1
|
Miyazaki M, Ono M, Otsuka R, Dopfer O, Fujii M. Electronic and vibrational spectroscopies of aromatic clusters with He in a supersonic jet: The case of neutral and cationic phenol-Hen (n = 1 and 2). J Chem Phys 2023; 159:134303. [PMID: 37787127 DOI: 10.1063/5.0169716] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2023] [Accepted: 09/15/2023] [Indexed: 10/04/2023] Open
Abstract
Van der Waals clusters composed of He and aromatic molecules provide fundamental information about intermolecular interactions in weakly bound systems. In this study, phenol-helium clusters (PhOH-Hen with n ≤ 2) are characterized for the first time by UV and IR spectroscopies. The S1 ← S0 origin and ionization energy both show small but additive shifts, suggesting π-bound structures of these clusters, a conclusion supported by rotational contour analyses of the S1 origin bands. The OH stretching vibrations of the PhOH moiety in the clusters match with those of bare PhOH in both the S0 and D0 states, illustrating the negligible perturbation of the He atoms on the molecular vibration. Matrix shifts induced by He attachment are discussed based on the observed band positions with the help of complementary quantum chemical calculations. For comparison, the UV and ionization spectra of PhOH-Ne are reported as well.
Collapse
Affiliation(s)
- Mitsuhiko Miyazaki
- Natural Science Division, Faculty of Core Research, Ochanomizu University, 2-1-1 Ohtsuka, Bunkyo-ku, Tokyo 112-8610, Japan
- Laboratory for Chemistry and Life Science, Institute of Innovative Research, Tokyo Institute of Technology, Yokohama 226-8503, Japan
| | - Megumi Ono
- School of Life Science and Technology, Tokyo Institute of Technology, 4259, Nagatsuta-cho, Midori-ku, Yokohama 226-8503, Japan
| | - Remina Otsuka
- School of Life Science and Technology, Tokyo Institute of Technology, 4259, Nagatsuta-cho, Midori-ku, Yokohama 226-8503, Japan
| | - Otto Dopfer
- Institut für Optik und Atomare Physik, Technische Universität Berlin, 10623 Berlin, Germany
- International Research Frontiers Initiative (IRFI), Institute of Innovation Research, Tokyo Institute of Technology, 4259, Nagatsuta-cho, Midori-ku, Yokohama 226-8503, Japan
| | - Masaaki Fujii
- Laboratory for Chemistry and Life Science, Institute of Innovative Research, Tokyo Institute of Technology, Yokohama 226-8503, Japan
- School of Life Science and Technology, Tokyo Institute of Technology, 4259, Nagatsuta-cho, Midori-ku, Yokohama 226-8503, Japan
- International Research Frontiers Initiative (IRFI), Institute of Innovation Research, Tokyo Institute of Technology, 4259, Nagatsuta-cho, Midori-ku, Yokohama 226-8503, Japan
| |
Collapse
|
2
|
Singh A, Bergmeister S, Azhagesan A, Scheier P, Vilesov AF. Infrared spectroscopy of cations in helium nanodroplets. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2023; 94:093002. [PMID: 37695112 DOI: 10.1063/5.0163390] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/16/2023] [Accepted: 08/21/2023] [Indexed: 09/12/2023]
Abstract
Here, we describe our pulsed helium droplet apparatus for spectroscopy of molecular ions. Our approach involves the doping of the droplets of about 10 nm in diameter with precursor molecules, such as ethylene, followed by electron impact ionization. Droplets containing ions are irradiated by the pulsed infrared laser beam. Vibrational excitation of the embedded cations leads to the evaporation of the helium atoms in the droplets and the release of the free ions, which are detected by the quadrupole mass spectrometer. In this work, we upgraded the experimental setup by introducing an octupole RF collision cell downstream from the electron impact ionizer. The implementation of the RF ion guide increases the transmission efficiency of the ions. Filling the collision cell with additional He gas leads to a decrease in the droplet size, enhancing sensitivity to the laser excitation. We show that the spectroscopic signal depends linearly on the laser pulse energy, and the number of ions generated per laser pulse is about 100 times greater than in our previous experiments. These improvements facilitate faster and more reproducible measurements of the spectra, yielding a handy laboratory technique for the spectroscopic study of diverse molecular ions and ionic clusters at low temperature (0.4 K) in He droplets.
Collapse
Affiliation(s)
- Amandeep Singh
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, USA
| | - Stefan Bergmeister
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, A-6020 Innsbruck, Austria
| | - Andrew Azhagesan
- Department of Computer Science, University of Southern California, Los Angeles, California 90089, USA
| | - Paul Scheier
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, A-6020 Innsbruck, Austria
| | - Andrey F Vilesov
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, USA
- Department of Physics, University of Southern California, Los Angeles, California 90089, USA
| |
Collapse
|
3
|
Fielicke A. Probing the binding and activation of small molecules by gas-phase transition metal clusters via IR spectroscopy. Chem Soc Rev 2023. [PMID: 37162518 DOI: 10.1039/d2cs00104g] [Citation(s) in RCA: 15] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
Isolated transition metal clusters have been established as useful models for extended metal surfaces or deposited metal particles, to improve the understanding of their surface chemistry and of catalytic reactions. For this objective, an important milestone has been the development of experimental methods for the size-specific structural characterization of clusters and cluster complexes in the gas phase. This review focusses on the characterization of molecular ligands, their binding and activation by small transition metal clusters, using cluster-size specific infrared action spectroscopy. A comprehensive overview and a critical discussion of the experimental data available to date is provided, reaching from the initial results obtained using line-tuneable CO2 lasers to present-day studies applying infrared free electron lasers as well as other intense and broadly tuneable IR laser sources.
Collapse
Affiliation(s)
- André Fielicke
- Fritz-Haber-Institut der Max-Planck-Gesellschaft, 14195 Berlin, Germany.
- Institut für Optik und Atomare Physik, Technische Universität Berlin, 10623 Berlin, Germany
| |
Collapse
|
4
|
Bergmeister S, Ganner L, Locher J, Zappa F, Scheier P, Gruber E. Spectroscopy of helium-tagged molecular ions-Development of a novel experimental setup. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2023; 94:055105. [PMID: 37191466 DOI: 10.1063/5.0144239] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/28/2023] [Accepted: 04/28/2023] [Indexed: 05/17/2023]
Abstract
In this contribution, we present an efficient and alternative method to the commonly used RF-multipole trap technique to produce He-tagged molecular ions at cryogenic temperatures, which are perfectly suitable for messenger spectroscopy. The seeding of dopant ions in multiply charged helium nanodroplets, in combination with a gentle extraction of the latter from the helium matrix, enables the efficient production of He-tagged ion species. With a quadrupole mass filter, a specific ion of interest is selected, merged with a laser beam, and the photoproducts are measured in a time-of-flight mass-spectrometer. The detection of the photofragment signal from a basically zero background is much more sensitive than the depletion of the same amount of signal from precursor ions, delivering high quality spectra at reduced data acquisition times. Proof-of-principle measurements of bare and He-tagged Ar-cluster ions, as well as of He-tagged C60 ions, are presented.
Collapse
Affiliation(s)
- Stefan Bergmeister
- Institute for Ion Physics and Applied Physics, University of Innsbruck, A-6020 Innsbruck, Austria
| | - Lisa Ganner
- Institute for Ion Physics and Applied Physics, University of Innsbruck, A-6020 Innsbruck, Austria
| | - Johannes Locher
- Institute for Ion Physics and Applied Physics, University of Innsbruck, A-6020 Innsbruck, Austria
| | - Fabio Zappa
- Institute for Ion Physics and Applied Physics, University of Innsbruck, A-6020 Innsbruck, Austria
| | - Paul Scheier
- Institute for Ion Physics and Applied Physics, University of Innsbruck, A-6020 Innsbruck, Austria
| | - Elisabeth Gruber
- Institute for Ion Physics and Applied Physics, University of Innsbruck, A-6020 Innsbruck, Austria
| |
Collapse
|
5
|
Albertini S, Gruber E, Zappa F, Krasnokutski S, Laimer F, Scheier P. Chemistry and physics of dopants embedded in helium droplets. MASS SPECTROMETRY REVIEWS 2022; 41:529-567. [PMID: 33993543 DOI: 10.1002/mas.21699] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/25/2021] [Revised: 04/20/2021] [Accepted: 04/20/2021] [Indexed: 05/18/2023]
Abstract
Helium droplets represent a cold inert matrix, free of walls with outstanding properties to grow complexes and clusters at conditions that are perfect to simulate cold and dense regions of the interstellar medium. At sub-Kelvin temperatures, barrierless reactions triggered by radicals or ions have been observed and studied by optical spectroscopy and mass spectrometry. The present review summarizes developments of experimental techniques and methods and recent results they enabled.
