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Yesiltepe Y, Govind N, Metz TO, Renslow RS. An initial investigation of accuracy required for the identification of small molecules in complex samples using quantum chemical calculated NMR chemical shifts. J Cheminform 2022; 14:64. [PMID: 36138446 PMCID: PMC9499888 DOI: 10.1186/s13321-022-00587-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2020] [Accepted: 02/06/2022] [Indexed: 11/24/2022] Open
Abstract
The majority of primary and secondary metabolites in nature have yet to be identified, representing a major challenge for metabolomics studies that currently require reference libraries from analyses of authentic compounds. Using currently available analytical methods, complete chemical characterization of metabolomes is infeasible for both technical and economic reasons. For example, unambiguous identification of metabolites is limited by the availability of authentic chemical standards, which, for the majority of molecules, do not exist. Computationally predicted or calculated data are a viable solution to expand the currently limited metabolite reference libraries, if such methods are shown to be sufficiently accurate. For example, determining nuclear magnetic resonance (NMR) spectroscopy spectra in silico has shown promise in the identification and delineation of metabolite structures. Many researchers have been taking advantage of density functional theory (DFT), a computationally inexpensive yet reputable method for the prediction of carbon and proton NMR spectra of metabolites. However, such methods are expected to have some error in predicted 13C and 1H NMR spectra with respect to experimentally measured values. This leads us to the question-what accuracy is required in predicted 13C and 1H NMR chemical shifts for confident metabolite identification? Using the set of 11,716 small molecules found in the Human Metabolome Database (HMDB), we simulated both experimental and theoretical NMR chemical shift databases. We investigated the level of accuracy required for identification of metabolites in simulated pure and impure samples by matching predicted chemical shifts to experimental data. We found 90% or more of molecules in simulated pure samples can be successfully identified when errors of 1H and 13C chemical shifts in water are below 0.6 and 7.1 ppm, respectively, and below 0.5 and 4.6 ppm in chloroform solvation, respectively. In simulated complex mixtures, as the complexity of the mixture increased, greater accuracy of the calculated chemical shifts was required, as expected. However, if the number of molecules in the mixture is known, e.g., when NMR is combined with MS and sample complexity is low, the likelihood of confident molecular identification increased by 90%.
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Affiliation(s)
- Yasemin Yesiltepe
- The Gene and Linda Voiland School of Chemical Engineering and Bioengineering, Washington State University, Pullman, WA, USA
- Earth and Biological Sciences Directorate, Pacific Northwest National Laboratory, Richland, WA, USA
| | - Niranjan Govind
- Earth and Biological Sciences Directorate, Pacific Northwest National Laboratory, Richland, WA, USA
| | - Thomas O Metz
- The Gene and Linda Voiland School of Chemical Engineering and Bioengineering, Washington State University, Pullman, WA, USA
| | - Ryan S Renslow
- The Gene and Linda Voiland School of Chemical Engineering and Bioengineering, Washington State University, Pullman, WA, USA.
- Earth and Biological Sciences Directorate, Pacific Northwest National Laboratory, Richland, WA, USA.
