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Li S, Deng P, Chang Q, Feng M, Shang Y, Song Y, Liu Y. In Situ Generation and High Bioresistance of Trityl-based Semiquinone Methide Radicals Under Anaerobic Conditions in Cellular Systems. Chemistry 2024; 30:e202400985. [PMID: 38932665 DOI: 10.1002/chem.202400985] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2024] [Revised: 06/02/2024] [Accepted: 06/25/2024] [Indexed: 06/28/2024]
Abstract
Bioreduction of spin labels and polarizing agents (generally stable radicals) has been an obstacle limiting the in-cell applications of pulsed electron paramagnetic resonance (EPR) spectroscopy and dynamic nuclear polarization (DNP). In this work, we have demonstrated that two semiquinone methide radicals (OXQM⋅ and CTQM⋅) can be easily produced from the trityl-based quinone methides (OXQM and CTQM) via reduction by various reducing agents including biothiols and ascorbate under anaerobic conditions. Both radicals have relatively low pKa's and exhibit EPR single line signals at physiological pH. Moreover, the bioreduction of OXQM in three cell lysates enables quantitative generation of OXQM⋅ which was most likely mediated by flavoenzymes. Importantly, the resulting OXQM⋅ exhibited extremely high stability in the E.coli lysate under anaerobic conditions with 76- and 14.3-fold slower decay kinetics as compared to the trityl OX063 and a gem-diethyl pyrrolidine nitroxide, respectively. Intracellular delivery of OXQM into HeLa cells was also achieved by covalent conjugation with a cell-permeable peptide as evidenced by the stable intracellular EPR signal from the OXQM⋅ moiety. Owing to extremely high resistance of OXQM⋅ towards bioreduction, OXQM and its derivatives show great application potential in in-cell EPR and in-cell DNP studies for various cells which can endure short-term anoxic treatments.
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Affiliation(s)
- Shuai Li
- The Province and Ministry Co-Sponsored Collaborative Innovation Center for Medical Epigenetics, Tianjin Key Laboratory on Technologies Enabling Development of Clinical Therapeutics and Diagnostics, School of Pharmacy, Tianjin Medical University, Tianjin, 300070, P. R. China
| | - Peng Deng
- The Province and Ministry Co-Sponsored Collaborative Innovation Center for Medical Epigenetics, Tianjin Key Laboratory on Technologies Enabling Development of Clinical Therapeutics and Diagnostics, School of Pharmacy, Tianjin Medical University, Tianjin, 300070, P. R. China
| | - Qi Chang
- The Province and Ministry Co-Sponsored Collaborative Innovation Center for Medical Epigenetics, Tianjin Key Laboratory on Technologies Enabling Development of Clinical Therapeutics and Diagnostics, School of Pharmacy, Tianjin Medical University, Tianjin, 300070, P. R. China
| | - Meirong Feng
- The Province and Ministry Co-Sponsored Collaborative Innovation Center for Medical Epigenetics, Tianjin Key Laboratory on Technologies Enabling Development of Clinical Therapeutics and Diagnostics, School of Pharmacy, Tianjin Medical University, Tianjin, 300070, P. R. China
| | - Yixuan Shang
- The Province and Ministry Co-Sponsored Collaborative Innovation Center for Medical Epigenetics, 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
- The Province and Ministry Co-Sponsored Collaborative Innovation Center for Medical Epigenetics, 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
- The Province and Ministry Co-Sponsored Collaborative Innovation Center for Medical Epigenetics, 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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Vanas A, Soetbeer J, Breitgoff FD, Hintz H, Sajid M, Polyhach Y, Godt A, Jeschke G, Yulikov M, Klose D. Intermolecular contributions, filtration effects and signal composition of SIFTER (single-frequency technique for refocusing). MAGNETIC RESONANCE (GOTTINGEN, GERMANY) 2023; 4:1-18. [PMID: 38269110 PMCID: PMC10807728 DOI: 10.5194/mr-4-1-2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/27/2022] [Accepted: 12/14/2022] [Indexed: 01/26/2024]
Abstract
To characterize structure and molecular order in the nanometre range, distances between electron spins and their distributions can be measured via dipolar spin-spin interactions by different pulsed electron paramagnetic resonance experiments. Here, for the single-frequency technique for refocusing dipolar couplings (SIFTER), the buildup of dipolar modulation signal and intermolecular contributions is analysed for a uniform random distribution of monoradicals and biradicals in frozen glassy solvent by using the product operator formalism for electron spin S = 1 / 2 . A dipolar oscillation artefact appearing at both ends of the SIFTER time trace is predicted, which originates from the weak coherence transfer between biradicals. The relative intensity of this artefact is predicted to be temperature independent but to increase with the spin concentration in the sample. Different compositions of the intermolecular background are predicted in the case of biradicals and in the case of monoradicals. Our theoretical account suggests that the appropriate procedure of extracting the intramolecular dipolar contribution (form factor) requires fitting and subtracting the unmodulated part, followed by division by an intermolecular background function that is different in shape. This scheme differs from the previously used heuristic background division approach. We compare our theoretical derivations to experimental SIFTER traces for nitroxide and trityl monoradicals and biradicals. Our analysis demonstrates a good qualitative match with the proposed theoretical description. The resulting perspectives for a quantitative analysis of SIFTER data are discussed.
