of Fluorazophore-L into POPC vesicles. The fluorescence lifetime was very long (125+/-5 ns under air) with monoexponential fluorescence decays.
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Affiliation(s)
- G Gramlich
- Institut für Physikalische Chemie der Universität Basel, CH-4056 Basel, Switzerland
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Bucher G, Wandel H, Sander W. 1,4-Naphthoquinonediazide-2-carboxylic acid: a diazo compound with a long-lived triplet excited state. J PHYS ORG CHEM 2001. [DOI: 10.1002/poc.354] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Zhang X, Erb C, Flammer J, Nau WM. Absolute rate constants for the quenching of reactive excited states by melanin and related 5,6-dihydroxyindole metabolites: implications for their antioxidant activity. Photochem Photobiol 2000; 71:524-33. [PMID: 10818782 DOI: 10.1562/0031-8655(2000)071<0524:arcftq>2.0.co;2] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The triplet-excited state of benzophenone and the singlet-excited state of 2,3-diazabicyclo[2.2.2]oct-2-ene (Fluorazophore-P) have been employed as kinetic probes to obtain information on the antioxidant activity of the skin and eye pigment melanin and its biogenetic precursors 5,6-dihydroxyindole (DHI) and 5,6-dihydroxyindole-2-carboxylic acid (DHICA). The excited states were generated by the laser-flash photolysis technique and their reaction kinetics was examined by time-resolved transient absorption or fluorescence spectroscopy, respectively. The reaction between triplet benzophenone and DHI produced with unit efficiency the corresponding 6O-centered semiquinone radical, which was characterized by its characteristic transient absorption. The quenching rate constants for DHI (3.1-8.4 x 10(9) M-1 s-1) and DHICA (3.3-5.5 x 10(9) M-1 s-1) were near the diffusion-controlled limit, indicating excellent antioxidant properties. Kinetic solvent effects were observed. The reactivity of synthetic melanin, assessed through the quenching rate constant of Fluorazophore-P and normalized to the number of monomer units, was more than one order of magnitude lower (2.7 x 10(8) M-1 s-1) than that of its precursors. The trend of the quenching rate constants, i.e. DHI > DHICA approximately alpha-tocopherol > melanin, along with the preferential solubility of DHICA in aqueous environments, serves to account for several experimental results from biochemical studies on the inhibition of lipid peroxidation by these natural antioxidants.
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Affiliation(s)
- X Zhang
- Departement Chemie, Universität Basel, Switzerland
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