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Chukanov NV, Kazheva ON, Fischer RX, Aksenov SM. Refinement of the crystal structure of fresnoite, Ba 2TiSi 2O 8, from Löhley (Eifel district, Germany); Gladstone-Dale compatibility, electronic polarizability and vibrational spectroscopy of minerals and inorganic compounds with pentacoordinated Ti IV and a titanyl bond. Acta Crystallogr B Struct Sci Cryst Eng Mater 2023; 79:184-194. [PMID: 36927600 DOI: 10.1107/s2052520622012045] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/26/2022] [Accepted: 12/21/2022] [Indexed: 03/18/2023]
Abstract
Most known compounds with five-coordinated Ti4+ are natural and synthetic titanosilicates. The crystal structure of natural fresnoite, Ba2TiSi2O8 [tetragonal, space group P4bm, a = 8.510 (1) Å, c = 5.197 (1) Å, V = 376.4 (1) Å3, Z = 2], has been refined to R = 0.011 on the basis of 807 unique single-crystal reflections with I > 2σ(I). Titanium has fivefold coordination with one short (`titanyl') bond of 1.692 (5) Å. Bonds in the TiO5 polyhedron are discussed in comparison to analogous coordination polyhedra in other minerals and compounds. A review of all known compounds with Ti4+O5 polyhedra shows that most of them are titanosilicates in which titanium forms a short Ti-O bond (∼1.61 to ∼1.77 Å). Poor Gladstone-Dale compatibility between chemical composition, optical characteristics and density of these compounds is explained by the anomalous contribution of [5]Ti4+ to the optical properties as shown by calculations based on the relationship between electronic polarizabilities and refractive indices. An improved Gladstone-Dale coefficient of 0.29 is suggested for TiO2 with [5]Ti4+. A negative correlation between `titanyl' bond lengths and wavenumbers of the bands of Ti-O stretching vibrations (in the range of 890-830 cm-1) in infrared and Raman spectra is observed.
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Affiliation(s)
- Nikita V Chukanov
- Federal Research Center of Problems of Chemical Physics and Medicinal Chemistry, Chernogolovka, 142432, Russian Federation
| | - Olga N Kazheva
- Laboratory of Arctic Mineralogy and Material Sciences, Kola Science Centre, Russian Academy of Sciences, 14 Fersman Street, Apatity, 184209, Russian Federation
| | - Reinhard X Fischer
- Universität Bremen, FB 5 Geowissenschaften, Klagenfurter Str. 2, Bremen, D-28359, Germany
| | - Sergey M Aksenov
- Laboratory of Arctic Mineralogy and Material Sciences, Kola Science Centre, Russian Academy of Sciences, 14 Fersman Street, Apatity, 184209, Russian Federation
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2
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Sekine Y, Nakamura R, Akiyoshi R, Hayami S. Ä-Coupling Dielectric Functionality with Magnetic Properties in Coordination Metal Complexes. Chempluschem 2023:e202200463. [PMID: 36859753 DOI: 10.1002/cplu.202200463] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2022] [Revised: 02/23/2023] [Accepted: 02/27/2023] [Indexed: 03/03/2023]
Abstract
Significant research has been conducted on molecular ferroelectric materials, including pure organic and inorganic compounds; however, studies on ferroelectric materials based on coordination metal complexes are scarce. Ferroelectric materials based on coordination metal complexes have tunable structures and designs, with coexistence or synergy between the ferroelectric behavior and magnetic properties. Compared to inorganic compounds, few coordination metal complexes exhibit coupling between the magnetic and dielectric properties. Coordination metal complexes with strong coupling between the magnetic and dielectric properties exhibit dielectric permittivity variations under external magnetic fields. Therefore, they have attracted substantial interest for their potential use in magnetoelectric devices. In this review, we discuss recent advances in coordination metal complexes, that exhibit coupled magnetic functionalities and ferroelectricity or dielectric properties, including single-molecule magnets, electron delocalization systems, and external stimuli responsive compounds.
