1
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Hartman JD, Capistran D. Predicting 51V nuclear magnetic resonance observables in molecular crystals. MAGNETIC RESONANCE IN CHEMISTRY : MRC 2024; 62:416-428. [PMID: 38114304 DOI: 10.1002/mrc.5420] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/05/2023] [Revised: 11/26/2023] [Accepted: 11/28/2023] [Indexed: 12/21/2023]
Abstract
Solid-state nuclear magnetic resonance (NMR) spectroscopy and quantum chemical density functional theory (DFT) calculations are widely used to characterize vanadium centers in biological and pharmaceutically relevant compounds. Several techniques have been recently developed to improve the accuracy of predicted NMR parameters obtained from DFT. Fragment-based and planewave-corrected methods employing hybrid density functionals are particularly effective tools for solid-state applications. A recent benchmark study involving molecular crystal compounds found that fragment-based NMR calculations using hybrid density functionals improve the accuracy of predicted 51V chemical shieldings by 20% relative to traditional planewave methods. This work extends the previous study, including a careful analysis of 51V chemical shift anisotropy, electric field gradient calculations, and a more extensive test set. The accuracy of planewave-corrected techniques and recently developed fragment-based methods using electrostatic embedding based on the polarized continuum model (PCM) are found to be highly competitive with previous methods. Planewave-corrected methods achieve a 34% improvement in the errors of predicted 51V chemical shieldings relative to planewave. Additionally, planewave-corrected and fragment-based calculations were performed using PCM embedding, improving the accuracy of predicted 51V chemical shielding (CS) tensor principal values by 30% andC q values by 15% relative to traditional planewave methods. The performance of these methods is further examined using a redox-active oxovandium complex and a common 51V NMR reference compound.
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Affiliation(s)
- Joshua D Hartman
- Department of Chemistry, University of California, Riverside, Riverside, California, USA
| | - Daniel Capistran
- Department of Chemistry, University of California, Riverside, Riverside, California, USA
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2
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Chaloupecká E, Tyrpekl V, Bártová K, Nishiyama Y, Dračínský M. NMR crystallography of amino acids. SOLID STATE NUCLEAR MAGNETIC RESONANCE 2024; 130:101921. [PMID: 38422809 DOI: 10.1016/j.ssnmr.2024.101921] [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: 11/23/2023] [Revised: 02/08/2024] [Accepted: 02/08/2024] [Indexed: 03/02/2024]
Abstract
The development of NMR crystallography methods requires a reliable database of chemical shifts measured for systems with known crystal structure. We measured and assigned carbon and hydrogen chemical shifts of twenty solid natural amino acids of known polymorphic structure, meticulously determined using powder X-ray diffraction. We then correlated the experimental data with DFT-calculated isotropic shieldings. The small size of the unit cell of most amino acids allowed for advanced computations using various families of DFT functionals, including generalized gradient approximation (GGA), meta-GGA and hybrid DFT functionals. We tested several combinations of functionals for geometry optimizations and NMR calculations. For carbon shieldings, the widely used GGA functional PBE performed very well, although an improvement could be achieved by adding shielding corrections calculated for isolated molecules using a hybrid functional. For hydrogen nuclei, we observed the best performance for NMR calculations carried out with structures optimized at the hybrid DFT level. The high fidelity of the calculations made it possible to assign additional signals that could not be assigned based on experiments alone, for example signals of two non-equivalent molecules in the unit cell of some of the amino acids.
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Affiliation(s)
- Ema Chaloupecká
- Institute of Organic Chemistry and Biochemistry, Czech Academy of Sciences, Flemingovo nám. 2, 160 00 Prague, Czech Republic; Department of Organic Chemistry, Faculty of Science, Charles University in Prague, Hlavova 2030, 128 40 Prague 2, Czech Republic
| | - Václav Tyrpekl
- Department of Inorganic Chemistry, Faculty of Science, Charles University in Prague, Hlavova 2030, 128 40 Prague 2, Czech Republic
| | - Kateřina Bártová
- Institute of Organic Chemistry and Biochemistry, Czech Academy of Sciences, Flemingovo nám. 2, 160 00 Prague, Czech Republic
| | | | - Martin Dračínský
- Institute of Organic Chemistry and Biochemistry, Czech Academy of Sciences, Flemingovo nám. 2, 160 00 Prague, Czech Republic.
