1
|
Langeland J, Persen NW, Gruber E, Kiefer HV, Kabylda AM, Bochenkova AV, Andersen LH. Controlling Light-Induced Proton Transfer from the GFP Chromophore. Chemphyschem 2021; 22:833-841. [PMID: 33591586 DOI: 10.1002/cphc.202100068] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2021] [Revised: 02/16/2021] [Indexed: 01/01/2023]
Abstract
Green Fluorescent Protein (GFP) is known to undergo excited-state proton transfer (ESPT). Formation of a short H-bond favors ultrafast ESPT in GFP-like proteins, such as the GFP S65T/H148D mutant, but the detailed mechanism and its quantum nature remain to be resolved. Here we study in vacuo, light-induced proton transfer from the GFP chromophore in hydrogen-bonded complexes with two anionic proton acceptors, I- and deprotonated trichloroacetic acid (TCA- ). We address the role of the strong H-bond and the quantum mechanical proton-density distribution in the excited state, which determines the proton-transfer probability. Our study shows that chemical modifications to the molecular network drastically change the proton-transfer probability and it can become strongly wavelength dependent. The proton-transfer branching ratio is found to be 60 % for the TCA complex and 10 % for the iodide complex, being highly dependent on the photon energy in the latter case. Using high-level ab initio calculations, we show that light-induced proton transfer takes place in S1 , revealing intrinsic photoacid properties of the isolated GFP chromophore in strongly bound H-bonded complexes. ESPT is found to be very sensitive to the topography of the highly anharmonic potential in S1 , depending on the quantum-density distribution upon vibrational excitation. We also show that the S1 potential-energy surface, and hence excited-state proton transfer, can be controlled by altering the chromophore microenvironment.
Collapse
Affiliation(s)
- Jeppe Langeland
- Department of Physics and Astronomy, Aarhus University, DK-8000, Aarhus C, Denmark
| | - Natascha W Persen
- Department of Physics and Astronomy, Aarhus University, DK-8000, Aarhus C, Denmark
| | - Elisabeth Gruber
- Department of Physics and Astronomy, Aarhus University, DK-8000, Aarhus C, Denmark
| | - Hjalte V Kiefer
- Department of Physics and Astronomy, Aarhus University, DK-8000, Aarhus C, Denmark
| | - Adil M Kabylda
- Department of Chemistry, Lomonosov Moscow State University, 119991, Moscow, Russia
| | | | - Lars H Andersen
- Department of Physics and Astronomy, Aarhus University, DK-8000, Aarhus C, Denmark
| |
Collapse
|
2
|
Gruber E, Strauss MA, Wegner HA, Andersen LH. Action-spectroscopy studies of positively charge-tagged azobenzene in solution and in the gas-phase. J Chem Phys 2019; 150:084303. [PMID: 30823747 DOI: 10.1063/1.5085743] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The absorption of a positively charge-tagged azobenzene molecule is studied in the gas-phase by measuring photoinduced fragmentation of ions as a function of time. This technique provides information on prompt as well as delayed fragmentation, and a single dissociation channel after one-photon absorption is identified. The spectra in solution, as well as in the gas-phase, show a weak S0 → S1, a strong S0 → S2, and a broad absorption band in the UV regime. The bands are assigned through time dependent density functional theory calculations. The ratio of the various absorption bands depends on the trans to cis isomerization fraction and may be tuned by light irradiation. Gas-phase absorption spectra are presented and discussed in terms of trans and cis isomers.
Collapse
Affiliation(s)
- Elisabeth Gruber
- Department of Physics and Astronomy, Aarhus University, 8000 Aarhus, Denmark
| | - Marcel A Strauss
- Institute of Organic Chemistry, Justus-Liebig University Giessen, 35392 Giessen, Germany
| | - Hermann A Wegner
- Institute of Organic Chemistry, Justus-Liebig University Giessen, 35392 Giessen, Germany
| | - Lars H Andersen
- Department of Physics and Astronomy, Aarhus University, 8000 Aarhus, Denmark
| |
Collapse
|
3
|
Lincke K, Langeland J, Madsen AØ, Kiefer HV, Skov L, Gruber E, Mikkelsen KV, Andersen LH, Nielsen MB. Elucidation of the intrinsic optical properties of hydrogen-bonded and protonated flavin chromophores by photodissociation action spectroscopy. Phys Chem Chem Phys 2018; 20:28678-28684. [DOI: 10.1039/c8cp05368e] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The intrinsic optical properties of the flavin chromophore when engaged in hydrogen bonding or being protonated were elucidated by photo-induced action spectroscopy and computations.