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Affiliation(s)
- Yoshihiro Sekine
- Department of Chemistry, Graduate School of Science and Technology, Kumamoto University, 2-39-1 Kurokami, Chuo-ku, Kumamoto, 860-8555, Japan
- Priority Organization for Innovation and Excellence, Kumamoto University, 2-39-1 Kurokami, Chuo-ku, Kumamoto, 860-8555, Japan
| | - Rikuto Nakamura
- Department of Chemistry, Graduate School of Science and Technology, Kumamoto University, 2-39-1 Kurokami, Chuo-ku, Kumamoto, 860-8555, Japan
| | - Ryohei Akiyoshi
- Department of Chemistry, School of Science, Kwansei Gakuin University, 1 Gakuen Uegahara, Sanda, Hyogo, 669-1330, Japan
| | - Shinya Hayami
- Department of Chemistry, Graduate School of Science and Technology, Kumamoto University, 2-39-1 Kurokami, Chuo-ku, Kumamoto, 860-8555, Japan
- Institute of Industrial Nanomaterials (IINa), Kumamoto University, 2-39-1 Kurokami, Chuo-ku, Kumamoto, 860-8555, Japan
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Rahman S, Wineman-Fisher V, Nagy PR, Al-Hamdani Y, Tkatchenko A, Varma S. Methyl-Induced Polarization Destabilizes the Noncovalent Interactions of N-Methylated Lysines. Chemistry 2021; 27:11005-11014. [PMID: 33999467 PMCID: PMC9830558 DOI: 10.1002/chem.202100644] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2021] [Indexed: 01/12/2023]
Abstract
Lysine methylation can modify noncovalent interactions by altering lysine's hydrophobicity as well as its electronic structure. Although the ramifications of the former are documented, the effects of the latter remain largely unknown. Understanding the electronic structure is important for determining how biological methylation modulates protein-protein binding, and the impact of artificial methylation experiments in which methylated lysines are used as spectroscopic probes and protein crystallization facilitators. The benchmarked first-principles calculations undertaken here reveal that methyl-induced polarization weakens the electrostatic attraction of amines with protein functional groups - salt bridges, hydrogen bonds and cation-π interactions weaken by as much as 10.3, 7.9 and 3.5 kT, respectively. Multipole analysis shows that weakened electrostatics is due to the altered inductive effects, which overcome increased attraction from methyl-enhanced polarizability and dispersion. Due to their fundamental nature, these effects are expected to be present in many cases. A survey of methylated lysines in protein structures reveals several cases in which methyl-induced polarization is the primary driver of altered noncovalent interactions; in these cases, destabilizations are found to be in the 0.6-4.7 kT range. The clearest case of where methyl-induced polarization plays a dominant role in regulating biological function is that of the PHD1-PHD2 domain, which recognizes lysine-methylated states on histones. These results broaden our understanding of how methylation modulates noncovalent interactions.