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2
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Fluorophore spectroscopy in aqueous glycerol solution: the interactions of glycerol with the fluorophore. Photochem Photobiol Sci 2021; 20:1397-1418. [PMID: 34609728 DOI: 10.1007/s43630-021-00096-w] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2021] [Accepted: 08/24/2021] [Indexed: 10/20/2022]
Abstract
A common perception exists that glycerol provides an inert-like environment modifying viscosity and index of refraction by its various concentrations in aqueous solution. Said perception is herein challenged by investigating the effects of the glycerol environment on the spectroscopic properties of fluorescein, as a representative fluorophore, using steady-state and time-resolved techniques and computational chemistry. Results strongly suggest that the fluorescence quantum yield, measured fluorescence lifetime (FLT), natural lifetime and calculated fluorescence lifetime are all highly sensitive to the presence of glycerol. Glycerol was found to impact both the ground and first excited states of fluorescein, quenching and modifying both absorption and emission spectra, affecting the fundamental electrical dipoles of the ground and first excited singlet states, and lowering FLT and quantum yield. Furthermore, the Stern-Volmer, Lippert-Mataga, Perrin and Strickler-Berg relations indicate that glycerol acts upon fluorescein in aqueous solution as a quencher and alters the fluorescein geometry. Predictions made by computational chemistry impressively correspond to experimental results, both indicating changes in the properties of fluorescein at around 35% v/v aqueous glycerol, a clear indication that glycerol is not an innocent medium. This study proposes the Strickler-Berg relation as a means of detecting non-negligible effects of a hosting medium on its host fluorophore. These new insights on the molecular structures, the interactions between glycerol and its host fluorophore, and the effects of one on the other may be essential for understanding fundamental phenomena in chemistry and related fields.
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Bendrea AD, Cianga L, Ailiesei GL, Ursu EL, Göen Colak D, Cianga I. 3,4-Ethylenedioxythiophene (EDOT) End-Group Functionalized Poly-ε-caprolactone (PCL): Self-Assembly in Organic Solvents and Its Coincidentally Observed Peculiar Behavior in Thin Film and Protonated Media. Polymers (Basel) 2021; 13:2720. [PMID: 34451259 PMCID: PMC8400159 DOI: 10.3390/polym13162720] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2021] [Revised: 08/10/2021] [Accepted: 08/12/2021] [Indexed: 01/05/2023] Open
Abstract
End-group functionalization of homopolymers is a valuable way to produce high-fidelity nanostructured and functional soft materials when the structures obtained have the capacity for self-assembly (SA) encoded in their structural details. Herein, an end-functionalized PCL with a π-conjugated EDOT moiety, (EDOT-PCL), designed exclusively from hydrophobic domains, as a functional "hydrophobic amphiphile", was synthesized in the bulk ROP of ε-caprolactone. The experimental results obtained by spectroscopic methods, including NMR, UV-vis, and fluorescence, using DLS and by AFM, confirm that in solvents with extremely different polarities (chloroform and acetonitrile), EDOT-PCL presents an interaction- and structure-based bias, which is strong and selective enough to exert control over supramolecular packing, both in dispersions and in the film state. This leads to the diversity of SA structures, including spheroidal, straight, and helical rods, as well as orthorhombic single crystals, with solvent-dependent shapes and sizes, confirming that EDOT-PCL behaves as a "block-molecule". According to the results from AFM imaging, an unexpected transformation of micelle-type nanostructures into single 2D lamellar crystals, through breakout crystallization, took place by simple acetonitrile evaporation during the formation of the film on the mica support at room temperature. Moreover, EDOT-PCL's propensity for spontaneous oxidant-free oligomerization in acidic media was proposed as a presumptive answer for the unexpected appearance of blue color during its dissolution in CDCl3 at a high concentration. FT-IR, UV-vis, and fluorescence techniques were used to support this claim. Besides being intriguing and unforeseen, the experimental findings concerning EDOT-PCL have raised new and interesting questions that deserve to be addressed in future research.
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Affiliation(s)
- Anca-Dana Bendrea
- Centre of Advanced Research in Bionanoconjugates and Biopolymers, “Petru Poni” Institute of Macromolecular Chemistry, 41A, Grigore-Ghica Voda Alley, 700487 Iasi, Romania; (A.-D.B.); (E.-L.U.)
| | - Luminita Cianga
- Centre of Advanced Research in Bionanoconjugates and Biopolymers, “Petru Poni” Institute of Macromolecular Chemistry, 41A, Grigore-Ghica Voda Alley, 700487 Iasi, Romania; (A.-D.B.); (E.-L.U.)