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3
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Hartman JD, Spock LE, Harper JK. Benchmark accuracy of predicted NMR observables for quadrupolar 14 N and 17 O nuclei in molecular crystals. MAGNETIC RESONANCE IN CHEMISTRY : MRC 2023; 61:253-267. [PMID: 36567433 DOI: 10.1002/mrc.5328] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/03/2022] [Revised: 12/21/2022] [Accepted: 12/22/2022] [Indexed: 06/17/2023]
Abstract
Nuclear quadrupole resonances for 14 N and 17 O nuclei are exquisitely sensitive to interactions with surrounding atoms. As a result, nitrogen and oxygen solid-state nuclear magnetic resonance (ssNMR) provides a powerful tool for investigating structure and dynamics in complex systems. First-principles calculations are increasingly used to facilitate spectral assignment and to evaluate and adjust crystal structures. Recent work combining the strengths of planewave density functional theory (DFT) calculations with a single molecule correction obtained using a higher level of theory has proven successful in improving the accuracy of predicted chemical shielding (CS) tensors and 17 O quadrupolar coupling constants ( C q ). Here we extend this work by examining the accuracy of predicted 14 N and 17 O electric field gradient (EFG) tensor components obtained using alternative planewave-corrections involving cluster and two-body fragment-based calculations. We benchmark the accuracy of CS and EFG tensor predictions for both nitrogen and oxygen using planewave, two-body fragment, and enhanced planewave-corrected techniques. Combining planewave and two-body fragment calculations reduces the error in predicted 17 O C q values by 35% relative to traditional planewave calculations. These enhanced planewave-correction methods improve the accuracy of 17 O and 14 N EFG tensor components by 15% relative to planewave DFT but yield minimal improvement relative to a simple molecular correction. However, in structural environments involving either high symmetry or strong intermolecular interactions, enhanced planewave-corrected methods provide a distinct advantage.
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Affiliation(s)
- Joshua D Hartman
- Department of Chemistry, University of California, Riverside, Riverside, California, USA
| | - Lilian E Spock
- Department of Chemistry, University of California, Riverside, Riverside, California, USA
| | - James K Harper
- Department of Chemistry and Biochemistry, Brigham Young University, Provo, Utah, USA
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4
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Iuliucci RJ, Hartman JD, Beran GJO. Do Models beyond Hybrid Density Functionals Increase the Agreement with Experiment for Predicted NMR Chemical Shifts or Electric Field Gradient Tensors in Organic Solids? J Phys Chem A 2023; 127:2846-2858. [PMID: 36940431 DOI: 10.1021/acs.jpca.2c07657] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/22/2023]
Abstract
Ab initio predictions of chemical shifts and electric field gradient (EFG) tensor components are frequently used to help interpret solid-state nuclear magnetic resonance (NMR) experiments. Typically, these predictions employ density functional theory (DFT) with generalized gradient approximation (GGA) functionals, though hybrid functionals have been shown to improve accuracy relative to experiment. Here, the performance of a dozen models beyond the GGA approximation are examined for the prediction of solid-state NMR observables, including meta-GGA, hybrid, and double-hybrid density functionals and second-order Møller-Plesset perturbation theory (MP2). These models are tested on organic molecular crystal data sets containing 169 experimental 13C and 15N chemical shifts and 114 17O and 14N EFG tensor components. To make these calculations affordable, gauge-including projector augmented wave (GIPAW) Perdew-Burke-Ernzerhof (PBE) calculations with periodic boundary conditions are combined with a local intramolecular correction computed at the higher level of theory. Within the context of typical NMR property calculations performed on a static, DFT-optimized crystal structure, the benchmarking finds that the double-hybrid DFT functionals produce errors versus experiment that are no smaller than those of hybrid functionals in the best cases, and they can be larger. MP2 errors versus experiment are even bigger. Overall, no practical advantages are found for using any of the tested double-hybrid functionals or MP2 to predict experimental solid-state NMR chemical shifts and EFG tensor components for routine organic crystals, especially given the higher computational cost of those methods. This finding likely reflects error cancellation benefiting the hybrid functionals. Improving the accuracy of the predicted chemical shifts and EFG tensors relative to experiment would probably require more robust treatments of the crystal structures, their dynamics, and other factors.