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Affiliation(s)
- Agathe Vanas
- Laboratory of Physical Chemistry, ETH Zürich, Vladimir-Prelog-Weg
2, 8093 Zurich, Switzerland
| | - Janne Soetbeer
- Laboratory of Physical Chemistry, ETH Zürich, Vladimir-Prelog-Weg
2, 8093 Zurich, Switzerland
| | - Frauke Diana Breitgoff
- Laboratory of Physical Chemistry, ETH Zürich, Vladimir-Prelog-Weg
2, 8093 Zurich, Switzerland
| | - Henrik Hintz
- Department of Chemistry, Bielefeld University, Universitätsstrasse
25, 33615 Bielefeld, Germany
| | - Muhammad Sajid
- Department of Chemistry, Bielefeld University, Universitätsstrasse
25, 33615 Bielefeld, Germany
| | - Yevhen Polyhach
- Laboratory of Physical Chemistry, ETH Zürich, Vladimir-Prelog-Weg
2, 8093 Zurich, Switzerland
| | - Adelheid Godt
- Department of Chemistry, Bielefeld University, Universitätsstrasse
25, 33615 Bielefeld, Germany
| | - Gunnar Jeschke
- Laboratory of Physical Chemistry, ETH Zürich, Vladimir-Prelog-Weg
2, 8093 Zurich, Switzerland
| | - Maxim Yulikov
- Laboratory of Physical Chemistry, ETH Zürich, Vladimir-Prelog-Weg
2, 8093 Zurich, Switzerland
| | - Daniel Klose
- Laboratory of Physical Chemistry, ETH Zürich, Vladimir-Prelog-Weg
2, 8093 Zurich, Switzerland
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Poncelet M, Ngendahimana T, Gluth TD, Hoblitzell EH, Eubank TD, Eaton GR, Eaton SS, Driesschaert B. Synthesis and characterization of a biocompatible 13C 1 isotopologue of trityl radical OX071 for in vivo EPR viscometry. Analyst 2022; 147:5643-5648. [PMID: 36373434 PMCID: PMC9729415 DOI: 10.1039/d2an01527g] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/15/2023]
Abstract
We describe the synthesis, characterization, and application of an isotopologue of the trityl radical OX071, labeled with 13C at the central carbon (13C1). This spin probe features large anisotropy of the hyperfine coupling with the 13C1 (I = 1/2), leading to an EPR spectrum highly sensitive to molecular tumbling. The high biocompatibility and lack of interaction with blood albumin allow for systemic delivery and in vivo measurement of tissue microviscosity by EPR.
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Affiliation(s)
- Martin Poncelet
- Department of Pharmaceutical Sciences, School of Pharmacy, West Virginia University, Morgantown, WV, 26506, USA
- In Vivo Multifunctional Magnetic Resonance center, Robert C. Byrd Health Sciences Center, West Virginia University, Morgantown, WV, 26506, USA.
| | - Thacien Ngendahimana
- Department of Chemistry and Biochemistry, University of Denver, Denver, CO 80210, USA
| | - Teresa D Gluth
- Department of Pharmaceutical Sciences, School of Pharmacy, West Virginia University, Morgantown, WV, 26506, USA
- In Vivo Multifunctional Magnetic Resonance center, Robert C. Byrd Health Sciences Center, West Virginia University, Morgantown, WV, 26506, USA.
| | - Emily H Hoblitzell
- In Vivo Multifunctional Magnetic Resonance center, Robert C. Byrd Health Sciences Center, West Virginia University, Morgantown, WV, 26506, USA.
- Department of Microbiology, Immunology, and Cell Biology, West Virginia University, School of Medicine, Morgantown, WV, 26506, USA
| | - Timothy D Eubank
- In Vivo Multifunctional Magnetic Resonance center, Robert C. Byrd Health Sciences Center, West Virginia University, Morgantown, WV, 26506, USA.
- Department of Microbiology, Immunology, and Cell Biology, West Virginia University, School of Medicine, Morgantown, WV, 26506, USA
| | - Gareth R Eaton
- Department of Chemistry and Biochemistry, University of Denver, Denver, CO 80210, USA
| | - Sandra S Eaton
- Department of Chemistry and Biochemistry, University of Denver, Denver, CO 80210, USA
| | - Benoit Driesschaert
- Department of Pharmaceutical Sciences, School of Pharmacy, West Virginia University, Morgantown, WV, 26506, USA
- In Vivo Multifunctional Magnetic Resonance center, Robert C. Byrd Health Sciences Center, West Virginia University, Morgantown, WV, 26506, USA.
- Eugene Bennett Department of Chemistry, West Virginia University, WV, 26506, USA
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Hofmann L, Ruthstein S. EPR Spectroscopy Provides New Insights into Complex Biological Reaction Mechanisms. J Phys Chem B 2022; 126:7486-7494. [PMID: 36137278 PMCID: PMC9549461 DOI: 10.1021/acs.jpcb.2c05235] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
![]()
In the last 20 years, the use of electron paramagnetic
resonance
(EPR) has made a pronounced and lasting impact in the field of structural
biology. The advantage of EPR spectroscopy over other structural techniques
is its ability to target even minor conformational changes in any
biomolecule or macromolecular complex, independent of its size or
complexity, or whether it is in solution or in the cell during a biological
or chemical reaction. Here, we focus on the use of EPR spectroscopy
to study transmembrane transport and transcription mechanisms. We
discuss experimental and analytical concerns when referring to studies
of two biological reaction mechanisms, namely, transfer of copper
ions by the human copper transporter hCtr1 and the mechanism of action
of the Escherichia coli copper-dependent
transcription factor CueR. Last, we elaborate on future avenues in
the field of EPR structural biology.
