1
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Bakó I, Pusztai L, Pothoczki S. Outstanding Properties of the Hydration Shell around β-d-Glucose: A Computational Study. ACS OMEGA 2024; 9:20331-20337. [PMID: 38737074 PMCID: PMC11080014 DOI: 10.1021/acsomega.4c00798] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/24/2024] [Revised: 04/10/2024] [Accepted: 04/12/2024] [Indexed: 05/14/2024]
Abstract
Ab initio molecular dynamics (AIMD) simulations have been performed on aqueous solutions of four simple sugars, α-d-glucose, β-d-glucose, α-d-mannose, and α-d-galactose. Hydrogen-bonding (HB) properties, such as the number of donor- and acceptor-type HB-s, and the lengths and strengths of hydrogen bonds between sugar and water molecules, have been determined. Related electronic properties, such as the dipole moments of water molecules and partial charges of the sugar O atoms, have also been calculated. The hydrophilic and hydrophobic shells were characterized by means of spatial distribution functions. β-d-Glucose was found to form the highest number of hydrophilic and the smallest number of hydrophobic connections to neighboring water molecules. The average sugar-water H-bond length was the shortest for β-d-glucose, which suggests that these are the strongest such H-bonds. Furthermore, β-d-glucose appears to stand out in terms of the symmetry properties of both its hydrophilic and hydrophobic hydration shells. In summary, in all aspects considered here, there seems to be a correlation between the distinct characteristics of β-d-glucose reported here and its outstanding solubility in water. Admittedly, our findings represent only some of the important factors that influence the solubility.
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Affiliation(s)
- Imre Bakó
- HUN-REN
Research Centre for Natural Sciences, Magyar tudósok körútja 2., H-1117 Budapest, Hungary
| | - László Pusztai
- HUN-REN
Wigner Research Centre for Physics, Konkoly-Thege M. út 29-33., H-1121 Budapest, Hungary
- International
Research Organization for Advanced Science and Technology (IROAST), Kumamoto University, 2-39-1 Kurokami, Chuo-ku, Kumamoto 860-8555, Japan
| | - Szilvia Pothoczki
- HUN-REN
Wigner Research Centre for Physics, Konkoly-Thege M. út 29-33., H-1121 Budapest, Hungary
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2
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Nishida Y, Aono R, Dohi H, Ding W, Uzawa H. 1H-NMR Karplus Analysis of Molecular Conformations of Glycerol under Different Solvent Conditions: A Consistent Rotational Isomerism in the Backbone Governed by Glycerol/Water Interactions. Int J Mol Sci 2023; 24:ijms24032766. [PMID: 36769086 PMCID: PMC9916874 DOI: 10.3390/ijms24032766] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2023] [Revised: 01/23/2023] [Accepted: 01/25/2023] [Indexed: 02/04/2023] Open
Abstract
Glycerol is a symmetrical, small biomolecule with high flexibility in molecular conformations. Using a 1H-NMR spectroscopic Karplus analysis in our way, we analyzed a rotational isomerism in the glycero backbone which generates three kinds of staggered conformers, namely gt (gauche-trans), gg (gauche-gauche), and tg (trans-gauche), at each of sn-1,2 and sn-2,3 positions. The Karplus analysis has disclosed that the three rotamers are consistently equilibrated in water keeping the relation of 'gt:gg:tg = 50:30:20 (%)' at a wide range of concentrations (5 mM~540 mM). The observed relation means that glycerol in water favors those symmetric conformers placing 1,2,3-triol groups in a gauche/gauche geometry. We have found also that the rotational isomerism is remarkably changed when the solvent is replaced with DMSO-d6 or dimethylformamide (DMF-d7). In these solvents, glycerol gives a relation of 'gt:gg:tg = 40:30:30 (%)', which means that a remarkable shift occurs in the equilibrium between gt and tg conformers. By this shift, glycerol turns to also take non-symmetric conformers orienting one of the two vicinal diols in an antiperiplanar geometry.
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Affiliation(s)
- Yoshihiro Nishida
- Molecular Chirality Research Center, Department of Applied Biological Chemistry, Institute of Environmental Horticulture, Chiba University, Matsudo 271-8510, Japan
- Correspondence:
| | - Reina Aono
- Molecular Chirality Research Center, Department of Applied Biological Chemistry, Institute of Environmental Horticulture, Chiba University, Matsudo 271-8510, Japan
| | - Hirofumi Dohi
- Molecular Chirality Research Center, Department of Applied Biological Chemistry, Institute of Environmental Horticulture, Chiba University, Matsudo 271-8510, Japan
| | - Wuxiao Ding
- Nanomaterials Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1 Higashi, Tsukuba 305-8565, Japan
| | - Hirotaka Uzawa
- Nanomaterials Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1 Higashi, Tsukuba 305-8565, Japan
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3
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Qiu X, Garden AL, Fairbanks AJ. Protecting group free glycosylation: one-pot stereocontrolled access to 1,2- trans glycosides and (1→6)-linked disaccharides of 2-acetamido sugars. Chem Sci 2022; 13:4122-4130. [PMID: 35440979 PMCID: PMC8985506 DOI: 10.1039/d2sc00222a] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2022] [Accepted: 03/12/2022] [Indexed: 11/21/2022] Open
Abstract
Unprotected 2-acetamido sugars may be directly converted into their oxazolines using 2-chloro-1,3-dimethylimidazolinium chloride (DMC), and a suitable base, in aqueous solution. Freeze drying and acid catalysed reaction with an alcohol as solvent produces the corresponding 1,2-trans-glycosides in good yield. Alternatively, dissolution in an aprotic solvent system and acidic activation in the presence of an excess of an unprotected glycoside as a glycosyl acceptor, results in the stereoselective formation of the corresponding 1,2-trans linked disaccharides without any protecting group manipulations. Reactions using aryl glycosides as acceptors are completely regioselective, producing only the (1→6)-linked disaccharides.