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Affiliation(s)
- Sanim Rahman
- Department of Cell Biology, Microbiology and Molecular Biology, University of South Florida, 4202 E. Fowler Ave., Tampa, FL-33620, USA,Current Address: Department of Biophysics and Biophysical Chemistry, Johns Hopkins University School of Medicine, Baltimore, MD-21205, USA
| | - Vered Wineman-Fisher
- Department of Cell Biology, Microbiology and Molecular Biology, University of South Florida, 4202 E. Fowler Ave., Tampa, FL-33620, USA
| | - Péter R. Nagy
- Department of Physical Chemistry and Materials Science, Budapest University of Technology and Economics, H-1521 Budapest, P.O.Box 91, Hungary
| | - Yasmine Al-Hamdani
- Department of Physics and Materials Science, University of Luxembourg, L-1511 Luxembourg City, Luxembourg
| | - Alexandre Tkatchenko
- Department of Physics and Materials Science, University of Luxembourg, L-1511 Luxembourg City, Luxembourg
| | - Sameer Varma
- Department of Cell Biology, Microbiology and Molecular Biology, University of South Florida, 4202 E. Fowler Ave., Tampa, FL-33620, USA,Department of Physics, University of South Florida, 4202 E. Fowler Ave., Tampa, FL-33620, USA
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Gao Y, Zhu Y, Li T, Chen Z, Jiang Q, Zhao Z, Liang X, Hu C. Unraveling the High-Activity Origin of Single-Atom Iron Catalysts for Organic Pollutant Oxidation via Peroxymonosulfate Activation. Environ Sci Technol 2021; 55:8318-8328. [PMID: 34028264 DOI: 10.1021/acs.est.1c01131] [Citation(s) in RCA: 66] [Impact Index Per Article: 22.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Single-atom catalysts (SACs) have emerged as efficient materials in the elimination of aqueous organic contaminants; however, the origin of high activity of SACs still remains elusive. Herein, we identify an 8.1-fold catalytic specific activity (reaction rate constant normalized to catalyst's specific surface area and dosage) enhancement that can be fulfilled with a single-atom iron catalyst (SA-Fe-NC) prepared via a cascade anchoring method compared to the iron nanoparticle-loaded catalyst, resulting in one of the most active currently known catalysts in peroxymonosulfate (PMS) conversion for organic pollutant oxidation. Experimental data and theoretical results unraveled that the high-activity origin of the SA-Fe-NC stems from the Fe-pyridinic N4 moiety, which dramatically increases active sites by not only creating the electron-rich Fe single atom as the catalytic site but also producing electron-poor carbon atoms neighboring pyridinic N as binding sites for PMS activation including synchronous PMS reduction and oxidation together with dissolved oxygen reduction. Moreover, the SA-Fe-NC exhibits excellent stability and applicability to realistic industrial wastewater remediation. This work offers a novel yet reasonable interpretation for why a small amount of iron in the SA-Fe-NC can deliver extremely superior specific activity in PMS activation and develops a promising catalytic oxidation system toward actual environmental cleanup.
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Affiliation(s)
- Yaowen Gao
- Institute of Environmental Research at Greater Bay, Key Laboratory for Water Quality and Conservation of the Pearl River Delta, Ministry of Education, Guangzhou University, Guangzhou 510006, China
| | - Yue Zhu
- Institute of Environmental Research at Greater Bay, Key Laboratory for Water Quality and Conservation of the Pearl River Delta, Ministry of Education, Guangzhou University, Guangzhou 510006, China
| | - Tong Li
- Institute of Environmental Research at Greater Bay, Key Laboratory for Water Quality and Conservation of the Pearl River Delta, Ministry of Education, Guangzhou University, Guangzhou 510006, China
| | - Zhenhuan Chen
- Institute of Environmental Research at Greater Bay, Key Laboratory for Water Quality and Conservation of the Pearl River Delta, Ministry of Education, Guangzhou University, Guangzhou 510006, China
| | - Qike Jiang
- Dalian National Laboratory for Clean Energy, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, China
| | - Zhiyu Zhao
- Institute of Environmental Research at Greater Bay, Key Laboratory for Water Quality and Conservation of the Pearl River Delta, Ministry of Education, Guangzhou University, Guangzhou 510006, China
| | - Xiaoying Liang
- Institute of Environmental Research at Greater Bay, Key Laboratory for Water Quality and Conservation of the Pearl River Delta, Ministry of Education, Guangzhou University, Guangzhou 510006, China
| | - Chun Hu
- Institute of Environmental Research at Greater Bay, Key Laboratory for Water Quality and Conservation of the Pearl River Delta, Ministry of Education, Guangzhou University, Guangzhou 510006, China
- Key Laboratory of Drinking Water Science and Technology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China
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Abstract
In this perspective, we discuss where and how accounting for electronic many-body polarization affects the accuracy of classical molecular dynamics simulations of biomolecules. While the effects of electronic polarization are highly pronounced for molecules with an opposite total charge, they are also non-negligible for interactions with overall neutral molecules. For instance, neglecting these effects in important biomolecules like amino acids and phospholipids affects the structure of proteins and membranes having a large impact on interpreting experimental data as well as building coarse grained models. With the combined advances in theory, algorithms and computational power it is currently realistic to perform simulations with explicit polarizable dipoles on systems with relevant sizes and complexity. Alternatively, the effects of electronic polarization can also be included at zero additional computational cost compared to standard fixed-charge force fields using the electronic continuum correction, as was recently demonstrated for several classes of biomolecules.