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Affiliation(s)
- Lukas Hofmann
- Department of Chemistry and the Institute of Nanotechnology & Advanced Materials, Faculty of Exact Sciences, Bar-Ilan University, Ramat-Gan 5290002, Israel
| | - Sharon Ruthstein
- Department of Chemistry and the Institute of Nanotechnology & Advanced Materials, Faculty of Exact Sciences, Bar-Ilan University, Ramat-Gan 5290002, Israel
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Abstract
Different types of spin labels are currently available for structural studies of biomolecules both in vitro and in cells using Electron Paramagnetic Resonance (EPR) and pulse dipolar spectroscopy (PDS). Each type of label has its own advantages and disadvantages, that will be addressed in this chapter. The spectroscopically distinct properties of the labels have fostered new applications of PDS aimed to simultaneously extract multiple inter-label distances on the same sample. In fact, combining different labels and choosing the optimal strategy to address their inter-label distances can increase the information content per sample, and this is pivotal to better characterize complex multi-component biomolecular systems. In this review, we provide a brief background of the spectroscopic properties of the four most common orthogonal spin labels for PDS measurements and focus on the various methods at disposal to extract homo- and hetero-label distances in proteins. We also devote a section to possible artifacts arising from channel crosstalk and provide few examples of applications in structural biology.
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Nishiuchi T, Ishii D, Aibara S, Sato H, Kubo T. Synthesis, properties and chemical modification of a persistent triisopropylsilylethynyl substituted tri(9-anthryl)methyl radical. Chem Commun (Camb) 2022; 58:3306-3309. [PMID: 35178540 DOI: 10.1039/d2cc00548d] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
In studies aimed at developing new organic spin materials, we prepared a triisopropylsilylethynyl substituted tri(9-anthryl)methyl (TAntM) radical. The TIPS-ethynyl group in this radical effectively suppresses its reactivity, resulting in extremely high stability in air for at least one month. Chemical modification of the radical using [4+2] Diels-Alder reaction proceeds even at room temperature. Because harsh conditions and metal-catalyzed reactions are not required, this post-modification strategy should be highly versatile for use in constructing unique spin-labelled molecules.
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Affiliation(s)
- Tomohiko Nishiuchi
- Department of Chemistry, Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043, Japan. .,Innovative Catalysis Science Division, Institute for Open and Transdisciplinary Research Initiatives, (ICS-OTRI), Osaka University, Suita, Osaka 565-0871, Japan
| | - Daisuke Ishii
- Department of Chemistry, Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043, Japan.
| | - Seito Aibara
- Department of Chemistry, Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043, Japan.
| | - Hiroyasu Sato
- Rigaku Corporation, 3-9-12 Matsubara, Akishima, Tokyo 196-8666, Japan
| | - Takashi Kubo
- Department of Chemistry, Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043, Japan. .,Innovative Catalysis Science Division, Institute for Open and Transdisciplinary Research Initiatives, (ICS-OTRI), Osaka University, Suita, Osaka 565-0871, Japan
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Kim Y, Byeon JE, Jeong GY, Kim SS, Song H, Lee E. Highly Stable 1,2-Dicarbonyl Radical Cations Derived from N-Heterocyclic Carbenes. J Am Chem Soc 2021; 143:8527-8532. [PMID: 33974426 DOI: 10.1021/jacs.1c00707] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Stable organic radicals have been of great academic interest not only in the context of fundamental understanding of reactive intermediates but also because of their numerous applications as functional materials. Apart from the early examples of triphenylmethyl and TEMPO derivatives, reports on air- and water-stable organic radicals are scarce, and their development remains a challenge. Herein, we present the design and synthesis of a novel organic radical based on a 1,2-dicarbonyl scaffold supported by N-heterocyclic carbenes (NHCs). The presented radical cations exhibit remarkable stability toward various harsh conditions, such as the presence of reactive chemicals (reductants, oxidants, strong acids, and bases) or high temperatures, by far exceeding the stability of triphenylmethyl and TEMPO radicals. In addition, physiological conditions including aqueous buffer and blood serum are tolerated. The steric and electronic stabilization provided by the two NHC moieties enabled the successful design of the highly stable radical.