Collapse
Affiliation(s)
- Simon Albertini
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Innsbruck, Austria
| | - Elisabeth Gruber
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Innsbruck, Austria
| | - Fabio Zappa
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Innsbruck, Austria
| | - Serge Krasnokutski
- Laboratory Astrophysics Group of the MPI for Astronomy, University of Jena, Jena, Germany
| | - Felix Laimer
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Innsbruck, Austria
| | - Paul Scheier
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Innsbruck, Austria
| |
Collapse
|
6
|
Müller D, Dopfer O. Microsolvation of H 2O +, H 3O +, and CH 3OH 2+ by He in a cryogenic ion trap: structure of solvation shells. Phys Chem Chem Phys 2022; 24:11222-11233. [PMID: 35481676 DOI: 10.1039/d2cp01192a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Due to the weak interactions of He atoms with neutral molecules and ions, the preparation of size-selected clusters for the spectroscopic characterization of their structures, energies, and large amplitude motions is a challenging task. Herein, we generate H2O+Hen (n ≤ 9) and H3O+Hen (n ≤ 5) clusters by stepwise addition of He atoms to mass-selected ions stored in a cryogenic 22-pole ion trap held at 5 K. The population of the clusters as a function of n provides insight into the structure of the first He solvation shell around these ions given by the anisotropy of the cation-He interaction potential. To rationalize the observed cluster size distributions, the structural, energetic, and vibrational properties of the clusters are characterized by ab initio calculations up to the CCSD(T)/aug-cc-pVTZ level. The cluster growth around both the open-shell H2O+ and closed-shell H3O+ ions begins by forming nearly linear and equivalent OH⋯He hydrogen bonds (H-bonds) leading to symmetric structures. The strength of these H-bonds decreases slightly with n due to noncooperative three-body induction forces and is weaker for H3O+ than for H2O+ due to both enhanced charge delocalization and reduced acidity of the OH protons. After filling all available H-bonded sites, addition of further He ligands around H2O+ (n = 3-4) occurs at the electrophilic singly occupied 2pz orbital of O leading to O⋯He p-bonds stabilized by induction and small charge transfer from H2O+ to He. As this orbital is filled for H3O+, He atoms occupy in the n = 4-6 clusters positions between the H-bonded He atoms, leading to a slightly distorted regular hexagon ring for n = 6. Comparison between H3O+Hen and CH3OH2+Hen illustrates that CH3 substitution substantially reduces the acidity of the OH protons, so that only clusters up to n = 2 can be observed. The structure of the solvation sub-shells is visible in both the binding energies and the predicted vibrational OH stretch and bend frequencies.
Collapse
Affiliation(s)
- David Müller
- Institut für Optik und Atomare Physik, Technische Universität Berlin, Hardenbergstr. 36, 10623 Berlin, Germany.
| | - Otto Dopfer
- Institut für Optik und Atomare Physik, Technische Universität Berlin, Hardenbergstr. 36, 10623 Berlin, Germany.
| |
Collapse
|
7
|
Thomas DA, Taccone M, Ober K, Mucha E, Meijer G, von Helden G. Helium Nanodroplet Infrared Action Spectroscopy of the Proton-Bound Dimer of Hydrogen Sulfate and Formate: Examining Nuclear Quantum Effects. J Phys Chem A 2021; 125:9279-9287. [PMID: 34652165 PMCID: PMC8558860 DOI: 10.1021/acs.jpca.1c05705] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
The proton-bound dimer of hydrogen sulfate and formate is an archetypal structure for ionic hydrogen-bonding complexes that contribute to biogenic aerosol nucleation. Of central importance for the structure and properties of this complex is the location of the bridging proton connecting the two conjugate base moieties. The potential energy surface for bridging proton translocation features two local minima, with the proton localized at either the formate or hydrogen sulfate moiety. However, electronic structure methods reveal a shallow potential energy surface governing proton translocation, with a barrier on the order of the zero-point energy. This shallow potential complicates structural assignment and necessitates a consideration of nuclear quantum effects. In this work, we probe the structure of this complex and its isotopologues, utilizing infrared (IR) action spectroscopy of ions captured in helium nanodroplets. The IR spectra indicate a structure in which a proton is shared between the hydrogen sulfate and formate moieties, HSO4-···H+···-OOCH. However, because of the nuclear quantum effects and vibrational anharmonicities associated with the shallow potential for proton translocation, the extent of proton displacement from the formate moiety remains unclear, requiring further experiments or more advanced theoretical treatments for additional insight.
Collapse
Affiliation(s)
- Daniel A Thomas
- Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin, Germany
| | - Martín Taccone
- Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin, Germany
| | - Katja Ober
- Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin, Germany
| | - Eike Mucha
- Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin, Germany
| | - Gerard Meijer
- Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin, Germany
| | - Gert von Helden
- Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin, Germany
| |
Collapse
|
8
|
Erukala S, Feinberg A, Singh A, Vilesov AF. Infrared spectroscopy of carbocations upon electron ionization of ethylene in helium nanodroplets. J Chem Phys 2021; 155:084306. [PMID: 34470362 DOI: 10.1063/5.0062171] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The electron impact ionization of helium droplets doped with ethylene molecules and clusters yields diverse CXHY + cations embedded in the droplets. The ionization primarily produces C2H2 +, C2H3 +, C2H4 +, and CH2 +, whereas larger carbocations are produced upon the reactions of the primary ions with ethylene molecules. The vibrational excitation of the cations leads to the release of bare cations and cations with a few helium atoms attached. The laser excitation spectra of the embedded cations show well resolved vibrational bands with a few wavenumber widths-an order of magnitude less than those previously obtained in solid matrices or molecular beams by tagging techniques. Comparison with the previous studies of free and tagged CH2 +, CH3 +, C2H2 +, C2H3 +, and C2H4 + cations shows that the helium matrix typically introduces a shift in the vibrational frequencies of less than about 20 cm-1, enabling direct comparisons with the results of quantum chemical calculations for structure determination. This work demonstrates a facile technique for the production and spectroscopic study of diverse carbocations, which act as important intermediates in gas and condensed phases.
Collapse
Affiliation(s)
- Swetha Erukala
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, USA
| | - Alexandra Feinberg
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, USA
| | - Amandeep Singh
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, USA
| | - Andrey F Vilesov
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, USA
| |
Collapse
|
9
|
Pandey R, Tran S, Zhang J, Yao Y, Kong W. Bimodal velocity and size distributions of pulsed superfluid helium droplet beams. J Chem Phys 2021; 154:134303. [PMID: 33832230 PMCID: PMC8018796 DOI: 10.1063/5.0047158] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2021] [Accepted: 03/15/2021] [Indexed: 11/14/2022] Open
Abstract
We report detailed measurements of velocities and sizes of superfluid helium droplets produced from an Even-Lavie pulse valve at stagnation pressures of 20-60 atm and temperatures between 5.7 and 18.0 K. By doping neutral droplets with Rhodamine 6G cations produced from an electrospray ionization source and detecting the positively charged droplets at two different locations along the beam path, we determine the velocities of the different groups of droplets. By subjecting the doped droplet beam to a retardation field, size distributions can then be analyzed. We discover that at stagnation temperatures above 8.0 K, a single group of droplets is observed at both locations, but at 8.0 K and below, two different groups of droplets with different velocities are detectable. The slower group, considered from fragmentation of liquid helium, cannot be deterred by the retardation voltage at 9 kV, implying an exceedingly large size. The faster group, considered from condensation of gaseous helium, has a bimodal distribution when the stagnation temperatures are below 12.3 K at 20 and 40 atm, or 16.1 K at 60 atm. We also report similar size measurements using low energy electrons for impact ionization, and this latter method can be used for facile in situ characterization of pulsed droplet beams. The mechanism of the bimodal size distribution of the condensation group and the reason for the coexistence of both the condensation and fragmentation groups remain elusive.
Collapse
Affiliation(s)
- Rahul Pandey
- Department of Chemistry, Oregon State University, Corvallis, Oregon 97331-4003, USA
| | - Steven Tran
- Department of Chemistry, Oregon State University, Corvallis, Oregon 97331-4003, USA
| | - Jie Zhang
- Department of Chemistry, Oregon State University, Corvallis, Oregon 97331-4003, USA
| | - Yuzhong Yao
- Department of Chemistry, Oregon State University, Corvallis, Oregon 97331-4003, USA
| | - Wei Kong
- Department of Chemistry, Oregon State University, Corvallis, Oregon 97331-4003, USA
| |
Collapse
|
10
|
Gloaguen E, Mons M, Schwing K, Gerhards M. Neutral Peptides in the Gas Phase: Conformation and Aggregation Issues. Chem Rev 2020; 120:12490-12562. [PMID: 33152238 DOI: 10.1021/acs.chemrev.0c00168] [Citation(s) in RCA: 39] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Combined IR and UV laser spectroscopic techniques in molecular beams merged with theoretical approaches have proven to be an ideal tool to elucidate intrinsic structural properties on a molecular level. It offers the possibility to analyze structural changes, in a controlled molecular environment, when successively adding aggregation partners. By this, it further makes these techniques a valuable starting point for a bottom-up approach in understanding the forces shaping larger molecular systems. This bottom-up approach was successfully applied to neutral amino acids starting around the 1990s. Ever since, experimental and theoretical methods developed further, and investigations could be extended to larger peptide systems. Against this background, the review gives an introduction to secondary structures and experimental methods as well as a summary on theoretical approaches. Vibrational frequencies being characteristic probes of molecular structure and interactions are especially addressed. Archetypal biologically relevant secondary structures investigated by molecular beam spectroscopy are described, and the influences of specific peptide residues on conformational preferences as well as the competition between secondary structures are discussed. Important influences like microsolvation or aggregation behavior are presented. Beyond the linear α-peptides, the main results of structural analysis on cyclic systems as well as on β- and γ-peptides are summarized. Overall, this contribution addresses current aspects of molecular beam spectroscopy on peptides and related species and provides molecular level insights into manifold issues of chemical and biochemical relevance.
