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Gigli L, Silva JM, Cerofolini L, Macedo AL, Geraldes CFGC, Suturina EA, Calderone V, Fragai M, Parigi G, Ravera E, Luchinat C. Machine Learning-Enhanced Quantum Chemistry-Assisted Refinement of the Active Site Structure of Metalloproteins. Inorg Chem 2024; 63:10713-10725. [PMID: 38805564 DOI: 10.1021/acs.inorgchem.4c01274] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/30/2024]
Abstract
Understanding the fine structural details of inhibitor binding at the active site of metalloenzymes can have a profound impact on the rational drug design targeted to this broad class of biomolecules. Structural techniques such as NMR, cryo-EM, and X-ray crystallography can provide bond lengths and angles, but the uncertainties in these measurements can be as large as the range of values that have been observed for these quantities in all the published structures. This uncertainty is far too large to allow for reliable calculations at the quantum chemical (QC) levels for developing precise structure-activity relationships or for improving the energetic considerations in protein-inhibitor studies. Therefore, the need arises to rely upon computational methods to refine the active site structures well beyond the resolution obtained with routine application of structural methods. In a recent paper, we have shown that it is possible to refine the active site of cobalt(II)-substituted MMP12, a metalloprotein that is a relevant drug target, by matching to the experimental pseudocontact shifts (PCS) those calculated using multireference ab initio QC methods. The computational cost of this methodology becomes a significant bottleneck when the starting structure is not sufficiently close to the final one, which is often the case with biomolecular structures. To tackle this problem, we have developed an approach based on a neural network (NN) and a support vector regression (SVR) and applied it to the refinement of the active site structure of oxalate-inhibited human carbonic anhydrase 2 (hCAII), another prototypical metalloprotein target. The refined structure gives a remarkably good agreement between the QC-calculated and the experimental PCS. This study not only contributes to the knowledge of CAII but also demonstrates the utility of combining machine learning (ML) algorithms with QC calculations, offering a promising avenue for investigating other drug targets and complex biological systems in general.
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Affiliation(s)
- Lucia Gigli
- Magnetic Resonance Center (CERM), University of Florence, Sesto Fiorentino 50019, Italy
- Department of Chemistry "Ugo Schiff", University of Florence, Sesto Fiorentino 50019, Italy
- Consorzio Interuniversitario Risonanze Magnetiche Metallo Proteine (CIRMMP), Sesto Fiorentino 50019, Italy
| | - José Malanho Silva
- Magnetic Resonance Center (CERM), University of Florence, Sesto Fiorentino 50019, Italy
- Department of Chemistry "Ugo Schiff", University of Florence, Sesto Fiorentino 50019, Italy
- Consorzio Interuniversitario Risonanze Magnetiche Metallo Proteine (CIRMMP), Sesto Fiorentino 50019, Italy
- UCIBIO, Department of Chemistry, NOVA School of Science and Technology, Universidade NOVA de Lisboa, 2819-516 Caparica, Portugal
| | - Linda Cerofolini
- Magnetic Resonance Center (CERM), University of Florence, Sesto Fiorentino 50019, Italy
- Department of Chemistry "Ugo Schiff", University of Florence, Sesto Fiorentino 50019, Italy
- Consorzio Interuniversitario Risonanze Magnetiche Metallo Proteine (CIRMMP), Sesto Fiorentino 50019, Italy
| | - Anjos L Macedo
- UCIBIO, Department of Chemistry, NOVA School of Science and Technology, Universidade NOVA de Lisboa, 2819-516 Caparica, Portugal
- Associate Laboratory i4HB─Institute for Health and Bioeconomy, NOVA School of Science and Technology, Universidade NOVA de Lisboa, 2819-516 Caparica, Portugal
| | - Carlos F G C Geraldes
- Department of Life Sciences, Faculty of Science and Technology, 3000-393 Coimbra, Portugal
- Coimbra Chemistry Center─Institute of Molecular Sciences (CCC-IMS), University of Coimbra, 3004-535 Coimbra, Portugal
| | | | - Vito Calderone
- Magnetic Resonance Center (CERM), University of Florence, Sesto Fiorentino 50019, Italy
- Department of Chemistry "Ugo Schiff", University of Florence, Sesto Fiorentino 50019, Italy
- Consorzio Interuniversitario Risonanze Magnetiche Metallo Proteine (CIRMMP), Sesto Fiorentino 50019, Italy
| | - Marco Fragai
- Magnetic Resonance Center (CERM), University of Florence, Sesto Fiorentino 50019, Italy
- Department of Chemistry "Ugo Schiff", University of Florence, Sesto Fiorentino 50019, Italy
- Consorzio Interuniversitario Risonanze Magnetiche Metallo Proteine (CIRMMP), Sesto Fiorentino 50019, Italy
| | - Giacomo Parigi
- Magnetic Resonance Center (CERM), University of Florence, Sesto Fiorentino 50019, Italy
- Department of Chemistry "Ugo Schiff", University of Florence, Sesto Fiorentino 50019, Italy
- Consorzio Interuniversitario Risonanze Magnetiche Metallo Proteine (CIRMMP), Sesto Fiorentino 50019, Italy
| | - Enrico Ravera
- Magnetic Resonance Center (CERM), University of Florence, Sesto Fiorentino 50019, Italy
- Department of Chemistry "Ugo Schiff", University of Florence, Sesto Fiorentino 50019, Italy
- Consorzio Interuniversitario Risonanze Magnetiche Metallo Proteine (CIRMMP), Sesto Fiorentino 50019, Italy
- Florence Data Science, University of Florence, Florence 50134, Italy
| | - Claudio Luchinat
- Magnetic Resonance Center (CERM), University of Florence, Sesto Fiorentino 50019, Italy
- Department of Chemistry "Ugo Schiff", University of Florence, Sesto Fiorentino 50019, Italy
- Consorzio Interuniversitario Risonanze Magnetiche Metallo Proteine (CIRMMP), Sesto Fiorentino 50019, Italy
- Giotto Biotech, S.R.L., Sesto Fiorentino 50019, Italy
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2
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Islam MA, Pell AJ. Delving into theoretical and computational considerations for accurate calculation of chemical shifts in paramagnetic transition metal systems using quantum chemical methods. Phys Chem Chem Phys 2024; 26:12786-12798. [PMID: 38619872 DOI: 10.1039/d4cp00683f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/16/2024]
Abstract
The chemical shielding tensor for a paramagnetic system has been derived from the macroscopically observed magnetization using the perturbation theory. An approach to calculate the paramagnetic chemical shifts in transition metal systems based on the spin-only magnetic susceptibility directly evaluated from the ab initio Hilbert space of the electronic Zeeman Hamiltonian has been discussed. Computationally, several advantages are associated with this approach: (a) it includes the state-specific paramagnetic Curie (first-order) and Van Vleck (second-order) contributions of the paramagnetic ion to the paramagnetic chemical shifts; (b) thus it avoids the system-specific modeling and evaluating effectively in terms of the electron paramagnetic resonance (EPR) spin Hamiltonian parameters of the magnetic moment of the paramagnetic ion formulated previously; (c) it can be utilized both in the point-dipole (PD) approximation (in the long-range) and with the quantum chemical (QC) method based the hyperfine tensors (in the short-range). Additionally, we have examined the predictive performance of various density functional theory (DFT) functionals of different families and commonly used core-augmented basis sets for nuclear magnetic resonance (NMR) chemical shifts. A selection of transition metal ion complexes with and without first-order orbital contributions, namely the [M(AcPyOx)3(BPh)]+ complexes of M = Mn2+, Ni2+ and Co2+ ions and CoTp2 complex and their reported NMR chemical shifts are studied from QC methods for illustration.