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Affiliation(s)
- Youngsuk Kim
- Department of Chemistry, Pohang University of Science and Technology (POSTECH), Pohang 37673, Republic of Korea
| | - Jung Eun Byeon
- Department of Chemistry, Pohang University of Science and Technology (POSTECH), Pohang 37673, Republic of Korea
| | - Gu Yoon Jeong
- Department of Chemistry, Pohang University of Science and Technology (POSTECH), Pohang 37673, Republic of Korea
| | - Seoung Su Kim
- Department of Chemistry, Pohang University of Science and Technology (POSTECH), Pohang 37673, Republic of Korea
| | - Hayoung Song
- Department of Chemistry, Pohang University of Science and Technology (POSTECH), Pohang 37673, Republic of Korea
| | - Eunsung Lee
- Department of Chemistry, Pohang University of Science and Technology (POSTECH), Pohang 37673, Republic of Korea
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8
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Heaven G, Hollas MA, Tabernero L, Fielding AJ. Spin Labeling of Surface Cysteines Using a Bromoacrylaldehyde Spin Label. APPLIED MAGNETIC RESONANCE 2021; 52:959-970. [PMID: 34776648 PMCID: PMC8550513 DOI: 10.1007/s00723-021-01350-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/27/2021] [Revised: 04/28/2021] [Accepted: 05/10/2021] [Indexed: 06/13/2023]
Abstract
UNLABELLED Structural investigations of proteins and their biological complexes are now frequently complemented by distance constraints between spin labeled cysteines generated using double electron-electron resonance (DEER) spectroscopy, via site directed spin labeling (SDSL). Methanethiosulfonate spin label (MTSSL), has become ubiquitous in the SDSL of proteins, however, has limitations owing to its high number of rotamers, and reducibility. In this article we introduce the use of bromoacrylaldehyde spin label (BASL) as a cysteine spin label, demonstrating an advantage over MTSSL due to its increased selectivity for surface cysteines, eliminating the need to 'knock out' superfluous cysteine residues. Applied to the multidomain protein, His domain protein tyrosine phosphatase (HD-PTP), we show that BASL can be easily added in excess with selective labeling, whereas MTSSL causes protein precipitation. Furthermore, using DEER, we were able to measure a single cysteine pair distance in a three cysteine domain within HD-PTP. The label has a further advantage of comprising a sulfide in a three-bond tether, making it a candidate for protein binding and in-cell studies. SUPPLEMENTARY INFORMATION The online version contains supplementary material available at 10.1007/s00723-021-01350-1.
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Affiliation(s)
- Graham Heaven
- Department of Chemistry, The University of Manchester, Manchester, M13 9PL UK
| | - Michael A. Hollas
- Department of Chemistry, The University of Manchester, Manchester, M13 9PL UK
| | - Lydia Tabernero
- School of Biological Sciences, Faculty of Biology Medicine and Health, University of Manchester, Manchester, M13 9PL UK
| | - Alistair J. Fielding
- Centre for Natural Products Discovery, School of Pharmacy and Biomolecular Sciences, Liverpool John Moores University, Liverpool, L3 3AF UK
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Chen L, Wu L, Tan X, Rockenbauer A, Song Y, Liu Y. Synthesis and Redox Properties of Water-Soluble Asymmetric Trityl Radicals. J Org Chem 2021; 86:8351-8364. [PMID: 34043350 DOI: 10.1021/acs.joc.1c00766] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Tetrathiatriarylmethyl (trityl) radicals have been recently shown to react with biological oxidoreductants including glutathione (GSH), ascorbic acid (Asc), and superoxide anion radical (O2•-). However, how the substituents affect the reactivity of trityl radicals is still unknown. In this work, five asymmetric trityl radicals were synthesized and their reactivities with GSH, Asc, and O2•- investigated. Under aerobic conditions, GSH induces fast decays for the thioether- (TSA) and N-methyleneglycine-substituted (TGA) derivatives and slow decay for the 4-carboxyphenyl-containing one (TPA). Under anaerobic conditions, the direct reduction of these radicals by GSH also occurs with rate constants (kGSH) from 1.8 × 10-4 M-1 s-1 for TPA to 1.0 × 10-2 M-1 s-1 for TGA. Moreover, these radicals can also react with O2•- with rate constants (kSO) from 1.2 × 103 M-1 s-1 for ET-01 to 1.6 × 104 M-1 s-1 for TGA. Surprisingly, these radicals are completely inert to Asc in both aerobic and anaerobic conditions. Additionally, the substituents exert an important effect on redox potentials of these trityl radicals. This work demonstrates that the redox properties of the trityl radicals strongly depend on their substituents, and TPA with high stability toward GSH shows great potential for intracellular applications.