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Affiliation(s)
- Xin Qiu
- School of Physical and Chemical Sciences, University of Canterbury Private Bag 4800 Christchurch 8140 New Zealand
| | - Anna L Garden
- Department of Chemistry, University of Otago Dunedin 9054 New Zealand.,The MacDiarmid Institute for Advanced Materials and Nanotechnology, Victoria University of Wellington Wellington 6140 New Zealand
| | - Antony J Fairbanks
- School of Physical and Chemical Sciences, University of Canterbury Private Bag 4800 Christchurch 8140 New Zealand .,Biomolecular Interaction Centre, University of Canterbury Private Bag 4800 Christchurch 8140 New Zealand
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4
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Ruda A, Widmalm G, Wohlert J. O-Methylation in Carbohydrates: An NMR and MD Simulation Study with Application to Methylcellulose. J Phys Chem B 2021; 125:11967-11979. [PMID: 34704449 PMCID: PMC8573740 DOI: 10.1021/acs.jpcb.1c07293] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
![]()
Methylated carbohydrates
are important from both biological and
technical perspectives. Specifically, methylcellulose is an interesting
cellulose derivative that has applications in foods, materials, cosmetics,
and many other fields. While the molecular dynamics simulation technique
has the potential for both advancing the fundamental understanding
of this polymer and aiding in the development of specific applications,
a general drawback is the lack of experimentally validated interaction
potentials for the methylated moieties. In the present study, simulations
using the GROMOS 56 carbohydrate force field are compared to NMR spin–spin
coupling constants related to the conformation of the exocyclic torsion
angle ω in d-glucopyranose and derivatives containing
a 6-O-methyl substituent and a 13C-isotopologue thereof.
A 3JCC Karplus-type relationship
is proposed for the C5–C6–O6–CMe torsion
angle. Moreover, solvation free energies are compared to experimental
data for small model compounds. Alkylation in the form of 6-O-methylation
affects exocyclic torsion only marginally. Computed solvation free
energies between nonmethylated and methylated molecules were internally
consistent, which validates the application of these interaction potentials
for more specialized purposes.
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Affiliation(s)
- Alessandro Ruda
- Department of Organic Chemistry, Arrhenius Laboratory, Stockholm University, SE-106 91 Stockholm, Sweden
| | - Göran Widmalm
- Department of Organic Chemistry, Arrhenius Laboratory, Stockholm University, SE-106 91 Stockholm, Sweden
| | - Jakob Wohlert
- Department of Fiber and Polymer Technology, School of Chemistry, Biotechnology and Health, KTH Royal Institute of Technology, SE-100 44 Stockholm, Sweden.,Wallenberg Wood Science Center, KTH Royal Institute of Technology, SE-100 44 Stockholm, Sweden
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5
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Feng X, Li F, Ding M, Zhang R, Shi T, Jiang W. Molecular dynamic simulation: Structural insights of multi-stranded curdlan in aqueous solution. Carbohydr Polym 2021; 261:117844. [PMID: 33766340 DOI: 10.1016/j.carbpol.2021.117844] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2020] [Revised: 02/01/2021] [Accepted: 02/18/2021] [Indexed: 12/28/2022]
Abstract
In this work, by using molecular dynamic simulation we provide microscale structure information which helps to reveal the molecular mechanisms concerning the multi-chain conformational behavior of short curdlan. Through simulations starting with different conformations of curldan dodecasaccharides, it is found that the right-handed triple helix is thermodynamically the most stable conformation in aqueous solutions, which is well maintained and stabilized by an inter-strand hydrogen bonding network of the C2 hydroxyls. Unlike any predicted forms, the inter-strand hydrogen bonds exhibit a left-handed double helix pattern with preferred global orientations. Temperature REMD results suggest that the formation of triple helix is temperature sensitive, but the already formed triple helix is not. Investigation of curdlan with numbers of repeating units from 3 to 12 captures a critical value of 6, which in a way elucidates the relationship between the formation of triple helix and the chain length.
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Affiliation(s)
- Xuan Feng
- State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, PR China; School of Applied Chemistry and Engineering, University of Science and Technology of China, Hefei 230026, PR China
| | - Fan Li
- State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, PR China
| | - Mingming Ding
- State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, PR China
| | - Ran Zhang
- State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, PR China.
| | - Tongfei Shi
- State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, PR China; School of Applied Chemistry and Engineering, University of Science and Technology of China, Hefei 230026, PR China.
| | - Wei Jiang
- State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, PR China; School of Applied Chemistry and Engineering, University of Science and Technology of China, Hefei 230026, PR China
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6
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Merino P, Delso I, Pereira S, Orta S, Pedrón M, Tejero T. Computational evidence of glycosyl cations. Org Biomol Chem 2021; 19:2350-2365. [PMID: 33481977 DOI: 10.1039/d0ob02373f] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Glycosyl cations are key intermediates in the glycosylation reactions taking place through a SN1-type mechanism. To obtain a reliable description of the glycosylation reaction mechanism a combination of computational studies and experimental data such as kinetic isotopic effects is needed. Computational studies have elucidated SN2-type glycosylation reaction mechanisms, but elucidation of mechanisms in which ion pairs can be formed presents some difficulties because of the recombination of the ions. Recent topological and dynamic studies open the door to the ultimate confirmation of the presence of glycosyl cations in the form of intimate ion pairs during certain glycosylation reactions. This review covers the state-of-the-art tools and applications of computational chemistry mainly developed during the last ten years to understand glycosylation reactions in which an oxocarbenium ion could be involved.
