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Langeland J, Lindkvist TT, Kjær C, Nielsen SB. Gas-phase Förster resonance energy transfer in mass-selected and trapped ions. MASS SPECTROMETRY REVIEWS 2024; 43:477-499. [PMID: 36514825 DOI: 10.1002/mas.21828] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/02/2022] [Revised: 10/21/2022] [Accepted: 11/25/2022] [Indexed: 06/17/2023]
Abstract
Förster Resonance Energy transfer (FRET) is a nonradiative process that may occur from an electronically excited donor to an acceptor when the emission spectrum of the donor overlaps with the absorption spectrum of the acceptor. FRET experiments have been done in the gas phase based on specially designed mass-spectroscopy setups with the goal to obtain structural information on biomolecular ions labeled with a FRET pair (i.e., donor and acceptor dyes) and to shed light on the energy-transfer process itself. Ions are accumulated in a radio-frequency ion trap or a Penning trap where mass selection of those of interest takes place, followed by photoexcitation. Gas-phase FRET is identified from detection of emitted light either from the donor, the acceptor, or both, or from a fragmentation channel that is specific to the acceptor when electronically excited. The challenge associated with the first approach is the collection and detection of photons emitted from a thin ion cloud that is not easily accessible while the second approach relies both on the photophysical and chemical behavior of the acceptor. In this review, we present the different instrumentation used for gas-phase FRET, including a discussion of advantages and disadvantages, and examples on how the technique has provided important structural information that is not easily obtainable otherwise. Furthermore, we describe how the spectroscopic properties of the dyes are affected by nearby electric fields, which is readily discernable from experiments on simple model systems with alkyl or π-conjugated bridges. Such spectral changes can have a significant effect on the FRET efficiency. Ideas for new directions are presented at the end with special focus on cold-ion spectroscopy.
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Affiliation(s)
- Jeppe Langeland
- Department of Physics and Astronomy, Aarhus University, Aarhus, Denmark
| | | | - Christina Kjær
- Department of Physics and Astronomy, Aarhus University, Aarhus, Denmark
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Kjaer C, Vu-Phung A, Toft Lindkvist T, Langeland J, Brøndsted Nielsen S. Cryogenic Ion Fluorescence Spectroscopy: FRET in Rhodamine Homodimers and Heterodimers. Chemistry 2023; 29:e202302166. [PMID: 37565666 DOI: 10.1002/chem.202302166] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2023] [Revised: 08/02/2023] [Accepted: 08/07/2023] [Indexed: 08/12/2023]
Abstract
The internal electronic communication between two or more light-absorbers is fundamental for energy-transport processes, a field of large current interest. Here the intrinsic photophysics of homo- and heterodimers of rhodamine cations were studied where just two methylene units bridge the dyes. Gas-phase experiments were done on frozen molecular ions at cryogenic temperatures using the newly built LUNA2 mass spectroscopy setup in Aarhus. Both absorption (from fluorescence excitation) and dispersed-fluorescence spectra were measured. In the gas phase, there is no dielectric screening from solvent molecules, and the effect of charges on transition energies is maximum. Indeed, bands are redshifted compared to those of monomer dyes due to the electric field that each dye senses from the other in a dimer. Importantly, also, as two chemically identical dyes in a homodimer do not experience the same field along the long axis, each dye has separate absorption. At low temperatures, it is therefore possible to selectively excite one dye. Fluorescence is dominantly from the dye with the lowest transition energy no matter which dye is photoexcited. Hence this work unequivocally demonstrates Förster Resonance Energy Transfer even in homodimers where one dye acts as donor and the other as acceptor.