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Affiliation(s)
- Josef Melcr
- Groningen Biomolecular Sciences and Biotechnology Institute and the Zernike Institute for Advanced Materials, University of Groningen, Groningen, Netherlands
| | - Jean-Philip Piquemal
- Laboratoire de Chimie Théorique, Sorbonne Université, UMR7616 CNRS, Paris, France
- Institut Universitaire de France, Paris, France
- Department of Biomedical Engineering, The University of Texas at Austin, Austin, TX, United States
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Nikitin A, Del Frate G. Development of Nonbonded Models for Metal Cations Using the Electronic Continuum Correction. J Comput Chem 2019; 40:2464-2472. [PMID: 31301182 DOI: 10.1002/jcc.26021] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2019] [Revised: 05/14/2019] [Accepted: 06/06/2019] [Indexed: 12/24/2022]
Abstract
The parametrization of classical nonbonded models of metal ions has been widely addressed in the recent years. Despite the continuous development of novel and more physically inspired functional forms, the 12-6 Lennard-Jones plus Coulomb potential is still the most adopted force field in molecular dynamics (MD) codes, owing to its simple form and easy implementation. However, due to the integer formal charge, unpolarizable force fields of ions may suffer from overestimated interatomic electrostatic interactions, leading to nonphysical clustering or repulsion between such full charges. The electronic continuum correction (ECC) can fix this problem through a simple inclusion of solvent polarization effects via ionic charge rescaling. In this work, the development of novel nonbonded models for mono, divalent, and highly charged metal ions is presented. For each metal species, the ionic charge has been scaled, according to the ECC. Lennard-Jones parameters have been optimized using experimental structural and thermodynamic properties as target quantities. Performances of the proposed models are discussed and compared with the literature data, while transferability attitudes among different and well-known water models are evaluated. © 2019 Wiley Periodicals, Inc.
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Affiliation(s)
- Alexei Nikitin
- Engelhardt Institute of Molecular Biology, Russian Academy of Sciences, Moscow, 119991, Russian Federation.,Scuola Normale Superiore, Piazza dei Cavalieri 7, I-56126, Pisa, Italy
| | - Gianluca Del Frate
- IMT School for Advanced Studies Lucca, Piazza S. Francesco 19, I-55100, Lucca, Italy
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Lemkul JA, MacKerell AD. Polarizable force field for RNA based on the classical drude oscillator. J Comput Chem 2018; 39:2624-2646. [PMID: 30515902 PMCID: PMC6284239 DOI: 10.1002/jcc.25709] [Citation(s) in RCA: 56] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2018] [Revised: 08/01/2018] [Accepted: 09/23/2018] [Indexed: 12/15/2022]
Abstract
RNA molecules are highly dynamic and capable of adopting a wide range of complex, folded structures. The factors driving the folding and dynamics of these structures are dependent on a balance of base pairing, hydration, base stacking, ion interactions, and the conformational sampling of the 2'-hydroxyl group in the ribose sugar. The representation of these features is a challenge for empirical force fields used in molecular dynamics simulations. Toward meeting this challenge, the inclusion of explicit electronic polarization is important in accurately modeling RNA structure. In this work, we present a polarizable force field for RNA based on the classical Drude oscillator model, which represents electronic degrees of freedom via negatively charged particles attached to their parent atoms by harmonic springs. Beginning with parametrization against quantum mechanical base stacking interaction energy and conformational energy data, we have extended the Drude-2017 nucleic acid force field to include RNA. The conformational sampling of a range of RNA sequences were used to validate the force field, including canonical A-form RNA duplexes, stem-loops, and complex tertiary folds that bind multiple Mg2+ ions. Overall, the Drude-2017 RNA force field reproduces important properties of these structures, including the conformational sampling of the 2'-hydroxyl and key interactions with Mg2+ ions. © 2018 Wiley Periodicals, Inc.
