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Kopp K, Westhofen L, Hett T, Felix Schwering-Sohnrey M, Mayländer M, Richert S, Schiemann O. Synthesis and dark state EPR properties of PDI-trityl dyads and triads. Chemistry 2024; 30:e202303635. [PMID: 38055217 DOI: 10.1002/chem.202303635] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2023] [Revised: 12/06/2023] [Accepted: 12/06/2023] [Indexed: 12/07/2023]
Abstract
Covalently-linked chromophore-radical systems with their unique optical and magnetic properties are useful for applications in, e. g., quantum information science. To expand the catalog of molecular systems, we synthesized and characterized six novel chromophore-radical and radical-chromophore-radical systems employing derivatives of perylene diimide (PDI) as the chromophore and trityl as the radical. The EPR properties of these compounds were evaluated in solution at cryogenic and room temperatures. In addition, the electron spin-spin coupling in the two bistrityl systems was investigated using DQC measurements. The presented results serve as a basis for further spectroscopic investigations under photoexcitation of the PDI core.
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Affiliation(s)
- Kevin Kopp
- Clausius-Institute of Physical and Theoretical Chemistry, University of Bonn, Wegelerstr. 12, 53115, Bonn, Germany
| | - Lars Westhofen
- Clausius-Institute of Physical and Theoretical Chemistry, University of Bonn, Wegelerstr. 12, 53115, Bonn, Germany
| | - Tobias Hett
- Clausius-Institute of Physical and Theoretical Chemistry, University of Bonn, Wegelerstr. 12, 53115, Bonn, Germany
| | | | - Maximilian Mayländer
- Institute of Physical Chemistry, University of Freiburg, Albertstr. 21, 79104, Freiburg, Germany
| | - Sabine Richert
- Institute of Physical Chemistry, University of Freiburg, Albertstr. 21, 79104, Freiburg, Germany
| | - Olav Schiemann
- Clausius-Institute of Physical and Theoretical Chemistry, University of Bonn, Wegelerstr. 12, 53115, Bonn, Germany
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2
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Grazia Concilio M, Frydman L. Steady state effects introduced by local relaxation modes on J-driven DNP-enhanced NMR. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2023; 355:107542. [PMID: 37672989 DOI: 10.1016/j.jmr.2023.107542] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/22/2023] [Revised: 08/03/2023] [Accepted: 08/26/2023] [Indexed: 09/08/2023]
Abstract
One of solution-state Nuclear Magnetic Resonance (NMR)'s main weaknesses, is its relative insensitivity. J-driven Dynamic Nuclear Polarization (JDNP) was recently proposed for enhancing solution-state NMR's sensitivity, by bypassing the limitations faced by conventional Overhauser DNP (ODNP), at the high magnetic fields where most analytical research is performed. By relying on biradicals with inter-electron exchange couplings Jex on the order of the electron Larmor frequency ωE, JDNP was predicted to introduce a transient enhancement in NMR's nuclear polarization at high magnetic fields, and for a wide range of rotational correlation times of medium-sized molecules in conventional solvents. This communication revisits the JDNP proposal, including additional effects and conditions that were not considered in the original treatment. These include relaxation mechanisms arising from local vibrational modes that often dominate electron relaxation in organic radicals, as well as the possibility of using biradicals with Jex of the order of the nuclear Larmor frequency ωN as potential polarizing agents. The presence of these new relaxation effects lead to variations in the JDNP polarization mechanism originally proposed, and indicate that triplet-to-singlet cross-relaxation processes may lead to a nuclear polarization enhancement that persists even at steady states. The physics and potential limitations of the ensuing theoretical derivations, are briefly discussed.
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Affiliation(s)
- Maria Grazia Concilio
- Department of Chemical and Biological Physics, Weizmann Institute of Science, Rehovot, Israel.