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Affiliation(s)
- Christina Kjaer
- Department of Physics and Astronomy, Aarhus University, Ny Munkegade 120, 8000, Aarhus C, Denmark
| | - André Vu-Phung
- Department of Physics and Astronomy, Aarhus University, Ny Munkegade 120, 8000, Aarhus C, Denmark
| | - Thomas Toft Lindkvist
- Department of Physics and Astronomy, Aarhus University, Ny Munkegade 120, 8000, Aarhus C, Denmark
| | - Jeppe Langeland
- Department of Physics and Astronomy, Aarhus University, Ny Munkegade 120, 8000, Aarhus C, Denmark
| | - Steen Brøndsted Nielsen
- Department of Physics and Astronomy, Aarhus University, Ny Munkegade 120, 8000, Aarhus C, Denmark
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Wu R, Metternich JB, Kamenik AS, Tiwari P, Harrison JA, Kessen D, Akay H, Benzenberg LR, Chan TWD, Riniker S, Zenobi R. Determining the gas-phase structures of α-helical peptides from shape, microsolvation, and intramolecular distance data. Nat Commun 2023; 14:2913. [PMID: 37217470 PMCID: PMC10203302 DOI: 10.1038/s41467-023-38463-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2022] [Accepted: 04/19/2023] [Indexed: 05/24/2023] Open
Abstract
Mass spectrometry is a powerful technique for the structural and functional characterization of biomolecules. However, it remains challenging to accurately gauge the gas-phase structure of biomolecular ions and assess to what extent native-like structures are maintained. Here we propose a synergistic approach which utilizes Förster resonance energy transfer and two types of ion mobility spectrometry (i.e., traveling wave and differential) to provide multiple constraints (i.e., shape and intramolecular distance) for structure-refinement of gas-phase ions. We add microsolvation calculations to assess the interaction sites and energies between the biomolecular ions and gaseous additives. This combined strategy is employed to distinguish conformers and understand the gas-phase structures of two isomeric α-helical peptides that might differ in helicity. Our work allows more stringent structural characterization of biologically relevant molecules (e.g., peptide drugs) and large biomolecular ions than using only a single structural methodology in the gas phase.
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Affiliation(s)
- Ri Wu
- Laboratorium für Organische Chemie, D-CHAB, ETH Zürich, 8093, Zurich, Switzerland
| | - Jonas B Metternich
- Laboratorium für Organische Chemie, D-CHAB, ETH Zürich, 8093, Zurich, Switzerland
| | - Anna S Kamenik
- Laboratorium für Physikalische Chemie, D-CHAB, ETH Zürich, 8093, Zurich, Switzerland
| | - Prince Tiwari
- Laboratorium für Organische Chemie, D-CHAB, ETH Zürich, 8093, Zurich, Switzerland
- Laboratory of Atmospheric Chemistry, Paul Scherrer Institute, Forschungsstrasse 111, 5232, Villigen PSI, Switzerland
| | - Julian A Harrison
- Laboratorium für Organische Chemie, D-CHAB, ETH Zürich, 8093, Zurich, Switzerland
| | - Dennis Kessen
- Laboratorium für Organische Chemie, D-CHAB, ETH Zürich, 8093, Zurich, Switzerland
- University of Münster, MEET Battery Research Center, Corrensstrasse 46, 48149, Münster, Germany
| | - Hasan Akay
- Laboratorium für Organische Chemie, D-CHAB, ETH Zürich, 8093, Zurich, Switzerland
| | - Lukas R Benzenberg
- Laboratorium für Organische Chemie, D-CHAB, ETH Zürich, 8093, Zurich, Switzerland
| | - T-W Dominic Chan
- Department of Chemistry, The Chinese University of Hong Kong, Hong Kong SAR, People's Republic of China
| | - Sereina Riniker
- Laboratorium für Physikalische Chemie, D-CHAB, ETH Zürich, 8093, Zurich, Switzerland.
| | - Renato Zenobi
- Laboratorium für Organische Chemie, D-CHAB, ETH Zürich, 8093, Zurich, Switzerland.