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Affiliation(s)
- Robbie J Iuliucci
- Department of Chemistry, Washington and Jefferson College, Washington, Pennsylvania 15301 United States
| | - Joshua D Hartman
- Department of Chemistry, University of California, Riverside, California 92521 United States
| | - Gregory J O Beran
- Department of Chemistry, University of California, Riverside, California 92521 United States
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5
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Hartman JD, Harper JK. Improving the accuracy of GIPAW chemical shielding calculations with cluster and fragment corrections. SOLID STATE NUCLEAR MAGNETIC RESONANCE 2022; 122:101832. [PMID: 36198253 DOI: 10.1016/j.ssnmr.2022.101832] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/28/2022] [Revised: 09/07/2022] [Accepted: 09/08/2022] [Indexed: 06/16/2023]
Abstract
Ab initio methods for predicting NMR parameters in the solid state are an essential tool for assigning experimental spectra and play an increasingly important role in structural characterizations. Recently, a molecular correction (MC) technique has been developed which combines the strengths of plane-wave methods (GIPAW) with single molecule calculations employing Gaussian basis sets. The GIPAW + MC method relies on a periodic calculation performed at a lower level of theory to model the crystalline environment. The GIPAW result is then corrected using a single molecule calculation performed at a higher level of theory. The success of the GIPAW + MC method in predicting a range of NMR parameters is a result of the highly local character of the tensors underlying the NMR observable. However, in applications involving strong intermolecular interactions we find that expanding the region treated at the higher level of theory more accurately captures local many-body contributions to the N15 NMR chemical shielding (CS) tensor. We propose alternative corrections to GIPAW which capture interactions between adjacent molecules at a higher level of theory using either fragment or cluster-based calculations. Benchmark calculations performed on N15 and C13 data sets show that these advanced GIPAW-corrected calculations improve the accuracy of chemical shielding tensor predictions relative to existing methods. Specifically, cluster-based N15 corrections show a 24% and 17% reduction in RMS error relative to GIPAW and GIPAW + MC calculations, respectively. Comparing the benchmark data sets using multiple computational models demonstrates that N15 CS tensor calculations are significantly more sensitive to intermolecular interactions relative to C13. However, fragment and cluster-based corrections that include direct hydrogen bond partners are sufficient for optimizing the accuracy of GIPAW-corrected methods. Finally, GIPAW-corrected methods are applied to the particularly challenging NMR spectral assignment of guanosine dihydrate which contains two guanosine molecules in the asymmetric unit.
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Affiliation(s)
- Joshua D Hartman
- Department of Chemistry, University of California, Riverside, Riverside, CA, United States.
| | - James K Harper
- Department of Chemistry and Biochemistry, Brigham Young University, Provo, UT, United States.