| | - Gabriela-Liliana Ailiesei
- NMR Spectroscopy Department, “Petru Poni” Institute of Macromolecular Chemistry, 41A, Grigore-Ghica Voda Alley, 700487 Iasi, Romania;
| | - Elena-Laura Ursu
- Centre of Advanced Research in Bionanoconjugates and Biopolymers, “Petru Poni” Institute of Macromolecular Chemistry, 41A, Grigore-Ghica Voda Alley, 700487 Iasi, Romania; (A.-D.B.); (E.-L.U.)
| | - Demet Göen Colak
- Department of Chemistry, Faculty of Science and Letters, Istanbul Technical University, Maslak, Istanbul 34469, Turkey;
| | - Ioan Cianga
- Centre of Advanced Research in Bionanoconjugates and Biopolymers, “Petru Poni” Institute of Macromolecular Chemistry, 41A, Grigore-Ghica Voda Alley, 700487 Iasi, Romania; (A.-D.B.); (E.-L.U.)
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4
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Identifying and explaining the regioselectivity of alkylation of 1,2,4-triazole-3-thiones using NMR, GIAO and DFT methods. J Mol Struct 2021. [DOI: 10.1016/j.molstruc.2020.128973] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
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5
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Artemov VG, Ryzhov A, Carlsen E, Kapralov PO, Ouerdane H. Nonrotational Mechanism of Polarization in Alcohols. J Phys Chem B 2020; 124:11022-11029. [PMID: 33225700 DOI: 10.1021/acs.jpcb.0c09380] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Chemical polarity governs various mechanical, chemical, and thermodynamic properties of dielectrics. Polar liquids have been amply studied, yet the basic mechanisms underpinning their dielectric properties remain not fully understood, as standard models following Debye's phenomenological approach do not account for quantum effects and cannot aptly reproduce the full dc-up-to-THz spectral range. Here, using the illustrative case of monohydric alcohols, we show that deep tunneling and the consequent intermolecular separation of excess protons and "proton-holes" in the polar liquids govern their static and dynamic dielectric properties on the same footing. We performed systematic ultrabroadband (0-10 THz) spectroscopy experiments with monohydric alcohols of different (0.4-1.6 nm) molecular lengths and show that the finite lifetime of molecular species and the proton-hole correlation length are the two principle parameters responsible for the dielectric response of all the studied alcohols across the entire frequency range. Our results demonstrate that a quantum nonrotational intermolecular mechanism drives the polarization in alcohols while the rotational mechanism of molecular polarization plays a secondary role, manifesting itself in the sub-terahertz region only.
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Affiliation(s)
- Vasily G Artemov
- Center for Energy Science and Technology, Skolkovo Institute of Science and Technology, 121205 Moscow, Russia
| | - Alexander Ryzhov
- Center for Energy Science and Technology, Skolkovo Institute of Science and Technology, 121205 Moscow, Russia
| | - Emma Carlsen
- Department of Chemistry and Biochemistry, Brigham Young University, 84602 Provo, Utah, United States
| | | | - Henni Ouerdane
- Center for Energy Science and Technology, Skolkovo Institute of Science and Technology, 121205 Moscow, Russia
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Philipp JK, Ludwig R. Clusters of Hydroxyl-Functionalized Cations Stabilized by Cooperative Hydrogen Bonds: The Role of Polarizability and Alkyl Chain Length. Molecules 2020; 25:E4972. [PMID: 33121087 PMCID: PMC7662246 DOI: 10.3390/molecules25214972] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2020] [Revised: 10/22/2020] [Accepted: 10/24/2020] [Indexed: 01/08/2023] Open
Abstract