Collapse
Affiliation(s)
- Eric Gloaguen
- CEA, CNRS, Université Paris-Saclay, CEA Paris-Saclay, Bât 522, 91191 Gif-sur-Yvette, France
| | - Michel Mons
- CEA, CNRS, Université Paris-Saclay, CEA Paris-Saclay, Bât 522, 91191 Gif-sur-Yvette, France
| | - Kirsten Schwing
- TU Kaiserslautern & Research Center Optimas, Erwin-Schrödinger-Straße 52, D-67663 Kaiserslautern, Germany
| | - Markus Gerhards
- TU Kaiserslautern & Research Center Optimas, Erwin-Schrödinger-Straße 52, D-67663 Kaiserslautern, Germany
| |
Collapse
|
11
|
Verma D, Erukala S, Vilesov AF. Infrared Spectroscopy of Water and Zundel Cations in Helium Nanodroplets. J Phys Chem A 2020; 124:6207-6213. [DOI: 10.1021/acs.jpca.0c05897] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Affiliation(s)
- Deepak Verma
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, United States
| | - Swetha Erukala
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, United States
| | - Andrey F. Vilesov
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, United States
- Department of Physics and Astronomy, University of Southern California, Los Angeles, California 90089, United States
| |
Collapse
|
12
|
Brieuc F, Schran C, Uhl F, Forbert H, Marx D. Converged quantum simulations of reactive solutes in superfluid helium: The Bochum perspective. J Chem Phys 2020; 152:210901. [DOI: 10.1063/5.0008309] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Affiliation(s)
- Fabien Brieuc
- Lehrstuhl für Theoretische Chemie, Ruhr-Universität Bochum, 44780 Bochum, Germany
| | - Christoph Schran
- Lehrstuhl für Theoretische Chemie, Ruhr-Universität Bochum, 44780 Bochum, Germany
| | - Felix Uhl
- Lehrstuhl für Theoretische Chemie, Ruhr-Universität Bochum, 44780 Bochum, Germany
| | - Harald Forbert
- Center for Solvation Science ZEMOS, Ruhr-Universität Bochum, 44780 Bochum, Germany
| | - Dominik Marx
- Lehrstuhl für Theoretische Chemie, Ruhr-Universität Bochum, 44780 Bochum, Germany
| |
Collapse
|
13
|
Davies JA, Besley NA, Yang S, Ellis AM. Infrared spectroscopy of a small ion solvated by helium: OH stretching region of HeN−HOCO+. J Chem Phys 2019; 151:194307. [DOI: 10.1063/1.5124137] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Julia A. Davies
- Department of Chemistry, University of Leicester, University Road, Leicester LE1 7RH, United Kingdom
| | - Nicholas A. Besley
- School of Chemistry, University of Nottingham, University Park, Nottingham NG7 2RD, United Kingdom
| | - Shengfu Yang
- Department of Chemistry, University of Leicester, University Road, Leicester LE1 7RH, United Kingdom
| | - Andrew M. Ellis
- Department of Chemistry, University of Leicester, University Road, Leicester LE1 7RH, United Kingdom
| |
Collapse
|
14
|
Alghamdi M, Zhang J, Kong W. Doping with multiple cations and failure of charge transfer in large ionized helium droplets. J Chem Phys 2019; 151:134307. [PMID: 31594345 DOI: 10.1063/1.5123735] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We report experimental observations of aniline (A) cations and He2 + when aniline is doped into ionized helium droplets. Large droplets containing 108 atoms are bombarded by energetic electrons, resulting in more than one positive charge in one droplet. When aniline encounters the charged droplets, some are ionized via charge transfer, while others can remain neutral in the presence of He2 + when the mass-to-charge ratio (m/z) of the droplet is sufficiently large. Upon resonant excitation of the dopant An or An + (n ≥ 1), He2 + can be ejected. The excitation spectrum of He2 + becomes a juxtaposition of the spectra of An and An +. Moreover, an anticorrelation between the yields of He2 + and A+ is observed with increasing energies of the ionizing electrons. We attribute this result to the combined effect of reduction in m/z of the droplets and the different locations of He2 + and neutral An. Limited by the penetration depths of the ionizing electrons and further assisted by the Coulomb repulsion of coexisting cations, He2 + is located within 20 nm of the surface, while neutral An has an average position inside a large droplet. Upon resonant excitation of the interior An, He2 + is preferentially ejected. With increasing energies of the colliding electrons, the m/z of the droplets are reduced, leading to less effective charge shielding and more effective charge transfer, until ultimately, all He2 + can be neutralized to form A+.
Collapse
Affiliation(s)
- Maha Alghamdi
- Department of Chemistry, Oregon State University, Corvallis, Oregon 97331-4003, USA
| | - Jie Zhang
- Department of Chemistry, Oregon State University, Corvallis, Oregon 97331-4003, USA
| | - Wei Kong
- Department of Chemistry, Oregon State University, Corvallis, Oregon 97331-4003, USA
| |
Collapse
|
15
|
Abstract
We report suppression of multiphoton ionization (MPI) of aniline doped large superfluid helium droplets containing over 5 × 106 atoms. In contrast, surface-bound sodium atoms and dimers are readily desorbed and ionized. Adequacy of the experimental conditions is also confirmed from ejection of embedded aniline cations from smaller droplets containing multiple cations, and MPI of gaseous aniline. The photoelectrons have a mean-free-path of less than 1 nm and a thermalization distance of 10 nm. In a droplet with a diameter of over 70 nm, effective charge recombination within the droplet is expected.
Collapse
|
16
|
Zeng HJ, Yang N, Johnson MA. Introductory lecture: advances in ion spectroscopy: from astrophysics to biology. Faraday Discuss 2019; 217:8-33. [PMID: 31094388 DOI: 10.1039/c9fd00030e] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
This introduction provides a historical context for the development of ion spectroscopy over the past half century by following the evolution of experimental methods to the present state-of-the-art. Rather than attempt a comprehensive review, we focus on how early work on small ions, carried out with fluorescence, direct absorption, and photoelectron spectroscopy, evolved into powerful technologies that can now address complex chemical problems ranging from catalysis to biophysics. One of these developments is the incorporation of cooling and temperature control to enable the general application of "messenger tagging" vibrational spectroscopy, first carried out using ionized supersonic jets and then with buffer gas cooling in radiofrequency ion traps. Some key advances in the application of time-resolved pump-probe techniques to follow ultrafast dynamics are also discussed, as are significant benchmarks in the refinement of ion mobility to allow spectroscopic investigation of large biopolymers with well-defined shapes. We close with a few remarks on challenges and opportunities to explore molecular level mechanics that drive macroscopic behavior.
Collapse
Affiliation(s)
- Helen J Zeng
- Sterling Chemistry Laboratory, Yale University, New Haven, CT 06520, USA.
| | - Nan Yang
- Sterling Chemistry Laboratory, Yale University, New Haven, CT 06520, USA.
| | - Mark A Johnson
- Sterling Chemistry Laboratory, Yale University, New Haven, CT 06520, USA.
| |
Collapse
|
17
|
Fischer J, Fuchs S, Slenczka A, Karra M, Friedrich B. Microsolvation of porphine molecules in superfluid helium nanodroplets as revealed by optical line shape at the electronic origin. J Chem Phys 2018; 149:244306. [PMID: 30599728 DOI: 10.1063/1.5052615] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We investigate the line shape at the electronic origin of single porphine molecules doped into superfluid helium droplets as a function of the droplet size. Helium droplets comprised of less than 105 atoms are generated from an expansion of gaseous helium, while droplets with more than 105 atoms originate from liquid helium. In contrast to our recent study on phthalocyanine, porphine is found to exhibit a solvent shift to the blue with respect to the gas-phase resonance frequency as well as a multiplet splitting. A comparison of the helium-induced features of phthalocyanine and porphine with those obtained in similar studies on tetracene and pentacene reveals that these occur chiefly as two kinds of excitations distinguished by their linewidths and their dependence on the droplet size. Moreover, at quasi-bulk conditions achieved with droplets in excess of 106 helium atoms, none of these four dopant species yields an optical spectrum that can be assigned to a plausible rotational band structure.