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6
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Hartman JD, Mathews A, Harper JK. Fast and Accurate Electric Field Gradient Calculations in Molecular Solids With Density Functional Theory. Front Chem 2021; 9:751711. [PMID: 34692646 PMCID: PMC8529703 DOI: 10.3389/fchem.2021.751711] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2021] [Accepted: 09/20/2021] [Indexed: 11/24/2022] Open
Abstract
Modern approaches for calculating electric field gradient (EFF) tensors in molecular solids rely upon plane-wave calculations employing periodic boundary conditions (PBC). In practice, models employing PBCs are limited to generalized gradient approximation (GGA) density functionals. Hybrid density functionals applied in the context of gauge-including atomic orbital (GIAO) calculations have been shown to substantially improve the accuracy of predicted NMR parameters. Here we propose an efficient method that effectively combines the benefits of both periodic calculations and single-molecule techniques for predicting electric field gradient tensors in molecular solids. Periodic calculations using plane-wave basis sets were used to model the crystalline environment. We then introduce a molecular correction to the periodic result obtained from a single-molecule calculation performed with a hybrid density functional. Single-molecule calculations performed using hybrid density functionals were found to significantly improve the agreement of predicted 17O quadrupolar coupling constants (C q ) with experiment. We demonstrate a 31% reduction in the RMS error for the predicted 17O C q values relative to standard plane-wave methods using a carefully constructed test set comprised of 22 oxygen-containing molecular crystals. We show comparable improvements in accuracy using five different hybrid density functionals and find predicted C q values to be relatively insensitive to the choice of basis set used in the single molecule calculation. Finally, the utility of high-accuracy 17O C q predictions is demonstrated by examining the disordered 4-Nitrobenzaldehyde crystal structure.
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Affiliation(s)
- Joshua D. Hartman
- Department of Chemistry, Mt. San Jacinto College, Menifee, CA, United States
| | - Amanda Mathews
- Department of Chemistry, Mt. San Jacinto College, Menifee, CA, United States
| | - James K. Harper
- Department of Chemistry and Biochemistry, Brigham Young University, Provo, UT, United States
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7
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Engel EA, Kapil V, Ceriotti M. Importance of Nuclear Quantum Effects for NMR Crystallography. J Phys Chem Lett 2021; 12:7701-7707. [PMID: 34355903 DOI: 10.1021/acs.jpclett.1c01987] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
The resolving power of solid-state nuclear magnetic resonance (NMR) crystallography depends heavily on the accuracy of computational predictions of NMR chemical shieldings of candidate structures, which are usually taken to be local minima in the potential energy. To test the limits of this approximation, we systematically study the importance of finite-temperature and quantum nuclear fluctuations for 1H, 13C, and 15N shieldings in polymorphs of three paradigmatic molecular crystals: benzene, glycine, and succinic acid. The effect of quantum fluctuations is comparable to the typical errors of shielding predictions for static nuclei with respect to experiments, and their inclusion improves the agreement with measurements, translating to more reliable assignment of the NMR spectra to the correct candidate structure. The use of integrated machine-learning models, trained on first-principles energies and shieldings, renders rigorous sampling of nuclear fluctuations affordable, setting a new standard for the calculations underlying NMR structure determinations.
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Affiliation(s)
- Edgar A Engel
- TCM Group, Cavendish Laboratory, University of Cambridge, J. J. Thomson Avenue, Cambridge CB3 0HE, United Kingdom
| | - Venkat Kapil
- Laboratory of Computational Science and Modeling, Institut des Matériaux, École Polytechnique Fédérale de Lausanne, 1015 Lausanne, Switzerland
| | - Michele Ceriotti
- Laboratory of Computational Science and Modeling, Institut des Matériaux, École Polytechnique Fédérale de Lausanne, 1015 Lausanne, Switzerland
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8
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Mathews A, Hartman JD. Accurate fragment-based 51-V chemical shift predictions in molecular crystals. SOLID STATE NUCLEAR MAGNETIC RESONANCE 2021; 114:101733. [PMID: 34082261 DOI: 10.1016/j.ssnmr.2021.101733] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/21/2021] [Revised: 04/28/2021] [Accepted: 04/28/2021] [Indexed: 06/12/2023]
Abstract
Nuclear magnetic resonance (NMR) spectroscopy plays a crucial role in determining molecular structure for complex biological and pharmaceutical compounds. NMR investigations are increasingly reliant on computation for mapping spectral features to chemical structures. Here we benchmark the accuracy of fragment-based 51V chemical shielding tensor calculations using a training set comprised of 10 biologically and pharmaceutically relevant oxovanadium complexes. Using our self-consistent reproduction of the Madelung potential (SCRMP) electrostatic embedding model, we demonstrate comparable performance between fragment methods and computationally demanding cluster-based techniques. Specifically, fragment methods employing hybrid density functionals are capable of reproducing the experimental 51V isotropic chemical shifts with a training set rms error of ~9 ppm, representing a 20% improvement over traditional plane wave techniques. We provide training set-derived linear regression models for mapping the absolute shieldings obtained from computation to the experimentally determined chemical shifts using four common density functionals; PBE0, B3LYP, PBE, and BLYP. Finally, we establish the utility of fragment methods and the reported regression parameters examining four oxovanadium structures excluded from the training set including the tetracoordinate oxovanadium silicate [Formula: see text] , VO15NGlySalbz which contains redox-active ligands, and the solid-state form of the common 51V NMR reference compound VOCl3.