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Affiliation(s)
- Md Ashraful Islam
- Centre de RMN à Très Hauts Champs de Lyon, UMR-5082, CNRS/UCB Lyon 1/ENS de Lyon, 69100 Villeurbanne, France.
| | - Andrew J Pell
- Centre de RMN à Très Hauts Champs de Lyon, UMR-5082, CNRS/UCB Lyon 1/ENS de Lyon, 69100 Villeurbanne, France.
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3
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Grifagni D, Silva JM, Querci L, Lepoivre M, Vallières C, Louro RO, Banci L, Piccioli M, Golinelli-Cohen MP, Cantini F. Biochemical and cellular characterization of the CISD3 protein: Molecular bases of cluster release and destabilizing effects of nitric oxide. J Biol Chem 2024; 300:105745. [PMID: 38354784 PMCID: PMC10937110 DOI: 10.1016/j.jbc.2024.105745] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2023] [Revised: 02/02/2024] [Accepted: 02/05/2024] [Indexed: 02/16/2024] Open
Abstract
The NEET proteins, an important family of iron-sulfur (Fe-S) proteins, have generated a strong interest due to their involvement in diverse diseases such as cancer, diabetes, and neurodegenerative disorders. Among the human NEET proteins, CISD3 has been the least studied, and its functional role is still largely unknown. We have investigated the biochemical features of CISD3 at the atomic and in cellulo levels upon challenge with different stress conditions i.e., iron deficiency, exposure to hydrogen peroxide, and nitric oxide. The redox and cellular stability properties of the protein agree on a predominance of reduced form of CISD3 in the cells. Upon the addition of iron chelators, CISD3 loses its Fe-S clusters and becomes unstructured, and its cellular level drastically decreases. Chemical shift perturbation measurements suggest that, upon cluster oxidation, the protein undergoes a conformational change at the C-terminal CDGSH domain, which determines the instability of the oxidized state. This redox-associated conformational change may be the source of cooperative electron transfer via the two [Fe2S2] clusters in CISD3, which displays a single sharp voltammetric signal at -31 mV versus SHE. Oxidized CISD3 is particularly sensitive to the presence of hydrogen peroxide in vitro, whereas only the reduced form is able to bind nitric oxide. Paramagnetic NMR provides clear evidence that, upon NO binding, the cluster is disassembled but iron ions are still bound to the protein. Accordingly, in cellulo CISD3 is unaffected by oxidative stress induced by hydrogen peroxide but it becomes highly unstable in response to nitric oxide treatment.
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Affiliation(s)
- Deborah Grifagni
- Magnetic Resonance Center and Department of Chemistry, University of Florence, Sesto Fiorentino, Italy
| | - José Malanho Silva
- Magnetic Resonance Center and Department of Chemistry, University of Florence, Sesto Fiorentino, Italy
| | - Leonardo Querci
- Magnetic Resonance Center and Department of Chemistry, University of Florence, Sesto Fiorentino, Italy
| | - Michel Lepoivre
- CNRS, Institut de Chimie des Substances Naturelles, UPR 2301, Université Paris-Saclay, Gif-sur-Yvette, France
| | - Cindy Vallières
- CNRS, Institut de Chimie des Substances Naturelles, UPR 2301, Université Paris-Saclay, Gif-sur-Yvette, France
| | - Ricardo O Louro
- Instituto de Tecnologia Química e Biológica António Xavier (ITQB-NOVA), Universidade Nova de Lisboa, Oeiras, Portugal
| | - Lucia Banci
- Magnetic Resonance Center and Department of Chemistry, University of Florence, Sesto Fiorentino, Italy
| | - Mario Piccioli
- Magnetic Resonance Center and Department of Chemistry, University of Florence, Sesto Fiorentino, Italy.
| | | | - Francesca Cantini
- Magnetic Resonance Center and Department of Chemistry, University of Florence, Sesto Fiorentino, Italy.