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Affiliation(s)
- Li Chen
- Tianjin Key Laboratory on Technologies Enabling Development of Clinical Therapeutics and Diagnostics, Department of Medicinal Chemistry, School of Pharmacy, Tianjin Medical University, Tianjin 300070, P. R. China
| | - Lanlan Wu
- Tianjin Key Laboratory on Technologies Enabling Development of Clinical Therapeutics and Diagnostics, Department of Medicinal Chemistry, School of Pharmacy, Tianjin Medical University, Tianjin 300070, P. R. China
| | - Xiaoli Tan
- Tianjin Key Laboratory on Technologies Enabling Development of Clinical Therapeutics and Diagnostics, Department of Medicinal Chemistry, School of Pharmacy, Tianjin Medical University, Tianjin 300070, P. R. China
| | - Antal Rockenbauer
- Institute of Materials and Environmental Chemistry, Research Centre for Natural Sciences, Hungarian Academy of Sciences, 1117 Budapest, Hungary.,Department of Physics, Budapest University of Technology and Economics, Budafoki ut 8, 1111 Budapest, Hungary
| | - Yuguang Song
- Tianjin Key Laboratory on Technologies Enabling Development of Clinical Therapeutics and Diagnostics, Department of Medicinal Chemistry, 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, Department of Medicinal Chemistry, School of Pharmacy, Tianjin Medical University, Tianjin 300070, P. R. China
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Fleck N, Heubach C, Hett T, Spicher S, Grimme S, Schiemann O. Ox-SLIM: Synthesis of and Site-Specific Labelling with a Highly Hydrophilic Trityl Spin Label. Chemistry 2021; 27:5292-5297. [PMID: 33404074 PMCID: PMC8048664 DOI: 10.1002/chem.202100013] [Citation(s) in RCA: 33] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2021] [Indexed: 01/04/2023]
Abstract
The combination of pulsed dipolar electron paramagnetic resonance spectroscopy (PDS) with site-directed spin labelling is a powerful tool in structural biology. Rational design of trityl-based spin labels has enabled studying biomolecular structures at room temperature and within cells. However, most current trityl spin labels suffer either from aggregation with proteins due to their hydrophobicity, or from bioconjugation groups not suitable for in-cell measurements. Therefore, we introduce here the highly hydrophilic trityl spin label Ox-SLIM. Engineered as a short-linked maleimide, it combines the most recent developments in one single molecule, as it does not aggregate with proteins, exhibits high resistance under in-cell conditions, provides a short linker, and allows for selective and efficient spin labelling via cysteines. Beyond establishing synthetic access to Ox-SLIM, its suitability as a spin label is illustrated and ultimately, highly sensitive PDS measurements are presented down to protein concentrations as low as 45 nm resolving interspin distances of up to 5.5 nm.
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Affiliation(s)
- Nico Fleck
- University of BonnInstitute of Physical and Theoretical ChemistryWegelerstr. 1253115BonnGermany
| | - Caspar Heubach
- University of BonnInstitute of Physical and Theoretical ChemistryWegelerstr. 1253115BonnGermany
| | - Tobias Hett
- University of BonnInstitute of Physical and Theoretical ChemistryWegelerstr. 1253115BonnGermany
| | - Sebastian Spicher
- University of BonnInstitute of Physical and Theoretical ChemistryBeringstr. 453115BonnGermany
| | - Stefan Grimme
- University of BonnInstitute of Physical and Theoretical ChemistryBeringstr. 453115BonnGermany
| | - Olav Schiemann
- University of BonnInstitute of Physical and Theoretical ChemistryWegelerstr. 1253115BonnGermany
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11
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Nguyen TB, Mac DH, Retailleau P. Room-Temperature Synthesis of Tetrasubstituted 1,3-Dithioles by Dimerizing Sulfuration of Chalcones with Elemental Sulfur. J Org Chem 2020; 85:13508-13516. [PMID: 33108186 DOI: 10.1021/acs.joc.0c01618] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Chalcones were found to undergo sulfurative dimerization with elemental sulfur to tetrasubstituted 1,3-dithioles. The reaction was found to proceed at room temperature in the presence of a nitrogen-base catalyst in DMSO.
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Affiliation(s)
- Thanh Binh Nguyen
- Institut de Chimie des Substances Naturelles, CNRS UPR 2301, Université Paris-Sud, Université Paris-Saclay, 1 avenue de la Terrasse, 91198 Gif-sur-Yvette, France
| | - Dinh Hung Mac
- Faculty of Chemistry, VNU University of Science, Vietnam National University in Hanoi, 19 Le Thanh Tong, Hanoi , Viet Nam
| | - Pascal Retailleau
- Institut de Chimie des Substances Naturelles, CNRS UPR 2301, Université Paris-Sud, Université Paris-Saclay, 1 avenue de la Terrasse, 91198 Gif-sur-Yvette, France
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12
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Kopp K, Schiemann O, Fleck N. Improved, Odorless Access to Benzo[1,2-d;4,5-d']- bis[1,3]dithioles and Tert-butyl Arylsulfides via C-S Cross Coupling. Molecules 2020; 25:molecules25163666. [PMID: 32806560 PMCID: PMC7464442 DOI: 10.3390/molecules25163666] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2020] [Revised: 08/07/2020] [Accepted: 08/11/2020] [Indexed: 11/26/2022] Open
Abstract
Benzo[1,2-d;4,5-d′]bis[1,3]dithioles are important building blocks within a range of functional materials such as fluorescent dyes, conjugated polymers, and stable trityl radicals. Access to these is usually gained via tert-butyl aryl sulfides, the synthesis of which requires the use of highly malodorous tert-butyl thiol and relies on SNAr-chemistry requiring harsh reaction conditions, while giving low yields. In the present work, S-tert-butyl isothiouronium bromide is successfully applied as an odorless surrogate for tert-butyl thiol. The C-S bond formation is carried out under palladium catalysis with the thiolate formed in situ resulting in high yields of tert-butyl aryl sulfides. The subsequent formation of benzo[1,2-d;4,5-d′]bis[1,3]dithioles is here achieved with scandium(III)triflate, a less harmful reagent than the usually used Lewis acids, e.g., boron trifluoride or tetrafluoroboric acid. This enables a convenient and environmentally more compliant access to high yields of benzo[1,2-d;4,5-d′]bis[1,3]dithioles.