We explore quantum chemical calculations for studying clusters of hydroxyl-functionalized cations kinetically stabilized by hydrogen bonding despite strongly repulsive electrostatic forces. In a comprehensive study, we calculate clusters of ammonium, piperidinium, pyrrolidinium, imidazolium, pyridinium, and imidazolium cations, which are prominent constituents of ionic liquids. All cations are decorated with hydroxy-alkyl chains allowing H-bond formation between ions of like charge. The cluster topologies comprise linear and cyclic clusters up to the size of hexamers. The ring structures exhibit cooperative hydrogen bonds opposing the repulsive Coulomb forces and leading to kinetic stability of the clusters. We discuss the importance of hydrogen bonding and dispersion forces for the stability of the differently sized clusters. We find the largest clusters when hydrogen bonding is maximized in cyclic topologies and dispersion interaction is properly taken into account. The kinetic stability of the clusters with short-chained cations is studied for the different types of cations ranging from hard to polarizable or exhibiting additional functional groups such as the acidic C(2)-H position in the imidazolium-based cation. Increasing the alkyl chain length, the cation effect diminishes and the kinetic stability is exclusively governed by the alkyl chain tether increasing the distance between the positively charged rings of the cations. With adding the counterion tetrafluoroborate (BF4-) to the cationic clusters, the binding energies immediately switch from strongly positive to strongly negative. In the neutral clusters, the OH functional groups of the cations can interact either with other cations or with the anions. The hexamer cluster with the cyclic H-bond motive and "released" anions is almost as stable as the hexamer built by H-bonded ion pairs exclusively, which is in accord with recent IR spectra of similar ionic liquids detecting both types of hydrogen bonding. For the cationic and neutral clusters, we discuss geometric and spectroscopic properties as sensitive probes of opposite- and like-charge interaction. Finally, we show that NMR proton chemical shifts and deuteron quadrupole coupling constants can be related to each other, allowing to predict properties which are not easily accessible by experiment.
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Affiliation(s)
- Jule K. Philipp
- Institut für Chemie, Abteilung Physikalische und Theoretische Chemie, Universität Rostock, 18059 Rostock, Germany;
| | - Ralf Ludwig
- Institut für Chemie, Abteilung Physikalische und Theoretische Chemie, Universität Rostock, 18059 Rostock, Germany;
- Department Life, Light & Matter, Universität Rostock, Albert-Einstein-Str. 25, 18059 Rostock, Germany
- Leibniz-Institut für Katalyse an der Universität Rostock e.V., Albert-Einstein-Str. 29a, 18059 Rostock, Germany
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7
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Siskos MG, Varras PC, Gerothanassis IP. DFT calculations of O–H⋯O 1H NMR chemical shifts in investigating enol-enol tautomeric equilibria: Probing the impacts of intramolecular hydrogen bonding vs stereoelectronic interactions. Tetrahedron 2020. [DOI: 10.1016/j.tet.2020.130979] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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8
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Báez JE, Shea KJ, Dennison PR, Obregón-Herrera A, Bonilla-Cruz J. Monodisperse oligo(δ-valerolactones) and oligo(ε-caprolactones) with docosyl (C22) end-groups. Polym Chem 2020. [DOI: 10.1039/d0py00576b] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Two different families of monodisperse oligoesters with α-hydroxyl-ω-docosyl (C22) terminal groups [oligo(δ-valerolactone) and oligo(ϵ-caprolactone)] were isolated by flash column chromatography (FCC).