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Ashworth EK, Langeland J, Stockett MH, Lindkvist TT, Kjær C, Bull JN, Nielsen SB. Cryogenic Fluorescence Spectroscopy of Ionic Fluorones in Gaseous and Condensed Phases: New Light on Their Intrinsic Photophysics. J Phys Chem A 2022; 126:9553-9563. [PMID: 36529970 DOI: 10.1021/acs.jpca.2c07231] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Fluorescence spectroscopy of gas-phase ions generated through electrospray ionization is an emerging technique able to probe intrinsic molecular photophysics directly without perturbations from solvent interactions. While there is ample scope for the ongoing development of gas-phase fluorescence techniques, the recent expansion into low-temperature operating conditions accesses a wealth of data on intrinsic fluorophore photophysics, offering enhanced spectral resolution compared with room-temperature measurements, without matrix effects hindering the excited-state dynamics. This perspective reviews current progress on understanding the photophysics of anionic fluorone dyes, which exhibit an unusually large Stokes shift in the gas phase, and discusses how comparison of gas- and condensed-phase fluorescence spectra can fingerprint structural dynamics. The capacity for temperature-dependent measurements of both fluorescence emission and excitation spectra helps establish the foundation for the use of fluorone dyes as fluorescent tags in macromolecular structure determination. We suggest ideas for technique development.
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Affiliation(s)
- Eleanor K Ashworth
- School of Chemistry, University of East Anglia, NorwichNR4 7TJ, United Kingdom
| | - Jeppe Langeland
- Department of Physics and Astronomy, Aarhus University, Aarhus8000, Denmark
| | - Mark H Stockett
- Department of Physics, Stockholm University, SE-10691Stockholm, Sweden
| | | | - Christina Kjær
- Department of Physics and Astronomy, Aarhus University, Aarhus8000, Denmark
| | - James N Bull
- School of Chemistry, University of East Anglia, NorwichNR4 7TJ, United Kingdom
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Zhao Y, Sørensen ER, Lindkvist TT, Kjaer C, Brøndsted Nielsen M, Chen L, Brøndsted Nielsen S. Triangular Rhodamine Triads and Their Intrinsic Photophysics Revealed from Gas-Phase Ion Fluorescence Experiments. Chemistry 2021; 27:10875-10882. [PMID: 34060662 DOI: 10.1002/chem.202101322] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2021] [Indexed: 11/10/2022]
Abstract
When ionic dyes are close together, the internal Coulomb interaction may affect their photophysics and the energy-transfer efficiency. To explore this, we have prepared triangular architectures of three rhodamines connected to a central triethynylbenzene unit (1,3,5-tris(buta-1,3-diyn-1-yl)benzene) based on acetylenic coupling reactions and measured fluorescence spectra of the isolated, triply charged ions in vacuo. We find from comparisons with previously reported monomer and dimer spectra that while polarization of the π-system causes redshifted emission, the separation between the rhodamines is too large for a Stark shift. This picture is supported by electrostatic calculations on model systems composed of three linear and polarizable ionic dyes in D3h configuration: The electric field that each dye experiences from the other two is too small to induce a dipole moment, both in the ground and the excited state. In the case of heterotrimers that contain either two rhodamine 575 (R575) and one R640 or one R575 and two R640, emission is almost purely from R640 although the polarization of the π-system expectedly diminishes the dipole-dipole interaction.
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Affiliation(s)
- Ying Zhao
- State Key Laboratory and Institute of Elemento-Organic Chemistry, College of Chemistry, Nankai University, Tianjin, 300071, P. R. China
| | | | | | - Christina Kjaer
- Department of Physics and Astronomy, Aarhus University, Aarhus, Denmark
| | | | - Li Chen
- State Key Laboratory and Institute of Elemento-Organic Chemistry, College of Chemistry, Nankai University, Tianjin, 300071, P. R. China
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Tiwari P, Metternich JB, Czar MF, Zenobi R. Breaking the Brightness Barrier: Design and Characterization of a Selected-Ion Fluorescence Measurement Setup with High Optical Detection Efficiency. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2021; 32:187-197. [PMID: 33236907 DOI: 10.1021/jasms.0c00264] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
A quadrupole ion trap (QIT) mass spectrometer has been modified and coupled with tunable laser excitation and highly sensitive fluorescence detection systems to perform fluorescence studies on mass-selected ions. Gaseous ions, generated using nanoelectrospray ionization (nano-ESI), are trapped in the QIT that allows optical access for laser irradiation. The emitted fluorescence is collected from a 5.0 mm diameter hole drilled into the ring electrode of the QIT and is directed toward the detection setup. Due to the small inner diameter (7.07 mm) of the ring electrode and a relatively large opening for fluorescence collection, a fluorescence collection efficiency of 2.3% is achieved. After some losses in transmission, around 1.8% of the emitted fluorescence reaches the detectors, more than any other similar instrument reported in the literature. This improved fluorescence collection translates to a much shorter measurement time for a fluorescence signal. Another key feature of this setup is the ability to perform a variety of fluorescence experiments on trapped ions including excitation and emission spectroscopy, lifetime measurement, and ion imaging. The capabilities of the instrument are demonstrated by measuring fluorescence spectra of dyes and biomolecules labeled with dyes in a range of different excitation and emission wavelengths, quantum yields, m/z, and different polarities. A fluorescence lifetime measurement and ion image of trapped rhodamine 6G cations are also shown. With a wide array of functionality and high fluorescence detection performance, this setup provides an opportunity to study biomolecular structures and photophysics of fluorophores in well-controlled environments.