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Affiliation(s)
| | - Alexander D. MacKerell
- Department of Pharmaceutical Sciences, School of Pharmacy, University of Maryland, Baltimore, MD 21201
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8
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Abstract
We present an extension of the CHARMM Drude polarizable force field to enable modeling of polysaccharides containing pyranose and furanose monosaccharides. The new force field parameters encompass 1↔2, 1→3, 1→4, and 1→6 pyranose-furanose linkages, 2→1 and 2→6 furanose-furanose linkages, 2→2, 2→3, and 2→4 furanose-pyranose, and 1↔1, 1→2, 1→3, 1→4, and 1→6 pyranose-pyranose linkages. For the glycosidic linkages, both simple model compounds and the full disaccharides with methylation at the reducing end were used for parameter optimization. The model compounds were chosen to be monomers or glycosidic-linked dimers of tetrahydropyran (THP) and tetrahydrofuran (THF). Target data for optimization included one- and two-dimensional potential energy scans of ω and the Φ/Ψ glycosidic dihedral angles in the model compounds and full disaccharides computed by quantum mechanical (QM) RIMP2/cc-pVQZ single point energies on MP2/6-31G(d) optimized structures. Also included in the target data are extensive sets of QM gas phase monohydrate water-saccharide interactions, dipole moments, and molecular polarizabilities for both model compounds and full disaccharides. The resulting polarizable model is shown to be in good agreement with a range of QM data, offering a significant improvement over the additive CHARMM36 carbohydrate force field, as well as experimental data including crystal structures and conformational properties of disaccharides and a trisaccharide in aqueous solution.
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Affiliation(s)
- Asaminew H. Aytenfisu
- Department of Pharmaceutical Sciences, School of Pharmacy, University of Maryland, Baltimore, 20 Penn Street, Baltimore, MD 21201, USA
| | - Mingjun Yang
- Department of Pharmaceutical Sciences, School of Pharmacy, University of Maryland, Baltimore, 20 Penn Street, Baltimore, MD 21201, USA
- XtalPi Inc., Shennan Road 6025, Futian District, Shenzhen, China
| | - Alexander D. MacKerell
- Department of Pharmaceutical Sciences, School of Pharmacy, University of Maryland, Baltimore, 20 Penn Street, Baltimore, MD 21201, USA
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Cobo J, Vicentes DE, Rodríguez R, Marchal A, Glidewell C. A concise synthesis of a highly substituted 6-(1H-benzimidazol-1-yl)-5-nitrosopyrimidin-2-amine: synthetic sequence and the molecular and supramolecular structures of one product and two intermediates. Acta Crystallogr C Struct Chem 2018; 74:696-702. [PMID: 29870005 DOI: 10.1107/s2053229618007015] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/23/2018] [Accepted: 05/08/2018] [Indexed: 11/10/2022]
Abstract
A concise and efficient synthesis of 6-benzimidazolyl-5-nitrosopyrimidines has been developed using Schiff base-type intermediates derived from N4-(2-aminophenyl)-6-methoxy-5-nitrosopyrimidine-2,4-diamine. 6-Methoxy-N4-{2-[(4-methylbenzylidene)amino]phenyl}-5-nitrosopyrimidine-2,4-diamine, (I), and N4-{2-[(ethoxymethylidene)amino]phenyl}-6-methoxy-5-nitrosopyrimidine-2,4-diamine, (III), both crystallize from dimethyl sulfoxide solution as the 1:1 solvates C19H18N6O2·C2H6OS, (Ia), and C14H16N6O3·C2H6OS, (IIIa), respectively. The interatomic distances in these intermediates indicate significant electronic polarization within the substituted pyrimidine system. In each of (Ia) and (IIIa), intermolecular N-H...O hydrogen bonds generate centrosymmetric four-molecule aggregates. Oxidative ring closure of intermediate (I), effected using ammonium hexanitratocerate(IV), produced 4-methoxy-6-[2-(4-methylphenyl-1H-benzimidazol-1-yl]-5-nitrosopyrimidin-2-amine, C19H16N6O2, (II) [Cobo et al. (2018). Private communication (CCDC 1830889). CCDC, Cambridge, England], where the extent of electronic polarization is much less than in (Ia) and (IIIa). A combination of N-H...N and C-H...O hydrogen bonds links the molecules of (II) into complex sheets.