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Affiliation(s)
- José E. Báez
- Department of Chemistry
- Division of Natural and Exact Sciences
- University of Guanajuato (UG)
- Guanajuato
- Gto. Mexico
| | - Kenneth J. Shea
- Department of Chemistry
- University of California
- Irvine
- Irvine
- 92697-2025
| | | | - Armando Obregón-Herrera
- Department of Biology
- Division of Natural and Exact Sciences
- University of Guanajuato (UG)
- Guanajuato
- Gto. Mexico
| | - José Bonilla-Cruz
- Centro de Investigación en Materiales Avanzados S.C. (CIMAV-Unidad Monterrey)
- Apodaca
- 66628 Mexico
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Sychrovský V, Šaman D, Fiala R, Humpa O, Sýkora J, Kessler P, Blechta V, Dobrev P, Schraml J. Ascorbigen A-NMR identification. MAGNETIC RESONANCE IN CHEMISTRY : MRC 2019; 57:1084-1096. [PMID: 31257662 DOI: 10.1002/mrc.4890] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/09/2019] [Revised: 05/03/2019] [Accepted: 05/06/2019] [Indexed: 06/09/2023]
Abstract
The connectivities of all atoms in ascorbigen A, an important metabolite, were determined unambiguously for the first time. The connectivity between carbon atoms was established by 2D INADEQUATE, and one-bond 13 C-13 C coupling constants were determined for all pairs of directly connected carbon atoms except for two strongly coupled carbon pairs. The 13 C-13 C coupling in one of the pairs was proved by a modification of standard INADEQUATE; however, the signals from the other pair were too weak to be observed. The connectivity within the two strongly coupled C-C pairs was confirmed by a combination of COSY and gHSQC; the latter experiment also identified all C-H bonds. The proton nuclear magnetic resonance (1 H NMR) spectra in dry dimethyl sulfoxide allowed identification and assignment of the signals due to NH and OH protons. The derived structure, 3-((1H-indol-3-yl)methyl)-3,3a,6-trihydroxytetrahydrofuro[3,2-b]furan-2(5H)-one, agrees with the structure suggested for ascorbigen A in 1966. The density functional theory (DFT) calculations showed that among 16 possible stereoisomers, only two complied with the almost zero value of the measured 3 J(H6-H6a). Of the two stereoisomers, 3S,3aS,6S,6aR and 3R,3aR,6R,6aS, the latter was excluded on synthetic grounds. The nuclear Overhauser effect measurements unveiled close proximity between H2' proton of the indole and the H6a proton of the tetrahydrofuro[3,2-b]furan part. Detailed structural interpretation of the measured NMR parameters by means of DFT NMR was hampered by rotational flexibility of the indole and tetrahydrofuro[3,2-b]furan parts and inadequacy of Polarizable Continuum Model (PCM) solvent model.
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Affiliation(s)
- Vladimír Sychrovský
- Institute of Organic Chemistry and Biochemistry of the CAS, Prague 6, Czech Republic
| | - David Šaman
- Institute of Organic Chemistry and Biochemistry of the CAS, Prague 6, Czech Republic
| | | | | | - Jan Sýkora
- Institute of Chemical Process Fundamentals of the CAS, Prague 6, Czech Republic
| | | | - Vratislav Blechta
- Institute of Chemical Process Fundamentals of the CAS, Prague 6, Czech Republic
| | - Petre Dobrev
- Institute of Experimental Botany of the CAS, Prague 6, Czech Republic
| | - Jan Schraml
- Institute of Chemical Process Fundamentals of the CAS, Prague 6, Czech Republic
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Iron MA, Gropp J. Cost-effective density functional theory (DFT) calculations of equilibrium isotopic fractionation in large organic molecules. Phys Chem Chem Phys 2019; 21:17555-17570. [PMID: 31342034 DOI: 10.1039/c9cp02975c] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The application of stable isotopes to address a wide range of biochemical, microbiological and environmental problems is hindered by the experimental difficulty and the computational cost of determining equilibrium isotopic fractionations (EIF) of large organic molecules. Here, we evaluate the factors that impact the accuracy of computed EIFs and develop a framework for cost-effective and accurate computation of EIFs by density functional theory (DFT). We generated two benchmark databases of experimentally determined EIFs, one for H isotopes and another for the isotopes of the heavy atoms C, N and O. The accuracy of several DFT exchange-correlation functionals in calculating EIFs was then evaluated by comparing the computational results to these experimental datasets. We find that with the def2-TZVP basis set, O3LYP had the lowest mean absolute deviation (21‰ and 3.9‰ for the isotopic fractionation of H and the heavier atoms, respectively), but the GGA/meta-GGA functionals τHCTHD3BJ, τHCTH and HCTH have similar performances (22‰ and 4.1‰, respectively, for τHCTHD3BJ). Leveraging the good performance of computationally efficient functionals, we provide a robust, practical, experimentally validated framework for using DFT to accurately predict EIFs of large organic molecules, including uncertainty estimates.