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4
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Silva JM, Cerofolini L, Carvalho AL, Ravera E, Fragai M, Parigi G, Macedo AL, Geraldes CFGC, Luchinat C. Elucidating the concentration-dependent effects of thiocyanate binding to carbonic anhydrase. J Inorg Biochem 2023; 244:112222. [PMID: 37068394 DOI: 10.1016/j.jinorgbio.2023.112222] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2023] [Revised: 03/28/2023] [Accepted: 04/09/2023] [Indexed: 04/19/2023]
Abstract
Many proteins naturally carry metal centers, with a large share of them being in the active sites of several enzymes. Paramagnetic effects are a powerful source of structural information and, therefore, if the native metal is paramagnetic, or it can be functionally substituted with a paramagnetic one, paramagnetic effects can be used to study the metal sites, as well as the overall structure of the protein. One notable example is cobalt(II) substitution for zinc(II) in carbonic anhydrase. In this manuscript we investigate the effects of sodium thiocyanate on the chemical environment of the metal ion of the human carbonic anhydrase II. The electron paramagnetic resonance (EPR) titration of the cobalt(II) protein with thiocyanate shows that the EPR spectrum changes from A-type to C-type on passing from 1:1 to 1:1000-fold ligand excess. This indicates the occurrence of a change in the electronic structure, which may reflect a sizable change in the metal coordination environment in turn caused by a modification of the frozen solvent glass. However, paramagnetic nuclear magnetic resonance (NMR) data indicate that the metal coordination cage remains unperturbed even in 1:1000-fold ligand excess. This result proves that the C-type EPR spectrum observed at large ligand concentration should be ascribed to the low temperature at which EPR measurements are performed, which impacts on the structure of the protein when it is destabilized by a high concentration of a chaotropic agent.
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Affiliation(s)
- José Malanho Silva
- Magnetic Resonance Center (CERM), University of Florence, Sesto Fiorentino 50019, Italy; UCIBIO, Department of Chemistry, NOVA School of Science and Technology, Universidade NOVA de Lisboa, 2819-516 Caparica, Portugal
| | - Linda Cerofolini
- Magnetic Resonance Center (CERM), University of Florence, Sesto Fiorentino 50019, Italy; Department of Chemistry "Ugo Schiff", University of Florence, Sesto Fiorentino 50019, Italy
| | - Ana Luísa Carvalho
- UCIBIO, Department of Chemistry, NOVA School of Science and Technology, Universidade NOVA de Lisboa, 2819-516 Caparica, Portugal; Associate Laboratory i4HB - Institute for Health and Bioeconomy, NOVA School of Science and Technology, Universidade NOVA de Lisboa, Caparica, Portugal
| | - Enrico Ravera
- Magnetic Resonance Center (CERM), University of Florence, Sesto Fiorentino 50019, Italy; Department of Chemistry "Ugo Schiff", University of Florence, Sesto Fiorentino 50019, Italy; Consorzio Interuniversitario Risonanze Magnetiche Metallo Proteine (CIRMMP), Sesto Fiorentino, 50019, Italy
| | - Marco Fragai
- Magnetic Resonance Center (CERM), University of Florence, Sesto Fiorentino 50019, Italy; Department of Chemistry "Ugo Schiff", University of Florence, Sesto Fiorentino 50019, Italy; Consorzio Interuniversitario Risonanze Magnetiche Metallo Proteine (CIRMMP), Sesto Fiorentino, 50019, Italy
| | - Giacomo Parigi
- Magnetic Resonance Center (CERM), University of Florence, Sesto Fiorentino 50019, Italy; Department of Chemistry "Ugo Schiff", University of Florence, Sesto Fiorentino 50019, Italy; Consorzio Interuniversitario Risonanze Magnetiche Metallo Proteine (CIRMMP), Sesto Fiorentino, 50019, Italy
| | - Anjos L Macedo
- UCIBIO, Department of Chemistry, NOVA School of Science and Technology, Universidade NOVA de Lisboa, 2819-516 Caparica, Portugal; Department of Chemistry "Ugo Schiff", University of Florence, Sesto Fiorentino 50019, Italy
| | - Carlos F G C Geraldes
- Department of Life Sciences, Faculty of Science and Technology, 3000-393 Coimbra, Portugal; Coimbra Chemistry Center- Institute of Molecular Sciences (CCC-IMS), University of Coimbra, 3004-535 Coimbra, Portugal
| | - Claudio Luchinat
- Magnetic Resonance Center (CERM), University of Florence, Sesto Fiorentino 50019, Italy; Department of Chemistry "Ugo Schiff", University of Florence, Sesto Fiorentino 50019, Italy; Consorzio Interuniversitario Risonanze Magnetiche Metallo Proteine (CIRMMP), Sesto Fiorentino, 50019, Italy; Giotto Biotech, S.R.L, Sesto Fiorentino, Florence 50019, Italy.
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5
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Ravera E, Gigli L, Fiorucci L, Luchinat C, Parigi G. The evolution of paramagnetic NMR as a tool in structural biology. Phys Chem Chem Phys 2022; 24:17397-17416. [PMID: 35849063 DOI: 10.1039/d2cp01838a] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Paramagnetic NMR data contain extremely accurate long-range information on metalloprotein structures and, when used in the frame of integrative structural biology approaches, they allow for the retrieval of structural details to a resolution that is not achievable using other techniques. Paramagnetic data thus represent an extremely powerful tool to refine protein models in solution, especially when coupled to X-ray or cryoelectron microscopy data, to monitor the formation of complexes and determine the relative arrangements of their components, and to highlight the presence of conformational heterogeneity. More recently, theoretical and computational advancements in quantum chemical calculations of paramagnetic NMR observables are progressively opening new routes in structural biology, because they allow for the determination of the structure within the coordination sphere of the metal center, thus acting as a loupe on sites that are difficult to observe but very important for protein function.