| | - Lucio Frydman
- Department of Chemical and Biological Physics, Weizmann Institute of Science, Rehovot, Israel
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3
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Abdullin D, Hett T, Fleck N, Kopp K, Cassidy S, Richert S, Schiemann O. Magneto-Structural Correlations in a Mixed Porphyrin(Cu 2+ )/Trityl Spin System: Magnitude, Sign, and Distribution of the Exchange Coupling Constant. Chemistry 2023; 29:e202203148. [PMID: 36519664 DOI: 10.1002/chem.202203148] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2022] [Revised: 12/14/2022] [Accepted: 12/15/2022] [Indexed: 12/23/2022]
Abstract
Tetrathiatriarylmethyl radicals (TAM or trityl) are receiving increasing attention in various fields of magnetic resonance such as imaging, dynamic nuclear polarization, spin labeling, and, more recently, molecular magnetism and quantum information technology. Here, a trityl radical attached via a phenyl bridge to a copper(II)tetraphenylporphyrin was synthesized, and its magnetic properties studied by multi-frequency continuous-wave electron paramagnetic resonance (EPR) spectroscopy and magnetic measurements. EPR revealed that the electron spin-spin coupling constant J between the trityl and Cu2+ spin centers is ferromagnetic with a magnitude of -2.3 GHz (-0.077 cm-1 , + J S → 1 S → 2 ${+J{\vec{S}}_{1}{\vec{S}}_{2}}$ convention) and a distribution width of 1.2 GHz (0.040 cm-1 ). With the help of density functional theory (DFT) calculations, the obtained ferromagnetic exchange coupling, which is unusual for para-substituted phenyl-bridged biradicals, could be related to the almost perpendicular orientation of the phenyl linker with respect to the porphyrin and trityl ring planes in the energy minimum, while the J distribution was rationalized by the temperature weighted rotation of the phenyl bridge about the molecular axis connecting both spin centers. This study exemplifies the importance of molecular dynamics for the homogeneity (or heterogeneity) of the magnetic properties of trityl-based systems.
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Affiliation(s)
- Dinar Abdullin
- Clausius-Institute of Physical and Theoretical Chemistry, University of Bonn, Wegelerstr. 12, 53115, Bonn, Germany
| | - Tobias Hett
- Clausius-Institute of Physical and Theoretical Chemistry, University of Bonn, Wegelerstr. 12, 53115, Bonn, Germany
| | - Nico Fleck
- Clausius-Institute of Physical and Theoretical Chemistry, University of Bonn, Wegelerstr. 12, 53115, Bonn, Germany.,Merck KGaA, Q20/001, Frankfurterstr. 250, 64293, Darmstadt, Germany
| | - Kevin Kopp
- Clausius-Institute of Physical and Theoretical Chemistry, University of Bonn, Wegelerstr. 12, 53115, Bonn, Germany
| | - Simon Cassidy
- Department of Chemistry, University of Oxford, South Parks Road, Oxford, OX1 3QR, UK
| | - Sabine Richert
- Institute of Physical Chemistry, University of Freiburg, Albertstr. 21, 79104, Freiburg, Germany
| | - Olav Schiemann
- Clausius-Institute of Physical and Theoretical Chemistry, University of Bonn, Wegelerstr. 12, 53115, Bonn, Germany.,Department of Chemical and Biological Physics, Weizmann Institute of Science, 761001, Rehovot, Israel
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4
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Concilio MG, Frydman L. Microwave-free J-driven dynamic nuclear polarization: A proposal for enhancing the sensitivity of solution-state NMR. Phys Rev E 2023; 107:035303. [PMID: 37073023 DOI: 10.1103/physreve.107.035303] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2022] [Accepted: 02/16/2023] [Indexed: 04/20/2023]
Abstract
J-driven dynamic nuclear polarization (JDNP) was recently proposed for enhancing the sensitivity of solution-state nuclear magnetic resonance (NMR), while bypassing the limitations faced by conventional (Overhauser) DNP at magnetic fields of interest in analytical applications. Like Overhauser DNP, JDNP also requires saturating the electronic polarization using high-frequency microwaves known to have poor penetration and associated heating effects in most liquids. The present microwave-free JDNP (MF-JDNP) proposal seeks to enhance solution NMR's sensitivity by shuttling the sample between higher and lower magnetic fields, with one of these fields providing an electron Larmor frequency that matches the interelectron exchange coupling J_{ex}. If spins cross this so-called JDNP condition sufficiently fast, we predict that a sizable nuclear polarization will be created without microwave irradiation. This MF-JDNP proposal requires radicals whose singlet-triplet self-relaxation rates are dominated by dipolar hyperfine relaxation, and shuttling times that can compete with these electron relaxation processes. This paper discusses the theory behind the MF-JDNP, as well as proposals for radicals and conditions that could enable this new approach to NMR sensitivity enhancement.