Collapse
Affiliation(s)
- Kasper Lincke
- Department of Chemistry, University of Copenhagen
- DK-2100 Copenhagen Ø
- Denmark
| | - Jeppe Langeland
- Department of Physics and Astronomy, Aarhus University
- DK-8000 Aarhus C
- Denmark
| | | | - Hjalte V. Kiefer
- Department of Physics and Astronomy, Aarhus University
- DK-8000 Aarhus C
- Denmark
| | - Louise Skov
- Department of Chemistry, University of Copenhagen
- DK-2100 Copenhagen Ø
- Denmark
| | - Elisabeth Gruber
- Department of Physics and Astronomy, Aarhus University
- DK-8000 Aarhus C
- Denmark
| | - Kurt V. Mikkelsen
- Department of Chemistry, University of Copenhagen
- DK-2100 Copenhagen Ø
- Denmark
| | - Lars H. Andersen
- Department of Physics and Astronomy, Aarhus University
- DK-8000 Aarhus C
- Denmark
| | | |
Collapse
|
4
|
PHOTO-STABILITY OF SUPER-HYDROGENATED PAHs DETERMINED BY ACTION SPECTROSCOPY EXPERIMENTS. ACTA ACUST UNITED AC 2016. [DOI: 10.3847/0004-637x/832/1/24] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
|
5
|
Svendsen A, Teiwes R, Kiefer HV, Andersen LH, Pedersen HB. Analysis of ionic photofragments stored in an electrostatic storage ring. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2016; 87:013111. [PMID: 26827313 DOI: 10.1063/1.4940423] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
A new method to analyze the properties of fragment ions created in storage ring experiments is presented. The technique relies on an acceleration of ionic fragments immediately after production whereby the fragments are stored in the storage ring. To obtain a fragment mass spectrum, the storage ring is exploited as an electrostatic analyzer (ESA) in which case the number of stored fragment ions is recorded as a function of the applied acceleration potential. However, the storage ring can additionally be employed as a time-of-flight (TOF) instrument by registering the temporal distribution of fragment ions. It is demonstrated that the combined ESA-TOF operation of the ring allows not only to determine fragment masses with much better resolution compared to the ESA mode alone but also enables the extraction of detailed information on the fragmentation dynamics. The method is described analytically and verified with photodissociation experiments on stored Cl2 (-) at an excitation wavelength of 530 nm.
Collapse
Affiliation(s)
- Annette Svendsen
- Department of Physics and Astronomy, Aarhus University, DK-8000 Aarhus C, Denmark
| | - Ricky Teiwes
- Department of Physics and Astronomy, Aarhus University, DK-8000 Aarhus C, Denmark
| | - Hjalte V Kiefer
- Department of Physics and Astronomy, Aarhus University, DK-8000 Aarhus C, Denmark
| | - Lars H Andersen
- Department of Physics and Astronomy, Aarhus University, DK-8000 Aarhus C, Denmark
| | - Henrik B Pedersen
- Department of Physics and Astronomy, Aarhus University, DK-8000 Aarhus C, Denmark
| |
Collapse
|
6
|
Kiefer HV, Lattouf E, Persen NW, Bochenkova AV, Andersen LH. How far can a single hydrogen bond tune the spectral properties of the GFP chromophore? Phys Chem Chem Phys 2015; 17:20056-60. [DOI: 10.1039/c5cp02764k] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Photoabsorption of the hydrogen-bonded HBDI·HBDI− dimer, simultaneously resembling the two states of the Green Fluorescent Protein chromophore, is measured in vacuum.
Collapse
Affiliation(s)
- Hjalte V. Kiefer
- Department of Physics and Astronomy
- Aarhus University
- DK-8000 Aarhus C
- Denmark
| | - Elie Lattouf
- Department of Physics and Astronomy
- Aarhus University
- DK-8000 Aarhus C
- Denmark
| | - Natascha W. Persen
- Department of Physics and Astronomy
- Aarhus University
- DK-8000 Aarhus C
- Denmark
| | - Anastasia V. Bochenkova
- Department of Physics and Astronomy
- Aarhus University
- DK-8000 Aarhus C
- Denmark
- Department of Chemistry
| | - Lars H. Andersen
- Department of Physics and Astronomy
- Aarhus University
- DK-8000 Aarhus C
- Denmark
| |
Collapse
|
7
|
Hilger RT, Santini RE, McLuckey SA. Tandem mass spectrometry in an electrostatic linear ion trap modified for surface-induced dissociation. Anal Chem 2014; 86:8822-8. [PMID: 25111536 DOI: 10.1021/ac502143p] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
A variety of ion traps are used in mass spectrometry. A key feature shared by most of them is the ability to perform tandem mass spectrometry (MS/MS). The Orbitrap is perhaps the most notable ion trap in which MS/MS has yet to be performed. An electrostatic linear ion trap (ELIT) is analogous to an orbitrap in that ions are trapped using solely electrostatic fields. However, the relatively simple ion motion within an ELIT facilitates analysis of fragment ions produced within the device. In this report, we describe an ELIT to which we have added a target for surface induced dissociation (SID). When combined with our previously described method for isolating a precursor ion trapped in an ELIT,1 this apparatus enables MS/MS to be performed. Measurement of product ion m/z is facilitated by the fact that the ELIT is isochronous over the energy range of 1850-2000 eV so that changes to ion energy during SID do not cause major m/z shifts. We demonstrate MS/MS by isolating and dissociating each compound in a four component mixture of tetraalkylphosphonium cations. We also discuss the optimization of collision energy and the length of time that the SID target is available for collision, two parameters that are important in the performance of these experiments.