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Sanzhaeva U, Poncelet M, Tseytlin O, Tseytlin M, Gencheva M, Eubank TD, Khramtsov VV, Driesschaert B. Synthesis, Characterization, and Application of a Highly Hydrophilic Triarylmethyl Radical for Biomedical EPR. J Org Chem 2020; 85:10388-10398. [PMID: 32698583 DOI: 10.1021/acs.joc.0c00557] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Stable tetrathiatriarylmethyl radicals have significantly contributed to the recent progress in biomedical electron paramagnetic resonance (EPR) due to their unmatched stability in biological media and long relaxation times. However, the lipophilic core of the most commonly used structure (Finland trityl) is responsible for its interaction with plasma biomacromolecules, such as albumin, and self-aggregation at high concentrations and/or low pH. While Finland trityl is generally considered inert toward many reactive radical species, we report that sulfite anion radical efficiently substitutes the three carboxyl moieties of Finland trityl with a high rate constant of 3.53 × 108 M-1 s-1, leading to a trisulfonated Finland trityl radical. This newly synthesized highly hydrophilic trityl radical shows an ultranarrow linewidth (ΔBpp = 24 mG), a lower affinity for albumin than Finland trityl, and a high aqueous solubility even at acidic pH. Therefore, this new tetrathiatriarylmethyl radical can be considered as a superior spin probe in comparison to the widely used Finland trityl. One of its potential applications was demonstrated by in vivo mapping oxygen in a mouse model of breast cancer. Moreover, we showed that one of the three sulfo groups can be easily substituted with S-, N-, and P-nucleophiles, opening access to various monofunctionalized sulfonated trityl radicals.
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Affiliation(s)
- Urikhan Sanzhaeva
- In Vivo Multifunctional Magnetic Resonance Center, Robert C. Byrd Health Sciences Center, West Virginia University, Morgantown, West Virginia 26506, United States.,Department of Biochemistry, West Virginia University, School of Medicine, Morgantown, West Virginia 26506, United States
| | - Martin Poncelet
- In Vivo Multifunctional Magnetic Resonance Center, Robert C. Byrd Health Sciences Center, West Virginia University, Morgantown, West Virginia 26506, United States.,Department of Pharmaceutical Sciences, West Virginia University, School of Pharmacy, Morgantown, West Virginia 26506, United States
| | - Oxana Tseytlin
- In Vivo Multifunctional Magnetic Resonance Center, Robert C. Byrd Health Sciences Center, West Virginia University, Morgantown, West Virginia 26506, United States.,Department of Biochemistry, West Virginia University, School of Medicine, Morgantown, West Virginia 26506, United States
| | - Mark Tseytlin
- In Vivo Multifunctional Magnetic Resonance Center, Robert C. Byrd Health Sciences Center, West Virginia University, Morgantown, West Virginia 26506, United States.,Department of Biochemistry, West Virginia University, School of Medicine, Morgantown, West Virginia 26506, United States
| | - Marieta Gencheva
- In Vivo Multifunctional Magnetic Resonance Center, Robert C. Byrd Health Sciences Center, West Virginia University, Morgantown, West Virginia 26506, United States.,Department of Microbiology, Immunology, and Cell Biology, West Virginia University, School of Medicine, Morgantown, West Virginia 26506, United States
| | - Timothy D Eubank
- In Vivo Multifunctional Magnetic Resonance Center, Robert C. Byrd Health Sciences Center, West Virginia University, Morgantown, West Virginia 26506, United States.,Department of Microbiology, Immunology, and Cell Biology, West Virginia University, School of Medicine, Morgantown, West Virginia 26506, United States
| | - Valery V Khramtsov
- In Vivo Multifunctional Magnetic Resonance Center, Robert C. Byrd Health Sciences Center, West Virginia University, Morgantown, West Virginia 26506, United States.,Department of Biochemistry, West Virginia University, School of Medicine, Morgantown, West Virginia 26506, United States
| | - Benoit Driesschaert
- In Vivo Multifunctional Magnetic Resonance Center, Robert C. Byrd Health Sciences Center, West Virginia University, Morgantown, West Virginia 26506, United States.,Department of Pharmaceutical Sciences, West Virginia University, School of Pharmacy, Morgantown, West Virginia 26506, United States
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14
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Fleck N, Heubach CA, Hett T, Haege FR, Bawol PP, Baltruschat H, Schiemann O. SLIM: A Short-Linked, Highly Redox-Stable Trityl Label for High-Sensitivity In-Cell EPR Distance Measurements. Angew Chem Int Ed Engl 2020; 59:9767-9772. [PMID: 32329172 PMCID: PMC7318235 DOI: 10.1002/anie.202004452] [Citation(s) in RCA: 54] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2020] [Indexed: 12/15/2022]
Abstract
The understanding of biomolecular function is coupled to knowledge about the structure and dynamics of these biomolecules, preferably acquired under native conditions. In this regard, pulsed dipolar EPR spectroscopy (PDS) in conjunction with site-directed spin labeling (SDSL) is an important method in the toolbox of biophysical chemistry. However, the currently available spin labels have diverse deficiencies for in-cell applications, for example, low radical stability or long bioconjugation linkers. In this work, a synthesis strategy is introduced for the derivatization of trityl radicals with a maleimide-functionalized methylene group. The resulting trityl spin label, called SLIM, yields narrow distance distributions, enables highly sensitive distance measurements down to concentrations of 90 nm, and shows high stability against reduction. Using this label, the guanine-nucleotide dissociation inhibitor (GDI) domain of Yersinia outer protein O (YopO) is shown to change its conformation within eukaryotic cells.
