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Thomas B, Jardón-Álvarez D, Carmieli R, van Tol J, Leskes M. The Effect of Disorder on Endogenous MAS-DNP: Study of Silicate Glasses and Crystals. THE JOURNAL OF PHYSICAL CHEMISTRY. C, NANOMATERIALS AND INTERFACES 2023; 127:4759-4772. [PMID: 36925559 PMCID: PMC10009812 DOI: 10.1021/acs.jpcc.2c08849] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/18/2022] [Revised: 02/05/2023] [Indexed: 06/18/2023]
Abstract
In dynamic nuclear polarization nuclear magnetic resonance (DNP-NMR) experiments, the large Boltzmann polarization of unpaired electrons is transferred to surrounding nuclei, leading to a significant increase in the sensitivity of the NMR signal. In order to obtain large polarization gains in the bulk of inorganic samples, paramagnetic metal ions are introduced as minor dopants acting as polarizing agents. While this approach has been shown to be very efficient in crystalline inorganic oxides, significantly lower enhancements have been reported when applying this approach to oxide glasses. In order to rationalize the origin of the difference in the efficiency of DNP in amorphous and crystalline inorganic matrices, we performed a detailed comparison in terms of their magnetic resonance properties. To diminish differences in the DNP performance arising from distinct nuclear interactions, glass and crystal systems of similar compositions were chosen, Li2OCaO·2SiO2 and Li2CaSiO4, respectively. Using Gd(III) as polarizing agent, DNP provided signal enhancements in the range of 100 for the crystalline sample, while only up to around factor 5 in the glass, for both 6Li and 29Si nuclei. We find that the drop in enhancement in glasses can be attributed to three main factors: shorter nuclear and electron relaxation times as well as the dielectric properties of glass and crystal. The amorphous nature of the glass sample is responsible for a high dielectric loss, leading to efficient microwave absorption and consequently lower effective microwave power and an increase in sample temperature which leads to further reduction of the electron relaxation time. These results help rationalize the observed sensitivity enhancements and provide guidance in identifying materials that could benefit from the DNP approach.
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Affiliation(s)
- Brijith Thomas
- Department
of Molecular Chemistry & Materials Science, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Daniel Jardón-Álvarez
- Department
of Molecular Chemistry & Materials Science, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Raanan Carmieli
- Department
of Chemical Research Support, Weizmann Institute
of Science, Rehovot 76100, Israel
| | - Johan van Tol
- National
High Magnetic Field Laboratory, Florida
State University, Tallahassee, Florida 32310, United States
| | - Michal Leskes
- Department
of Molecular Chemistry & Materials Science, Weizmann Institute of Science, Rehovot 76100, Israel
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2
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Miao Q, Nitsche C, Orton H, Overhand M, Otting G, Ubbink M. Paramagnetic Chemical Probes for Studying Biological Macromolecules. Chem Rev 2022; 122:9571-9642. [PMID: 35084831 PMCID: PMC9136935 DOI: 10.1021/acs.chemrev.1c00708] [Citation(s) in RCA: 35] [Impact Index Per Article: 17.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2021] [Indexed: 12/11/2022]
Abstract
Paramagnetic chemical probes have been used in electron paramagnetic resonance (EPR) and nuclear magnetic resonance (NMR) spectroscopy for more than four decades. Recent years witnessed a great increase in the variety of probes for the study of biological macromolecules (proteins, nucleic acids, and oligosaccharides). This Review aims to provide a comprehensive overview of the existing paramagnetic chemical probes, including chemical synthetic approaches, functional properties, and selected applications. Recent developments have seen, in particular, a rapid expansion of the range of lanthanoid probes with anisotropic magnetic susceptibilities for the generation of structural restraints based on residual dipolar couplings and pseudocontact shifts in solution and solid state NMR spectroscopy, mostly for protein studies. Also many new isotropic paramagnetic probes, suitable for NMR measurements of paramagnetic relaxation enhancements, as well as EPR spectroscopic studies (in particular double resonance techniques) have been developed and employed to investigate biological macromolecules. Notwithstanding the large number of reported probes, only few have found broad application and further development of probes for dedicated applications is foreseen.