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Affiliation(s)
- Pedro Merino
- Unidad de Glicobiología. Instituto de Biocomputación y Física de Sistemas Complejos (BIFI), Universidad de Zaragoza, 50009 Zaragoza, Spain.
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7
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Abraham RJ, Cooper MA, Reid M. The use of MM/QM calculations of 13C chemical shifts in the conformational analysis of some monosaccharides and sucrose. NEW J CHEM 2021. [DOI: 10.1039/d0nj04227g] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The 13C NMR chemical shifts of some common pyranose monosaccharides in D2O solution were predicted using a combined molecular mechanics (Pcmod 9.1/MMFF94) and ab initio (GIAO (B3LYP/DFT, 6-31G(d))) model.
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Affiliation(s)
| | - M. Ashley Cooper
- The Chemistry Department
- University of Liverpool
- Liverpool L69 7ZD
- UK
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8
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Feng X, Li F, Ding M, Zhang R, Shi T. Molecular dynamic simulation: Conformational properties of single-stranded curdlan in aqueous solution. Carbohydr Polym 2020; 250:116906. [PMID: 33049882 DOI: 10.1016/j.carbpol.2020.116906] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2020] [Revised: 08/04/2020] [Accepted: 08/04/2020] [Indexed: 01/08/2023]
Abstract
Recently, molecular dynamic simulation technique has been proved to be a powerful tool providing structural insights for better understanding the functionality of carbohydrates. Here, by using molecular dynamic simulation method we investigated the detailed conformational properties of the single-stranded curdlan with 12 glucose units. The results showed that the right-handed 6/1 helix structure was thermodynamically the most stable conformation in solution. The formation of the helix conformation was determined by many factors such as the glycosidic linkage, explicit water solvation and hydrogen bonds. When temperature was increased, the representative helix conformation was found becoming unstable giving rise to metastable conformations because when water mobility was accelerated with temperature, the hydrogen bonding strength between the curdlan chain and water went down, breaking the continuity of the hydrogen bonding network of water and hydroxyl groups. When the number of repeating glucose units varied from 6 to 24, the major helix conformation remained, but the conformational properties of longer chains were more apparently aff ;ected by chain flexibility.
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Affiliation(s)
- Xuan Feng
- State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, PR China; School of Applied Chemistry and Engineering, University of Science and Technology of China, Hefei 230026, PR China
| | - Fan Li
- State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, PR China.
| | - Mingming Ding
- State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, PR China
| | - Ran Zhang
- State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, PR China.
| | - Tongfei Shi
- State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, PR China; School of Applied Chemistry and Engineering, University of Science and Technology of China, Hefei 230026, PR China
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9
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Dvores MP, Çarçabal P, Maître P, Simons JP, Gerber RB. Gas phase dynamics, conformational transitions and spectroscopy of charged saccharides: the oxocarbenium ion, protonated anhydrogalactose and protonated methyl galactopyranoside. Phys Chem Chem Phys 2020; 22:4144-4157. [PMID: 32039431 DOI: 10.1039/c9cp06572e] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Protonated intermediates are postulated to be involved in the rate determining step of many sugar reactions. This paper presents a study of protonated sugar species, isolated in the gas phase, using a combination of infrared multiple photon dissociation (IRMPD) spectroscopy, classical ab initio molecular dynamics (AIMD) and quantum mechanical vibrational self-consistent field (VSCF) calculations. It provides a likely identification of the reactive intermediate oxocarbenium ion structure in a d-galactosyl system as well as the saccharide pyrolysis product anhydrogalactose (that suggests oxocarbenium ion stabilization), along with the spectrum of the protonated parent species: methyl d-galactopyranoside-H+. Its vibrational fingerprint indicates intramolecular proton sharing. Classical AIMD simulations for galactosyl oxocarbenium ions, conducted in the temperature range ∼300-350 K (using B3LYP potentials on-the-fly) reveal efficient transitions on the picosecond timescale. Multiple conformers are likely to exist under the experimental conditions and along with static VSCF calculations, they have facilitated the identification of the individual structural motifs of the galactosyl oxocarbenium ion and protonated anhydrogalactose ion conformers that contribute to the observed experimental spectra. These results demonstrate the power of experimental IRMPD spectroscopy combined with dynamics simulations and with computational spectroscopy at the anharmonic level to unravel conformer structures of protonated saccharides, and to provide information on their lifetimes.
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Affiliation(s)
- M P Dvores
- Institute of Chemistry and the Fritz Haber Research Center, The Hebrew University, Jerusalem 91904, Israel.