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Affiliation(s)
- Enrico Ravera
- Magnetic Resonance Center (CERM), University of Florence, via Luigi Sacconi 6, Sesto Fiorentino, 50019, Italy.,Department of Chemistry "Ugo Schiff", University of Florence, via della Lastruccia 3, Sesto Fiorentino, 50019, Italy.,Consorzio Interuniversitario Risonanze Magnetiche Metallo Proteine (CIRMMP), via Luigi Sacconi 6, Sesto Fiorentino, 50019, Italy.
| | - Lucia Gigli
- Magnetic Resonance Center (CERM), University of Florence, via Luigi Sacconi 6, Sesto Fiorentino, 50019, Italy.,Department of Chemistry "Ugo Schiff", University of Florence, via della Lastruccia 3, Sesto Fiorentino, 50019, Italy.,Consorzio Interuniversitario Risonanze Magnetiche Metallo Proteine (CIRMMP), via Luigi Sacconi 6, Sesto Fiorentino, 50019, Italy.
| | - Letizia Fiorucci
- Magnetic Resonance Center (CERM), University of Florence, via Luigi Sacconi 6, Sesto Fiorentino, 50019, Italy.,Department of Chemistry "Ugo Schiff", University of Florence, via della Lastruccia 3, Sesto Fiorentino, 50019, Italy.,Consorzio Interuniversitario Risonanze Magnetiche Metallo Proteine (CIRMMP), via Luigi Sacconi 6, Sesto Fiorentino, 50019, Italy.
| | - Claudio Luchinat
- Magnetic Resonance Center (CERM), University of Florence, via Luigi Sacconi 6, Sesto Fiorentino, 50019, Italy.,Department of Chemistry "Ugo Schiff", University of Florence, via della Lastruccia 3, Sesto Fiorentino, 50019, Italy.,Consorzio Interuniversitario Risonanze Magnetiche Metallo Proteine (CIRMMP), via Luigi Sacconi 6, Sesto Fiorentino, 50019, Italy.
| | - Giacomo Parigi
- Magnetic Resonance Center (CERM), University of Florence, via Luigi Sacconi 6, Sesto Fiorentino, 50019, Italy.,Department of Chemistry "Ugo Schiff", University of Florence, via della Lastruccia 3, Sesto Fiorentino, 50019, Italy.,Consorzio Interuniversitario Risonanze Magnetiche Metallo Proteine (CIRMMP), via Luigi Sacconi 6, Sesto Fiorentino, 50019, Italy.
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6
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Parigi G, Ravera E, Luchinat C. Paramagnetic effects in NMR for protein structures and ensembles: Studies of metalloproteins. Curr Opin Struct Biol 2022; 74:102386. [DOI: 10.1016/j.sbi.2022.102386] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2021] [Revised: 03/29/2022] [Accepted: 04/07/2022] [Indexed: 11/28/2022]
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7
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Lang L, Ravera E, Parigi G, Luchinat C, Neese F. Theoretical analysis of the long-distance limit of NMR chemical shieldings. J Chem Phys 2022; 156:154115. [PMID: 35459319 DOI: 10.1063/5.0088162] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
After some years of controversy, it was recently demonstrated how to obtain the correct long-distance limit [point-dipole approximation (PDA)] of pseudo-contact nuclear magnetic resonance chemical shifts from rigorous first-principles quantum mechanics [Lang et al., J. Phys. Chem. Lett. 11, 8735 (2020)]. This result confirmed the classical Kurland-McGarvey theory. In the present contribution, we elaborate on these results. In particular, we provide a detailed derivation of the PDA both from the Van den Heuvel-Soncini equation for the chemical shielding tensor and from a spin Hamiltonian approximation. Furthermore, we discuss in detail the PDA within the approximate density functional theory and Hartree-Fock theories. In our previous work, we assumed a relatively crude effective nuclear charge approximation for the spin-orbit coupling operator. Here, we overcome this assumption by demonstrating that the derivation is also possible within the fully relativistic Dirac equation and even without the assumption of a specific form for the Hamiltonian. Crucial ingredients for the general derivation are a Hamiltonian that respects gauge invariance, the multipolar gauge, and functional derivatives of the Hamiltonian, where it is possible to identify the first functional derivative with the electron number current density operator. The present work forms an important foundation for future extensions of the Kurland-McGarvey theory beyond the PDA, including induced magnetic quadrupole and higher moments to describe the magnetic hyperfine field.
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Affiliation(s)
- Lucas Lang
- Max-Planck-Institut für Kohlenforschung, Kaiser-Wilhelm-Platz 1, 45470 Mülheim an der Ruhr, Germany
| | - Enrico Ravera
- Magnetic Resonance Center (CERM), University of Florence, and Consorzio Interuniversitario Risonanze Magnetiche di Metalloproteine (CIRMMP), Via Sacconi 6, Sesto Fiorentino 50019, Italy
| | - Giacomo Parigi
- Magnetic Resonance Center (CERM), University of Florence, and Consorzio Interuniversitario Risonanze Magnetiche di Metalloproteine (CIRMMP), Via Sacconi 6, Sesto Fiorentino 50019, Italy
| | - Claudio Luchinat
- Magnetic Resonance Center (CERM), University of Florence, and Consorzio Interuniversitario Risonanze Magnetiche di Metalloproteine (CIRMMP), Via Sacconi 6, Sesto Fiorentino 50019, Italy
| | - Frank Neese
- Max-Planck-Institut für Kohlenforschung, Kaiser-Wilhelm-Platz 1, 45470 Mülheim an der Ruhr, Germany
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Müntener T, Joss D, Häussinger D, Hiller S. Pseudocontact Shifts in Biomolecular NMR Spectroscopy. Chem Rev 2022; 122:9422-9467. [PMID: 35005884 DOI: 10.1021/acs.chemrev.1c00796] [Citation(s) in RCA: 21] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Paramagnetic centers in biomolecules, such as specific metal ions that are bound to a protein, affect the nuclei in their surrounding in various ways. One of these effects is the pseudocontact shift (PCS), which leads to strong chemical shift perturbations of nuclear spins, with a remarkably long range of 50 Å and beyond. The PCS in solution NMR is an effect originating from the anisotropic part of the dipole-dipole interaction between the magnetic momentum of unpaired electrons and nuclear spins. The PCS contains spatial information that can be exploited in multiple ways to characterize structure, function, and dynamics of biomacromolecules. It can be used to refine structures, magnify effects of dynamics, help resonance assignments, allows for an intermolecular positioning system, and gives structural information in sensitivity-limited situations where all other methods fail. Here, we review applications of the PCS in biomolecular solution NMR spectroscopy, starting from early works on natural metalloproteins, following the development of non-natural tags to chelate and attach lanthanoid ions to any biomolecular target to advanced applications on large biomolecular complexes and inside living cells. We thus hope to not only highlight past applications but also shed light on the tremendous potential the PCS has in structural biology.