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Affiliation(s)
- Nico Fleck
- Institute of Physical and Theoretical ChemistryUniversity of BonnWegelerstr. 1253115BonnGermany
| | - Caspar A. Heubach
- Institute of Physical and Theoretical ChemistryUniversity of BonnWegelerstr. 1253115BonnGermany
| | - Tobias Hett
- Institute of Physical and Theoretical ChemistryUniversity of BonnWegelerstr. 1253115BonnGermany
| | - Florian R. Haege
- Institute of Physical and Theoretical ChemistryUniversity of BonnWegelerstr. 1253115BonnGermany
| | - Pawel P. Bawol
- Institute of Physical and Theoretical ChemistryUniversity of BonnRömerstr. 16453117BonnGermany
| | - Helmut Baltruschat
- Institute of Physical and Theoretical ChemistryUniversity of BonnRömerstr. 16453117BonnGermany
| | - Olav Schiemann
- Institute of Physical and Theoretical ChemistryUniversity of BonnWegelerstr. 1253115BonnGermany
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15
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Wili N, Hintz H, Vanas A, Godt A, Jeschke G. Distance measurement between trityl radicals by pulse dressed electron paramagnetic resonance with phase modulation. MAGNETIC RESONANCE (GOTTINGEN, GERMANY) 2020; 1:75-87. [PMID: 37904888 PMCID: PMC10500722 DOI: 10.5194/mr-1-75-2020] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/17/2020] [Accepted: 04/29/2020] [Indexed: 11/01/2023]
Abstract
Distance measurement in the nanometre range is among the most important applications of pulse electron paramagnetic resonance today, especially in biological applications. The longest distance that can be measured by all presently used pulse sequences is determined by the phase memory time T m of the observed spins. Here we show that one can measure the dipolar coupling during strong microwave irradiation by using an appropriate frequency- or phase-modulation scheme, i.e. by applying pulse sequences in the nutating frame. This decouples the electron spins from the surrounding nuclear spins and thus leads to significantly longer relaxation times of the microwave-dressed spins (i.e. the rotating frame relaxation times T 1 ρ and T 2 ρ ) compared to T m . The electron-electron dipolar coupling is not decoupled as long as both spins are excited, which can be implemented for trityl radicals at Q-band frequencies (35 GHz, 1.2 T). We show results for two bis-trityl rulers with inter-electron distances of about 4.1 and 5.3 nm and discuss technical challenges and possible next steps.
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Affiliation(s)
- Nino Wili
- Department of Chemistry and Applied Biosciences, Laboratory of Physical Chemistry, ETH Zurich, Vladimir-Prelog-Weg 2, 8093 Zurich, Switzerland
| | - Henrik Hintz
- Faculty of Chemistry and Center for Molecular Materials (CM2), Bielefeld University, Universitätsstrasse 25, 33615 Bielefeld, Germany
| | - Agathe Vanas
- Department of Chemistry and Applied Biosciences, 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
| | - Gunnar Jeschke
- Department of Chemistry and Applied Biosciences, Laboratory of Physical Chemistry, ETH Zurich, Vladimir-Prelog-Weg 2, 8093 Zurich, Switzerland
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16
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Fleck N, Heubach CA, Hett T, Haege FR, Bawol PP, Baltruschat H, Schiemann O. SLIM: A Short‐Linked, Highly Redox‐Stable Trityl Label for High‐Sensitivity In‐Cell EPR Distance Measurements. Angew Chem Int Ed Engl 2020. [DOI: 10.1002/ange.202004452] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Affiliation(s)
- Nico Fleck
- Institute of Physical and Theoretical ChemistryUniversity of Bonn Wegelerstr. 12 53115 Bonn Germany
| | - Caspar A. Heubach
- Institute of Physical and Theoretical ChemistryUniversity of Bonn Wegelerstr. 12 53115 Bonn Germany
| | - Tobias Hett
- Institute of Physical and Theoretical ChemistryUniversity of Bonn Wegelerstr. 12 53115 Bonn Germany
| | - Florian R. Haege
- Institute of Physical and Theoretical ChemistryUniversity of Bonn Wegelerstr. 12 53115 Bonn Germany
| | - Pawel P. Bawol
- Institute of Physical and Theoretical ChemistryUniversity of Bonn Römerstr. 164 53117 Bonn Germany
| | - Helmut Baltruschat
- Institute of Physical and Theoretical ChemistryUniversity of Bonn Römerstr. 164 53117 Bonn Germany
| | - Olav Schiemann
- Institute of Physical and Theoretical ChemistryUniversity of Bonn Wegelerstr. 12 53115 Bonn Germany
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17
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Tormyshev VM, Chubarov AS, Krumkacheva OA, Trukhin DV, Rogozhnikova OY, Spitsyna AS, Kuzhelev AA, Koval VV, Fedin MV, Godovikova TS, Bowman MK, Bagryanskaya EG. Methanethiosulfonate Derivative of OX063 Trityl: A Promising and Efficient Reagent for Side-Directed Spin Labeling of Proteins. Chemistry 2020; 26:2705-2712. [PMID: 31851392 DOI: 10.1002/chem.201904587] [Citation(s) in RCA: 31] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2019] [Revised: 11/30/2019] [Indexed: 12/20/2022]
Abstract
Trityl radicals (TAMs) have recently appeared as an alternative source of spin labels for measuring long distances in biological systems. Finland trityl radical (FTAM) served as the basis for this new generation of spin labels, but FTAM is rather lipophilic and susceptible to self-aggregation, noncovalent binding with lipophilic sites of proteins, and noncovalent docking at the termini of duplex DNA. In this paper the very hydrophilic OX063 TAM with very low toxicity and little tendency for aggregation is used as the basis for a spin label. Human serum albumin (HSA) labeled with OX063 has an intense narrow line typical of TAM radicals in solution, whereas HSA labeled with FTAM shows broad lines and extensive aggregation. In pulse EPR measurements, the measured phase memory time TM for HSA labeled with OX063 is 6.3 μs at 50 K, the longest yet obtained with a TAM-based spin label. The lowered lipophilicity also decreases side products in the labeling reaction.