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Affiliation(s)
- Maria Grazia Concilio
- Department of Chemical and Biological Physics, Weizmann Institute of Science, Rehovot, Israel
| | - Lucio Frydman
- Department of Chemical and Biological Physics, Weizmann Institute of Science, Rehovot, Israel
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5
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Concilio MG, Kuprov I, Frydman L. J-Driven dynamic nuclear polarization for sensitizing high field solution state NMR. Phys Chem Chem Phys 2022; 24:2118-2125. [PMID: 35024715 DOI: 10.1039/d1cp04186j] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Dynamic nuclear polarization (DNP) is widely used to enhance solid state nuclear magnetic resonance (NMR) sensitivity. Its efficiency as a generic signal-enhancing approach for liquid state NMR, however, decays rapidly with magnetic field B0, unless mediated by scalar interactions arising only in exceptional cases. This has prevented a more widespread use of DNP in structural and dynamical solution NMR analyses. This study introduces a potential solution to this problem, relying on biradicals with exchange couplings Jex of the order of the electron Larmor frequency ωE. Numerical and analytical calculations show that in such Jex ≈ ±ωE cases a phenomenon akin to that occurring in chemically induced DNP (CIDNP) happens, leading to different relaxation rates for the biradical singlet and triplet states which are hyperfine-coupled to the nuclear α or β states. Microwave irradiation can then generate a transient nuclear polarization build-up with high efficiency, at all magnetic fields that are relevant in contemporary NMR, and for all rotational diffusion correlation times that occur in small- and medium-sized molecules in conventional solvents.
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Affiliation(s)
- Maria Grazia Concilio
- Department of Chemical and Biological Physics, Weizmann Institute of Science, Rehovot, Israel.
| | - Ilya Kuprov
- School of Chemistry, University of Southampton, Southampton, UK
| | - Lucio Frydman
- Department of Chemical and Biological Physics, Weizmann Institute of Science, Rehovot, Israel. .,National High Magnetic Field Laboratory, Tallahassee, Florida, USA
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6
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Concilio MG, Soundararajan M, Frydman L, Kuprov I. High-field solution state DNP using cross-correlations. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2021; 326:106940. [PMID: 33865207 DOI: 10.1016/j.jmr.2021.106940] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/25/2020] [Revised: 02/08/2021] [Accepted: 02/09/2021] [Indexed: 06/12/2023]
Abstract
At the magnetic fields of common NMR instruments, electron Zeeman frequencies are too high for efficient electron-nuclear dipolar cross-relaxation to occur in solution. The rate of that process fades with the electron Zeeman frequency as ω-2 - in the absence of isotropic hyperfine couplings, liquid state dynamic nuclear polarisation (DNP) in high-field magnets is therefore impractical. However, contact coupling and dipolar cross-relaxation are not the only mechanisms that can move electron magnetisation to nuclei in liquids: multiple cross-correlated (CC) relaxation processes also exist, involving various combinations of interaction tensor anisotropies. The rates of some of those processes have more favourable high-field behaviour than dipolar cross-relaxation, but due to the difficulty of their numerical - and particularly analytical - treatment, they remain largely uncharted. In this communication, we report analytical evaluation of every rotationally driven relaxation process in liquid state for 1e1n and 2e1n spin systems, as well as numerical optimisations of the steady-state DNP with respect to spin Hamiltonian parameters. A previously unreported cross-correlated DNP (CCDNP) mechanism was identified for the 2e1n system, involving multiple relaxation interference effects and inter-electron exchange coupling. Using simulations, we found realistic spin Hamiltonian parameters that yield stronger nuclear polarisation at high magnetic fields than dipolar cross-relaxation.
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Affiliation(s)
- Maria Grazia Concilio
- Department of Chemical and Biological Physics, Weizmann Institute of Science, Rehovot, Israel; School of Chemistry, University of Southampton, Southampton, UK.
| | | | - Lucio Frydman
- Department of Chemical and Biological Physics, Weizmann Institute of Science, Rehovot, Israel; National High Magnetic Field Laboratory, Tallahassee, FL, USA.
| | - Ilya Kuprov
- School of Chemistry, University of Southampton, Southampton, UK.