Collapse
Affiliation(s)
- Ryan T Hilger
- Department of Chemistry, Purdue University , West Lafayette, Indiana 47907-2084, United States
| | | | | |
Collapse
|
8
|
Nielsen SB, Nielsen MB, Rubio A. Spectroscopy of nitrophenolates in vacuo: effect of spacer, configuration, and microsolvation on the charge-transfer excitation energy. Acc Chem Res 2014; 47:1417-25. [PMID: 24673172 DOI: 10.1021/ar500025h] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
In a charge-transfer (CT) transition, electron density moves from one end of the molecule (donor) to the other end (acceptor). This type of transition is of paramount importance in nature, for example, in photosynthesis, and it governs the excitation of several protein biochromophores and luminophores such as the oxyluciferin anion that accounts for light emission from fireflies. Both transition energy and oscillator strength are linked to the coupling between the donor and acceptor groups: The weaker the coupling, the smaller the excitation energy. But a weak coupling necessarily also causes a low oscillator strength possibly preventing direct excitation (basically zero probability in the noncoupling case). The coupling is determined by the actual spacer between the two groups, and whether the spacer acts as an insulator or a conductor. However, it can be difficult or even impossible to distinguish the effect of the spacer from that of local solvent molecules that often cause large solvent shifts due to different ground-state and excited-state stabilization. This calls for gas-phase spectroscopy experiments where absorption by the isolated molecule is identified to unequivocally establish the intrinsic molecular properties with no perturbations from a microenvironment. From such insight, the effect of a protein microenvironment on the CT excited state can be deduced. In this Account, we review our results over the last 5 years from mass spectroscopy experiments using specially designed apparatus on several charged donor-acceptor ions that are based on the nitrophenolate moiety and π-extended derivatives, which are textbook examples of donor-acceptor chromophores. The phenolate oxygen is the donor, and the nitro group is the acceptor. The choice of this system is also based on the fact that phenolate is a common structural motif of biochromophores and luminophores, for example, it is a constituent of the oxyluciferin anion. A presentation of the setups used for gas-phase ion spectroscopy in Aarhus is given, and we address issues of whether double bonds or triple bonds best convey electronic coupling between the phenolate oxygen and the nitro group, the significance of separating the donor and acceptor spatially, the influence of cross-conjugation versus linear conjugation, and along this line ortho versus meta versus para configuration, and not least the effect of a single solvent molecule (water, methanol, or acetonitrile). From systematic studies, a clear picture has emerged that has been supported by high-level calculations of electronically excited states. Our work shows that CC2 coupled-cluster calculations of vertical excitation energies are within 0.2 eV of experimental band maxima, and importantly, that the theoretical method is excellent in predicting the relative order of excitation energies of a series of nitrophenolates. Finally, we discuss future challenges such as following the change in absorption as a function of the number of solvent molecules and when gradually approaching the bulk limit.
Collapse
Affiliation(s)
- Steen Brøndsted Nielsen
- Department
of Physics and Astronomy, Aarhus University, Ny Munkegade 120, DK-8000 Aarhus C, Denmark
| | - Mogens Brøndsted Nielsen
- Department of Chemistry & Center for Exploitation of Solar Energy, University of Copenhagen, Universitetsparken 5, DK-2100 Copenhagen Ø, Denmark
| | - Angel Rubio
- NanoBio Spectroscopy
Group and ETSF Centre for Scientific Development, Centro Mixto CSICUPV/EHU
“Fisica de Materiales”, University of the Basque Country
UPV/EHU Centro Joxe Mari Korta, Avenida
de Tolosa, 72, E-20018 Donostia-San Sebastian, Spain
| |
Collapse
|
9
|
Nielsen LM, Hoffmann SV, Nielsen SB. Electronic coupling between photo-excited stacked bases in DNA and RNA strands with emphasis on the bright states initially populated. Photochem Photobiol Sci 2014; 12:1273-85. [PMID: 23545881 DOI: 10.1039/c3pp25438k] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
In biology the interplay between multiple light-absorbers gives rise to complex quantum effects such as superposition states that are of extreme importance for life, both for harvesting solar energy and likely protecting nucleic acids from radiation damage. Still the characteristics of these states and their quantum dynamics are a much debated issue. While the electronic properties of single bases are fairly well understood, the situation for strands is complicated by the fact that stacked bases electronically couple when photoexcited. These newly arising states are denoted as exciton states and are simply linear combinations of localised wavefunctions that involve N - 1 ground-state bases and one base in its excited state (cf. the Frenkel exciton model). There is disagreement over the number of bases, N, that coherently couple, i.e., the spatial extent of the exciton, and how electronic deexcitation back to the ground state occurs. The importance of dark charge-transfer states has been inferred both from time-resolved fluorescence and transient absorption experiments. These states were suggested to be responsible for long deexcitation times but it is unclear whether 'long' is tens of picoseconds or nanoseconds. In this review paper, we focus on the bright states initially populated and discuss their nature based on information obtained from systematic absorption and circular dichroism experiments on single strands of different lengths. Our results from the last five years are compared with those from other groups, and are discussed in the context of successive deexcitation schemes. Pieces to the puzzle have come from different experiments and theory but a complete description has yet to emerge. As such the story about DNA/RNA photophysical decay mechanisms resembles the tale about the blind men and the elephant where all see the beast in different, correct but incomplete ways.
Collapse
|
10
|
Christensen MA, Della Pia EA, Houmøller J, Thomsen S, Wanko M, Bond AD, Rubio A, Brøndsted Nielsen S, Brøndsted Nielsen M. Cross-Conjugation vs. Linear Conjugation in Donor-Bridge-Acceptor Nitrophenol Chromophores. European J Org Chem 2014. [DOI: 10.1002/ejoc.201301642] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
|
11
|
Pedersen SØ, Støchkel K, Byskov CS, Baggesen LM, Nielsen SB. Gas-phase spectroscopy of protonated adenine, adenosine 5'-monophosphate and monohydrated ions. Phys Chem Chem Phys 2013; 15:19748-52. [PMID: 24141603 DOI: 10.1039/c3cp53742k] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Microsolvation of chromophore ions commonly has large effects on their electronic structure and as a result on their optical absorption spectra. Here spectroscopy of protonated adenine (AdeH(+)) and its complex with one water molecule isolated in vacuo was done using a home-built mass spectrometer in combination with a tuneable pulsed laser system. Experiments also included the protonated adenosine 5'-monophosphate nucleotide (AMPH(+)). In the case of bare AdeH(+) ions, one-photon absorption leads to four dominant fragment ions corresponding to ammonium and ions formed after loss of either NH3, HCN, or NH2CN. The yields of these were measured as a function of the wavelength of the light from 210 nm to 300 nm, and they were combined to obtain the total photoinduced dissociation at each wavelength (i.e., action spectrum). A broad band between 230 nm and 290 nm and the tail of a band with maximum below 210 nm (high-energy band) are seen. In the case of AdeH(+)(H2O), the dominant dissociation channel after photoexcitation in the low-energy band was simply loss of H2O while photodissociation of protonated AMP revealed two dominant dissociation channels associated with the formation of either AdeH(+) or loss of H3PO4. The action spectra of AdeH(+), AdeH(+)(H2O), and AMPH(+) are almost identical in the 230-290 nm region, and they resemble the absorption spectrum of protonated adenine in aqueous solution recorded at low pH. Hence from our work it is firmly established that the lowest-energy transitions are independent of the surroundings.