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Affiliation(s)
- Qing Miao
- Leiden
Institute of Chemistry, Leiden University, Einsteinweg 55, Leiden 2333 CC, The Netherlands
- School
of Chemistry &Chemical Engineering, Shaanxi University of Science & Technology, Xi’an710021, China
| | - Christoph Nitsche
- Research
School of Chemistry, The Australian National
University, Sullivans Creek Road, Canberra, Australian Capital Territory 2601, Australia
| | - Henry Orton
- Research
School of Chemistry, The Australian National
University, Sullivans Creek Road, Canberra, Australian Capital Territory 2601, Australia
- ARC
Centre of Excellence for Innovations in Peptide & Protein Science,
Research School of Chemistry, Australian
National University, Sullivans Creek Road, Canberra, Australian Capital Territory 2601, Australia
| | - Mark Overhand
- Leiden
Institute of Chemistry, Leiden University, Einsteinweg 55, Leiden 2333 CC, The Netherlands
| | - Gottfried Otting
- Research
School of Chemistry, The Australian National
University, Sullivans Creek Road, Canberra, Australian Capital Territory 2601, Australia
- ARC
Centre of Excellence for Innovations in Peptide & Protein Science,
Research School of Chemistry, Australian
National University, Sullivans Creek Road, Canberra, Australian Capital Territory 2601, Australia
| | - Marcellus Ubbink
- Leiden
Institute of Chemistry, Leiden University, Einsteinweg 55, Leiden 2333 CC, The Netherlands
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3
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Jardón-Álvarez D, Malka T, van Tol J, Feldman Y, Carmieli R, Leskes M. Monitoring electron spin fluctuations with paramagnetic relaxation enhancement. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2022; 336:107143. [PMID: 35085928 DOI: 10.1016/j.jmr.2022.107143] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/25/2021] [Revised: 12/30/2021] [Accepted: 01/03/2022] [Indexed: 06/14/2023]
Abstract
The magnetic interactions between the spin of an unpaired electron and the surrounding nuclear spins can be exploited to gain structural information, to reduce nuclear relaxation times as well as to create nuclear hyperpolarization via dynamic nuclear polarization (DNP). A central aspect that determines how these interactions manifest from the point of view of NMR is the timescale of the fluctuations of the magnetic moment of the electron spins. These fluctuations, however, are elusive, particularly when electron relaxation times are short or interactions among electronic spins are strong. Here we map the fluctuations by analyzing the ratio between longitudinal and transverse nuclear relaxation times T1/T2, a quantity which depends uniquely on the rate of the electron fluctuations and the Larmor frequency of the involved nuclei. This analysis enables rationalizing the evolution of NMR lineshapes, signal quenching as well as DNP enhancements as a function of the concentration of the paramagnetic species and the temperature, demonstrated here for LiMg1-xMnxPO4 and Fe(III) doped Li4Ti5O12, respectively. For the latter, we observe a linear dependence of the DNP enhancement and the electron relaxation time within a temperature range between 100 and 300 K.
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Affiliation(s)
- Daniel Jardón-Álvarez
- Department of Molecular Chemistry and Materials Science, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Tahel Malka
- Department of Molecular Chemistry and Materials Science, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Johan van Tol
- National High Magnetic Field Laboratory, Florida State University, 1800 E. Paul Dirac Dr, Tallahassee, FL 32310, United States
| | - Yishay Feldman
- Department of Chemical Research Support, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Raanan Carmieli
- Department of Chemical Research Support, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Michal Leskes
- Department of Molecular Chemistry and Materials Science, Weizmann Institute of Science, Rehovot 76100, Israel.
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4
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Reif B. Deuteration for High-Resolution Detection of Protons in Protein Magic Angle Spinning (MAS) Solid-State NMR. Chem Rev 2021; 122:10019-10035. [PMID: 34870415 DOI: 10.1021/acs.chemrev.1c00681] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Proton detection developed in the last 20 years as the method of choice to study biomolecules in the solid state. In perdeuterated proteins, proton dipolar interactions are strongly attenuated, which allows yielding of high-resolution proton spectra. Perdeuteration and backsubstitution of exchangeable protons is essential if samples are rotated with MAS rotation frequencies below 60 kHz. Protonated samples can be investigated directly without spin dilution using proton detection methods in case the MAS frequency exceeds 110 kHz. This review summarizes labeling strategies and the spectroscopic methods to perform experiments that yield assignments, quantitative information on structure, and dynamics using perdeuterated samples. Techniques for solvent suppression, H/D exchange, and deuterium spectroscopy are discussed. Finally, experimental and theoretical results that allow estimation of the sensitivity of proton detected experiments as a function of the MAS frequency and the external B0 field in a perdeuterated environment are compiled.