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7
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Scherer A, Tischlik S, Weickert S, Wittmann V, Drescher M. Optimising broadband pulses for DEER depends on concentration and distance range of interest. MAGNETIC RESONANCE (GOTTINGEN, GERMANY) 2020; 1:59-74. [PMID: 37904889 PMCID: PMC10500711 DOI: 10.5194/mr-1-59-2020] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/17/2020] [Accepted: 04/26/2020] [Indexed: 11/01/2023]
Abstract
EPR distance determination in the nanometre region has become an important tool for studying the structure and interaction of macromolecules. Arbitrary waveform generators (AWGs), which have recently become commercially available for EPR spectrometers, have the potential to increase the sensitivity of the most common technique, double electron-electron resonance (DEER, also called PELDOR), as they allow the generation of broadband pulses. There are several families of broadband pulses, which are different in general pulse shape and the parameters that define them. Here, we compare the most common broadband pulses. When broadband pulses lead to a larger modulation depth, they also increase the background decay of the DEER trace. Depending on the dipolar evolution time, this can significantly increase the noise level towards the end of the form factor and limit the potential increase in the modulation-to-noise ratio (MNR). We found asymmetric hyperbolic secant (HS{ 1 , 6 } ) pulses to perform best for short DEER traces, leading to a MNR improvement of up to 86 % compared to rectangular pulses. For longer traces we found symmetric hyperbolic secant (HS{ 1 , 1 } ) pulses to perform best; however, the increase compared to rectangular pulses goes down to 43 %.
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Affiliation(s)
- Andreas Scherer
- Department of Chemistry and Konstanz Research School Chemical Biology,
University of Konstanz, Konstanz, Germany
| | - Sonja Tischlik
- Department of Chemistry and Konstanz Research School Chemical Biology,
University of Konstanz, Konstanz, Germany
| | - Sabrina Weickert
- Department of Chemistry and Konstanz Research School Chemical Biology,
University of Konstanz, Konstanz, Germany
| | - Valentin Wittmann
- Department of Chemistry and Konstanz Research School Chemical Biology,
University of Konstanz, Konstanz, Germany
| | - Malte Drescher
- Department of Chemistry and Konstanz Research School Chemical Biology,
University of Konstanz, Konstanz, Germany
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8
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Meyer A, Dechert S, Dey S, Höbartner C, Bennati M. Measurement of Angstrom to Nanometer Molecular Distances with
19
F Nuclear Spins by EPR/ENDOR Spectroscopy. Angew Chem Int Ed Engl 2020. [DOI: 10.1002/ange.201908584] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Affiliation(s)
- Andreas Meyer
- Research Group EPR Spectroscopy Max Planck Institute for Biophysical Chemistry Am Fassberg 11 37077 Göttingen Germany
| | - Sebastian Dechert
- Department of Chemistry Georg-August-University Tammannstr 37077 Göttingen Germany
| | - Surjendu Dey
- Institute of Organic Chemistry Julius-Maximilians-University Würzburg Am Hubland 97074 Würzburg Germany
| | - Claudia Höbartner
- Institute of Organic Chemistry Julius-Maximilians-University Würzburg Am Hubland 97074 Würzburg Germany
| | - Marina Bennati
- Research Group EPR Spectroscopy Max Planck Institute for Biophysical Chemistry Am Fassberg 11 37077 Göttingen Germany
- Department of Chemistry Georg-August-University Tammannstr 37077 Göttingen Germany
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9
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Meyer A, Dechert S, Dey S, Höbartner C, Bennati M. Measurement of Angstrom to Nanometer Molecular Distances with 19 F Nuclear Spins by EPR/ENDOR Spectroscopy. Angew Chem Int Ed Engl 2020; 59:373-379. [PMID: 31539187 PMCID: PMC6973229 DOI: 10.1002/anie.201908584] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2019] [Revised: 09/02/2019] [Indexed: 12/22/2022]
Abstract
Spectroscopic and biophysical methods for structural determination at atomic resolution are fundamental in studies of biological function. Here we introduce an approach to measure molecular distances in bio-macromolecules using 19 F nuclear spins and nitroxide radicals in combination with high-frequency (94 GHz/3.4 T) electron-nuclear double resonance (ENDOR). The small size and large gyromagnetic ratio of the 19 F label enables to access distances up to about 1.5 nm with an accuracy of 0.1-1 Å. The experiment is not limited by the size of the bio-macromolecule. Performance is illustrated on synthesized fluorinated model compounds as well as spin-labelled RNA duplexes. The results demonstrate that our simple but strategic spin-labelling procedure combined with state-of-the-art spectroscopy accesses a distance range crucial to elucidate active sites of nucleic acids or proteins in the solution state.