Collapse
Affiliation(s)
- Sara Øvad Pedersen
- Department of Physics and Astronomy, Aarhus University, DK-8000 Aarhus C, Denmark.
| | | | | | | | | |
Collapse
|
12
|
Houmøller J, Wanko M, Støchkel K, Rubio A, Brøndsted Nielsen S. On the Effect of a Single Solvent Molecule on the Charge-Transfer Band of a Donor–Acceptor Anion. J Am Chem Soc 2013; 135:6818-21. [DOI: 10.1021/ja4025275] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Jørgen Houmøller
- Department of Physics and Astronomy, Aarhus University, Ny Munkegade 120, DK-8000 Aarhus
C, Denmark
| | - Marius Wanko
- Nano-Bio Spectroscopy
Group
and ETSF Scientific Development Centre, Departamento de Fisica de
Materiales, Universidad del País Vasco/Euskal Herriko Unibertsitatea (UPV/EHU), Centro de Fisica de
Materiales CSIC-UPV/EHU-MPC and DIPC, Av. Tolosa 72, E-20018 San Sebastian,
Spain
| | - Kristian Støchkel
- Department of Physics and Astronomy, Aarhus University, Ny Munkegade 120, DK-8000 Aarhus
C, Denmark
| | - Angel Rubio
- Nano-Bio Spectroscopy
Group
and ETSF Scientific Development Centre, Departamento de Fisica de
Materiales, Universidad del País Vasco/Euskal Herriko Unibertsitatea (UPV/EHU), Centro de Fisica de
Materiales CSIC-UPV/EHU-MPC and DIPC, Av. Tolosa 72, E-20018 San Sebastian,
Spain
| | - Steen Brøndsted Nielsen
- Department of Physics and Astronomy, Aarhus University, Ny Munkegade 120, DK-8000 Aarhus
C, Denmark
| |
Collapse
|
13
|
Støchkel K, Hansen CN, Houmøller J, Nielsen LM, Anggara K, Linares M, Norman P, Nogueira F, Maltsev OV, Hintermann L, Nielsen SB, Naumov P, Milne BF. On the Influence of Water on the Electronic Structure of Firefly Oxyluciferin Anions from Absorption Spectroscopy of Bare and Monohydrated Ions in Vacuo. J Am Chem Soc 2013; 135:6485-93. [DOI: 10.1021/ja311400t] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Kristian Støchkel
- Department of Physics and Astronomy, Aarhus University, Ny Munkegade, DK-8000 Aarhus C,
Denmark
| | | | - Jørgen Houmøller
- Department of Physics and Astronomy, Aarhus University, Ny Munkegade, DK-8000 Aarhus C,
Denmark
| | | | - Kelvin Anggara
- Department of Physics and Astronomy, Aarhus University, Ny Munkegade, DK-8000 Aarhus C,
Denmark
| | - Mathieu Linares
- Division of Computational
Physics,
Department of Physics, Chemistry and Biology (IFM), Linköping University, SE-581 83 Linköping, Sweden
| | - Patrick Norman
- Division of Computational
Physics,
Department of Physics, Chemistry and Biology (IFM), Linköping University, SE-581 83 Linköping, Sweden
| | - Fernando Nogueira
- Centre for Computational Physics,
Department of Physics, University of Coimbra, Rua Larga, 3004-516 Coimbra, Portugal
| | - Oleg V. Maltsev
- Department Chemie, Technische Universität München, Lichtenbergstrasse
4, 85748 Garching bei München, Germany
| | - Lukas Hintermann
- Department Chemie, Technische Universität München, Lichtenbergstrasse
4, 85748 Garching bei München, Germany
| | - Steen Brøndsted Nielsen
- Department of Physics and Astronomy, Aarhus University, Ny Munkegade, DK-8000 Aarhus C,
Denmark
| | - Panče Naumov
- New York University Abu Dhabi, P.O. Box 129188, Abu Dhabi, United Arab Emirates
- Institute for Chemical Research and
the Hakubi Center for Advanced Research, Kyoto University, Uji, Kyoto 611-0011, Japan
| | - Bruce F. Milne
- Centre for Computational Physics,
Department of Physics, University of Coimbra, Rua Larga, 3004-516 Coimbra, Portugal
| |
Collapse
|
14
|
Houmøller J, Kaufman SH, Støchkel K, Tribedi LC, Brøndsted Nielsen S, Weber JM. On the Photoabsorption by Permanganate Ions in Vacuo and the Role of a Single Water Molecule. New Experimental Benchmarks for Electronic Structure Theory. Chemphyschem 2013; 14:1133-7. [DOI: 10.1002/cphc.201300019] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2013] [Indexed: 11/07/2022]
|
15
|
Toker Y, Rahbek DB, Kiefer HV, Rajput J, Antoine R, Dugourd P, Nielsen SB, Bochenkova AV, Andersen LH. Photoresponse of the protonated Schiff-base retinal chromophore in the gas phase. Phys Chem Chem Phys 2013; 15:19566-9. [DOI: 10.1039/c3cp51759d] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
|
16
|
Nielsen LM, Pedersen SØ, Kirketerp MBS, Nielsen SB. Absorption by DNA single strands of adenine isolated in vacuo: the role of multiple chromophores. J Chem Phys 2012; 136:064302. [PMID: 22360182 DOI: 10.1063/1.3679444] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
The degree of electronic coupling between DNA bases is a topic being up for much debate. Here we report on the intrinsic electronic properties of isolated DNA strands in vacuo free of solvent, which is a good starting point for high-level excited states calculations. Action spectra of DNA single strands of adenine reveal sign of exciton coupling between stacked bases from blueshifted absorption bands (~3 nm) relative to that of the dAMP mononucleotide (one adenine base). The bands are blueshifted by about 10 nm compared to those of solvated strands, which is a shift similar to that for the adenine molecule and the dAMP mononucleotide. Desolvation has little effect on the bandwidth, which implies that inhomogenous broadening of the absorption bands in aqueous solution is of minor importance compared to, e.g., conformational disorder. Finally, at high photon energies, internal conversion competes with electron detachment since dissociation of the bare photoexcited ions on the microsecond time scale is measured.