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Affiliation(s)
- Bernd Reif
- Bayerisches NMR Zentrum (BNMRZ) at the Department of Chemistry, Technische Universität München (TUM), Lichtenbergstr. 4, 85747 Garching, Germany.,Helmholtz-Zentrum München (HMGU), Deutsches Forschungszentrum für Gesundheit und Umwelt, Institute of Structural Biology (STB), Ingolstädter Landstr. 1, 85764 Neuherberg, Germany
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5
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Di Mauro GM, Hardin NZ, Ramamoorthy A. Lipid-nanodiscs formed by paramagnetic metal chelated polymer for fast NMR data acquisition. BIOCHIMICA ET BIOPHYSICA ACTA. BIOMEMBRANES 2020; 1862:183332. [PMID: 32360741 PMCID: PMC7340147 DOI: 10.1016/j.bbamem.2020.183332] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/18/2020] [Revised: 04/21/2020] [Accepted: 04/27/2020] [Indexed: 02/07/2023]
Abstract
Lipid-nanodiscs have been shown to be an exciting innovation as a membrane-mimicking system for studies on membrane proteins by a variety of biophysical techniques, including NMR spectroscopy. Although NMR spectroscopy is unique in enabling the atomic-resolution investigation of dynamic structures of membrane-associated molecules, it, unfortunately, suffers from intrinsically low sensitivity. The long data acquisition often used to enhance the sensitivity is not desirable for sensitive membrane proteins. Instead, paramagnetic relaxation enhancement (PRE) has been used to reduce NMR data acquisition time or to reduce the amount of sample required to acquire an NMR spectra. However, the PRE approach involves the introduction of external paramagnetic probes in the system, which can induce undesired changes in the sample and on the observed NMR spectra. For example, the addition of paramagnetic ions, as frequently used, can denature the protein via direct interaction and also through sample heating. In this study, we show how the introduction of paramagnetic tags on the outer belt of polymer-nanodiscs can be used to speed-up data acquisition by significantly reducing the spin-lattice relaxation (T1) times with minimum-to-no alteration of the spectral quality. Our results also demonstrate the feasibility of using different types of paramagnetic ions (Eu3+, Gd3+, Dy3+, Er3+, Yb3+) for NMR studies on lipid-nanodiscs. Experimental results characterizing the formation of lipid-nanodiscs by the metal-chelated polymer, and their increased tolerance toward metal ions are also reported.
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Affiliation(s)
- Giacomo M Di Mauro
- Department of Chemistry, University of Michigan, Ann Arbor, MI 48109-1055, USA
| | - Nathaniel Z Hardin
- Department of Chemistry, University of Michigan, Ann Arbor, MI 48109-1055, USA
| | - Ayyalusamy Ramamoorthy
- Department of Chemistry, University of Michigan, Ann Arbor, MI 48109-1055, USA; Biophysics and Chemistry Department, The University of Michigan, Ann Arbor, MI 48109-1055, USA; Macromolecular Science and Engineering, The University of Michigan, Ann Arbor, MI 48109-1055, USA; Biomedical Engineering, The University of Michigan, Ann Arbor, MI 48109-1055, USA.
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6
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Zhang R, Nishiyama Y, Ramamoorthy A. Exploiting heterogeneous time scale of dynamics to enhance 2D HETCOR solid-state NMR sensitivity. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2019; 309:106615. [PMID: 31669793 DOI: 10.1016/j.jmr.2019.106615] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/26/2019] [Revised: 09/11/2019] [Accepted: 10/03/2019] [Indexed: 06/10/2023]
Abstract
Multidimensional solid-state NMR spectroscopy plays a significant role in offering atomic-level insights into molecular systems. In particular, heteronuclear chemical shift correlation (HETCOR) experiments could provide local chemical and structural information in terms of spatial heteronuclear proximity and through-bond connectivity. In solid state, the transfer of magnetization between heteronuclei, a key step in HETCOR experiments, is usually achieved using cross-polarization (CP) or insensitive nuclei enhanced by polarization transfer (INEPT) depending on the sample characteristics and magic-angle-spinning (MAS) frequency. But, for a multiphase system constituting molecular components that differ in their time scales of mobilities, CP efficiency is pretty low for mobile components because of the averaging of heteronuclear dipolar couplings whereas INEPT is inefficient for immobile components due to the short T2 and can yield through-space connectivity due to strong proton spin diffusion for immobile components especially under moderate spinning speeds. Herein, in this study we present two 2D pulse sequences that enable the sequential acquisition of 13C/1H HETCOR NMR spectra for the rigid and mobile components by taking full advantage of the abundant proton magnetization in a single experiment with barely increasing the overall experimental time. In particular, the 13C-detected HETCOR experiment could be applied under slow MAS conditions, where a multiple-pulse sequence is typically employed to enhance 1H spectral resolution in the indirect dimension. In contrast, the 1H-detected HETCOR experiment should be applied under ultrafast MAS, where CP and heteronuclear nuclear Overhauser effect (NOE) polarization transfer are combined to enhance 13C signal intensities for mobile components. These pulse sequences are experimentally demonstrated on two model systems to obtain 2D 13C/1H chemical shift correlation spectra of rigid and mobile components independently and separately. These pulse sequences can be used for dynamics based spectral editing and resonance assignments. Therefore, we believe the proposed 2D HETCOR NMR pulse sequences will be beneficial for the structural studies of heterogeneous systems containing molecular components that differ in their time scale of motions for understanding the interplay of structures and properties.