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Affiliation(s)
- Andreas Meyer
- Research Group EPR SpectroscopyMax Planck Institute for Biophysical ChemistryAm Fassberg 1137077GöttingenGermany
| | - Sebastian Dechert
- Department of ChemistryGeorg-August-UniversityTammannstr37077GöttingenGermany
| | - Surjendu Dey
- Institute of Organic ChemistryJulius-Maximilians-University WürzburgAm Hubland97074WürzburgGermany
| | - Claudia Höbartner
- Institute of Organic ChemistryJulius-Maximilians-University WürzburgAm Hubland97074WürzburgGermany
| | - Marina Bennati
- Research Group EPR SpectroscopyMax Planck Institute for Biophysical ChemistryAm Fassberg 1137077GöttingenGermany
- Department of ChemistryGeorg-August-UniversityTammannstr37077GöttingenGermany
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10
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Abdullin D, Brehm P, Fleck N, Spicher S, Grimme S, Schiemann O. Pulsed EPR Dipolar Spectroscopy on Spin Pairs with one Highly Anisotropic Spin Center: The Low-Spin Fe III Case. Chemistry 2019; 25:14388-14398. [PMID: 31386227 PMCID: PMC6900076 DOI: 10.1002/chem.201902908] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2019] [Revised: 08/05/2019] [Indexed: 02/01/2023]
Abstract
Pulsed electron paramagnetic resonance (EPR) dipolar spectroscopy (PDS) offers several methods for measuring dipolar coupling constants and thus the distance between electron spin centers. Up to now, PDS measurements have been mostly applied to spin centers whose g-anisotropies are moderate and therefore have a negligible effect on the dipolar coupling constants. In contrast, spin centers with large g-anisotropy yield dipolar coupling constants that depend on the g-values. In this case, the usual methods of extracting distances from the raw PDS data cannot be applied. Here, the effect of the g-anisotropy on PDS data is studied in detail on the example of the low-spin Fe3+ ion. First, this effect is described theoretically, using the work of Bedilo and Maryasov (Appl. Magn. Reson. 2006, 30, 683-702) as a basis. Then, two known Fe3+ /nitroxide compounds and one new Fe3+ /trityl compound were synthesized and PDS measurements were carried out on them using a method called relaxation induced dipolar modulation enhancement (RIDME). Based on the theoretical results, a RIDME data analysis procedure was developed, which facilitated the extraction of the inter-spin distance and the orientation of the inter-spin vector relative to the Fe3+ g-tensor frame from the RIDME data. The accuracy of the determined distances and orientations was confirmed by comparison with MD simulations. This method can thus be applied to the highly relevant class of metalloproteins with, for example, low-spin Fe3+ ions.
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Affiliation(s)
- Dinar Abdullin
- Institute of Physical and Theoretical ChemistryUniversity of Bonn53115BonnGermany
| | - Philipp Brehm
- Institute of Physical and Theoretical ChemistryUniversity of Bonn53115BonnGermany
- Current address: Institute of Inorganic ChemistryUniversity of Bonn53115BonnGermany
| | - Nico Fleck
- Institute of Physical and Theoretical ChemistryUniversity of Bonn53115BonnGermany
| | - Sebastian Spicher
- Mulliken Center for Theoretical ChemistryUniversity of Bonn53115BonnGermany
| | - Stefan Grimme
- Mulliken Center for Theoretical ChemistryUniversity of Bonn53115BonnGermany
| | - Olav Schiemann
- Institute of Physical and Theoretical ChemistryUniversity of Bonn53115BonnGermany
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11
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Li Y, Zhai W, Liao Y, Nie J, Han G, Song Y, Li S, Hou J, Liu Y. Synthesis of Central Chirality-Containing Triarylmethanols and Triarylmethyl Radicals with Extraordinarily Stable Configurations. J Org Chem 2019; 84:11774-11782. [PMID: 31454244 DOI: 10.1021/acs.joc.9b01675] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Triarylmethanol adopts a propeller-shaped conformation with either right-handed (P) or left-handed (M) configuration. Herein, new triarylmethanols with two chiral centers were obtained via introduction of two cis-hydroxyl groups on the side chains, affording four stereoisomers. These four stereoisomers were easily separated by silica gel column chromatography into two pairs of propeller-shaped enantiomers, as shown by NMR and X-ray crystallographic studies. High-performance liquid chromatography (HPLC) studies showed that the configurations of the hydroxyl-bearing triarylmethanols are much more stable than those of the bulky tert-butyldimethylsilyl-protected precursors, inconsistent with the general strategy in which the steric repulsion is largely responsible for the configurational stability. Similarly, two hydroxyl-bearing tetrathiatriarylmethyl (TAM) radicals also exhibit excellent configurational stability and are thus separable by CS-HPLC into four stereoisomers. Interestingly, both helical chirality from triaryl group (M or P) and central chirality (R and S) on the side chain have little effect on their electron paramagnetic resonance properties. Our present study provides a new strategy to construct configurationally stable triaryl compounds and demonstrates that the side chain on TAM radicals is a new site for their structural modifications.