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Affiliation(s)
- Thomas Müntener
- Biozentrum, University of Basel, Spitalstrasse 41, 4056 Basel, Switzerland
| | - Daniel Joss
- Department of Chemistry, University of Basel, St. Johanns-Ring 19, 4056 Basel, Switzerland
| | - Daniel Häussinger
- Department of Chemistry, University of Basel, St. Johanns-Ring 19, 4056 Basel, Switzerland
| | - Sebastian Hiller
- Biozentrum, University of Basel, Spitalstrasse 41, 4056 Basel, Switzerland
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9
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Santana FS, Perfetti M, Briganti M, Sacco F, Poneti G, Ravera E, Soares JF, Sessoli R. A dysprosium single molecule magnet outperforming current pseudocontact shift agents. Chem Sci 2022; 13:5860-5871. [PMID: 35685802 PMCID: PMC9132026 DOI: 10.1039/d2sc01619b] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2022] [Accepted: 04/26/2022] [Indexed: 12/19/2022] Open
Abstract
A common criterion for designing performant single molecule magnets and pseudocontact shift tags is a large magnetic anisotropy. In this article we present a dysprosium complex chemically designed to exhibit strong easy-axis type magnetic anisotropy that is preserved in dichloromethane solution at room temperature. Our detailed theoretical and experimental studies on the magnetic properties allowed explaining several features typical of highly performant SMMs. Moreover, the NMR characterization shows remarkably large chemical shifts, outperforming the current state-of-the art PCS tags. A robust dysprosium(iii) single molecule magnet with large uniaxial magnetic anisotropy induces pseudocontact shifts at almost doubled distance compared to standard shift agents.![]()
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Affiliation(s)
- Francielli S. Santana
- Departamento de Química, Universidade Federal do Paraná, Centro Politécnico, 81530-900 Curitiba, PR, Brazil
| | - Mauro Perfetti
- Department of Chemistry “U. Schiff”, University of Florence, Via della Lastruccia 3-13, Sesto Fiorentino, 50019, Italy
- Research Unit Firenze, INSTM, I-50019 Sesto Fiorentino, Firenze, Italy
| | - Matteo Briganti
- Departamento de Química, Universidade Federal do Paraná, Centro Politécnico, 81530-900 Curitiba, PR, Brazil
- Department of Chemistry “U. Schiff”, University of Florence, Via della Lastruccia 3-13, Sesto Fiorentino, 50019, Italy
| | - Francesca Sacco
- Department of Chemistry “U. Schiff”, University of Florence, Via della Lastruccia 3-13, Sesto Fiorentino, 50019, Italy
- Magnetic Resonance Center (CERM), University of Florence, Via Luigi Sacconi 6, Sesto Fiorentino, 50019, Italy
- Consorzio Interuniversitario Risonanze Magnetiche di Metalloproteine, Via Luigi Sacconi 6, Sesto Fiorentino, 50019, Italy
| | - Giordano Poneti
- Instituto de Química, Universidade Federal do Rio de Janeiro, Centro de Tecnologia – Cidade Universitária, Avenida Athos da Silveira Ramos, 149, 21941-909 Rio de Janeiro, Brazil
| | - Enrico Ravera
- Department of Chemistry “U. Schiff”, University of Florence, Via della Lastruccia 3-13, Sesto Fiorentino, 50019, Italy
- Magnetic Resonance Center (CERM), University of Florence, Via Luigi Sacconi 6, Sesto Fiorentino, 50019, Italy
- Consorzio Interuniversitario Risonanze Magnetiche di Metalloproteine, Via Luigi Sacconi 6, Sesto Fiorentino, 50019, Italy
| | - Jaísa F. Soares
- Departamento de Química, Universidade Federal do Paraná, Centro Politécnico, 81530-900 Curitiba, PR, Brazil
| | - Roberta Sessoli
- Department of Chemistry “U. Schiff”, University of Florence, Via della Lastruccia 3-13, Sesto Fiorentino, 50019, Italy
- Research Unit Firenze, INSTM, I-50019 Sesto Fiorentino, Firenze, Italy
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10
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Ott JC, Suturina EA, Kuprov I, Nehrkorn J, Schnegg A, Enders M, Gade LH. Observability of Paramagnetic NMR Signals at over 10 000 ppm Chemical Shifts. Angew Chem Int Ed Engl 2021; 60:22856-22864. [PMID: 34351041 PMCID: PMC8518043 DOI: 10.1002/anie.202107944] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2021] [Indexed: 12/27/2022]
Abstract
We report an experimental observation of 31 P NMR resonances shifted by over 10 000 ppm (meaning percent range, and a new record for solutions), and similar 1 H chemical shifts, in an intermediate-spin square planar ferrous complex [tBu (PNP)Fe-H], where PNP is a carbazole-based pincer ligand. Using a combination of electronic structure theory, nuclear magnetic resonance, magnetometry, and terahertz electron paramagnetic resonance, the influence of magnetic anisotropy and zero-field splitting on the paramagnetic shift and relaxation enhancement is investigated. Detailed spin dynamics simulations indicate that, even with relatively slow electron spin relaxation (T1 ≈10-11 s), it remains possible to observe NMR signals of directly metal-bonded atoms because pronounced rhombicity in the electron zero-field splitting reduces nuclear paramagnetic relaxation enhancement.