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Affiliation(s)
- Amanda Mathews
- Department of Chemistry, Mt. San Jacinto College, Menifee, CA, USA
| | - Joshua D Hartman
- Department of Chemistry, Mt. San Jacinto College, Menifee, CA, USA.
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9
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Analyzing Discrepancies in Chemical-Shift Predictions of Solid Pyridinium Fumarates. Molecules 2021; 26:molecules26133857. [PMID: 34202841 PMCID: PMC8270278 DOI: 10.3390/molecules26133857] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2021] [Revised: 06/21/2021] [Accepted: 06/21/2021] [Indexed: 01/29/2023] Open
Abstract
Highly accurate chemical-shift predictions in molecular solids are behind the success and rapid development of NMR crystallography. However, unusually large errors of predicted hydrogen and carbon chemical shifts are sometimes reported. An understanding of these deviations is crucial for the reliability of NMR crystallography. Here, recently reported large deviations of predicted hydrogen and carbon chemical shifts of a series of solid pyridinium fumarates are thoroughly analyzed. The influence of the geometry optimization protocol and of the computational level of NMR calculations on the accuracy of predicted chemical shifts is investigated. Periodic calculations with GGA, meta-GGA and hybrid functionals are employed. Furthermore, molecular corrections at the coupled-cluster singles-and-doubles (CCSD) level are calculated. The effect of nuclear delocalization on the structure and NMR shielding is also investigated. The geometry optimization with a computationally demanding hybrid functional leads to a substantial improvement in proton chemical-shift predictions.
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10
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Wang L, Elliott AB, Moore SD, Beran GJO, Hartman JD, Harper JK. Modeling Small Structural and Environmental Differences in Solids with 15 N NMR Chemical Shift Tensors. Chemphyschem 2021; 22:1008-1017. [PMID: 33604988 DOI: 10.1002/cphc.202000985] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2020] [Revised: 01/28/2021] [Indexed: 11/09/2022]
Abstract
The ability to theoretically predict accurate NMR chemical shifts in solids is increasingly important due to the role such shifts play in selecting among proposed model structures. Herein, two theoretical methods are evaluated for their ability to assign 15 N shifts from guanosine dihydrate to one of the two independent molecules present in the lattice. The NMR data consist of 15 N shift tensors from 10 resonances. Analysis using periodic boundary or fragment methods consider a benchmark dataset to estimate errors and predict uncertainties of 5.6 and 6.2 ppm, respectively. Despite this high accuracy, only one of the five sites were confidently assigned to a specific molecule of the asymmetric unit. This limitation is not due to negligible differences in experimental data, as most sites exhibit differences of >6.0 ppm between pairs of resonances representing a given position. Instead, the theoretical methods are insufficiently accurate to make assignments at most positions.