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Affiliation(s)
- Yingchun Li
- Tianjin Key Laboratory on Technologies Enabling Development of Clinical Therapeutics and Diagnostics, School of Pharmacy , Tianjin Medical University , Tianjin 300070 , P. R. China
| | - Weixiang Zhai
- Tianjin Key Laboratory on Technologies Enabling Development of Clinical Therapeutics and Diagnostics, School of Pharmacy , Tianjin Medical University , Tianjin 300070 , P. R. China
| | - Yongfang Liao
- Tianjin Key Laboratory on Technologies Enabling Development of Clinical Therapeutics and Diagnostics, School of Pharmacy , Tianjin Medical University , Tianjin 300070 , P. R. China
| | - Jiangping Nie
- Tianjin Key Laboratory on Technologies Enabling Development of Clinical Therapeutics and Diagnostics, School of Pharmacy , Tianjin Medical University , Tianjin 300070 , P. R. China
| | - Guifang Han
- Tianjin Key Laboratory on Technologies Enabling Development of Clinical Therapeutics and Diagnostics, School of Pharmacy , Tianjin Medical University , Tianjin 300070 , P. R. China
| | - Yuguang Song
- Tianjin Key Laboratory on Technologies Enabling Development of Clinical Therapeutics and Diagnostics, School of Pharmacy , Tianjin Medical University , Tianjin 300070 , P. R. China
| | - Shaoyong Li
- Tianjin Key Laboratory on Technologies Enabling Development of Clinical Therapeutics and Diagnostics, School of Pharmacy , Tianjin Medical University , Tianjin 300070 , P. R. China
| | - Jingli Hou
- Tianjin Key Laboratory on Technologies Enabling Development of Clinical Therapeutics and Diagnostics, School of Pharmacy , Tianjin Medical University , Tianjin 300070 , P. R. China
| | - Yangping Liu
- Tianjin Key Laboratory on Technologies Enabling Development of Clinical Therapeutics and Diagnostics, School of Pharmacy , Tianjin Medical University , Tianjin 300070 , P. R. China
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12
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Bleicken S, Assafa TE, Zhang H, Elsner C, Ritsch I, Pink M, Rajca S, Jeschke G, Rajca A, Bordignon E. gem-Diethyl Pyrroline Nitroxide Spin Labels: Synthesis, EPR Characterization, Rotamer Libraries and Biocompatibility. ChemistryOpen 2019; 8:1057-1065. [PMID: 31463171 PMCID: PMC6709561 DOI: 10.1002/open.201900119] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2019] [Indexed: 12/29/2022] Open
Abstract
The availability of bioresistant spin labels is crucial for the optimization of site-directed spin labeling protocols for EPR structural studies of biomolecules in a cellular context. As labeling can affect proteins' fold and/or function, having the possibility to choose between different spin labels will increase the probability to produce spin-labeled functional proteins. Here, we report the synthesis and characterization of iodoacetamide- and maleimide-functionalized spin labels based on the gem-diethyl pyrroline structure. The two nitroxide labels are compared to conventional gem-dimethyl analogs by site-directed spin labeling (SDSL) electron paramagnetic resonance (EPR) spectroscopy, using two water soluble proteins: T4 lysozyme and Bid. To foster their use for structural studies, we also present rotamer libraries for these labels, compatible with the MMM software. Finally, we investigate the "true" biocompatibility of the gem-diethyl probes comparing the resistance towards chemical reduction of the NO group in ascorbate solutions and E. coli cytosol at different spin concentrations.