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Affiliation(s)
- Mark A Iron
- Computational Chemistry Unit, Department of Chemical Research Support, Weizmann Institute of Science, Rehovot, 7610001, Israel.
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11
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Mari SH, Varras PC, Atia-tul-Wahab, Choudhary IM, Siskos MG, Gerothanassis IP. Solvent-Dependent Structures of Natural Products Based on the Combined Use of DFT Calculations and 1H-NMR Chemical Shifts. Molecules 2019; 24:E2290. [PMID: 31226776 PMCID: PMC6631582 DOI: 10.3390/molecules24122290] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2019] [Revised: 06/13/2019] [Accepted: 06/18/2019] [Indexed: 01/09/2023] Open
Abstract
Detailed solvent and temperature effects on the experimental 1H-NMR chemical shifts of the natural products chrysophanol (1), emodin (2), and physcion (3) are reported for the investigation of hydrogen bonding, solvation and conformation effects in solution. Very small chemical shift of │Δδ│ < 0.3 ppm and temperature coefficients │Δδ/ΔΤ│ ≤ 2.1 ppb/K were observed in DMSO-d6, acetone-d6 and CDCl3 for the C(1)-OH and C(8)-OH groups which demonstrate that they are involved in a strong intramolecular hydrogen bond. On the contrary, large chemical shift differences of 5.23 ppm at 298 K and Δδ/ΔΤ values in the range of -5.3 to -19.1 ppb/K between DMSO-d6 and CDCl3 were observed for the C(3)-OH group which demonstrate that the solvation state of the hydroxyl proton is a key factor in determining the value of the chemical shift. DFT calculated 1H-NMR chemical shifts, using various functionals and basis sets, the conductor-like polarizable continuum model, and discrete solute-solvent hydrogen bond interactions, were found to be in very good agreement with the experimental 1H-NMR chemical shifts even with computationally less demanding level of theory. The 1H-NMR chemical shifts of the OH groups which participate in intramolecular hydrogen bond are dependent on the conformational state of substituents and, thus, can be used as molecular sensors in conformational analysis. When the X-ray structures of chrysophanol (1), emodin (2), and physcion (3) were used as input geometries, the DFT-calculated 1H-NMR chemical shifts were shown to strongly deviate from the experimental chemical shifts and no functional dependence could be obtained. Comparison of the most important intramolecular data of the DFT calculated and the X-ray structures demonstrate significant differences for distances involving hydrogen atoms, most notably the intramolecular hydrogen bond O-H and C-H bond lengths which deviate by 0.152 tο 0.132 Å and 0.133 to 0.100 Å, respectively, in the two structural methods. Further differences were observed in the conformation of -OH, -CH3, and -OCH3 substituents.
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Affiliation(s)
- Saima H. Mari
- H.E.J. Research Institute of chemistry, International Center for Chemical and Biological Sciences, University of Karachi, Karachi 7527, Pakistan; Saimahassanmari123@gmail (S.H.M.); (I.M.C.)
| | - Panayiotis C. Varras
- Section of Organic Chemistry & Biochemistry, Department of Chemistry, University of Ioannina, GR-45110 Ioannina, Greece; (P.C.V.); (M.G.S.)
| | - Atia-tul-Wahab
- Dr. Panjwani Center for Molecular Medicine and Drug Research, International Center for Chemical and Biological Sciences, University of Karachi, Karachi 7527, Pakistan
| | - Iqbal M. Choudhary
- H.E.J. Research Institute of chemistry, International Center for Chemical and Biological Sciences, University of Karachi, Karachi 7527, Pakistan; Saimahassanmari123@gmail (S.H.M.); (I.M.C.)