Collapse
Affiliation(s)
- J Fischer
- Institut für Physikalische und Theoretische Chemie, Universität Regensburg, 93053 Regensburg, Germany
| | - S Fuchs
- Institut für Physikalische und Theoretische Chemie, Universität Regensburg, 93053 Regensburg, Germany
| | - A Slenczka
- Institut für Physikalische und Theoretische Chemie, Universität Regensburg, 93053 Regensburg, Germany
| | - M Karra
- Fritz-Haber-Insitut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin, Germany
| | - B Friedrich
- Fritz-Haber-Insitut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin, Germany
| |
Collapse
|
18
|
Debiossac M, Schätti J, Kriegleder M, Geyer P, Shayeghi A, Mayor M, Arndt M, Köhler V. Tailored photocleavable peptides: fragmentation and neutralization pathways in high vacuum. Phys Chem Chem Phys 2018; 20:11412-11417. [PMID: 29645042 PMCID: PMC5932999 DOI: 10.1039/c8cp01058g] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2018] [Accepted: 03/23/2018] [Indexed: 01/31/2023]
Abstract
Photocleavable tags (PCTs) have the potential for excellent spatio-temporal control over the release of subunits of complex molecules. Here, we show that electrosprayed oligopeptides, functionalized by a tailored ortho-nitroarylether can undergo site-specific photo-activated cleavage under UV irradiation (266 nm) in high vacuum. The comparison of UV photodissociation (UVPD) and collision-induced dissociation (CID) points to the thermal nature of the cleavage mechanism, a picture corroborated by the temperature dependence of the process. Two competing photodissociation pathways can be identified. In one case a phenolate anion is separated from a neutral zwitterion. In the other case a neutral phenol derivative leaves a negatively charged peptide behind. To understand the factors favoring one channel over the other, we investigate the influence of the peptide length, the nature of the phenolic group and the position of the nitro-group (ortho vs. para). The observed gas phase cleavage of a para-nitro benzylic ether markedly differs from the established behavior in solution.
Collapse
Affiliation(s)
- M. Debiossac
- Faculty of Physics, University of Vienna , VCQ, Boltzmanngasse 5 , A-1090 Vienna , Austria .
| | - J. Schätti
- Department of Chemistry, University of Basel , Mattenstrasse 24a, BPR 1096 , CH-4058 Basel , Switzerland .
| | - M. Kriegleder
- Faculty of Physics, University of Vienna , VCQ, Boltzmanngasse 5 , A-1090 Vienna , Austria .
| | - P. Geyer
- Faculty of Physics, University of Vienna , VCQ, Boltzmanngasse 5 , A-1090 Vienna , Austria .
| | - A. Shayeghi
- Faculty of Physics, University of Vienna , VCQ, Boltzmanngasse 5 , A-1090 Vienna , Austria .
| | - M. Mayor
- Department of Chemistry, University of Basel , Mattenstrasse 24a, BPR 1096 , CH-4058 Basel , Switzerland .
- Institute of Nanotechnology (INT), Karlsruhe Institute of Technology (KIT) , Hermann-von-Helmholtz-Platz 1 , D-76344 Eggenstein-Leopoldshafen , Germany
- Lehn Institute of Functional Materials (LIFM), Sun Yat-Sen University (SYSU) , Xingang Rd. W. , Guangzhou , China
| | - M. Arndt
- Faculty of Physics, University of Vienna , VCQ, Boltzmanngasse 5 , A-1090 Vienna , Austria .
| | - V. Köhler
- Department of Chemistry, University of Basel , Mattenstrasse 24a, BPR 1096 , CH-4058 Basel , Switzerland .
| |
Collapse
|
19
|
|
20
|
Fine J, Verma D, Jones CF, Wittig C, Vilesov AF. Formation of He4+via electron impact of helium droplets. J Chem Phys 2018; 148:044302. [DOI: 10.1063/1.5001715] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Jordan Fine
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, USA
| | - Deepak Verma
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, USA
| | - Curtis F. Jones
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, USA
| | - Curt Wittig
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, USA
| | - Andrey F. Vilesov
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, USA
| |
Collapse
|
21
|
Alghamdi M, Zhang J, Oswalt A, Porter JJ, Mehl RA, Kong W. Doping of Green Fluorescent Protein into Superfluid Helium Droplets: Size and Velocity of Doped Droplets. J Phys Chem A 2017; 121:6671-6678. [PMID: 28825305 PMCID: PMC5713884 DOI: 10.1021/acs.jpca.7b05718] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
We report doping of green fluorescent protein from an electrospray ionization (ESI) source into superfluid helium droplets. From analyses of the time profiles of the doped droplets, we identify two distinct groups of droplets. The faster group has a smaller average size, on the order of 106 helium atoms/droplet, and the slower group is much larger, by at least an order of magnitude. The relative populations of these two groups depend on the temperature of the droplet source: from 11 to 5 K, the signal intensity of the slower droplet group gradually increases, from near the detection limit to comparable to that of the faster group. We postulate that the smaller droplets are formed via condensation of gaseous helium upon expansion from the pulsed valve, while the larger droplets develop from fragmentation of ejected liquid helium. Our results on the size and velocity of the condensation peak at higher source temperatures (>7 K) agree with previous reports, but those at lower temperatures (<7 K) seem to be off. We attribute this discrepancy to the masking effect of the exceedingly large droplets from the fragmentation peak in previous measurements of droplet sizes. Within the temperature range of our investigation, although the expansion condition changes from subcritical to supercritical, there is no abrupt change in either the velocity distribution or the size distribution of the condensation peak, and the most salient effect is in the increasing intensity of the fragmentation peak. The absolute doping efficiency, as expressed by the ratio of ion-doped droplets over the total number of ions from the ESI source, is on the order of 10-4, while only hundreds of doped ions have been detected. Further improvements in the ESI source are key to extending the technology for future experiments. On the other hand, the separation of the two groups of droplets in velocity is beneficial for size selection of only the smaller droplets for future experiments of electron diffraction.
Collapse
Affiliation(s)
- Maha Alghamdi
- Department of Chemistry, Oregon State University, Corvallis, Oregon 97331, USA
| | - Jie Zhang
- Department of Chemistry, Oregon State University, Corvallis, Oregon 97331, USA
| | - Andrew Oswalt
- Department of Chemistry, Oregon State University, Corvallis, Oregon 97331, USA
| | - Joseph J. Porter
- Department of Biochemistry and Biophysics, Oregon State University, 2011 Agricultural and Life Science building, Corvallis, Oregon 97331, USA
| | - Ryan A. Mehl
- Department of Biochemistry and Biophysics, Oregon State University, 2011 Agricultural and Life Science building, Corvallis, Oregon 97331, USA
| | - Wei Kong
- Department of Chemistry, Oregon State University, Corvallis, Oregon 97331, USA
| |
Collapse
|
22
|
${{{\rm{C}}}_{60}}^{+}$ and the Diffuse Interstellar Bands: An Independent Laboratory Check. ACTA ACUST UNITED AC 2017. [DOI: 10.3847/1538-4357/aa82bc] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
|
23
|
Mani D, Fischer T, Schwan R, Dey A, Redlich B, Van der Meer AFG, Schwaab G, Havenith M. A helium nanodroplet setup for mid and far-infrared spectroscopy using pulsed-free-electron lasers: vibrational spectra of propargyl alcohol. RSC Adv 2017. [DOI: 10.1039/c7ra08102b] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Helium nanodroplets spectroscopy in combination with free electron laser. The combination is suitable for studying molecular clusters in 66–3600 cm−1 spectral range, covering the important low-frequency large amplitude intra and inter-molecular motions.