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Affiliation(s)
- Stephanie Bleicken
- Faculty of Chemistry and BiochemistryRuhr University Bochum, Universitaetsstrasse 15044801BochumGermany
- ZEMOSRuhr University BochumUniversitaetsstrasse 150, 44801BochumGermany
| | - Tufa E. Assafa
- Faculty of Chemistry and BiochemistryRuhr University Bochum, Universitaetsstrasse 15044801BochumGermany
| | - Hui Zhang
- Department of ChemistryUniversity of Nebraska, LincolnNebraska68588-0304USA
| | - Christina Elsner
- Faculty of Chemistry and BiochemistryRuhr University Bochum, Universitaetsstrasse 15044801BochumGermany
| | - Irina Ritsch
- ETH ZurichLaboratory of Physical ChemistryVladimir-Prelog-Weg 2CH-8093ZurichSwitzerland.
| | - Maren Pink
- IUMSC, Department of ChemistryIndiana UniversityBloomington, Indiana47405-7102USA
| | - Suchada Rajca
- Department of ChemistryUniversity of Nebraska, LincolnNebraska68588-0304USA
| | - Gunnar Jeschke
- ETH ZurichLaboratory of Physical ChemistryVladimir-Prelog-Weg 2CH-8093ZurichSwitzerland.
| | - Andrzej Rajca
- Department of ChemistryUniversity of Nebraska, LincolnNebraska68588-0304USA
| | - Enrica Bordignon
- Faculty of Chemistry and BiochemistryRuhr University Bochum, Universitaetsstrasse 15044801BochumGermany
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13
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Site Selective and Efficient Spin Labeling of Proteins with a Maleimide-Functionalized Trityl Radical for Pulsed Dipolar EPR Spectroscopy. Molecules 2019; 24:molecules24152735. [PMID: 31357628 PMCID: PMC6696014 DOI: 10.3390/molecules24152735] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2019] [Revised: 07/24/2019] [Accepted: 07/25/2019] [Indexed: 01/18/2023] Open
Abstract
Pulsed dipolar electron paramagnetic resonance spectroscopy (PDS) in combination with site-directed spin labeling (SDSL) of proteins and oligonucleotides is a powerful tool in structural biology. Instead of using the commonly employed gem-dimethyl-nitroxide labels, triarylmethyl (trityl) spin labels enable such studies at room temperature, within the cells and with single-frequency electron paramagnetic resonance (EPR) experiments. However, it has been repeatedly reported that labeling of proteins with trityl radicals led to low labeling efficiencies, unspecific labeling and label aggregation. Therefore, this work introduces the synthesis and characterization of a maleimide-functionalized trityl spin label and its corresponding labeling protocol for cysteine residues in proteins. The label is highly cysteine-selective, provides high labeling efficiencies and outperforms the previously employed methanethiosulfonate-functionalized trityl label. Finally, the new label is successfully tested in PDS measurements on a set of doubly labeled Yersinia outer protein O (YopO) mutants.
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14
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Fleck N, Hett T, Brode J, Meyer A, Richert S, Schiemann O. C–C Cross-Coupling Reactions of Trityl Radicals: Spin Density Delocalization, Exchange Coupling, and a Spin Label. J Org Chem 2019; 84:3293-3303. [DOI: 10.1021/acs.joc.8b03229] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Affiliation(s)
- Nico Fleck
- Institute of Physical and Theoretical Chemistry, Rheinische Friedrich-Wilhelms-University Bonn, Wegelerstr. 12, 53115 Bonn, Germany
| | - Tobias Hett
- Institute of Physical and Theoretical Chemistry, Rheinische Friedrich-Wilhelms-University Bonn, Wegelerstr. 12, 53115 Bonn, Germany
| | - Jonas Brode
- Institute of Physical and Theoretical Chemistry, Rheinische Friedrich-Wilhelms-University Bonn, Wegelerstr. 12, 53115 Bonn, Germany
| | - Andreas Meyer
- Institute of Physical and Theoretical Chemistry, Rheinische Friedrich-Wilhelms-University Bonn, Wegelerstr. 12, 53115 Bonn, Germany
| | - Sabine Richert
- Institute of Physical Chemistry, University of Freiburg, Albertstraße 21, 79104 Freiburg, Germany
| | - Olav Schiemann
- Institute of Physical and Theoretical Chemistry, Rheinische Friedrich-Wilhelms-University Bonn, Wegelerstr. 12, 53115 Bonn, Germany
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15
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Hintz H, Vanas A, Klose D, Jeschke G, Godt A. Trityl Radicals with a Combination of the Orthogonal Functional Groups Ethyne and Carboxyl: Synthesis without a Statistical Step and EPR Characterization. J Org Chem 2019; 84:3304-3320. [DOI: 10.1021/acs.joc.8b03234] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Henrik Hintz