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Affiliation(s)
- Luther Wang
- Department of Chemistry and Biochemistry, Brigham Young University, 84602, Provo, UT, USA
| | - Alexander B Elliott
- Department of Chemistry, University of Central Florida, 4111 Libra Drive, 32816, Orlando, FL, USA
| | - Sean D Moore
- Burnett School of Biomedical Sciences, University of Central Florida, 4110 Libra Drive, 32816, Orlando, FL, USA
| | - Gregory J O Beran
- Department of Chemistry, University of California, 92521, Riverside, CA, USA
| | - Joshua D Hartman
- Department of Chemistry, Mt. San Jacinto College, 92583, San Jacinto, CA, USA
| | - James K Harper
- Department of Chemistry and Biochemistry, Brigham Young University, 84602, Provo, UT, USA
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11
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Wang L, Harper JK. Refining crystal structures using 13C NMR chemical shift tensors as a target function. CrystEngComm 2021. [DOI: 10.1039/d1ce00960e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A two-step process is described for refining crystal structures from any source.
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Affiliation(s)
- Luther Wang
- Department of Chemistry and Biochemistry, Brigham Young University, Provo UT 84602, USA
| | - James K. Harper
- Department of Chemistry and Biochemistry, Brigham Young University, Provo UT 84602, USA
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12
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Holmes ST, Vojvodin CS, Schurko RW. Dispersion-Corrected DFT Methods for Applications in Nuclear Magnetic Resonance Crystallography. J Phys Chem A 2020; 124:10312-10323. [DOI: 10.1021/acs.jpca.0c06372] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Sean T. Holmes
- Department of Chemistry & Biochemistry, Florida State University, Tallahassee, Florida 32306, United States
- National High Magnetic Field Laboratory, Tallahassee, Florida 32310, United States
| | - Cameron S. Vojvodin
- Department of Chemistry & Biochemistry, Florida State University, Tallahassee, Florida 32306, United States
- National High Magnetic Field Laboratory, Tallahassee, Florida 32310, United States
| | - Robert W. Schurko
- Department of Chemistry & Biochemistry, Florida State University, Tallahassee, Florida 32306, United States
- National High Magnetic Field Laboratory, Tallahassee, Florida 32310, United States
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13
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Dračínský M, Vícha J, Bártová K, Hodgkinson P. Towards Accurate Predictions of Proton NMR Spectroscopic Parameters in Molecular Solids. Chemphyschem 2020; 21:2075-2083. [PMID: 32691463 DOI: 10.1002/cphc.202000629] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2020] [Revised: 07/20/2020] [Indexed: 12/18/2022]
Abstract
The factors contributing to the accuracy of quantum-chemical calculations for the prediction of proton NMR chemical shifts in molecular solids are systematically investigated. Proton chemical shifts of six solid amino acids with hydrogen atoms in various bonding environments (CH, CH2 , CH3 , OH, SH and NH3 ) were determined experimentally using ultra-fast magic-angle spinning and proton-detected 2D NMR experiments. The standard DFT method commonly used for the calculations of NMR parameters of solids is shown to provide chemical shifts that deviate from experiment by up to 1.5 ppm. The effects of the computational level (hybrid DFT functional, coupled-cluster calculation, inclusion of relativistic spin-orbit coupling) are thoroughly discussed. The effect of molecular dynamics and nuclear quantum effects are investigated using path-integral molecular dynamics (PIMD) simulations. It is demonstrated that the accuracy of the calculated proton chemical shifts is significantly better when these effects are included in the calculations.