Collapse
|
17
|
Støchkel K, Milne BF, Nielsen SB. Absorption Spectrum of the Firefly Luciferin Anion Isolated in Vacuo. J Phys Chem A 2011; 115:2155-9. [DOI: 10.1021/jp110120c] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Kristian Støchkel
- Department of Physics and Astronomy, Aarhus University, Ny Munkegade, DK-8000 Aarhus C, Denmark
| | - Bruce F. Milne
- Centre for Computational Physics, Physics Department, University of Coimbra, Rua Larga, 3004-516, Coimbra, Portugal
| | - Steen Brøndsted Nielsen
- Department of Physics and Astronomy, Aarhus University, Ny Munkegade, DK-8000 Aarhus C, Denmark
| |
Collapse
|
18
|
Støchkel K, Wyer JA, Kirketerp MBS, Brøndsted Nielsen S. Laser pump-probe experiments on microsecond to millisecond timescales at an electrostatic ion storage ring: triplet-triplet absorption by protoporphyrin-IX anions. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2010; 21:1884-1888. [PMID: 20696594 DOI: 10.1016/j.jasms.2010.07.004] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/20/2010] [Revised: 06/30/2010] [Accepted: 07/09/2010] [Indexed: 05/29/2023]
Abstract
Here we demonstrate that pump-probe experiments can be carried out on microsecond to millisecond timescales using an electrostatic ion storage ring. As a test case, we have chosen protoporhyrin IX anions that have lifetimes with respect to dissociation after photoexcitation on this time scale. Ions were photoexcited on one side of the ring with either 430- or 535-nm light (pump) and then allowed to take a certain number of revolutions before they were photoexcited by a second laser pulse (probe) with wavelengths between 650 and 950 nm. If ions were first excited by the pump, an increased yield of neutral products caused by the absorption of red light was measured in a microchannel plate detector located on the other side of the ring. This implies that it is possible to pick out ions that were photoexcited by the pump pulse and to spectroscopically characterize these ions. We report absorption spectra of 535 nm photoexcited porphyrin anions, with time delays of 0.19 and 0.57 ms between the pump and probe pulses, and find that absorption occurs over a broad region in the red.
Collapse
Affiliation(s)
- Kristian Støchkel
- Department of Physics and Astronomy, Aarhus University, Aarhus, Denmark.
| | | | | | | |
Collapse
|
19
|
Kirketerp MBS, Petersen MÅ, Wanko M, Zettergren H, Rubio A, Nielsen MB, Nielsen SB. Double-Bond versus Triple-Bond Bridges: Does it Matter for the Charge-Transfer Absorption by Donor-Acceptor Chromophores? Chemphyschem 2010; 11:2495-8. [DOI: 10.1002/cphc.201000464] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
|
20
|
Aravind G, Antoine R, Klaerke B, Lemoine J, Racaud A, Rahbek DB, Rajput J, Dugourd P, Andersen LH. Sub-microsecond photodissociation pathways of gas phase adenosine 5'-monophosphate nucleotide ions. Phys Chem Chem Phys 2010; 12:3486-90. [PMID: 20355289 DOI: 10.1039/b921038e] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
The sub-microsecond dissociation pathways for the protonated and deprotonated forms of adenosine 5'-monophosphate were probed in the gas phase using a linear time of flight spectrometer. The studies show two dissociation pathways for the AMP ions indicating dominant ergodic pathways in the photodissociation of these species. The photofragmentation was determined to be a single photon process for the AMP ions. Photodetachment of the AMP anion excited at 266 nm was not observed, leaving dissociation as the prominent pathway for relaxation of the excess energy in the biomolecule. The photofragments were analysed at the electrostatic ion storage ring (ELISA) and found to be similar to collision induced fragments in the case of anions but different in the case of cations.