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Affiliation(s)
- Jonas C. Ott
- Anorganisch-Chemisches InstitutUniversität HeidelbergIm Neuenheimer Feld 27669120HeidelbergGermany
| | | | - Ilya Kuprov
- School of ChemistryUniversity of SouthamptonSouthamptonSO17 1BJUK
| | - Joscha Nehrkorn
- EPR Research GroupMPI for Chemical Energy ConversionStiftstrasse 34–3645470Mülheim RuhrGermany
| | - Alexander Schnegg
- EPR Research GroupMPI for Chemical Energy ConversionStiftstrasse 34–3645470Mülheim RuhrGermany
| | - Markus Enders
- Anorganisch-Chemisches InstitutUniversität HeidelbergIm Neuenheimer Feld 27669120HeidelbergGermany
| | - Lutz H. Gade
- Anorganisch-Chemisches InstitutUniversität HeidelbergIm Neuenheimer Feld 27669120HeidelbergGermany
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11
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Ott JC, Suturina EA, Kuprov I, Nehrkorn J, Schnegg A, Enders M, Gade LH. Observability of Paramagnetic NMR Signals at over 10 000 ppm Chemical Shifts. Angew Chem Int Ed Engl 2021. [DOI: 10.1002/ange.202107944] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Jonas C. Ott
- Anorganisch-Chemisches Institut Universität Heidelberg Im Neuenheimer Feld 276 69120 Heidelberg Germany
| | | | - Ilya Kuprov
- School of Chemistry University of Southampton Southampton SO17 1BJ UK
| | - Joscha Nehrkorn
- EPR Research Group MPI for Chemical Energy Conversion Stiftstrasse 34–36 45470 Mülheim Ruhr Germany
| | - Alexander Schnegg
- EPR Research Group MPI for Chemical Energy Conversion Stiftstrasse 34–36 45470 Mülheim Ruhr Germany
| | - Markus Enders
- Anorganisch-Chemisches Institut Universität Heidelberg Im Neuenheimer Feld 276 69120 Heidelberg Germany
| | - Lutz H. Gade
- Anorganisch-Chemisches Institut Universität Heidelberg Im Neuenheimer Feld 276 69120 Heidelberg Germany
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12
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Determining the structure and binding mechanism of oxytocin-Cu 2+ complex using paramagnetic relaxation enhancement NMR analysis. J Biol Inorg Chem 2021; 26:809-815. [PMID: 34459989 DOI: 10.1007/s00775-021-01897-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2021] [Accepted: 08/23/2021] [Indexed: 12/30/2022]
Abstract
Oxytocin is a neuropeptide that binds copper ions in nature. The structure of oxytocin in interaction with Cu2+ was determined here by NMR, showing which atoms of the peptide are involved in binding. Paramagnetic relaxation enhancement NMR analyses indicated a binding mechanism where the amino terminus was required for binding and subsequently Tyr2, Ile3 and Gln4 bound in that order. The aromatic ring of Tyr2 formed a π-cation interaction with Cu2+. Oxytocin copper complex structure revealed by paramagnetic relaxation enhancement NMR analyses.
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13
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Ravera E, Gigli L, Czarniecki B, Lang L, Kümmerle R, Parigi G, Piccioli M, Neese F, Luchinat C. A Quantum Chemistry View on Two Archetypical Paramagnetic Pentacoordinate Nickel(II) Complexes Offers a Fresh Look on Their NMR Spectra. Inorg Chem 2021; 60:2068-2075. [PMID: 33478214 PMCID: PMC7877564 DOI: 10.1021/acs.inorgchem.0c03635] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
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Quantum chemical methods for calculating paramagnetic NMR observables are becoming
increasingly accessible and are being included in the inorganic chemistry practice.
Here, we test the performance of these methods in the prediction of proton hyperfine
shifts of two archetypical high-spin pentacoordinate nickel(II) complexes (NiSAL-MeDPT
and NiSAL-HDPT), which, for a variety of reasons, turned out to be perfectly suited to
challenge the predictions to the finest level of detail. For NiSAL-MeDPT, new NMR
experiments yield an assignment that perfectly matches the calculations. The slightly
different hyperfine shifts from the two “halves” of the molecules related
by a pseudo-C2 axis, which are experimentally divided into
two well-defined spin systems, are also straightforwardly distinguished by the
calculations. In the case of NiSAL-HDPT, for which no X-ray structure is available, the
quality of the calculations allowed us to refine its structure using as a starting
template the structure of NiSAL-MeDPT. State-of-the-art
quantum chemical methods and paramagnetism-tailored
NMR experiments provide a deep insight on the relation between the
spectra and the electronic structure for two paramagnetic pentacoordinate
nickel(II) complexes.
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Affiliation(s)
- Enrico Ravera
- Department of Chemistry "Ugo Schiff″, University of Florence, Via della Lastruccia 3, 50019 Sesto Fiorentino, Italy.,Magnetic Resonance Center, University of Florence and Consorzio Interuniversitario Risonanze Magnetiche di Metalloproteine, Via L. Sacconi 6, 50019, Sesto Fiorentino, Italy
| | - Lucia Gigli
- Department of Chemistry "Ugo Schiff″, University of Florence, Via della Lastruccia 3, 50019 Sesto Fiorentino, Italy.,Magnetic Resonance Center, University of Florence and Consorzio Interuniversitario Risonanze Magnetiche di Metalloproteine, Via L. Sacconi 6, 50019, Sesto Fiorentino, Italy
| | - Barbara Czarniecki
- Bruker Biospin Corporation, Industriestrasse 26, 8117 Fällanden, Switzerland
| | - Lucas Lang
- Max-Planck-Institut für Kohlenforschung, Kaiser-Wilhelm-Platz 1, 45470 Mülheim an der Ruhr, Germany
| | - Rainer Kümmerle
- Bruker Biospin Corporation, Industriestrasse 26, 8117 Fällanden, Switzerland
| | - Giacomo Parigi
- Department of Chemistry "Ugo Schiff″, University of Florence, Via della Lastruccia 3, 50019 Sesto Fiorentino, Italy.,Magnetic Resonance Center, University of Florence and Consorzio Interuniversitario Risonanze Magnetiche di Metalloproteine, Via L. Sacconi 6, 50019, Sesto Fiorentino, Italy
| | - Mario Piccioli
- Department of Chemistry "Ugo Schiff″, University of Florence, Via della Lastruccia 3, 50019 Sesto Fiorentino, Italy.,Magnetic Resonance Center, University of Florence and Consorzio Interuniversitario Risonanze Magnetiche di Metalloproteine, Via L. Sacconi 6, 50019, Sesto Fiorentino, Italy