| | - P Çarçabal
- Université Paris-Saclay, CNRS, Institut des Sciences Moléculaires d'Orsay, 91405, Orsay, France
| | - P Maître
- Université Paris-Saclay, CNRS, Institut de Chimie Physique, 91405, Orsay, France
| | - J P Simons
- Department of Chemistry, Physical and Theoretical Chemistry Laboratory, Oxford University, South Parks Road, Oxford OX1 3QZ, UK
| | - R B Gerber
- Institute of Chemistry and the Fritz Haber Research Center, The Hebrew University, Jerusalem 91904, Israel. and Department of Chemistry, University of California Irvine, CA 92697, USA
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10
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NMR solution geometry of saccharides containing the 6-O-(α-D-glucopyranosyl)-α/β-D-glucopyranose (isomaltose) or 6-O-(α-D-galactopyranosyl)-α/β-D-glucopyranose (melibiose) core. Carbohydr Res 2019; 473:18-35. [DOI: 10.1016/j.carres.2018.12.012] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2018] [Revised: 12/19/2018] [Accepted: 12/19/2018] [Indexed: 12/26/2022]
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11
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Lee KH, Schnupf U, Sumpter BG, Irle S. Performance of Density-Functional Tight-Binding in Comparison to Ab Initio and First-Principles Methods for Isomer Geometries and Energies of Glucose Epimers in Vacuo and Solution. ACS OMEGA 2018; 3:16899-16915. [PMID: 31458314 PMCID: PMC6643604 DOI: 10.1021/acsomega.8b02213] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/29/2018] [Accepted: 11/07/2018] [Indexed: 05/12/2023]
Abstract
Density functional theory (DFT) is a widely used methodology for the computation of molecular and electronic structure, and we confirm that B3LYP and the high-level ab initio G3B3 method are in excellent agreement for the lowest-energy isomers of the 16 glucose epimers. Density-functional tight-binding (DFTB) is an approximate version of DFT with typically comparable accuracy that is 2 to 3 orders of magnitude faster, therefore generally very suitable for processing large numbers of complex structures. Conformational isomerism in sugars is well known to give rise to a large number of isomer structures. On the basis of a comprehensive study of glucose epimers in vacuo and aqueous solution, we found that the performance of DFTB is on par to B3LYP in terms of geometrical parameters excluding hydrogen bonds and isomer energies. However, DFTB underestimates both hydrogen bonding interactions as well as torsional barriers associated with rotations of the hydroxy groups, resulting in a counterintuitive overemphasis of hydrogen bonding in both gas phase as well as in water. Although the associated root mean squared deviation from B3LYP within epimer isomer groups is only on the order of 1 kcal/mol, this deviation affects the correct assignment of major isomer ordering, which span less than 10 kcal/mol. Both second- as well as third-order DFTB methods are exhibiting similar deviations from B3LYP. Even after the inclusion of empirical dispersion corrections in vacuum, these deviations remain for a large majority of isomer energies and geometries when compared to dispersion-corrected B3LYP.
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Affiliation(s)
- Ka Hung Lee
- Department
of Chemistry, Graduate School of Science, Nagoya University, Nagoya 464-8602, Japan
- Bredesen
Center for Interdisciplinary Research and Graduate Education, University of Tennessee, Knoxville, Tennessee 37996, United States
| | - Udo Schnupf
- Department
of Chemistry and Biochemistry, Bradley University, Peoria, Illinois 61625, United States
- E-mail: (U.S.)
| | - Bobby G. Sumpter
- Computational Sciences and Engineering Division &
Chemical Sciences
Division and Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - Stephan Irle
- Department
of Chemistry, Graduate School of Science, Nagoya University, Nagoya 464-8602, Japan
- Computational Sciences and Engineering Division &
Chemical Sciences
Division and Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
- E-mail: (S.I.)
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12
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Lomas JS. Intramolecular O-H⋯O and C-H⋯O hydrogen bond cooperativity in D-glucopyranose and D-galactopyranose-A DFT/GIAO, QTAIM/IQA, and NCI approach. MAGNETIC RESONANCE IN CHEMISTRY : MRC 2018; 56:748-766. [PMID: 29498091 DOI: 10.1002/mrc.4728] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/01/2017] [Revised: 02/07/2018] [Accepted: 02/07/2018] [Indexed: 06/08/2023]
Abstract
Density functional theory calculations are used to compute proton nuclear magnetic resonance (NMR) chemical shifts, interatomic distances, atom-atom interaction energies, and atomic charges for partial structures and conformers of α-D-glucopyranose, β-D-glucopyranose, and α-D-galactopyranose built up by introducing OH groups into 2-methyltetrahydropyran stepwisely. For the counterclockwise conformers, the most marked effects on the NMR shift and the charge on the OH1 proton are produced by OH2, those of OH3 and OH4 being somewhat smaller. This argues for a diminishing cooperative effect. The effect of OH6 depends on the configuration of the hydroxymethyl group and the position, axial or equatorial, of OH4, which controls hydrogen bonding in the 1,3-diol motif. Variations in the interaction energies reveal that a "new" hydrogen bond is sometimes formed at the expense of a preexisting one, probably due to geometrical constraints. Whereas previous work showed that complexing a conformer with pyridine affects only the nearest neighbour, successive OH groups increase the interaction energy of the N⋯H1 hydrogen bond and reduce its length. Analogous results are obtained for the clockwise conformers. The interaction energies for C-H⋯OH hydrogen bonding between axial CH protons and OH groups in certain conformers are much smaller than for O-H⋯OH bonds but they are largely covalent, whereas those of the latter are predominantly coulombic. These interactions are modified by complexation with pyridine in the same way as O-H⋯OH interactions: the computed NMR shifts of the CH protons increase, the atom-atom distances are shorter, and interaction energies are enhanced.