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Affiliation(s)
- Martin Dračínský
- Institute of Organic Chemistry and Biochemistry, AS CR, Flemingovo nám. 2, Prague, CZ-16610, Czech Republic
| | - Jan Vícha
- Institute of Organic Chemistry and Biochemistry, AS CR, Flemingovo nám. 2, Prague, CZ-16610, Czech Republic.,Centre of Polymer Systems, Tomas Bata University in Zlín, Tomáše Bati 5678, Zlín, CZ-760 01, Czech Republic
| | - Kateřina Bártová
- Institute of Organic Chemistry and Biochemistry, AS CR, Flemingovo nám. 2, Prague, CZ-16610, Czech Republic
| | - Paul Hodgkinson
- Department of Chemistry, Durham University, South Road, DH1 3LE, Durham, UK
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14
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Unzueta PA, Beran GJO. Polarizable continuum models provide an effective electrostatic embedding model for fragment-based chemical shift prediction in challenging systems. J Comput Chem 2020; 41:2251-2265. [PMID: 32748418 DOI: 10.1002/jcc.26388] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2020] [Revised: 06/04/2020] [Accepted: 07/04/2020] [Indexed: 12/25/2022]
Abstract
Ab initio nuclear magnetic resonance chemical shift prediction provides an important tool for interpreting and assigning experimental spectra, but it becomes computationally prohibitive in large systems. The computational costs can be reduced considerably by fragmentation of the large system into a series of contributions from many smaller subsystems. However, the presence of charged functional groups and the need to partition the system across covalent bonds create complications in biomolecules that typically require the use of large fragments and careful descriptions of the electrostatic environment. The present work shows how a model that combines chemical shielding contributions from non-overlapping monomer and dimer fragments embedded in a polarizable continuum model provides a simple, easy-to-implement, and computationally inexpensive approach for predicting chemical shifts in complex systems. The model's performance proves rather insensitive to the continuum dielectric constant, making the selection of the optimal embedding dielectric less critical. The PCM-embedded fragment model is demonstrated to perform well across systems ranging from molecular crystals to proteins.
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Affiliation(s)
- Pablo A Unzueta
- Department of Chemistry, Univeristy of California, Riverside, California, USA
| | - Gregory J O Beran
- Department of Chemistry, Univeristy of California, Riverside, California, USA
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15
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Holmes ST, Engl OG, Srnec MN, Madura JD, Quiñones R, Harper JK, Schurko RW, Iuliucci RJ. Chemical Shift Tensors of Cimetidine Form A Modeled with Density Functional Theory Calculations: Implications for NMR Crystallography. J Phys Chem A 2020; 124:3109-3119. [DOI: 10.1021/acs.jpca.0c00421] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Affiliation(s)
- Sean T. Holmes
- Department of Chemistry & Biochemistry, Florida State University, Tallahassee, Florida 32306, United States
| | - Olivia G. Engl
- Department of Chemistry, Washington and Jefferson College, Washington, Pennsylvania 15301, United States
| | - Matthew N. Srnec
- Department of Chemistry, Physics, & Engineering, Franciscan University, Steubenville, Ohio 43952, United States
| | - Jeffry D. Madura
- Department of Chemistry & Biochemistry, Center for Computational Sciences, Duquesne University, Pittsburgh, Pennsylvania 15282, United States
| | - Rosalynn Quiñones
- Department of Chemistry, Marshall University, Huntington, West Virginia 25755, United States
| | - James K. Harper
- Department of Chemistry & Biochemistry, Brigham Young University, Provo, Utah 84602, United States
| | - Robert W. Schurko
- Department of Chemistry & Biochemistry, Florida State University, Tallahassee, Florida 32306, United States
| | - Robbie J. Iuliucci
- Department of Chemistry, Washington and Jefferson College, Washington, Pennsylvania 15301, United States
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16
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Hofstetter A, Balodis M, Paruzzo FM, Widdifield CM, Stevanato G, Pinon AC, Bygrave PJ, Day GM, Emsley L. Rapid Structure Determination of Molecular Solids Using Chemical Shifts Directed by Unambiguous Prior Constraints. J Am Chem Soc 2019; 141:16624-16634. [PMID: 31117663 PMCID: PMC7540916 DOI: 10.1021/jacs.9b03908] [Citation(s) in RCA: 33] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
NMR-based crystallography approaches involving the combination of crystal structure prediction methods, ab initio calculated chemical shifts and solid-state NMR experiments are powerful methods for crystal structure determination of microcrystalline powders. However, currently structural information obtained from solid-state NMR is usually included only after a set of candidate crystal structures has already been independently generated, starting from a set of single-molecule conformations. Here, we show with the case of ampicillin that this can lead to failure of structure determination. We propose a crystal structure determination method that includes experimental constraints during conformer selection. In order to overcome the problem that experimental measurements on the crystalline samples are not obviously translatable to restrict the single-molecule conformational space, we propose constraints based on the analysis of absent cross-peaks in solid-state NMR correlation experiments. We show that these absences provide unambiguous structural constraints on both the crystal structure and the gas-phase conformations, and therefore can be used for unambiguous selection. The approach is parametrized on the crystal structure determination of flutamide, flufenamic acid, and cocaine, where we reduce the computational cost by around 50%. Most importantly, the method is then shown to correctly determine the crystal structure of ampicillin, which would have failed using current methods because it adopts a high-energy conformer in its crystal structure. The average positional RMSE on the NMR powder structure is ⟨rav⟩ = 0.176 Å, which corresponds to an average equivalent displacement parameter Ueq = 0.0103 Å2.