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Affiliation(s)
- Prince Tiwari
- Department of Chemistry and Applied Biosciences, ETH Zürich, Vladimir-Prelog-Weg 3, 8093 Zürich, Switzerland
| | - Jonas B Metternich
- Department of Chemistry and Applied Biosciences, ETH Zürich, Vladimir-Prelog-Weg 3, 8093 Zürich, Switzerland
| | - Martin F Czar
- Department of Chemistry and Applied Biosciences, ETH Zürich, Vladimir-Prelog-Weg 3, 8093 Zürich, Switzerland
| | - Renato Zenobi
- Department of Chemistry and Applied Biosciences, ETH Zürich, Vladimir-Prelog-Weg 3, 8093 Zürich, Switzerland
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Petersen AU, Kjær C, Jensen C, Brøndsted Nielsen M, Brøndsted Nielsen S. Gas‐Phase Ion Fluorescence Spectroscopy of Tailor‐made Rhodamine Homo‐ and Heterodyads: Quenching of Electronic Communication by π‐Conjugated Linkers. Angew Chem Int Ed Engl 2020; 59:20946-20955. [DOI: 10.1002/anie.202008314] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2020] [Revised: 08/11/2020] [Indexed: 01/19/2023]
Affiliation(s)
| | - Christina Kjær
- Department of Physics and Astronomy Aarhus University Denmark
| | - Cecilie Jensen
- Department of Chemistry University of Copenhagen Denmark
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Petersen AU, Kjær C, Jensen C, Brøndsted Nielsen M, Brøndsted Nielsen S. Gas‐Phase Ion Fluorescence Spectroscopy of Tailor‐made Rhodamine Homo‐ and Heterodyads: Quenching of Electronic Communication by π‐Conjugated Linkers. Angew Chem Int Ed Engl 2020. [DOI: 10.1002/ange.202008314] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Affiliation(s)
| | - Christina Kjær
- Department of Physics and Astronomy Aarhus University Denmark
| | - Cecilie Jensen
- Department of Chemistry University of Copenhagen Denmark
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Kjær C, Zhao Y, Stockett MH, Chen L, Hansen K, Nielsen SB. Gas-phase Förster resonance energy transfer in mass-selected ions with methylene or peptide linkers between two dyes: a concerted dance of charges. Phys Chem Chem Phys 2020; 22:11095-11100. [DOI: 10.1039/d0cp01287d] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Emission from gaseous rhodamine 640 is redshifted when the dye is tethered to rhodamine 575 due to internal Coulomb interaction.
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Affiliation(s)
- Christina Kjær
- Department of Physics and Astronomy
- Aarhus University
- Denmark
| | - Ying Zhao
- State Key Laboratory and Institute of Elemento-Organic Chemistry
- College of Chemistry
- Nankai University
- Tianjin 300071
- P. R. China
| | | | - Li Chen
- State Key Laboratory and Institute of Elemento-Organic Chemistry
- College of Chemistry
- Nankai University
- Tianjin 300071
- P. R. China
| | - Klavs Hansen
- Center for Joint Quantum Studies and Department of Physics
- Tianjin University
- 92 Weijin Road
- China
- Department of Physics
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