Collapse
Affiliation(s)
- Devendra Mani
- Lehrstuhl für Physikalische Chemie II
- Ruhr Universität Bochum
- 44801 Bochum
- Germany
| | - Theo Fischer
- Lehrstuhl für Physikalische Chemie II
- Ruhr Universität Bochum
- 44801 Bochum
- Germany
| | - Raffael Schwan
- Lehrstuhl für Physikalische Chemie II
- Ruhr Universität Bochum
- 44801 Bochum
- Germany
| | - Arghya Dey
- Lehrstuhl für Physikalische Chemie II
- Ruhr Universität Bochum
- 44801 Bochum
- Germany
- Radboud University
| | - Britta Redlich
- Radboud University
- Institute for Molecules and Materials
- FELIX Laboratory
- 6525 ED Nijmegen
- The Netherlands
| | - A. F. G. Van der Meer
- Radboud University
- Institute for Molecules and Materials
- FELIX Laboratory
- 6525 ED Nijmegen
- The Netherlands
| | - Gerhard Schwaab
- Lehrstuhl für Physikalische Chemie II
- Ruhr Universität Bochum
- 44801 Bochum
- Germany
| | - Martina Havenith
- Lehrstuhl für Physikalische Chemie II
- Ruhr Universität Bochum
- 44801 Bochum
- Germany
| |
Collapse
|
24
|
Atomically resolved phase transition of fullerene cations solvated in helium droplets. Nat Commun 2016; 7:13550. [PMID: 27874002 PMCID: PMC5121423 DOI: 10.1038/ncomms13550] [Citation(s) in RCA: 72] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2016] [Accepted: 10/13/2016] [Indexed: 12/11/2022] Open
Abstract
Helium has a unique phase diagram and below 25 bar it does not form a solid even at the lowest temperatures. Electrostriction leads to the formation of a solid layer of helium around charged impurities at much lower pressures in liquid and superfluid helium. These so-called ‘Atkins snowballs' have been investigated for several simple ions. Here we form HenC60+ complexes with n exceeding 100 via electron ionization of helium nanodroplets doped with C60. Photofragmentation of these complexes is measured by merging a tunable narrow-bandwidth laser beam with the ions. A switch from red- to blueshift of the absorption frequency of HenC60+ on addition of He atoms at n=32 is associated with a phase transition in the attached helium layer from solid to partly liquid (melting of the Atkins snowball). Elaborate molecular dynamics simulations using a realistic force field and including quantum effects support this interpretation. 'Atkins snowballs', solid layers of helium around an ion core in bulk superfluid He, have been investigated for simple ions but many properties remain unknown. Here, the authors show via photofragmentation experiments that a phase transition occurs in C60-doped He droplets depending on the number of He atoms.
Collapse
|
25
|
Schwing K, Gerhards M. Investigations on isolated peptides by combined IR/UV spectroscopy in a molecular beam – structure, aggregation, solvation and molecular recognition. INT REV PHYS CHEM 2016. [DOI: 10.1080/0144235x.2016.1229331] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
|
26
|
He Y, Zhang J, Kong W. Electron diffraction of CBr4 in superfluid helium droplets: A step towards single molecule diffraction. J Chem Phys 2016; 145:034307. [PMID: 27448887 PMCID: PMC4958107 DOI: 10.1063/1.4958931] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2016] [Accepted: 07/05/2016] [Indexed: 11/14/2022] Open
Abstract
We demonstrate the practicality of electron diffraction of single molecules inside superfluid helium droplets using CBr4 as a testing case. By reducing the background from pure undoped droplets via multiple doping, with small corrections for dimers and trimers, clearly resolved diffraction rings of CBr4 similar to those of gas phase molecules can be observed. The experimental data from CBr4 doped droplets are in agreement with both theoretical calculations and with experimental results of gaseous species. The abundance of monomers and clusters in the droplet beam also qualitatively agrees with the Poisson statistics. Possible extensions of this approach to macromolecular ions will also be discussed. This result marks the first step in building a molecular goniometer using superfluid helium droplet cooling and field induced orientation. The superior cooling effect of helium droplets is ideal for field induced orientation, but the diffraction background from helium is a concern. This work addresses this background issue and identifies a possible solution. Accumulation of diffraction images only becomes meaningful when all images are produced from molecules oriented in the same direction, and hence a molecular goniometer is a crucial technology for serial diffraction of single molecules.
Collapse
Affiliation(s)
- Yunteng He
- Department of Chemistry, Oregon State University, Corvallis, Oregon 97331-4003, USA
| | - Jie Zhang
- Department of Chemistry, Oregon State University, Corvallis, Oregon 97331-4003, USA
| | - Wei Kong
- Department of Chemistry, Oregon State University, Corvallis, Oregon 97331-4003, USA
| |
Collapse
|
27
|
Leal A, Zhang X, Barranco M, Cargnoni F, Hernando A, Mateo D, Mella M, Drabbels M, Pi M. Dynamics of photoexcited Ba(+) cations in (4)He nanodroplets. J Chem Phys 2016; 144:094302. [PMID: 26957164 DOI: 10.1063/1.4942850] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
We present a joint experimental and theoretical study on the desolvation of Ba(+) cations in (4)He nanodroplets excited via the 6p ← 6s transition. The experiments reveal an efficient desolvation process yielding mainly bare Ba(+) cations and Ba(+)Hen exciplexes with n = 1 and 2. The speed distributions of the ions are well described by Maxwell-Boltzmann distributions with temperatures ranging from 60 to 178 K depending on the excitation frequency and Ba(+) Hen exciplex size. These results have been analyzed by calculations based on a time-dependent density functional description for the helium droplet combined with classical dynamics for the Ba(+). In agreement with experiment, the calculations reveal the dynamical formation of exciplexes following excitation of the Ba(+) cation. In contrast to experimental observation, the calculations do not reveal desolvation of excited Ba(+) cations or exciplexes, even when relaxation pathways to lower lying states are included.
Collapse
Affiliation(s)
- Antonio Leal
- Departament ECM, Facultat de Física, and INUB, Universitat de Barcelona, Diagonal 645, 08028 Barcelona, Spain
| | - Xiaohang Zhang
- Laboratoire de Chimie Physique Moléculaire, Swiss Federal Institute of Technology Lausanne (EPFL), CH-1015 Lausanne, Switzerland
| | - Manuel Barranco
- Departament ECM, Facultat de Física, and INUB, Universitat de Barcelona, Diagonal 645, 08028 Barcelona, Spain
| | - Fausto Cargnoni
- Istituto di Scienze e Tecnologie Molecolari (ISTM), Consiglio Nazionale delle Ricerche, via Golgi 19, 20133 Milano, Italy
| | - Alberto Hernando
- Social Thermodynamics Applied Research (SThAR), EPFL Innovation Park, Bâtiment C, CH-1015 Lausanne, Switzerland
| | - David Mateo
- Department of Chemistry and Biochemistry, California State University at Northridge, Northridge, California 91330, USA
| | - Massimo Mella
- Dipartimento di Scienza ed Alta Tecnologia, Università degli Studi dell'Insubria, via Valleggio 11, 22100 Como, Italy
| | - Marcel Drabbels
- Laboratoire de Chimie Physique Moléculaire, Swiss Federal Institute of Technology Lausanne (EPFL), CH-1015 Lausanne, Switzerland
| | - Martí Pi
- Departament ECM, Facultat de Física, and INUB, Universitat de Barcelona, Diagonal 645, 08028 Barcelona, Spain
| |
Collapse
|
28
|
González Flórez AI, Mucha E, Ahn DS, Gewinner S, Schöllkopf W, Pagel K, von Helden G. Charge-Induced Unzipping of Isolated Proteins to a Defined Secondary Structure. Angew Chem Int Ed Engl 2016; 55:3295-9. [PMID: 26847383 PMCID: PMC4770441 DOI: 10.1002/anie.201510983] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2015] [Indexed: 11/08/2022]
Abstract
Here we present a combined experimental and theoretical study on the secondary structure of isolated proteins as a function of charge state. In infrared spectra of the proteins ubiquitin and cytochrome c, amide I (C=O stretch) and amide II (N-H bend) bands can be found at positions that are typical for condensed-phase proteins. For high charge states a new band appears, substantially red-shifted from the amide II band observed at lower charge states. The observations are interpreted in terms of Coulomb-driven transitions in secondary structures from mostly helical to extended C5 -type hydrogen-bonded structures. Support for this interpretation comes from simple energy considerations as well as from quantum chemical calculations on model peptides. This transition in secondary structure is most likely universal for isolated proteins that occur in mass spectrometric experiments.