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Affiliation(s)
- John S Lomas
- ITODYS (CNRS UMR-7086), Paris Diderot University, Sorbonne Paris Cité, F-75205, Paris, France
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13
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Kerins L, Byrne S, Gabba A, Murphy PV. Anomer Preferences for Glucuronic and Galacturonic Acid and Derivatives and Influence of Electron-Withdrawing Substituents. J Org Chem 2018; 83:7714-7729. [DOI: 10.1021/acs.joc.8b00610] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Louise Kerins
- School of Chemistry, National University of Ireland Galway, University Road, Galway, Ireland
| | - Sylvester Byrne
- School of Chemistry, National University of Ireland Galway, University Road, Galway, Ireland
| | - Adele Gabba
- School of Chemistry, National University of Ireland Galway, University Road, Galway, Ireland
| | - Paul V. Murphy
- School of Chemistry, National University of Ireland Galway, University Road, Galway, Ireland
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14
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Comparative conformational studies of 3,4,6-tri- O -acetyl-1,5-anhydro-2-deoxyhex-1-enitols at the DFT level. Carbohydr Res 2018; 462:13-27. [DOI: 10.1016/j.carres.2018.03.013] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2018] [Revised: 03/20/2018] [Accepted: 03/25/2018] [Indexed: 11/24/2022]
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15
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Bestaoui-Berrekhchi-Berrahma N, Springborg M, Berrekhchi-Berrahma C, Sekkal-Rahal M. DFT and MP2 conformational study of 3,6-anhydro-α-d-galactose in gas phase and in aqueous solvent. COMPUT THEOR CHEM 2018. [DOI: 10.1016/j.comptc.2018.01.015] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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16
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Amarasekara H, Dharuman S, Kato T, Crich D. Synthesis of Conformationally-Locked cis- and trans-Bicyclo[4.4.0] Mono-, Di-, and Trioxadecane Modifications of Galacto- and Glucopyranose; Experimental Limiting 3J H,H Coupling Constants for the Estimation of Carbohydrate Side Chain Populations and Beyond. J Org Chem 2018; 83:881-897. [PMID: 29241001 PMCID: PMC5775050 DOI: 10.1021/acs.joc.7b02891] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Hexopyranose side chains populate three staggered conformations, whose proportions can be determined from the three sets of ideal limiting 3JH5,H6R and 3JH5,H6S coupling constants in combination with the time-averaged experimental coupling constants. Literature values for the limiting coupling constants, obtained by the study of model compounds, the use of the Haasnoot-Altona and related equations, or quantum mechanical computations, can result in computed negative populations of one of the three ideal conformations. Such values arise from errors in the limiting coupling constants and/or from the population of nonideal conformers. We describe the synthesis and analysis of a series of cis- and trans-fused mono-, di-, and trioxabicyclo[4.4.0]octane-like compounds. Correction factors for the application of data from internal models (-CH(OR)-CH(OR)-) to terminal systems (-CH(OR)-CH2(OR)) are deduced from comparison of further models, and applied where necessary. Limiting coupling constants so-derived are applied to the side chain conformations of three model hexopyranosides, resulting in calculated conformer populations without negative values. Although, developed primarily for hexopyranose side chains, the limiting coupling constants are suitable, with the correction factors presented, for application to the side chains of higher carbon sugars and to conformation analysis of acyclic diols and their derivatives in a more general sense.
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Affiliation(s)
- Harsha Amarasekara
- Department of Chemistry, Wayne State University , Detroit, Michigan 48202, United States
| | - Suresh Dharuman
- Department of Chemistry, Wayne State University , Detroit, Michigan 48202, United States
| | - Takayuki Kato
- Department of Chemistry, Wayne State University , Detroit, Michigan 48202, United States
| | - David Crich
- Department of Chemistry, Wayne State University , Detroit, Michigan 48202, United States
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17
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Lacetera A, Berbís MÁ, Nurisso A, Jiménez-Barbero J, Martín-Santamaría S. Computational Chemistry Tools in Glycobiology: Modelling of Carbohydrate–Protein Interactions. COMPUTATIONAL TOOLS FOR CHEMICAL BIOLOGY 2017. [DOI: 10.1039/9781788010139-00145] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Molecular modelling provides a major impact in the field of glycosciences, helping in the characterisation of the molecular basis of the recognition between lectins from pathogens and human glycoconjugates, and in the design of glycocompounds with anti-infectious properties. The conformational properties of oligosaccharides are complex, and therefore, the simulation of these properties is a challenging task. Indeed, the development of suitable force fields is required for the proper simulation of important problems in glycobiology, such as the interatomic interactions responsible for oligosaccharide and glycoprotein dynamics, including O-linkages in oligo- and polysaccharides, and N- and O-linkages in glycoproteins. The computational description of representative examples is discussed, herein, related to biologically active oligosaccharides and their interaction with lectins and other proteins, and the new routes open for the design of glycocompounds with promising biological activities.
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Affiliation(s)
- Alessandra Lacetera
- Center for Biological Research CIB-CSIC. Ramiro de Maeztu, 9 28040-Madrid Spain
| | - M. Álvaro Berbís
- Center for Biological Research CIB-CSIC. Ramiro de Maeztu, 9 28040-Madrid Spain
| | - Alessandra Nurisso
- School of Pharmaceutical Sciences University of Geneva, University of Lausanne, Rue Michel Servet 1 CH-1211 Geneva 4 Switzerland
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18
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Lomas JS, Joubert L. On the importance of intramolecular hydrogen bond cooperativity in d-glucose - an NMR and QTAIM approach. MAGNETIC RESONANCE IN CHEMISTRY : MRC 2017; 55:893-901. [PMID: 28432857 DOI: 10.1002/mrc.4599] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/23/2017] [Revised: 03/15/2017] [Accepted: 04/18/2017] [Indexed: 05/16/2023]
Abstract
The idea that hydrogen bond cooperativity is responsible for the structure and reactivity of carbohydrates is examined. Density functional theory and gauge-including atomic orbital calculations on the known conformers of the α and β anomers of d-glucopyranose in the gas phase are used to compute proton NMR chemical shifts and interatomic distances, which are taken as criteria for probing intramolecular interactions. Atom-atom interaction energies are calculated by the interacting quantum atoms approach in the framework of the quantum theory of atoms in molecules. Association of OH1 in the counterclockwise conformers with a strong acceptor, pyridine, is accompanied by cooperative participation from OH2, but there is no significant change in the bonding of the two following 1,2-diol motifs. The OH6... O5 (G-g+/cc/t and G+g-/cc/t conformers) or OH6... O4 (Tg+/cc/t conformer) distance is reduced, and the OH6 proton is slightly deshielded. In the latter case, this shortening and the associated increase in the OH6-O4 interaction energy may be interpreted as a small cooperative effect, but intermolecular interaction energies are practically the same for all three conformers. In most of the pyridine complexes, one ortho proton interacts with the endocyclic oxygen O5. Analogous results are obtained when the clockwise conformer, G-g+/cl/g-, detected for the α anomer, and a hypothetical conformer, Tt/cl/g-, are complexed with pyridine through OH6. Generally, the cooperative effect does not go beyond the first two OH groups of a chain. Copyright © 2017 John Wiley & Sons, Ltd.