Collapse
Affiliation(s)
- G Aravind
- Department of Physics and Astronomy, Aarhus University, DK-8000 Aarhus C, Denmark
| | | | | | | | | | | | | | | | | |
Collapse
|
21
|
Rajput J, Rahbek DB, Aravind G, Andersen LH. Spectral tuning of the photoactive yellow protein chromophore by H-bonding. Biophys J 2010; 98:488-92. [PMID: 20141763 DOI: 10.1016/j.bpj.2009.10.025] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2009] [Revised: 10/19/2009] [Accepted: 10/19/2009] [Indexed: 11/24/2022] Open
Abstract
Spectral tuning in the photoactive yellow protein (PYP) is investigated by performing gas-phase absorption measurements on a PYP-model chromophore with two water molecules hydrogen-bonded to it. The photoabsorption maximum shows an unusually large blue shift of 0.71 eV in going from the bare to the hydrogen-bonded chromophore. It is concluded that several interactions within the PYP protein are mutually cancelling each other, yielding an absorption maximum that is close to the absorption maximum of the bare chromophore. The system breaks apart upon photoexcitation in the gas phase by releasing the two water molecules, leaving the chromophore itself intact. The hydrogen-bonding interactions thus play an important role in stabilizing the gas phase chromophore against photofragmentation. The relaxation dynamics for the breakup process was also studied, and the timescale of relaxation via fragmentation was found to be < 25 ns.
Collapse
Affiliation(s)
- J Rajput
- Department of Physics and Astronomy, Aarhus University, Aarhus, Denmark
| | | | | | | |
Collapse
|
22
|
Ehlerding A, Wyer JA, Zettergren H, Kirketerp MBS, Nielsen SB. UV Photodissociation of Protonated Gly-Trp and Trp-Gly Dipeptides and Their Complexes with Crown Ether in an Electrostatic Ion Storage Ring. J Phys Chem A 2009; 114:299-303. [DOI: 10.1021/jp9086317] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Affiliation(s)
- Anneli Ehlerding
- Department of Physics and Astronomy, Aarhus University, Ny Munkegade, DK-8000 Aarhus C, Denmark
| | - Jean Ann Wyer
- Department of Physics and Astronomy, Aarhus University, Ny Munkegade, DK-8000 Aarhus C, Denmark
| | - Henning Zettergren
- Department of Physics and Astronomy, Aarhus University, Ny Munkegade, DK-8000 Aarhus C, Denmark
| | | | - Steen Brøndsted Nielsen
- Department of Physics and Astronomy, Aarhus University, Ny Munkegade, DK-8000 Aarhus C, Denmark
| |
Collapse
|
23
|
Kadhane U, Pérot M, Lucas B, Barat M, Fayeton J, Jouvet C, Ehlerding A, Kirketerp MB, Nielsen SB, Wyer J, Zettergren H. Photodissociation of protonated tryptamine and its supramolecular complex with 18-crown-6 ether: Dissociation times and channels, absorption spectra, and excited states calculations. Chem Phys Lett 2009. [DOI: 10.1016/j.cplett.2009.08.064] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
|
24
|
Rocha-Rinza T, Christiansen O, Rajput J, Gopalan A, Rahbek DB, Andersen LH, Bochenkova AV, Granovsky AA, Bravaya KB, Nemukhin AV, Christiansen KL, Nielsen MB. Gas Phase Absorption Studies of Photoactive Yellow Protein Chromophore Derivatives. J Phys Chem A 2009; 113:9442-9. [DOI: 10.1021/jp904660w] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Tomás Rocha-Rinza
- Lundbeck Foundation Center for Theoretical Chemistry and Center for Oxygen Microscopy and Imaging (COMI), Department of Chemistry, University of Aarhus, DK-8000 Aarhus C, Denmark, Department of Physics and Astronomy, University of Aarhus, DK-8000 Aarhus C, Denmark, Department of Chemistry, M.V. Lomonosov Moscow State University, Moscow 119991, Russia, and Department of Chemistry, University of Copenhagen, DK-2100 Copenhagen Ø, Denmark
| | - Ove Christiansen
- Lundbeck Foundation Center for Theoretical Chemistry and Center for Oxygen Microscopy and Imaging (COMI), Department of Chemistry, University of Aarhus, DK-8000 Aarhus C, Denmark, Department of Physics and Astronomy, University of Aarhus, DK-8000 Aarhus C, Denmark, Department of Chemistry, M.V. Lomonosov Moscow State University, Moscow 119991, Russia, and Department of Chemistry, University of Copenhagen, DK-2100 Copenhagen Ø, Denmark
| | - Jyoti Rajput
- Lundbeck Foundation Center for Theoretical Chemistry and Center for Oxygen Microscopy and Imaging (COMI), Department of Chemistry, University of Aarhus, DK-8000 Aarhus C, Denmark, Department of Physics and Astronomy, University of Aarhus, DK-8000 Aarhus C, Denmark, Department of Chemistry, M.V. Lomonosov Moscow State University, Moscow 119991, Russia, and Department of Chemistry, University of Copenhagen, DK-2100 Copenhagen Ø, Denmark
| | - Aravind Gopalan
- Lundbeck Foundation Center for Theoretical Chemistry and Center for Oxygen Microscopy and Imaging (COMI), Department of Chemistry, University of Aarhus, DK-8000 Aarhus C, Denmark, Department of Physics and Astronomy, University of Aarhus, DK-8000 Aarhus C, Denmark, Department of Chemistry, M.V. Lomonosov Moscow State University, Moscow 119991, Russia, and Department of Chemistry, University of Copenhagen, DK-2100 Copenhagen Ø, Denmark