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Affiliation(s)
- Rongchun Zhang
- Biophysics and Department of Chemistry, Biomedical Engineering, Maromolecular Science and Engineering, University of Michigan, Ann Arbor, MI 48109-1055, USA
| | - Yusuke Nishiyama
- NMR Science and Development Division, RIKEN SPring-8 Center, Nanocrystallography Unit, RIKEN-JEOL Collaboration Center, RIKEN, Yokohama, Kanagawa 230-0045, Japan; JEOL RESONANCE Inc., Musashino, Akishima, Tokyo 196-8558, Japan.
| | - Ayyalusamy Ramamoorthy
- Biophysics and Department of Chemistry, Biomedical Engineering, Maromolecular Science and Engineering, University of Michigan, Ann Arbor, MI 48109-1055, USA.
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7
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Tang M, Lam D. Paramagnetic solid-state NMR of proteins. SOLID STATE NUCLEAR MAGNETIC RESONANCE 2019; 103:9-16. [PMID: 31585788 DOI: 10.1016/j.ssnmr.2019.101621] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/05/2019] [Revised: 09/24/2019] [Accepted: 09/24/2019] [Indexed: 06/10/2023]
Abstract
The paramagnetic properties of metal ions and stable radicals can affect NMR spectra, which can lead to changes in peak intensities, relaxation times and chemical shifts. The changes from paramagnetic effects provide intriguing opportunities for solid-state NMR studies of proteins. In this review, we summarized the trends and progress of paramagnetic solid-state NMR of proteins in the past decade, and showed that paramagnetic effects have great potential applications for sensitivity enhancement, structure determination and topological analysis for microcrystalline proteins, protein complexes, protein aggregates and membrane proteins.
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Affiliation(s)
- Ming Tang
- Department of Chemistry, College of Staten Island - Ph.D. Programs in Chemistry and Biochemistry, The Graduate Center of the City University of New York, New York, NY, 10016, USA.
| | - Dennis Lam
- Department of Chemistry, College of Staten Island - Ph.D. Programs in Chemistry and Biochemistry, The Graduate Center of the City University of New York, New York, NY, 10016, USA
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8
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Jaroniec CP. Two decades of progress in structural and dynamic studies of amyloids by solid-state NMR. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2019; 306:42-47. [PMID: 31311708 PMCID: PMC6703944 DOI: 10.1016/j.jmr.2019.07.015] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/14/2019] [Revised: 06/22/2019] [Accepted: 07/08/2019] [Indexed: 05/09/2023]
Abstract
In this perspective article I briefly highlight the rapid progress made over the past two decades in atomic level structural and dynamic studies of amyloids, which are representative of non-crystalline biomacromolecular assemblies, by magic-angle spinning solid-state NMR spectroscopy. Given new and continuing developments in solid-state NMR instrumentation and methodology, ongoing research in this area promises to contribute to an improved understanding of amyloid structure, polymorphism, interactions, assembly mechanisms, and biological function and toxicity.
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Affiliation(s)
- Christopher P Jaroniec
- Department of Chemistry and Biochemistry, The Ohio State University, 100 West 18th Avenue, Columbus, OH 43210, USA.
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9
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Mukhopadhyay D, Gupta C, Theint T, Jaroniec CP. Peptide bond conformation in peptides and proteins probed by dipolar coupling-chemical shift tensor correlation solid-state NMR. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2018; 297:152-160. [PMID: 30396157 PMCID: PMC6289736 DOI: 10.1016/j.jmr.2018.10.015] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/29/2018] [Revised: 10/25/2018] [Accepted: 10/26/2018] [Indexed: 05/30/2023]
Abstract
Multidimensional magic-angle spinning solid-state NMR experiments are described that permit cis and trans peptide bonds in uniformly 13C,15N-labeled peptides and proteins to be unambiguously distinguished in residue-specific manner by determining the relative orientations of the amide 13C' CSA and 1H-15N dipolar coupling tensors. The experiments are demonstrated for model peptides glycylglycine and 2,5-diketopiperazine containing trans and cis peptide bonds, respectively. Subsequently, the measurements are extended to two representative proteins that contain exclusively trans peptide bonds, microcrystalline B3 immunoglobulin domain of protein G and Y145Stop human prion protein amyloid fibrils, to illustrate their applicability to a wide range of protein systems.