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Affiliation(s)
- John S Lomas
- ITODYS (CNRS UMR-7086), Univ Paris Diderot, Sorbonne Paris Cité, F-75205, Paris, France
| | - Laurent Joubert
- Normandy Univ., COBRA UMR 6014 & FR 3038, Université de Rouen, INSA Rouen, CNRS, 1 rue Tesnière, F-76821, Mont St Aignan Cedex, France
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Del Vigo EA, Marino C, Stortz CA. Exhaustive rotamer search of the 4C1 conformation of α- and β-d-galactopyranose. Carbohydr Res 2017; 448:136-147. [DOI: 10.1016/j.carres.2017.05.003] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2017] [Revised: 04/03/2017] [Accepted: 05/05/2017] [Indexed: 10/19/2022]
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20
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Ahmadi S, ManickamAchari V, Hussain Z, Hashim R. Epimeric and anomeric relationship of octyl- α - d -gluco/galactosides: Insight from density functional theory and atom in molecules studies. COMPUT THEOR CHEM 2017. [DOI: 10.1016/j.comptc.2017.03.023] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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21
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Tan Y, Zhao N, Liu J, Li P, Stedwell CN, Yu L, Polfer NC. Vibrational Signatures of Isomeric Lithiated N-acetyl-D-hexosamines by Gas-Phase Infrared Multiple-Photon Dissociation (IRMPD) Spectroscopy. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2017; 28:539-550. [PMID: 28050874 DOI: 10.1007/s13361-016-1575-x] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/17/2016] [Revised: 11/22/2016] [Accepted: 11/25/2016] [Indexed: 05/14/2023]
Abstract
Three lithiated N-acetyl-D-hexosamine (HexNAc) isomers, N-acetyl-D-glucosamine (GlcNAc), N-acetyl-D-galactosamine (GalNAc), and N-acetyl-D-mannosamine (ManNAc) are investigated as model monosaccharide derivatives by gas-phase infrared multiple-photon dissociation (IRMPD) spectroscopy. The hydrogen stretching region, which is attributed to OH and NH stretching modes, reveals some distinguishing spectral features of the lithium-adducted complexes that are useful in terms of differentiating these isomers. In order to understand the effect of lithium coordination on saccharide structure, and therefore anomericity, chair configuration, and hydrogen bonding networks, the conformational preferences of lithiated GlcNAc, GalNAc, and ManNAc are studied by comparing the experimental measurements with density functional theory (DFT) calculations. The experimental results of lithiated GlcNAc and GalNAc show a good match to the theoretical spectra of low-energy structures adopting a 4 C 1 chair conformation, consistent with this motif being the dominant conformation in condensed-phase monosaccharides. The epimerization effect upon going to lithiated ManNAc is significant, as in this case the 1 C 4 chair conformers give a more compelling match with the experimental results, consistent with their lower calculated energies. A contrasting computational study of these monosaccharides in their neutral form suggests that the lithium cation coordination with Lewis base oxygens can play a key role in favoring particular structural motifs (e.g., a 4 C 1 versus 1 C 4 ) and disrupting hydrogen bond networks, thus exhibiting specific IR spectral features between these closely related lithium-chelated complexes. Graphical Abstract ᅟ.
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Affiliation(s)
- Yanglan Tan
- Department of Chemistry, University of Florida, Gainesville, FL, 32611, USA
- Institute for Nutritional Sciences, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, 200031, China
| | - Ning Zhao
- Department of Chemistry, University of Florida, Gainesville, FL, 32611, USA
| | - Jinfeng Liu
- State Key Laboratory of Precision Spectroscopy, Institute of Theoretical and Computational Science, East China Normal University, Shanghai, 200062, China
| | - Pengfei Li
- Department of Chemistry, Michigan State University, East Lansing, MI, 48824, USA
| | - Corey N Stedwell
- Department of Chemistry, University of Florida, Gainesville, FL, 32611, USA
| | - Long Yu
- Department of Chemistry, University of Florida, Gainesville, FL, 32611, USA
| | - Nicolas C Polfer
- Department of Chemistry, University of Florida, Gainesville, FL, 32611, USA.
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22
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Gaweda K, Plazinski W. Pyranose ring conformations in mono- and oligosaccharides: a combined MD and DFT approach. Phys Chem Chem Phys 2017; 19:20760-20772. [DOI: 10.1039/c7cp02920a] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
A two-step computational protocol is proposed to efficiently study the conformational properties of hexopyranoses with a special emphasis on their ring-inversion-properties. By applying it, the errors resulting from overestimating the contribution of the hydrogen bond-rich, low-energy structures that are not abundant in aqueous solutions are avoided.