| | - Dennis B. Rahbek
- Lundbeck Foundation Center for Theoretical Chemistry and Center for Oxygen Microscopy and Imaging (COMI), Department of Chemistry, University of Aarhus, DK-8000 Aarhus C, Denmark, Department of Physics and Astronomy, University of Aarhus, DK-8000 Aarhus C, Denmark, Department of Chemistry, M.V. Lomonosov Moscow State University, Moscow 119991, Russia, and Department of Chemistry, University of Copenhagen, DK-2100 Copenhagen Ø, Denmark
| | - Lars H. Andersen
- Lundbeck Foundation Center for Theoretical Chemistry and Center for Oxygen Microscopy and Imaging (COMI), Department of Chemistry, University of Aarhus, DK-8000 Aarhus C, Denmark, Department of Physics and Astronomy, University of Aarhus, DK-8000 Aarhus C, Denmark, Department of Chemistry, M.V. Lomonosov Moscow State University, Moscow 119991, Russia, and Department of Chemistry, University of Copenhagen, DK-2100 Copenhagen Ø, Denmark
| | - Anastasia V. Bochenkova
- Lundbeck Foundation Center for Theoretical Chemistry and Center for Oxygen Microscopy and Imaging (COMI), Department of Chemistry, University of Aarhus, DK-8000 Aarhus C, Denmark, Department of Physics and Astronomy, University of Aarhus, DK-8000 Aarhus C, Denmark, Department of Chemistry, M.V. Lomonosov Moscow State University, Moscow 119991, Russia, and Department of Chemistry, University of Copenhagen, DK-2100 Copenhagen Ø, Denmark
| | - Alexander A. Granovsky
- Lundbeck Foundation Center for Theoretical Chemistry and Center for Oxygen Microscopy and Imaging (COMI), Department of Chemistry, University of Aarhus, DK-8000 Aarhus C, Denmark, Department of Physics and Astronomy, University of Aarhus, DK-8000 Aarhus C, Denmark, Department of Chemistry, M.V. Lomonosov Moscow State University, Moscow 119991, Russia, and Department of Chemistry, University of Copenhagen, DK-2100 Copenhagen Ø, Denmark
| | - Ksenia B. Bravaya
- Lundbeck Foundation Center for Theoretical Chemistry and Center for Oxygen Microscopy and Imaging (COMI), Department of Chemistry, University of Aarhus, DK-8000 Aarhus C, Denmark, Department of Physics and Astronomy, University of Aarhus, DK-8000 Aarhus C, Denmark, Department of Chemistry, M.V. Lomonosov Moscow State University, Moscow 119991, Russia, and Department of Chemistry, University of Copenhagen, DK-2100 Copenhagen Ø, Denmark
| | - Alexander V. Nemukhin
- Lundbeck Foundation Center for Theoretical Chemistry and Center for Oxygen Microscopy and Imaging (COMI), Department of Chemistry, University of Aarhus, DK-8000 Aarhus C, Denmark, Department of Physics and Astronomy, University of Aarhus, DK-8000 Aarhus C, Denmark, Department of Chemistry, M.V. Lomonosov Moscow State University, Moscow 119991, Russia, and Department of Chemistry, University of Copenhagen, DK-2100 Copenhagen Ø, Denmark
| | - Kasper Lincke Christiansen
- Lundbeck Foundation Center for Theoretical Chemistry and Center for Oxygen Microscopy and Imaging (COMI), Department of Chemistry, University of Aarhus, DK-8000 Aarhus C, Denmark, Department of Physics and Astronomy, University of Aarhus, DK-8000 Aarhus C, Denmark, Department of Chemistry, M.V. Lomonosov Moscow State University, Moscow 119991, Russia, and Department of Chemistry, University of Copenhagen, DK-2100 Copenhagen Ø, Denmark
| | - Mogens Brøndsted Nielsen
- Lundbeck Foundation Center for Theoretical Chemistry and Center for Oxygen Microscopy and Imaging (COMI), Department of Chemistry, University of Aarhus, DK-8000 Aarhus C, Denmark, Department of Physics and Astronomy, University of Aarhus, DK-8000 Aarhus C, Denmark, Department of Chemistry, M.V. Lomonosov Moscow State University, Moscow 119991, Russia, and Department of Chemistry, University of Copenhagen, DK-2100 Copenhagen Ø, Denmark
| |
Collapse
|
25
|
Wyer JA, Ehlerding A, Zettergren H, Kirketerp MBS, Brøndsted Nielsen S. Tagging of Protonated Ala-Tyr and Tyr-Ala by Crown Ether Prevents Direct Hydrogen Loss and Proton Mobility after Photoexcitation: Importance for Gas-Phase Absorption Spectra, Dissociation Lifetimes, and Channels. J Phys Chem A 2009; 113:9277-85. [DOI: 10.1021/jp904053d] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Jean Ann Wyer
- Department of Physics and Astronomy, Aarhus University, Ny Munkegade, DK-8000 Aarhus C, Denmark
| | - Anneli Ehlerding
- Department of Physics and Astronomy, Aarhus University, Ny Munkegade, DK-8000 Aarhus C, Denmark
| | - Henning Zettergren
- Department of Physics and Astronomy, Aarhus University, Ny Munkegade, DK-8000 Aarhus C, Denmark
| | - Maj-Britt S. Kirketerp
- Department of Physics and Astronomy, Aarhus University, Ny Munkegade, DK-8000 Aarhus C, Denmark
| | - Steen Brøndsted Nielsen