- Dr. Panjwani Center for Molecular Medicine and Drug Research, International Center for Chemical and Biological Sciences, University of Karachi, Karachi 7527, Pakistan
| | - Michael G. Siskos
- Section of Organic Chemistry & Biochemistry, Department of Chemistry, University of Ioannina, GR-45110 Ioannina, Greece; (P.C.V.); (M.G.S.)
| | - Ioannis P. Gerothanassis
- H.E.J. Research Institute of chemistry, International Center for Chemical and Biological Sciences, University of Karachi, Karachi 7527, Pakistan; Saimahassanmari123@gmail (S.H.M.); (I.M.C.)
- Section of Organic Chemistry & Biochemistry, Department of Chemistry, University of Ioannina, GR-45110 Ioannina, Greece; (P.C.V.); (M.G.S.)
- Dr. Panjwani Center for Molecular Medicine and Drug Research, International Center for Chemical and Biological Sciences, University of Karachi, Karachi 7527, Pakistan
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12
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An automated framework for NMR chemical shift calculations of small organic molecules. J Cheminform 2018; 10:52. [PMID: 30367288 PMCID: PMC6755567 DOI: 10.1186/s13321-018-0305-8] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2018] [Accepted: 10/09/2018] [Indexed: 12/04/2022] Open
Abstract
When using nuclear magnetic resonance (NMR) to assist in chemical identification in complex samples, researchers commonly rely on databases for chemical shift spectra. However, authentic standards are typically depended upon to build libraries experimentally. Considering complex biological samples, such as blood and soil, the entirety of NMR spectra required for all possible compounds would be infeasible to ascertain due to limitations of available standards and experimental processing time. As an alternative, we introduce the in silico Chemical Library Engine (ISiCLE) NMR chemical shift module to accurately and automatically calculate NMR chemical shifts of small organic molecules through use of quantum chemical calculations. ISiCLE performs density functional theory (DFT)-based calculations for predicting chemical properties—specifically NMR chemical shifts in this manuscript—via the open source, high-performance computational chemistry software, NWChem. ISiCLE calculates the NMR chemical shifts of sets of molecules using any available combination of DFT method, solvent, and NMR-active nuclei, using both user-selected reference compounds and/or linear regression methods. Calculated NMR chemical shifts are provided to the user for each molecule, along with comparisons with respect to a number of metrics commonly used in the literature. Here, we demonstrate ISiCLE using a set of 312 molecules, ranging in size up to 90 carbon atoms. For each, calculation of NMR chemical shifts have been performed with 8 different levels of DFT theory, and with solvation effects using the implicit solvent Conductor-like Screening Model. The DFT method dependence of the calculated chemical shifts have been systematically investigated through benchmarking and subsequently compared to experimental data available in the literature. Furthermore, ISiCLE has been applied to a set of 80 methylcyclohexane conformers, combined via Boltzmann weighting and compared to experimental values. We demonstrate that our protocol shows promise in the automation of chemical shift calculations and, ultimately, the expansion of chemical shift libraries.
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DFT-calculated structures based on 1H NMR chemical shifts in solution vs. structures solved by single-crystal X-ray and crystalline-sponge methods: Assessing specific sources of discrepancies. Tetrahedron 2018. [DOI: 10.1016/j.tet.2018.07.038] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Molchanov S, Gryff-Keller A. Solvation of Amides in DMSO and CDCl3: An Attempt at Quantitative DFT-Based Interpretation of 1H and 13C NMR Chemical Shifts. J Phys Chem A 2017; 121:9645-9653. [DOI: 10.1021/acs.jpca.7b10110] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Sergey Molchanov
- Faculty of Chemistry, Warsaw University of Technology, Noakowskiego 3, 00-664 Warsaw, Poland
| | - Adam Gryff-Keller
- Faculty of Chemistry, Warsaw University of Technology, Noakowskiego 3, 00-664 Warsaw, Poland
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15
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Iron MA. Evaluation of the Factors Impacting the Accuracy of 13C NMR Chemical Shift Predictions using Density Functional Theory-The Advantage of Long-Range Corrected Functionals. J Chem Theory Comput 2017; 13:5798-5819. [PMID: 29016125 DOI: 10.1021/acs.jctc.7b00772] [Citation(s) in RCA: 65] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The various factors influencing the accuracy of 13C NMR calculations using density functional theory (DFT), including the basis set, exchange-correlation (XC) functional, and isotropic shielding calculation method, are evaluated. A wide selection of XC functionals (over 70) were considered, and it was found that long-range corrected functionals offer a significant improvement over the other classes of functionals. Based on a thorough study, it is recommended that for calculating NMR chemical shifts (δ) one should use the CSGT method, the COSMO solvation model, and the LC-TPSSTPSS exchange-correlation functional in conjunction with the cc-pVTZ basis set. A selection of problems in natural product identification are considered in light of the newly recommended level of theory.