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Affiliation(s)
- Justo Cobo
- Departamento de Química Inorgánica y Orgánica, Universidad de Jaén, 23071 Jaén, Spain
| | - Daniel E Vicentes
- Departamento de Química Inorgánica y Orgánica, Universidad de Jaén, 23071 Jaén, Spain
| | - Ricaurte Rodríguez
- Departamento de Química, Universidad Nacional de Colombia, Bogotá, Colombia
| | - Antonio Marchal
- Departamento de Química Inorgánica y Orgánica, Universidad de Jaén, 23071 Jaén, Spain
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Aleksandrov A, Lin FY, Roux B, MacKerell AD. Combining the polarizable Drude force field with a continuum electrostatic Poisson-Boltzmann implicit solvation model. J Comput Chem 2018; 39:1707-1719. [PMID: 29737546 DOI: 10.1002/jcc.25345] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2017] [Revised: 02/26/2018] [Accepted: 04/08/2018] [Indexed: 12/13/2022]
Abstract
In this work, we have combined the polarizable force field based on the classical Drude oscillator with a continuum Poisson-Boltzmann/solvent-accessible surface area (PB/SASA) model. In practice, the positions of the Drude particles experiencing the solvent reaction field arising from the fixed charges and induced polarization of the solute must be optimized in a self-consistent manner. Here, we parameterized the model to reproduce experimental solvation free energies of a set of small molecules. The model reproduces well-experimental solvation free energies of 70 molecules, yielding a root mean square difference of 0.8 kcal/mol versus 2.5 kcal/mol for the CHARMM36 additive force field. The polarization work associated with the solute transfer from the gas-phase to the polar solvent, a term neglected in the framework of additive force fields, was found to make a large contribution to the total solvation free energy, comparable to the polar solute-solvent solvation contribution. The Drude PB/SASA also reproduces well the electronic polarization from the explicit solvent simulations of a small protein, BPTI. Model validation was based on comparisons with the experimental relative binding free energies of 371 single alanine mutations. With the Drude PB/SASA model the root mean square deviation between the predicted and experimental relative binding free energies is 3.35 kcal/mol, lower than 5.11 kcal/mol computed with the CHARMM36 additive force field. Overall, the results indicate that the main limitation of the Drude PB/SASA model is the inability of the SASA term to accurately capture non-polar solvation effects. © 2018 Wiley Periodicals, Inc.
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Affiliation(s)
- Alexey Aleksandrov
- Laboratoire d'Optique et Biosciences, CNRS, INSERM, Ecole Polytechnique, Palaiseau F-91128, France
| | - Fang-Yu Lin
- Department of Pharmaceutical Sciences, School of Pharmacy, University of Maryland, 20 Penn Street, Baltimore, Maryland 21201
| | - Benoît Roux
- Department of Biochemistry and Molecular Biology, Gordon Center for Integrative Science, 929 E57th Street, University of Chicago, Chicago, Illinois 60637
| | - Alexander D MacKerell
- Department of Pharmaceutical Sciences, School of Pharmacy, University of Maryland, 20 Penn Street, Baltimore, Maryland 21201
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11
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Abstract
The current status of classical force fields for proteins is reviewed. These include additive force fields as well as the latest developments in the Drude and AMOEBA polarizable force fields. Parametrization strategies developed specifically for the Drude force field are described and compared with the additive CHARMM36 force field. Results from molecular simulations of proteins and small peptides are summarized to illustrate the performance of the Drude and AMOEBA force fields.