Collapse
Affiliation(s)
| | - Eike Mucha
- Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195, Berlin, Germany
| | - Doo-Sik Ahn
- Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195, Berlin, Germany
| | - Sandy Gewinner
- Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195, Berlin, Germany
| | - Wieland Schöllkopf
- Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195, Berlin, Germany
| | - Kevin Pagel
- Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195, Berlin, Germany
- Institut für Chemie und Biochemie der Freien Universität Berlin, Takustrasse 3, 14195, Berlin, Germany
| | - Gert von Helden
- Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195, Berlin, Germany.
| |
Collapse
|
29
|
González Flórez AI, Mucha E, Ahn DS, Gewinner S, Schöllkopf W, Pagel K, von Helden G. Ladungsinduziertes Entwinden isolierter Proteine zu einer definierten Sekundärstruktur. Angew Chem Int Ed Engl 2016. [DOI: 10.1002/ange.201510983] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
| | - Eike Mucha
- Fritz-Haber-Institut der Max-Planck-Gesellschaft; Faradayweg 4-6 14195 Berlin Deutschland
| | - Doo-Sik Ahn
- Fritz-Haber-Institut der Max-Planck-Gesellschaft; Faradayweg 4-6 14195 Berlin Deutschland
| | - Sandy Gewinner
- Fritz-Haber-Institut der Max-Planck-Gesellschaft; Faradayweg 4-6 14195 Berlin Deutschland
| | - Wieland Schöllkopf
- Fritz-Haber-Institut der Max-Planck-Gesellschaft; Faradayweg 4-6 14195 Berlin Deutschland
| | - Kevin Pagel
- Fritz-Haber-Institut der Max-Planck-Gesellschaft; Faradayweg 4-6 14195 Berlin Deutschland
- Institut für Chemie und Biochemie der Freien Universität Berlin; Takustraße 3 14195 Berlin Deutschland
| | - Gert von Helden
- Fritz-Haber-Institut der Max-Planck-Gesellschaft; Faradayweg 4-6 14195 Berlin Deutschland
| |
Collapse
|
30
|
Katzy R, Singer M, Izadnia S, LaForge AC, Stienkemeier F. Doping He droplets by laser ablation with a pulsed supersonic jet source. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2016; 87:013105. [PMID: 26827307 DOI: 10.1063/1.4939668] [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
Laser ablation offers the possibility to study a rich number of atoms, molecules, and clusters in the gas phase. By attaching laser ablated materials to helium nanodroplets, one can gain highly resolved spectra of isolated species in a cold, weakly perturbed system. Here, we present a new setup for doping pulsed helium nanodroplet beams by means of laser ablation. In comparison to more well-established techniques using a continuous nozzle, pulsed nozzles show significant differences in the doping efficiency depending on certain experimental parameters (e.g., position of the ablation plume with respect to the droplet formation, nozzle design, and expansion conditions). In particular, we demonstrate that when the ablation region overlaps with the droplet formation region, one also creates a supersonic beam of helium atoms seeded with the sample material. The processes are characterized using a surface ionization detector. The overall doping signal is compared to that of conventional oven cell doping showing very similar dependence on helium stagnation conditions, indicating a comparable doping process. Finally, the ablated material was spectroscopically studied via laser induced fluorescence.
Collapse
Affiliation(s)
- R Katzy
- Physikalisches Institut, Universität Freiburg, 79104 Freiburg, Germany
| | - M Singer
- Physikalisches Institut, Universität Freiburg, 79104 Freiburg, Germany
| | - S Izadnia
- Physikalisches Institut, Universität Freiburg, 79104 Freiburg, Germany
| | - A C LaForge
- Physikalisches Institut, Universität Freiburg, 79104 Freiburg, Germany
| | - F Stienkemeier
- Physikalisches Institut, Universität Freiburg, 79104 Freiburg, Germany
| |
Collapse
|
31
|
Tanyag RMP, Bernando C, Jones CF, Bacellar C, Ferguson KR, Anielski D, Boll R, Carron S, Cryan JP, Englert L, Epp SW, Erk B, Foucar L, Gomez LF, Hartmann R, Neumark DM, Rolles D, Rudek B, Rudenko A, Siefermann KR, Ullrich J, Weise F, Bostedt C, Gessner O, Vilesov AF. Communication: X-ray coherent diffractive imaging by immersion in nanodroplets. STRUCTURAL DYNAMICS (MELVILLE, N.Y.) 2015; 2:051102. [PMID: 26798821 PMCID: PMC4711653 DOI: 10.1063/1.4933297] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/27/2015] [Accepted: 10/05/2015] [Indexed: 05/12/2023]
Abstract
Lensless x-ray microscopy requires the recovery of the phase of the radiation scattered from a specimen. Here, we demonstrate a de novo phase retrieval technique by encapsulating an object in a superfluid helium nanodroplet, which provides both a physical support and an approximate scattering phase for the iterative image reconstruction. The technique is robust, fast-converging, and yields the complex density of the immersed object. Images of xenon clusters embedded in superfluid helium droplets reveal transient configurations of quantum vortices in this fragile system.
Collapse
Affiliation(s)
- Rico Mayro P Tanyag
- Department of Chemistry, University of Southern California , Los Angeles, California 90089, USA
| | - Charles Bernando
- Department of Physics and Astronomy, University of Southern California , Los Angeles, California 90089, USA
| | - Curtis F Jones
- Department of Chemistry, University of Southern California , Los Angeles, California 90089, USA
| | | | - Ken R Ferguson
- Linac Coherent Light Source, LCLS, SLAC National Accelerator Laboratory , 2575 Sand Hill Road, Menlo Park, California 94025, USA
| | | | | | - Sebastian Carron
- Linac Coherent Light Source, LCLS, SLAC National Accelerator Laboratory , 2575 Sand Hill Road, Menlo Park, California 94025, USA
| | - James P Cryan
- Chemical Sciences Division, Lawrence Berkeley National Laboratory , Berkeley, California 94720, USA
| | - Lars Englert
- Max-Planck-Institut für extraterrestrische Physik , Giessenbachstraße, 85741 Garching, Germany
| | | | | | | | - Luis F Gomez
- Department of Chemistry, University of Southern California , Los Angeles, California 90089, USA
| | | | | | | | | | | | - Katrin R Siefermann
- Chemical Sciences Division, Lawrence Berkeley National Laboratory , Berkeley, California 94720, USA
| | | | - Fabian Weise
- Chemical Sciences Division, Lawrence Berkeley National Laboratory , Berkeley, California 94720, USA
| | | | - Oliver Gessner
- Chemical Sciences Division, Lawrence Berkeley National Laboratory , Berkeley, California 94720, USA
| | | |
Collapse
|
32
|
Zhang J, Chen L, Freund WM, Kong W. Effective doping of low energy ions into superfluid helium droplets. J Chem Phys 2015; 143:074201. [PMID: 26298127 PMCID: PMC4545055 DOI: 10.1063/1.4928689] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2015] [Accepted: 08/05/2015] [Indexed: 11/14/2022] Open
Abstract
We report a facile method of doping cations from an electrospray ionization (ESI) source into superfluid helium droplets. By decelerating and stopping the ion pulse of reserpine and substance P from an ESI source in the path of the droplet beam, about 10(4) ion-doped droplets (one ion per droplet) can be recorded, corresponding to a pickup efficiency of nearly 1 out of 1000 ions. We attribute the success of this simple approach to the long residence time of the cations in the droplet beam. The resulting size of the doped droplets, on the order of 10(5)/droplet, is measured using deflection and retardation methods. Our method does not require an ion trap in the doping region, which significantly simplifies the experimental setup and procedure for future spectroscopic and diffraction studies.
Collapse
Affiliation(s)
- Jie Zhang
- Department of Chemistry, Oregon State University, Corvallis, Oregon 97331, USA
| | - Lei Chen
- Department of Chemistry, Oregon State University, Corvallis, Oregon 97331, USA
| | - William M Freund
- Department of Chemistry, Oregon State University, Corvallis, Oregon 97331, USA
| | - Wei Kong
- Department of Chemistry, Oregon State University, Corvallis, Oregon 97331, USA
| |
Collapse
|
33
|
He Y, Zhang J, Li Y, Freund WM, Kong W. Facile time-of-flight methods for characterizing pulsed superfluid helium droplet beams. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2015; 86:084102. [PMID: 26329210 PMCID: PMC4537483 DOI: 10.1063/1.4928107] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/19/2015] [Accepted: 07/25/2015] [Indexed: 05/29/2023]
Abstract
We present two facile time-of-flight (TOF) methods of detecting superfluid helium droplets and droplets with neutral dopants. Without an electron gun and with only a heated filament and pulsed electrodes, the electron impact ionization TOF mass spectrometer can resolve ionized helium clusters such as He2(+) and He4(+), which are signatures of superfluid helium droplets. Without ionizing any helium atoms, multiphoton non-resonant laser ionization of CCl4 doped in superfluid helium droplets at 266 nm generates complex cluster ions of dopant fragments with helium atoms, including (He)(n)C(+), (He)(n)Cl(+), and (He)(n)CCl(+). Using both methods, we have characterized our cryogenic pulsed valve—the Even-Lavie valve. We have observed a primary pulse with larger helium droplets traveling at a slower speed and a rebound pulse with smaller droplets at a faster speed. In addition, the pickup efficiency of dopant is higher for the primary pulse when the nozzle temperature is higher than 13 K, and the total time duration of the doped droplet pulse is only on the order of 20 μs. These results stress the importance of fast and easy characterization of the droplet beam for sensitive measurements such as electron diffraction of doped droplets.