| | - Frank Neese
- Max-Planck-Institut für Kohlenforschung, Kaiser-Wilhelm-Platz 1, 45470 Mülheim an der Ruhr, Germany
| | - Claudio Luchinat
- Department of Chemistry "Ugo Schiff″, University of Florence, Via della Lastruccia 3, 50019 Sesto Fiorentino, Italy.,Magnetic Resonance Center, University of Florence and Consorzio Interuniversitario Risonanze Magnetiche di Metalloproteine, Via L. Sacconi 6, 50019, Sesto Fiorentino, Italy
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14
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Lang L, Ravera E, Parigi G, Luchinat C, Neese F. Solution of a Puzzle: High-Level Quantum-Chemical Treatment of Pseudocontact Chemical Shifts Confirms Classic Semiempirical Theory. J Phys Chem Lett 2020; 11:8735-8744. [PMID: 32930598 PMCID: PMC7584370 DOI: 10.1021/acs.jpclett.0c02462] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2020] [Accepted: 09/15/2020] [Indexed: 06/11/2023]
Abstract
A recently popularized approach for the calculation of pseudocontact shifts (PCSs) based on first-principles quantum chemistry (QC) leads to different results than the classic "semiempirical" equation involving the susceptibility tensor. Studies that attempted a comparison of theory and experiment led to conflicting conclusions with respect to the preferred theoretical approach. In this Letter, we show that after inclusion of previously neglected terms in the full Hamiltonian, one can deduce the semiempirical equations from a rigorous QC-based treatment. It also turns out that in the long-distance limit, one can approximate the complete A tensor in terms of the g tensor. By means of Kohn-Sham density functional theory calculations, we numerically confirm the long-distance expression for the A tensor and the theoretically predicted scaling behavior of the different terms. Our derivation suggests a computational strategy in which one calculates the susceptibility tensor and inserts it into the classic equation for the PCS.
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Affiliation(s)
- Lucas Lang
- Max-Planck-Institut
für Kohlenforschung, Kaiser-Wilhelm-Platz 1, 45470 Mülheim an der Ruhr, Germany
| | - Enrico Ravera
- Magnetic
Resonance Center (CERM), University of Florence,
and Consorzio Interuniversitario Risonanze Magnetiche di Metalloproteine
(CIRMMP), via Sacconi
6, Sesto Fiorentino 50019, Italy
- Department
of Chemistry “Ugo Schiff”, University of Florence, via della Lastruccia 3, Sesto Fiorentino 50019, Italy
| | - Giacomo Parigi
- Magnetic
Resonance Center (CERM), University of Florence,
and Consorzio Interuniversitario Risonanze Magnetiche di Metalloproteine
(CIRMMP), via Sacconi
6, Sesto Fiorentino 50019, Italy
- Department
of Chemistry “Ugo Schiff”, University of Florence, via della Lastruccia 3, Sesto Fiorentino 50019, Italy
| | - Claudio Luchinat
- Magnetic
Resonance Center (CERM), University of Florence,
and Consorzio Interuniversitario Risonanze Magnetiche di Metalloproteine
(CIRMMP), via Sacconi
6, Sesto Fiorentino 50019, Italy
- Department
of Chemistry “Ugo Schiff”, University of Florence, via della Lastruccia 3, Sesto Fiorentino 50019, Italy
| | - Frank Neese
- Max-Planck-Institut
für Kohlenforschung, Kaiser-Wilhelm-Platz 1, 45470 Mülheim an der Ruhr, Germany
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15
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Blahut J, Benda L, Kotek J, Pintacuda G, Hermann P. Paramagnetic Cobalt(II) Complexes with Cyclam Derivatives: Toward 19F MRI Contrast Agents. Inorg Chem 2020; 59:10071-10082. [DOI: 10.1021/acs.inorgchem.0c01216] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Affiliation(s)
- Jan Blahut
- Department of Inorganic Chemistry, Faculty of Science, Charles University, Hlavova 2030, 12843 Prague 2, Czech Republic
- High-Field NMR Centre, CNRS FRE2034/UCB de Lyon 1/ENS de Lyon, 5 rue de la Doua, 69100 Lyon-Villeurbanne, France
| | - Ladislav Benda
- High-Field NMR Centre, CNRS FRE2034/UCB de Lyon 1/ENS de Lyon, 5 rue de la Doua, 69100 Lyon-Villeurbanne, France
| | - Jan Kotek
- Department of Inorganic Chemistry, Faculty of Science, Charles University, Hlavova 2030, 12843 Prague 2, Czech Republic
| | - Guido Pintacuda
- High-Field NMR Centre, CNRS FRE2034/UCB de Lyon 1/ENS de Lyon, 5 rue de la Doua, 69100 Lyon-Villeurbanne, France
| | - Petr Hermann
- Department of Inorganic Chemistry, Faculty of Science, Charles University, Hlavova 2030, 12843 Prague 2, Czech Republic
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16
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Parigi G, Ravera E, Luchinat C. Magnetic susceptibility and paramagnetism-based NMR. PROGRESS IN NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY 2019; 114-115:211-236. [PMID: 31779881 DOI: 10.1016/j.pnmrs.2019.06.003] [Citation(s) in RCA: 34] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/08/2019] [Revised: 06/17/2019] [Accepted: 06/17/2019] [Indexed: 05/18/2023]
Abstract
The magnetic interactions between the nuclear magnetic moment and the magnetic moment of unpaired electron(s) depend on the structure and dynamics of the molecules where the paramagnetic center is located and of their partners. The long-range nature of the magnetic interactions is thus a reporter of invaluable information for structural biology studies, when other techniques often do not provide enough data for the atomic-level characterization of the system. This precious information explains the flourishing of paramagnetism-assisted NMR studies in recent years. Many paramagnetic effects are related to the magnetic susceptibility of the paramagnetic metal. Although these effects have been known for more than half a century, different theoretical models and new approaches have been proposed in the last decade. In this review, we have summarized the consequences for NMR spectroscopy of magnetic interactions between nuclear and electron magnetic moments, and thus of the presence of a magnetic susceptibility due to metals, and we do so using a unified notation.