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Affiliation(s)
- Dwaipayan Mukhopadhyay
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH 43210, United States
| | - Chitrak Gupta
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH 43210, United States
| | - Theint Theint
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH 43210, United States
| | - Christopher P Jaroniec
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH 43210, United States.
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10
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Theint T, Xia Y, Nadaud PS, Mukhopadhyay D, Schwieters CD, Surewicz K, Surewicz WK, Jaroniec CP. Structural Studies of Amyloid Fibrils by Paramagnetic Solid-State Nuclear Magnetic Resonance Spectroscopy. J Am Chem Soc 2018; 140:13161-13166. [PMID: 30295029 DOI: 10.1021/jacs.8b06758] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Application of paramagnetic solid-state NMR to amyloids is demonstrated, using Y145Stop human prion protein modified with nitroxide spin-label or EDTA-Cu2+ tags as a model. By using sample preparation protocols based on seeding with preformed fibrils, we show that paramagnetic protein analogs can be induced into adopting the wild-type amyloid structure. Measurements of residue-specific intramolecular and intermolecular paramagnetic relaxation enhancements enable determination of protein fold within the fibril core and protofilament assembly. These methods are expected to be widely applicable to other amyloids and protein assemblies.
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Affiliation(s)
- Theint Theint
- Department of Chemistry and Biochemistry , The Ohio State University , Columbus , Ohio 43210 , United States
| | - Yongjie Xia
- Department of Chemistry and Biochemistry , The Ohio State University , Columbus , Ohio 43210 , United States
| | - Philippe S Nadaud
- Department of Chemistry and Biochemistry , The Ohio State University , Columbus , Ohio 43210 , United States
| | - Dwaipayan Mukhopadhyay
- Department of Chemistry and Biochemistry , The Ohio State University , Columbus , Ohio 43210 , United States
| | - Charles D Schwieters
- Center for Information Technology , National Institutes of Health , Bethesda , Maryland 20892 , United States
| | - Krystyna Surewicz
- Department of Physiology and Biophysics , Case Western Reserve University , Cleveland , Ohio 44106 , United States
| | - Witold K Surewicz
- Department of Physiology and Biophysics , Case Western Reserve University , Cleveland , Ohio 44106 , United States
| | - Christopher P Jaroniec
- Department of Chemistry and Biochemistry , The Ohio State University , Columbus , Ohio 43210 , United States
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11
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Orton HW, Otting G. Accurate Electron-Nucleus Distances from Paramagnetic Relaxation Enhancements. J Am Chem Soc 2018; 140:7688-7697. [PMID: 29790335 DOI: 10.1021/jacs.8b03858] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Measurements of paramagnetic relaxation enhancements (PREs) in 1H NMR spectra are an important tool to obtain long-range distance information in proteins, but quantitative interpretation is easily compromised by nonspecific intermolecular PREs. Here we show that PREs generated by lanthanides with anisotropic magnetic susceptibilities offer a route to accurate calibration-free distance measurements. As these lanthanides change 1H chemical shifts due to pseudocontact shifts, the relaxation rates in the paramagnetic and diamagnetic state can be measured with a single sample that simultaneously contains the protein labeled with a paramagnetic and a diamagnetic lanthanide ion. Nonspecific intermolecular PREs are thus automatically subtracted when calculating the PREs as the difference in nuclear relaxation rates between paramagnetic and diamagnetic protein. Although PREs from lanthanides with anisotropic magnetic susceptibilities are complicated by additional cross-correlation effects and residual dipolar couplings (RDCs) in the paramagnetic state, these effects can be controlled by the choice of lanthanide ion and experimental conditions. Using calbindin D9k with erbium, we succeeded in measuring intramolecular PREs with unprecedented accuracy, resulting in distance predictions with a root-mean-square-deviation of <0.9 Å in the range 11-24 Å.
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Affiliation(s)
- Henry W Orton
- Research School of Chemistry , Australian National University , Canberra , Australian Capital Territory 2601 , Australia
| | - Gottfried Otting
- Research School of Chemistry , Australian National University , Canberra , Australian Capital Territory 2601 , Australia
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