Collapse
Affiliation(s)
- Yunteng He
- Department of Chemistry, Oregon State University, Corvallis, Oregon 97331, USA
| | - Jie Zhang
- Department of Chemistry, Oregon State University, Corvallis, Oregon 97331, USA
| | - Yang Li
- Department of Chemistry, Oregon State University, Corvallis, Oregon 97331, USA
| | - William M Freund
- Department of Chemistry, Oregon State University, Corvallis, Oregon 97331, USA
| | - Wei Kong
- Department of Chemistry, Oregon State University, Corvallis, Oregon 97331, USA
| |
Collapse
|
34
|
Chen L, Zhang J, Freund WM, Kong W. Effect of kinetic energy on the doping efficiency of cesium cations into superfluid helium droplets. J Chem Phys 2015; 143:044310. [PMID: 26233132 PMCID: PMC4522010 DOI: 10.1063/1.4927471] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2015] [Accepted: 07/15/2015] [Indexed: 11/14/2022] Open
Abstract
We present an experimental investigation of the effect of kinetic energy on the ion doping efficiency of superfluid helium droplets using cesium cations from a thermionic emission source. The kinetic energy of Cs(+) is controlled by the bias voltage of a collection grid collinearly arranged with the droplet beam. Efficient doping from ions with kinetic energies from 20 eV up to 480 V has been observed in different sized helium droplets. The relative ion doping efficiency is determined by both the kinetic energy of the ions and the average size of the droplet beam. At a fixed source temperature, the number of doped droplets increases with increasing grid voltage, while the relative ion doping efficiency decreases. This result implies that not all ions are captured upon encountering with a sufficiently large droplet, a deviation from the near unity doping efficiency for closed shell neutral molecules. We propose that this drop in ion doping efficiency with kinetic energy is related to the limited deceleration rate inside a helium droplet. When the source temperature changes from 14 K to 17 K, the relative ion doping efficiency decreases rapidly, perhaps due to the lack of viable sized droplets. The size distribution of the Cs(+)-doped droplet beam can be measured by deflection and by energy filtering. The observed doped droplet size is about 5 × 10(6) helium atoms when the source temperature is between 14 K and 17 K.
Collapse
Affiliation(s)
- Lei Chen
- Department of Chemistry, Oregon State University, Corvallis, Oregon 97331, USA
| | - Jie Zhang
- Department of Chemistry, Oregon State University, Corvallis, Oregon 97331, USA
| | - William M Freund
- Department of Chemistry, Oregon State University, Corvallis, Oregon 97331, USA
| | - Wei Kong
- Department of Chemistry, Oregon State University, Corvallis, Oregon 97331, USA
| |
Collapse
|
35
|
González Flórez AI, Ahn DS, Gewinner S, Schöllkopf W, von Helden G. IR spectroscopy of protonated leu-enkephalin and its 18-crown-6 complex embedded in helium droplets. Phys Chem Chem Phys 2015; 17:21902-11. [DOI: 10.1039/c5cp02172c] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Ultracold IR spectra of protonated leu-enkephalin and its 18-crown-6 complex embedded in superfluid helium droplets have been recorded using a free-electron laser as radiation source.
Collapse
Affiliation(s)
| | - Doo-Sik Ahn
- Fritz-Haber-Institut der Max-Planck-Gesellschaft
- 14195 Berlin
- Germany
| | - Sandy Gewinner
- Fritz-Haber-Institut der Max-Planck-Gesellschaft
- 14195 Berlin
- Germany
| | | | - Gert von Helden
- Fritz-Haber-Institut der Max-Planck-Gesellschaft
- 14195 Berlin
- Germany
| |
Collapse
|
36
|
Zhang X, Drabbels M. Elementary Excitations of Superfluid Helium Droplets Probed by Ion Spectroscopy. J Phys Chem Lett 2014; 5:3100-3105. [PMID: 26276319 DOI: 10.1021/jz501530e] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Electronic spectra of molecules in helium droplets reveal spectral features that are related to the elementary excitations of the superfluid helium environment. In order to determine to what extent the interaction strength of the molecule with the helium affects these excitations, the spectrum corresponding to the B̃(2)A″ ← X̃ (2)A″ transition of 2,5-difluorophenol cations in helium droplets has been recorded. The vibronic resonances reveal a sharp zero-phonon line whose width is largely determined by the rotational band contour, followed by a broad structureless phonon wing at higher frequencies. The splitting between the zero-phonon line and phonon wing is approximately half of that found for neutral 2,5-difluorophenol. This difference is attributed to the increased helium density around the ion due to its strong interaction with the helium.
Collapse
Affiliation(s)
- Xiaohang Zhang
- Laboratoire de Chimie Physique Moléculaire, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
| | - Marcel Drabbels
- Laboratoire de Chimie Physique Moléculaire, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
| |
Collapse
|
37
|
|
38
|
DiStasio RA, Gobre VV, Tkatchenko A. Many-body van der Waals interactions in molecules and condensed matter. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2014; 26:213202. [PMID: 24805055 DOI: 10.1088/0953-8984/26/21/213202] [Citation(s) in RCA: 88] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
This work reviews the increasing evidence that many-body van der Waals (vdW) or dispersion interactions play a crucial role in the structure, stability and function of a wide variety of systems in biology, chemistry and physics. Starting with the exact expression for the electron correlation energy provided by the adiabatic connection fluctuation-dissipation theorem, we derive both pairwise and many-body interatomic methods for computing the long-range dispersion energy by considering a model system of coupled quantum harmonic oscillators within the random-phase approximation. By coupling this approach to density functional theory, the resulting many-body dispersion (MBD) method provides an accurate and efficient scheme for computing the frequency-dependent polarizability and many-body vdW energy in molecules and materials with a finite electronic gap. A select collection of applications are presented that ascertain the fundamental importance of these non-bonded interactions across the spectrum of intermolecular (the S22 and S66 benchmark databases), intramolecular (conformational energies of alanine tetrapeptide) and supramolecular (binding energy of the 'buckyball catcher') complexes, as well as molecular crystals (cohesive energies in oligoacenes). These applications demonstrate that electrodynamic response screening and beyond-pairwise many-body vdW interactions--both captured at the MBD level of theory--play a quantitative, and sometimes even qualitative, role in describing the properties considered herein. This work is then concluded with an in-depth discussion of the challenges that remain in the future development of reliable (accurate and efficient) methods for treating many-body vdW interactions in complex materials and provides a roadmap for navigating many of the research avenues that are yet to be explored.
Collapse
Affiliation(s)
- Robert A DiStasio
- Department of Chemistry, Princeton University, Princeton, NJ 08544, USA
| | | | | |
Collapse
|
39
|
Rijs AM, Oomens J. IR Spectroscopic Techniques to Study Isolated Biomolecules. Top Curr Chem (Cham) 2014; 364:1-42. [DOI: 10.1007/128_2014_621] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
|
40
|
Brauer NB, Smolarek S, Loginov E, Mateo D, Hernando A, Pi M, Barranco M, Buma WJ, Drabbels M. Critical Landau velocity in helium nanodroplets. PHYSICAL REVIEW LETTERS 2013; 111:153002. [PMID: 24160595 DOI: 10.1103/physrevlett.111.153002] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/06/2013] [Indexed: 06/02/2023]
Abstract
The best-known property of superfluid helium is the vanishing viscosity that objects experience while moving through the liquid with speeds below the so-called critical Landau velocity. This critical velocity is generally considered a macroscopic property as it is related to the collective excitations of the helium atoms in the liquid. In the present work we determine to what extent this concept can still be applied to nanometer-scale, finite size helium systems. To this end, atoms and molecules embedded in helium nanodroplets of various sizes are accelerated out of the droplets by means of optical excitation, and the speed distributions of the ejected particles are determined. The measurements reveal the existence of a critical velocity in these systems, even for nanodroplets consisting of only a thousand helium atoms. Accompanying theoretical simulations based on a time-dependent density functional description of the helium confirm and further elucidate this experimental finding.
Collapse
Affiliation(s)
- Nils B Brauer
- Laboratoire de Chimie Physique Moléculaire, Ecole polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
| | | | | | | | | | | | | | | | | |
Collapse
|
41
|
Pentlehner D, Nielsen JH, Slenczka A, Mølmer K, Stapelfeldt H. Impulsive laser induced alignment of molecules dissolved in helium nanodroplets. PHYSICAL REVIEW LETTERS 2013; 110:093002. [PMID: 23496707 DOI: 10.1103/physrevlett.110.093002] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/07/2012] [Indexed: 06/01/2023]
Abstract
We show that a 450 fs nonresonant, moderately intense, linearly polarized laser pulse can induce field-free molecular axis alignment of methyliodide (CH(3)I) molecules dissolved in a helium nanodroplet. Time-resolved measurements reveal rotational dynamics much slower than that of isolated molecules and absence of the sharp transient alignment recurrences characteristic of gas phase molecules. Our results presage a range of new opportunities for exploring both molecular dynamics in a dissipative environment and the properties of He nanodroplets.