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Affiliation(s)
- Albert Hofstetter
- Institut des Sciences et Ingénierie Chimiques , École Polytechnique Fédérale de Lausanne (EPFL) , 1015 Lausanne , Switzerland
| | - Martins Balodis
- Institut des Sciences et Ingénierie Chimiques , École Polytechnique Fédérale de Lausanne (EPFL) , 1015 Lausanne , Switzerland
| | - Federico M Paruzzo
- Institut des Sciences et Ingénierie Chimiques , École Polytechnique Fédérale de Lausanne (EPFL) , 1015 Lausanne , Switzerland
| | - Cory M Widdifield
- Department of Chemistry, Mathematics and Science Center , Oakland University , 146 Library Drive , Rochester , Michigan 48309-4479 , United States
| | - Gabriele Stevanato
- Institut des Sciences et Ingénierie Chimiques , École Polytechnique Fédérale de Lausanne (EPFL) , 1015 Lausanne , Switzerland
| | - Arthur C Pinon
- Institut des Sciences et Ingénierie Chimiques , École Polytechnique Fédérale de Lausanne (EPFL) , 1015 Lausanne , Switzerland
| | - Peter J Bygrave
- School of Chemistry , University of Southampton , Highfield , Southampton SO17 1BJ , United Kingdom
| | - Graeme M Day
- School of Chemistry , University of Southampton , Highfield , Southampton SO17 1BJ , United Kingdom
| | - Lyndon Emsley
- Institut des Sciences et Ingénierie Chimiques , École Polytechnique Fédérale de Lausanne (EPFL) , 1015 Lausanne , Switzerland
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Dračínský M, Unzueta P, Beran GJO. Improving the accuracy of solid-state nuclear magnetic resonance chemical shift prediction with a simple molecular correction. Phys Chem Chem Phys 2019; 21:14992-15000. [PMID: 31237586 DOI: 10.1039/c9cp01666j] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
A fast, straightforward method for computing NMR chemical shieldings of crystalline solids is proposed. The method combines the advantages of both conventional approaches: periodic calculations using plane-wave basis sets and molecular computational approaches. The periodic calculations capture the periodic nature of crystalline solids, but the computational level of the electronic structure calculation is limited to general-gradient-approximation (GGA) density functionals. It is demonstrated that a correction to the GGA result calculated on an isolated molecule at a higher level of theory significantly improves the correlations between experimental and calculated chemical shifts while adding almost no additional computational cost. Corrections calculated with a hybrid density functional improved the accuracy of 13C, 15N and 17O chemical shift predictions significantly and allowed identifying errors in previously published experimental data. Applications of the approach to crystalline isocytosine, methacrylamide, and testosterone are presented.
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Affiliation(s)
- Martin Dračínský
- Institute of Organic Chemistry and Biochemistry, AS CR, Flemingovo 2, Prague, Czech Republic.
| | - Pablo Unzueta
- Department of Chemistry, University of California, Riverside, California 92521, USA
| | - Gregory J O Beran
- Department of Chemistry, University of California, Riverside, California 92521, USA
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