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Affiliation(s)
- Karolina Gaweda
- Jerzy Haber Institute of Catalysis and Surface Chemistry
- Polish Academy of Sciences
- 30-239 Cracow
- Poland
| | - Wojciech Plazinski
- Jerzy Haber Institute of Catalysis and Surface Chemistry
- Polish Academy of Sciences
- 30-239 Cracow
- Poland
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23
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Lonardi A, Oborský P, Hünenberger PH. Solvent-Modulated Influence of Intramolecular Hydrogen-Bonding on the Conformational Properties of the Hydroxymethyl Group in Glucose and Galactose: A Molecular Dynamics Simulation Study. Helv Chim Acta 2016. [DOI: 10.1002/hlca.201600158] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Affiliation(s)
- Alice Lonardi
- Laboratory of Physical Chemistry; ETH Hönggerberg; HCI; CH-8093 Zürich Switzerland
| | - Pavel Oborský
- Laboratory of Physical Chemistry; ETH Hönggerberg; HCI; CH-8093 Zürich Switzerland
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24
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Dhakal B, Buda S, Crich D. Stereoselective Synthesis of 5-epi-α-Sialosides Related to the Pseudaminic Acid Glycosides. Reassessment of the Stereoselectivity of the 5-Azido-5-deacetamidosialyl Thioglycosides and Use of Triflate as Nucleophile in the Zbiral Deamination of Sialic Acids. J Org Chem 2016; 81:10617-10630. [PMID: 27806203 PMCID: PMC5148678 DOI: 10.1021/acs.joc.6b02221] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
With a view to the eventual synthesis of glycosyl donors for the stereocontrolled synthesis of pseudaminic acid glycosides, the stereocontrolled synthesis of a d-glycero-d-gulo sialic acid adamantanylthioglycoside carrying an axial azide at the 5-position is described. The synthesis employs levulinic acid as nucleophile in the oxidative deamination of an N-acetylneuraminic acid thioglycoside leading to the formation of a 3-deoxy-d-glycero-d-galacto-2-nonulosonic acid (KDN) derivative selectively protected as 5-O-levulinate. Replacement of the levulinate by triflate enables introduction of the axial azide and hence formation of the glycosyl donor. A shorter synthesis uses trifluoromethanesulfonate as nucleophile in the oxidative deamination step when the 5-O-triflyl KDN derivative is obtained directly. Glycosylation reactions conducted with the 5-azido-d-glycero-d-gulo-configured sialyl adamantanylthioglycoside at -78 °C are selective for the formation of the equatorial glycosides, suggesting that the synthesis of equatorial pseudaminic acid glycosides will be possible as suitable donors become available. A comparable N-acetylneuraminic acid adamantanylthioglycoside carrying an equatorial azide at the 5-position was also found to be selective for equatorial glycoside formation under the same conditions, suggesting that reinvestigation of other azide-protected NeuAc donors is merited. Glycosylation stereoselectivity in the d-glycero-d-gulo series is discussed in terms of the side-chain conformation of the donor.
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Affiliation(s)
- Bibek Dhakal
- Department of Chemistry, Wayne State University, Detroit, MI 48202, USA
| | - Szymon Buda
- Department of Chemistry, Wayne State University, Detroit, MI 48202, USA
| | - David Crich
- Department of Chemistry, Wayne State University, Detroit, MI 48202, USA
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25
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Dharuman S, Crich D. Determination of the Influence of Side-Chain Conformation on Glycosylation Selectivity using Conformationally Restricted Donors. Chemistry 2016; 22:4535-42. [PMID: 26880055 PMCID: PMC4792696 DOI: 10.1002/chem.201505019] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2015] [Indexed: 01/28/2023]
Abstract
The synthesis of a series of conformationally locked mannopyranosyl thioglycosides in which the C6-O6 bond adopts either the gauche,gauche, gauche,trans, or trans,gauche conformation is described, and their influence on glycosylation stereoselectivity investigated. Two 4,6-O-benzylidene-protected mannosyl thioglycosides carrying axial or equatorial methyl groups at the 6-position were also synthesized and the selectivity of their glycosylation reactions studied to enable a distinction to be made between steric and stereoelectronic effects. The presence of an axial methoxy group at C6 in the bicyclic donor results in a decreased preference for formation of the β-mannoside, whereas an axial methyl group has little effect on selectivity. The result is rationalized in terms of through-space stabilization of a transient intermediate oxocarbenium ion by the axial methoxy group resulting in a higher degree of SN 1-like character in the glycosylation reaction. Comparisons are made with literature examples and exceptions are discussed in terms of pervading steric effects layered on top of the basic stereoelectronic effect.
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Affiliation(s)
- Suresh Dharuman
- Department of Chemistry, Wayne State University, Detroit, MI, 48202, USA
| | - David Crich
- Department of Chemistry, Wayne State University, Detroit, MI, 48202, USA.