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Affiliation(s)
- Pedro E M Lopes
- Department of Pharmaceutical Sciences, School of Pharmacy, University of Maryland, 20 Penn Street HSFII, Baltimore, MD, 21201, USA
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12
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Kim J, Fujiwara A, Sawada T, Kim Y, Sugimoto K, Kato K, Tanaka H, Ishikado M, Shamoto SI, Takata M. Evidence of electronic polarization of the As ion in the superconducting phase of F-doped LaFeAsO. IUCrJ 2014; 1:155-159. [PMID: 25075333 PMCID: PMC4086433 DOI: 10.1107/s2052252514005636] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/16/2014] [Accepted: 03/12/2014] [Indexed: 06/03/2023]
Abstract
Understanding the nature of superconductivity in iron-based compounds is essential in the development of new strategies to increase T c. Using a charge density analysis based on synchrotron radiation X-ray powder diffraction data, we found that the charge carriers only accumulated in the iron layer of the superconducting phase of LaFeAsO1 - x F x at low temperatures. Analysis of the electrostatic potential distribution revealed the concerted enhancement of the electronic polarization of the As ions and the carrier redistribution. This suggests that the enhanced electronic polarization of the As ion plays an important role in inducing high T c superconductivity, and that the polaron concept, which has been previously regarded as an untenable mechanism, should be reconsidered for the description of the iron-arsenide superconducting phase.
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Affiliation(s)
- Jungeun Kim
- Japan Synchrotron Radiation Research Institute, Kouto, Sayo-cho, Hyogo 679-5198, Japan
- RIKEN SPring-8 Center, Kouto, Sayo-cho, Hyogo 679-5148, Japan
| | - Akihiko Fujiwara
- Japan Synchrotron Radiation Research Institute, Kouto, Sayo-cho, Hyogo 679-5198, Japan
| | - Tomohiro Sawada
- Department of Advanced Materials Science, The University of Tokyo, Kashiwa, Chiba 277-8561, Japan
| | - Younghun Kim
- Department of Advanced Materials Science, The University of Tokyo, Kashiwa, Chiba 277-8561, Japan
| | - Kunihisa Sugimoto
- Japan Synchrotron Radiation Research Institute, Kouto, Sayo-cho, Hyogo 679-5198, Japan
- RIKEN SPring-8 Center, Kouto, Sayo-cho, Hyogo 679-5148, Japan
| | - Kenichi Kato
- Japan Synchrotron Radiation Research Institute, Kouto, Sayo-cho, Hyogo 679-5198, Japan
- RIKEN SPring-8 Center, Kouto, Sayo-cho, Hyogo 679-5148, Japan
| | - Hiroshi Tanaka
- Department of Materials Science, Shimane University, 1060 Nishi-kawatsu-cho, Matsue, Shimane 690-8504, Japan
| | - Motoyuki Ishikado
- Comprehensive Research Organization for Science and Society (CROSS), Ibaraki 319-1106, Japan
- Japan Atomic Energy Agency, Ibaraki 319-1195, Japan
| | | | - Masaki Takata
- Japan Synchrotron Radiation Research Institute, Kouto, Sayo-cho, Hyogo 679-5198, Japan
- RIKEN SPring-8 Center, Kouto, Sayo-cho, Hyogo 679-5148, Japan
- Department of Advanced Materials Science, The University of Tokyo, Kashiwa, Chiba 277-8561, Japan
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