- Department of Physics and Astronomy, Aarhus University, Ny Munkegade, DK-8000 Aarhus C, Denmark
| |
Collapse
|
26
|
Suhr Kirketerp MB, Åxman Petersen M, Wanko M, Andres Espinosa Leal L, Zettergren H, Raymo FM, Rubio A, Brøndsted Nielsen M, Brøndsted Nielsen S. Absorption Spectra of 4-Nitrophenolate Ions Measuredin Vacuoand in Solution. Chemphyschem 2009; 10:1207-9. [DOI: 10.1002/cphc.200900174] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
|
27
|
Lykkegaard MK, Zettergren H, Kirketerp MBS, Ehlerding A, Wyer JA, Kadhane U, Nielsen SB. Photodissociation of Isolated Ferric Heme and Heme-His Cations in an Electrostatic Ion Storage Ring. J Phys Chem A 2009; 113:1440-4. [DOI: 10.1021/jp809626v] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Affiliation(s)
- Morten Køcks Lykkegaard
- Department of Physics and Astronomy, University of Aarhus, Ny Munkegade, DK-8000 Aarhus C, Denmark
| | - Henning Zettergren
- Department of Physics and Astronomy, University of Aarhus, Ny Munkegade, DK-8000 Aarhus C, Denmark
| | - Maj-Britt Suhr Kirketerp
- Department of Physics and Astronomy, University of Aarhus, Ny Munkegade, DK-8000 Aarhus C, Denmark
| | - Anneli Ehlerding
- Department of Physics and Astronomy, University of Aarhus, Ny Munkegade, DK-8000 Aarhus C, Denmark
| | - Jean Ann Wyer
- Department of Physics and Astronomy, University of Aarhus, Ny Munkegade, DK-8000 Aarhus C, Denmark
| | - Umesh Kadhane
- Department of Physics and Astronomy, University of Aarhus, Ny Munkegade, DK-8000 Aarhus C, Denmark
| | - Steen Brøndsted Nielsen
- Department of Physics and Astronomy, University of Aarhus, Ny Munkegade, DK-8000 Aarhus C, Denmark
| |
Collapse
|
28
|
Ryhding T, Suhr Kirketerp MB, Kadhane U, Lykkegaard MK, Panja S, Nielsen SB, Nielsen MB. Upon the intrinsic optical properties of oligo(p-phenyleneethynylene)s (OPEs). Synthesis of OPE3 for experimental gas-phase absorption studies. Tetrahedron 2008. [DOI: 10.1016/j.tet.2008.08.068] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
|
29
|
Kadhane U, Andersen JU, Ehlerding A, Hvelplund P, Kirketerp MBS, Lykkegaard MK, Nielsen SB, Panja S, Wyer JA, Zettergren H. Photodissociation of protonated tryptophan and alteration of dissociation pathways by complexation with crown ether. J Chem Phys 2008; 129:184304. [DOI: 10.1063/1.3009222] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
|
30
|
Lammich L, Rajput J, Andersen LH. Photodissociation pathways of gas-phase photoactive yellow protein chromophores. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2008; 78:051916. [PMID: 19113164 DOI: 10.1103/physreve.78.051916] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/23/2008] [Indexed: 05/27/2023]
Abstract
The absorption dynamics of two model chromophores of the photoactive yellow protein were studied in gas-phase experiments. Using different time-resolving techniques with an overall sensitivity ranging from seconds down to a few nanoseconds, complex dynamics were revealed for the p -coumaric acid anion, involving both fragmentation and electron detachment as possible photoresponse channels. For the trans-thiophenyl-p-coumarate model, despite its more complex molecular structure, simpler decay dynamics showing only fragmentation were observed.
Collapse
Affiliation(s)
- Lutz Lammich
- Department of Physics and Astronomy, University of Aarhus, 8000 Aarhus C, Denmark
| | | | | |
Collapse
|
31
|
Lykkegaard MK, Ehlerding A, Hvelplund P, Kadhane U, Kirketerp MBS, Nielsen SB, Panja S, Wyer JA, Zettergren H. A Soret Marker Band for Four-Coordinate Ferric Heme Proteins from Absorption Spectra of Isolated Fe(III)-Heme+ and Fe(III)-Heme+(His) Ions in Vacuo. J Am Chem Soc 2008; 130:11856-7. [DOI: 10.1021/ja803460c] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Affiliation(s)
- Morten Køcks Lykkegaard
- Department of Physics and Astronomy, University of Aarhus, Ny Munkegade, DK-8000 Aarhus C, Denmark
| | - Anneli Ehlerding
- Department of Physics and Astronomy, University of Aarhus, Ny Munkegade, DK-8000 Aarhus C, Denmark
| | - Preben Hvelplund
- Department of Physics and Astronomy, University of Aarhus, Ny Munkegade, DK-8000 Aarhus C, Denmark
| | - Umesh Kadhane
- Department of Physics and Astronomy, University of Aarhus, Ny Munkegade, DK-8000 Aarhus C, Denmark
| | - Maj-Britt Suhr Kirketerp
- Department of Physics and Astronomy, University of Aarhus, Ny Munkegade, DK-8000 Aarhus C, Denmark
| | - Steen Brøndsted Nielsen
- Department of Physics and Astronomy, University of Aarhus, Ny Munkegade, DK-8000 Aarhus C, Denmark
| | - Subhasis Panja
- Department of Physics and Astronomy, University of Aarhus, Ny Munkegade, DK-8000 Aarhus C, Denmark
| | - Jean Ann Wyer
- Department of Physics and Astronomy, University of Aarhus, Ny Munkegade, DK-8000 Aarhus C, Denmark
| | - Henning Zettergren
- Department of Physics and Astronomy, University of Aarhus, Ny Munkegade, DK-8000 Aarhus C, Denmark
| |
Collapse
|