- Faculty of Chemistry and Center for Molecular Materials (CM2), Bielefeld University, Universitätsstrasse 25, 33615 Bielefeld, Germany
| | - Agathe Vanas
- Laboratory of Physical Chemistry, ETH Zurich, Vladimir-Prelog-Weg 2, 8093 Zurich, Switzerland
| | - Daniel Klose
- Laboratory of Physical Chemistry, ETH Zurich, Vladimir-Prelog-Weg 2, 8093 Zurich, Switzerland
| | - Gunnar Jeschke
- Laboratory of Physical Chemistry, ETH Zurich, Vladimir-Prelog-Weg 2, 8093 Zurich, Switzerland
| | - Adelheid Godt
- Faculty of Chemistry and Center for Molecular Materials (CM2), Bielefeld University, Universitätsstrasse 25, 33615 Bielefeld, Germany
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16
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Jobelius H, Wagner N, Schnakenburg G, Meyer A. Verdazyls as Possible Building Blocks for Multifunctional Molecular Materials: A Case Study on 1,5-Diphenyl-3-( p-iodophenyl)-verdazyl Focusing on Magnetism, Electron Transfer and the Applicability of the Sonogashira-Hagihara Reaction. Molecules 2018; 23:E1758. [PMID: 30021960 PMCID: PMC6100452 DOI: 10.3390/molecules23071758] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2018] [Revised: 07/15/2018] [Accepted: 07/16/2018] [Indexed: 11/16/2022] Open
Abstract
This work explores the use of Kuhn verdazyl radicals as building blocks in multifunctional molecular materials in an exemplary study, focusing on the magnetic and the electron transfer (ET) characteristics, but also addressing the question whether chemical modification by cross-coupling is possible. The ET in solution is studied spectroscopically, whereas solid state measurements afford information about the magnetic susceptibility or the conductivity of the given samples. The observed results are rationalized based on the chemical structures of the molecules, which have been obtained by X-ray crystallography. The crystallographically observed molecular structures as well as the interpretation based on the spectroscopic and physical measurements are backed up by DFT calculations. The measurements indicate that only weak, antiferromagnetic (AF) coupling is observed in Kuhn verdazyls owed to the low tendency to form face-to-face stacks, but also that steric reasons alone are not sufficient to explain this behavior. Furthermore, it is also demonstrated that ET reactions proceed rapidly in verdazyl/verdazylium redox couples and that Kuhn verdazyls are suited as donor molecules in ET reactions.
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Affiliation(s)
- Hannah Jobelius
- Institute of Physical and Theoretical Chemistry, University of Bonn, 53115 Bonn, Germany.
| | - Norbert Wagner
- Institute of Inorganic Chemistry, University of Bonn, 53121 Bonn, Germany.
| | | | - Andreas Meyer
- Institute of Physical and Theoretical Chemistry, University of Bonn, 53115 Bonn, Germany.
- Max-Planck-Institute for Biophysical Chemistry, 37077 Göttingen, Germany.
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17
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Meyer A, Jassoy JJ, Spicher S, Berndhäuser A, Schiemann O. Performance of PELDOR, RIDME, SIFTER, and DQC in measuring distances in trityl based bi- and triradicals: exchange coupling, pseudosecular coupling and multi-spin effects. Phys Chem Chem Phys 2018; 20:13858-13869. [DOI: 10.1039/c8cp01276h] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
The performance of pulsed EPR methods for distance measurements is evaluated on three different trityl model systems.
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Affiliation(s)
- Andreas Meyer
- Institute of Physical and Theoretical Chemistry
- Rheinische Friedrich-Wilhelms-University Bonn
- 53115 Bonn
- Germany
| | - Jean Jacques Jassoy
- Institute of Physical and Theoretical Chemistry
- Rheinische Friedrich-Wilhelms-University Bonn
- 53115 Bonn
- Germany
| | - Sebastian Spicher
- Institute of Physical and Theoretical Chemistry
- Rheinische Friedrich-Wilhelms-University Bonn
- 53115 Bonn
- Germany
| | - Andreas Berndhäuser
- Institute of Physical and Theoretical Chemistry
- Rheinische Friedrich-Wilhelms-University Bonn
- 53115 Bonn
- Germany
| | - Olav Schiemann
- Institute of Physical and Theoretical Chemistry
- Rheinische Friedrich-Wilhelms-University Bonn
- 53115 Bonn
- Germany
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