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Affiliation(s)
- Mark A Iron
- Computational Chemistry Unit, Department of Chemical Research Support, Weizmann Institute of Science , Rehovot 7610001, Israel
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Siskos MG, Choudhary MI, Tzakos AG, Gerothanassis IP. 1H ΝΜR chemical shift assignment, structure and conformational elucidation of hypericin with the use of DFT calculations – The challenge of accurate positions of labile hydrogens. Tetrahedron 2016. [DOI: 10.1016/j.tet.2016.10.072] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
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Lomas JS, Joubert L, Maurel F. Association of symmetrical alkane diols with pyridine: DFT/GIAO calculation of 1 H NMR chemical shifts. MAGNETIC RESONANCE IN CHEMISTRY : MRC 2016; 54:805-814. [PMID: 27247256 DOI: 10.1002/mrc.4457] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/18/2016] [Revised: 05/04/2016] [Accepted: 05/05/2016] [Indexed: 06/05/2023]
Abstract
Proton nuclear magnetic resonance (NMR) shifts of the free diol and of its 1 : 1 and 1 : 2 hydrogen-bonded complexes with pyridine have been computed for five symmetrical alkane diols on the basis of density functional theory, by applying the gauge-including atomic orbital method to geometry-optimized conformers. For certain conformers, intramolecular OH···OH interactions, evidenced by high NMR OH proton shifts, are further enhanced on going from the free diol to the corresponding 1 : 1 diol/pyridine complex. This is confirmed by atoms-in-molecules and non-covalent interaction plots. The computed OH and CH proton shifts for the diol and the two complexes correlate well with values obtained by analysing data from the NMR titration of the diols in benzene against pyridine. Shift values for the diols in neat pyridine are calculated by weighting the shifts of the various protons in the three forms (free diol, 1 : 1 and 1 : 2 diol/pyridine complexes) according to the experimentally determined association constants. The results are in good agreement with those observed, and after empirical scaling, the root mean square difference is 0.18 ppm. Copyright © 2016 John Wiley & Sons, Ltd.
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Affiliation(s)
- John S Lomas
- ITODYS (UMR 7086), Univ Paris Diderot, Sorbonne Paris Cité, Paris, France
| | - Laurent Joubert
- Normandy Univ., COBRA UMR 6014 & FR 3038, Université de Rouen, INSA Rouen, CNRS, France
| | - François Maurel
- ITODYS (UMR 7086), Univ Paris Diderot, Sorbonne Paris Cité, Paris, France
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Reddy DS, Kutateladze AG. Structure Revision of an Acorane Sesquiterpene Cordycepol A. Org Lett 2016; 18:4860-4863. [DOI: 10.1021/acs.orglett.6b02341] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- D. Sai Reddy
- Department of Chemistry and
Biochemistry, University of Denver, Denver, Colorado 80208, United States
| | - Andrei G. Kutateladze
- Department of Chemistry and
Biochemistry, University of Denver, Denver, Colorado 80208, United States
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Correlation between 1H NMR chemical shifts of hydroxyl protons in n-hexanol/cyclohexane and molecular association properties investigated using density functional theory. Chem Phys Lett 2016. [DOI: 10.1016/j.cplett.2015.12.025] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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