Collapse
|
42
|
Sunahori FX, Yang G, Kitova EN, Klassen JS, Xu Y. Chirality recognition of the protonated serine dimer and octamer by infrared multiphoton dissociation spectroscopy. Phys Chem Chem Phys 2013; 15:1873-86. [DOI: 10.1039/c2cp43296j] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
|
43
|
Asmis KR. Structure characterization of metal oxide clusters by vibrational spectroscopy: possibilities and prospects. Phys Chem Chem Phys 2012; 14:9270-81. [PMID: 22569919 DOI: 10.1039/c2cp40762k] [Citation(s) in RCA: 95] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
This article summarizes the methodological progress that has been made in the vibrational spectroscopy of isolated polynuclear metal oxide clusters, with particular emphasis on free electron laser-based infrared action spectroscopy of gas phase clusters, over the last decade. The possibilities, limitations and prospects of the various experimental approaches are discussed using representative examples from pivotal studies in the field.
Collapse
Affiliation(s)
- Knut R Asmis
- Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, D-14195 Berlin, Germany.
| |
Collapse
|
44
|
Abstract
Helium droplets spanning a wide size range, N(He) = 10(3)-10(10), were formed in a continuous-nozzle beam expansion at different nozzle temperatures and a constant stagnation pressure of 20 bars. The average sizes of the droplets have been obtained by attenuation of the droplet beam through collisions with argon and helium gases at room temperature. The results obtained are in good agreement with previous measurements in the size range N(He) = 10(5)-10(7). Moreover, the measurements give the average sizes in the previously uncharacterized range of very large droplets of 10(7)-10(10) atoms. The droplet sizes and beam flux increase rapidly at nozzle temperatures below 6 K, which is ascribed to the formation of droplets within the nozzle interior. The mass spectra of the droplet beam upon electron impact ionization have also been obtained. The spectra show a large increase in the intensity of the He(4) (+) signal upon increase of the droplet size, an effect which can be used as a secondary size standard in the droplet size range N(He) = 10(4)-10(9) atoms.
Collapse
Affiliation(s)
- Luis F Gomez
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, USA
| | | | | | | |
Collapse
|
45
|
Zhang X, Brauer NB, Berden G, Rijs AM, Drabbels M. Mid-infrared spectroscopy of molecular ions in helium nanodroplets. J Chem Phys 2012; 136:044305. [DOI: 10.1063/1.3678011] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
|
46
|
Filsinger F, Ahn DS, Meijer G, von Helden G. Photoexcitation of mass/charge selected hemin+, caught in helium nanodroplets. Phys Chem Chem Phys 2012; 14:13370-7. [DOI: 10.1039/c2cp42071f] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
|
47
|
Antoine R, Dugourd P. Visible and ultraviolet spectroscopy of gas phase protein ions. Phys Chem Chem Phys 2011; 13:16494-509. [PMID: 21811728 DOI: 10.1039/c1cp21531k] [Citation(s) in RCA: 106] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Optical spectroscopy has contributed enormously to our knowledge of the structure and dynamics of atoms and molecules and is now emerging as a cornerstone of the gas phase methods available for investigating biomolecular ions. This article focuses on the UV and visible spectroscopy of peptide and protein ions stored in ion traps, with emphasis placed on recent results obtained on protein polyanions, by electron photodetachment experiments. We show that among a large number of possible de-excitation pathways, the relaxation of biomolecular polyanions is mainly achieved by electron emission following photo-excitation in electronically excited states. Electron photodetachment is a fast process that occurs prior to relaxation on vibrational degrees of freedom. Electron photodetachment yield can then be used to record gas phase action spectra for systems as large as entire proteins, without the limitation of system size that would arise from energy redistribution on numerous modes and prevent fragmentation after the absorption of a photon. The optical activity of proteins in the near UV is directly related to the electronic structure and optical absorption of aromatic amino acids (Trp, Phe and Tyr). UV spectra for peptides and proteins containing neutral, deprotonated and radical aromatic amino acids were recorded. They displayed strong bathochromic shifts. In particular, the results outline the privileged role played by open shell ions in molecular spectroscopy which, in the case of biomolecules, is directly related to their reactivity and biological functions. The optical shifts observed are sufficient to provide unambiguous fingerprints of the electronic structure of chromophores without the requirement of theoretical calculations. They constitute benchmarks for calculating the absorption spectra of chromophores embedded in entire proteins and could be used in the future to study biochemical processes in the gas phase involving charge transfer in aromatic amino acids, such as in the mediation of electron transfer or redox reactions. We then addressed the important question of the sensitivity of protein optical spectra to the intrinsic properties of protein ions, including conformation, charge state, etc., and to environmental factors. We report optical spectra for different charge states of insulin, for ubiquitin starting from native and denaturated solutions, and for apo-myoglobin protein. All these spectra are compared critically to spectra recorded in solution, in order to assess solvent effects. We also report the spectra of peptides complexed with metal cations and show that complexation gives rise to new optical transitions related to charge transfer types of excitation. The perspectives of this work include integrative approaches where UV-Vis spectroscopy could, for example, be combined with ion mobility spectrometry and high level calculations for protein structural characterization. It could also be used in spectroscopy to probe biological processes in the gas phase, with different light sources including VUV radiation (to probe different types of excitations) and ultra short pulses with time and phase modulation (to probe and control the dynamics of de-excitation or charge transfer events), and with the derivatization of proteins with chromophores to modulate their optical properties. We also envision that photo-excitation will play an important role in the future to produce intermediates with new chemical and reactive properties. Another promising route is to conduct activated electron photodetachment dissociation experiments.
Collapse
|
48
|
Christen W, Radcliffe P, Przystawik A, Diederich T, Tiggesbäumker J. Argon Solvent Effects on Optical Properties of Silver Metal Clusters. J Phys Chem A 2011; 115:8779-82. [DOI: 10.1021/jp200487s] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- W. Christen
- Institut für Chemie, Humboldt-Universität zu Berlin, Brook-Taylor-Str. 2, 12489 Berlin, Germany, and
| | - P. Radcliffe
- Institut für Physik, Universität Rostock, Universitätsplatz 3, 18051 Rostock, Germany
| | - A. Przystawik
- Institut für Physik, Universität Rostock, Universitätsplatz 3, 18051 Rostock, Germany
| | - Th. Diederich
- Institut für Physik, Universität Rostock, Universitätsplatz 3, 18051 Rostock, Germany
| | - J. Tiggesbäumker
- Institut für Physik, Universität Rostock, Universitätsplatz 3, 18051 Rostock, Germany
| |
Collapse
|
49
|
Vehmanen E, Ghazarian V, Sams C, Khachatryan I, Eloranta J, Apkarian VA. Injection of atoms and molecules in a superfluid helium fountain: Cu and Cu2He(n) (n = 1, ..., ∞). J Phys Chem A 2011; 115:7077-88. [PMID: 21449544 DOI: 10.1021/jp1123986] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We introduce an experimental platform designed around a thermomechanical helium fountain, which is aimed at investigating spectroscopy and dynamics of atoms and molecules in the superfluid and at its vapor interface. Laser ablation of copper, efficient cooling and transport of Cu and Cu(2) through helium vapor (1.5 K < T < 20 K), formation of linear and T-shaped Cu(2)-He complexes, and their continuous evolution into large Cu(2)-He(n) clusters and droplets are among the processes that are illustrated. Reflection is the dominant quantum scattering channel of translationally cold copper atoms (T = 1.7 K) at the fountain interface. Cu(2) dimers mainly travel through the fountain unimpeded. However, the conditions of fountain flow and transport of molecules can be controlled to demonstrate injection and, in particular, injection into a nondivergent columnar fountain with a plug velocity of about 1 m/s. The experimental observables are interpreted with the aid of bosonic density functional theory calculations and ab initio interaction potentials.
Collapse
Affiliation(s)
- Esa Vehmanen
- Department of Chemistry, Nanoscience Center, University of Jyväskylä, P.O. Box 35, FIN 40014, Finland
| | | | | | | | | | | |
Collapse
|
50
|
Tkatchenko A, Rossi M, Blum V, Ireta J, Scheffler M. Unraveling the stability of polypeptide helices: critical role of van der Waals interactions. PHYSICAL REVIEW LETTERS 2011; 106:118102. [PMID: 21469900 DOI: 10.1103/physrevlett.106.118102] [Citation(s) in RCA: 79] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/11/2010] [Indexed: 05/30/2023]
Abstract
Folding and unfolding processes are important for the functional capability of polypeptides and proteins. In contrast with a physiological environment (solvated or condensed phases), an in vacuo study provides well-defined "clean room" conditions to analyze the intramolecular interactions that largely control the structure, stability, and folding or unfolding dynamics. Here we show that a proper consideration of van der Waals (vdW) dispersion forces in density-functional theory (DFT) is essential, and a recently developed DFT+vdW approach enables long time-scale ab initio molecular dynamics simulations at an accuracy close to "gold standard" quantum-chemical calculations. The results show that the inclusion of vdW interactions qualitatively changes the conformational landscape of alanine polypeptides, and greatly enhances the thermal stability of helical structures, in agreement with gas-phase experiments.
Collapse
Affiliation(s)
- Alexandre Tkatchenko
- Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, D-14195 Berlin, Germany
| | | | | | | | | |
Collapse
|