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Affiliation(s)
- Giacomo Parigi
- Magnetic Resonance Center (CERM) and Interuniversity Consortium for Magnetic Resonance of Metallo Proteins (CIRMMP), Via L. Sacconi 6, 50019 Sesto Fiorentino, Italy; Department of Chemistry "Ugo Schiff", University of Florence, Via della Lastruccia 3, 50019 Sesto Fiorentino, Italy
| | - Enrico Ravera
- Magnetic Resonance Center (CERM) and Interuniversity Consortium for Magnetic Resonance of Metallo Proteins (CIRMMP), Via L. Sacconi 6, 50019 Sesto Fiorentino, Italy; Department of Chemistry "Ugo Schiff", University of Florence, Via della Lastruccia 3, 50019 Sesto Fiorentino, Italy
| | - Claudio Luchinat
- Magnetic Resonance Center (CERM) and Interuniversity Consortium for Magnetic Resonance of Metallo Proteins (CIRMMP), Via L. Sacconi 6, 50019 Sesto Fiorentino, Italy; Department of Chemistry "Ugo Schiff", University of Florence, Via della Lastruccia 3, 50019 Sesto Fiorentino, Italy.
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17
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Joss D, Häussinger D. Design and applications of lanthanide chelating tags for pseudocontact shift NMR spectroscopy with biomacromolecules. PROGRESS IN NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY 2019; 114-115:284-312. [PMID: 31779884 DOI: 10.1016/j.pnmrs.2019.08.002] [Citation(s) in RCA: 38] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/31/2019] [Revised: 08/21/2019] [Accepted: 08/24/2019] [Indexed: 05/14/2023]
Abstract
In this review, lanthanide chelating tags and their applications to pseudocontact shift NMR spectroscopy as well as analysis of residual dipolar couplings are covered. A complete overview is presented of DOTA-derived and non-DOTA-derived lanthanide chelating tags, critical points in the design of lanthanide chelating tags as appropriate linker moieties, their stability under reductive conditions, e.g., for in-cell applications, the magnitude of the anisotropy transferred from the lanthanide chelating tag to the biomacromolecule under investigation and structural properties, as well as conformational bias of the lanthanide chelating tags are discussed. Furthermore, all DOTA-derived lanthanide chelating tags used for PCS NMR spectroscopy published to date are displayed in tabular form, including their anisotropy parameters, with all employed lanthanide ions, CB-Ln distances and tagging reaction conditions, i.e., the stoichiometry of lanthanide chelating tags, pH, buffer composition, temperature and reaction time. Additionally, applications of lanthanide chelating tags for pseudocontact shifts and residual dipolar couplings that have been reported for proteins, protein-protein and protein-ligand complexes, carbohydrates, carbohydrate-protein complexes, nucleic acids and nucleic acid-protein complexes are presented and critically reviewed. The vast and impressive range of applications of lanthanide chelating tags to structural investigations of biomacromolecules in solution clearly illustrates the significance of this particular field of research. The extension of the repertoire of lanthanide chelating tags from proteins to nucleic acids holds great promise for the determination of valuable structural parameters and further developments in characterizing intermolecular interactions.
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Affiliation(s)
- Daniel Joss
- University of Basel, St. Johanns-Ring 19, 4056 Basel, Switzerland.
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18
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Ravera E, Parigi G, Luchinat C. What are the methodological and theoretical prospects for paramagnetic NMR in structural biology? A glimpse into the crystal ball. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2019; 306:173-179. [PMID: 31331762 DOI: 10.1016/j.jmr.2019.07.027] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/29/2019] [Revised: 05/16/2019] [Accepted: 07/08/2019] [Indexed: 06/10/2023]
Abstract
NMR spectroscopy is very sensitive to the presence of unpaired electrons, which perturb the NMR chemical shifts, J splittings and nuclear relaxation rates. These paramagnetic effects have attracted increasing attention over the last decades, and their use is expected to increase further in the future because they can provide structural information not easily achievable with other techniques. In fact, paramagnetic data provide long range structural restraints that can be used to assess the accuracy of crystal structures in solution and to improve them by simultaneous refinements with the X-ray data. They are also precious for obtaining information on the conformational variability of biomolecular systems, possibly in conjunction with SAXS and/or DEER data. We foresee that new tools will be developed in the next years for the simultaneous analysis of the paramagnetic data with data obtained from different techniques, in order to take advantage synergistically of the information content of all of them. Of course, the use of the paramagnetic data for structural purposes requires the knowledge of the relationship between these data and the molecular coordinates. Recently, the equations commonly used, dating back to half a century ago, have been questioned by first principle quantum chemistry calculations. Our prediction is that further theoretical/computational improvements will essentially confirm the validity of the old semi-empirical equations for the analysis of the experimental paramagnetic data.
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Affiliation(s)
- Enrico Ravera
- Magnetic Resonance Center (CERM) and Interuniversity Consortium for Magnetic Resonance of Metallo Proteins (CIRMMP), Via L. Sacconi 6, 50019 Sesto Fiorentino, Italy; Department of Chemistry "Ugo Schiff", University of Florence, Via della Lastruccia 3, 50019 Sesto Fiorentino, Italy
| | - Giacomo Parigi
- Magnetic Resonance Center (CERM) and Interuniversity Consortium for Magnetic Resonance of Metallo Proteins (CIRMMP), Via L. Sacconi 6, 50019 Sesto Fiorentino, Italy; Department of Chemistry "Ugo Schiff", University of Florence, Via della Lastruccia 3, 50019 Sesto Fiorentino, Italy
| | - Claudio Luchinat
- Magnetic Resonance Center (CERM) and Interuniversity Consortium for Magnetic Resonance of Metallo Proteins (CIRMMP), Via L. Sacconi 6, 50019 Sesto Fiorentino, Italy; Department of Chemistry "Ugo Schiff", University of Florence, Via della Lastruccia 3, 50019 Sesto Fiorentino, Italy.
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