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Affiliation(s)
- Victor M Tormyshev
- N. N. Vorozhtsov Novosibirsk Institute of Organic Chemistry SB RAS, Pr. Lavrentjeva 9, Novosibirsk, 630090, Russia
| | - Alexey S Chubarov
- Institute of Chemical Biology and Fundamental Medicine SB RAS, Pr. Lavrentjeva 8, Novosibirsk, 630090, Russia
| | - Olesya A Krumkacheva
- N. N. Vorozhtsov Novosibirsk Institute of Organic Chemistry SB RAS, Pr. Lavrentjeva 9, Novosibirsk, 630090, Russia.,International Tomography Center SB RAS, Institutskaya Str. 3a, Novosibirsk, 630090, Russia
| | - Dmitry V Trukhin
- N. N. Vorozhtsov Novosibirsk Institute of Organic Chemistry SB RAS, Pr. Lavrentjeva 9, Novosibirsk, 630090, Russia
| | - Olga Yu Rogozhnikova
- N. N. Vorozhtsov Novosibirsk Institute of Organic Chemistry SB RAS, Pr. Lavrentjeva 9, Novosibirsk, 630090, Russia
| | - Anna S Spitsyna
- N. N. Vorozhtsov Novosibirsk Institute of Organic Chemistry SB RAS, Pr. Lavrentjeva 9, Novosibirsk, 630090, Russia
| | - Andrey A Kuzhelev
- N. N. Vorozhtsov Novosibirsk Institute of Organic Chemistry SB RAS, Pr. Lavrentjeva 9, Novosibirsk, 630090, Russia
| | - Vladimir V Koval
- Institute of Chemical Biology and Fundamental Medicine SB RAS, Pr. Lavrentjeva 8, Novosibirsk, 630090, Russia
| | - Matvey V Fedin
- International Tomography Center SB RAS, Institutskaya Str. 3a, Novosibirsk, 630090, Russia
| | - Tatyana S Godovikova
- Institute of Chemical Biology and Fundamental Medicine SB RAS, Pr. Lavrentjeva 8, Novosibirsk, 630090, Russia
| | - Michael K Bowman
- Department of Chemistry and Biochemistry, The University of Alabama, Tuscaloosa, Alabama, 35487-0336, USA
| | - Elena G Bagryanskaya
- N. N. Vorozhtsov Novosibirsk Institute of Organic Chemistry SB RAS, Pr. Lavrentjeva 9, Novosibirsk, 630090, Russia
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18
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Poncelet M, Huffman JL, Khramtsov VV, Dhimitruka I, Driesschaert B. Synthesis of hydroxyethyl tetrathiatriarylmethyl radicals OX063 and OX071. RSC Adv 2019; 9:35073-35076. [PMID: 32483485 PMCID: PMC7263632 DOI: 10.1039/c9ra08633a] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
We report the synthesis of hydroxyethyl tetrathiatriarylmethyl radical OX063 and its deuterated analogue OX071 for biomedical EPR applications. Synthesis of OX063 and OX063-d24 spin probes and DNP agents.![]()
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Affiliation(s)
- Martin Poncelet
- Department of Pharmaceutical Sciences, School of Pharmacy, West Virginia University, Morgantown, WV, 26506, USA.,In Vivo Multifunctional Magnetic Resonance center, Robert C. Byrd Health Sciences Center, West Virginia University, Morgantown, WV, 26506, USA
| | - Justin L Huffman
- Department of Pharmaceutical Sciences, School of Pharmacy, West Virginia University, Morgantown, WV, 26506, USA.,In Vivo Multifunctional Magnetic Resonance center, Robert C. Byrd Health Sciences Center, West Virginia University, Morgantown, WV, 26506, USA
| | - Valery V Khramtsov
- In Vivo Multifunctional Magnetic Resonance center, Robert C. Byrd Health Sciences Center, West Virginia University, Morgantown, WV, 26506, USA.,Department of Biochemistry, School of Medicine, West Virginia University, Morgantown, WV, 26506, USA
| | - Ilirian Dhimitruka
- School of Health and Natural Sciences, Mercy College, Dobbs Ferry, NY 10522, USA
| | - Benoit Driesschaert
- Department of Pharmaceutical Sciences, School of Pharmacy, West Virginia University, Morgantown, WV, 26506, USA.,In Vivo Multifunctional Magnetic Resonance center, Robert C. Byrd Health Sciences Center, West Virginia University, Morgantown, WV, 26506, USA
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19
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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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20
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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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