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26
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Plazinski W, Lonardi A, Hünenberger PH. Revision of the GROMOS 56A6(CARBO) force field: Improving the description of ring-conformational equilibria in hexopyranose-based carbohydrates chains. J Comput Chem 2015; 37:354-65. [PMID: 26525424 DOI: 10.1002/jcc.24229] [Citation(s) in RCA: 71] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2015] [Revised: 10/03/2015] [Accepted: 10/06/2015] [Indexed: 01/19/2023]
Abstract
This article describes a revised version 56A6(CARBO_R) of the GROMOS 56A6(CARBO) force field for hexopyranose-based carbohydrates. The simulated properties of unfunctionalized hexopyranoses are unaltered with respect to 56A6CARBO . In the context of both O1 -alkylated hexopyranoses and oligosaccharides, the revision stabilizes the regular (4) C1 chair for α-anomers, with the opposite effect for β-anomers. As a result, spurious ring inversions observed in α(1→4)-linked chains when using the original 56A6(CARBO) force field are alleviated. The (4) C1 chair is now the most stable conformation for all d-hexopyranose residues, irrespective of the linkage type and anomery, and of the position of the residue along the chain. The methylation of a d-hexopyranose leads to a systematic shift in the ring-inversion free energy ((4) C1 to (1) C4 ) by 7-8 kJ mol(-1), positive for the α-anomers and negative for the β-anomers, which is qualitatively compatible with the expected enhancement of the anomeric effect upon methylation at O1. The ring-inversion free energies for residues within chains are typically smaller in magnitude compared to those of the monomers, and correlate rather poorly with the latter. This suggests that the crowding of ring substituents upon chain formation alters the ring flexibility in a nonsystematic fashion. In general, the description of carbohydrate chains afforded by 56A6(CARBO_R) suggests a significant extent of ring flexibility, i.e., small but often non-negligible equilibrium populations of inverted chairs, and challenges the "textbook" picture of conformationally locked carbohydrate rings.
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Affiliation(s)
- Wojciech Plazinski
- Laboratory of Physical Chemistry, ETH Hönggerberg, HCI, Zürich, CH-8093, Switzerland.,J. Haber Institute of Catalysis and Surface Chemistry, Polish Academy of Sciences, Ul. Niezapominajek 8, Cracow, 30-239, Poland
| | - Alice Lonardi
- Laboratory of Physical Chemistry, ETH Hönggerberg, HCI, Zürich, CH-8093, Switzerland
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28
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Abstract
High-resolution NMR and density functional theory (DFT) calculations have been applied to analysis of heparin pentasaccharide 3D structure in aqueous solution. The fully optimized molecular geometry of two pentasaccharide conformations (differing from each other in the form, one (1)C4 and the other (2)S0, of the sulfated iduronic acid residue) were obtained using the B3LYP/6-311+G(d,p) level of theory in the presence of solvent, the latter included as explicit water molecules. The presented approach enabled insight into variations of the bond lengths, bond angles, and torsion angles, formations of intra- and intermolecular hydrogen bonds, and ionic interactions in the two pentasaccharide conformations. A rather complex hydrogen bond network is formed, including inter-residue and intraresidue bonds between the NH group in the GlcN,3,6S with oxygens linked to C-2 at the IdoA2S residue and the glycosidic O-1 and the neighboring OSO3(-) group linked to C-3 in the same residue. On the other hand, because the first hydration shell is strongly influenced by strong ion-ion and ion-dipole interactions between sodium ions, sulfates, carboxylates, and -OH groups, ionic interactions play an important role in the stabilization of the 3D structure. The DFT-computed three-bond proton-proton coupling constants also showed that best agreement with experiment was obtained with a weighted average of 15:85 ((1)C4/(2)S0) of the sulfated iduronic acid forms indicating that the ratio is even more shifted toward the (2)S0 form than previously supposed. The DFT-computed pentasaccharide conformation differs from the previously published data, with the main changes at the glycosidic linkages, namely, the ψ1 torsion angles and the ϕ3 angle. The comparison of the glycosidic linkage torsion angle values in solution with the antithrombin-pentasaccharide complex also indicates that the pentasaccharide conformation changes upon binding to antithrombin III. The data supports the assumption that the protein selects the more populated (2)S0 conformer of heparin pentasaccharide and, consequently, the binding process of heparin pentasaccharide with antithrombin III is energetically more favorable than formerly expected.
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Affiliation(s)
- Miloš Hricovíni
- Institute of Chemistry, Slovak Academy of Sciences , 845 38 Bratislava, Slovakia
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29
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Patel DS, Pendrill R, Mallajosyula SS, Widmalm G, MacKerell AD. Conformational properties of α- or β-(1→6)-linked oligosaccharides: Hamiltonian replica exchange MD simulations and NMR experiments. J Phys Chem B 2014; 118:2851-71. [PMID: 24552401 PMCID: PMC3979472 DOI: 10.1021/jp412051v] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Conformational sampling for a set of 10 α- or β-(1→6)-linked oligosaccharides has been studied using explicit solvent Hamiltonian replica exchange (HREX) simulations and NMR spectroscopy techniques. Validation of the force field and simulation methodology is done by comparing calculated transglycosidic J coupling constants and proton-proton distances with the corresponding NMR data. Initial calculations showed poor agreement, for example, with >3 Hz deviation of the calculated (3)J(H5,H6R) values from the experimental data, prompting optimization of the ω torsion angle parameters associated with (1→6)-linkages. The resulting force field is in overall good agreement (i.e., within ∼0.5 Hz deviation) from experimental (3)J(H5,H6R) values, although some small limitations are evident. Detailed hydrogen bonding analysis indicates that most of the compounds lack direct intramolecular H-bonds between the two monosaccharides; however, minor sampling of the O6···HO2' hydrogen bond is present in three compounds. The results verify the role of the gauche effect between O5 and O6 atoms in gluco- and manno-configured pyranosides causing the ω torsion angle to sample an equilibrium between the gt and gg rotamers. Conversely, galacto-configured pyranosides sample a population distribution in equilibrium between gt and tg rotamers, while the gg rotamer populations are minor. Water radial distribution functions suggest decreased accessibility to the O6 atom in the (1→6)-linkage as compared to the O6' atom in the nonreducing sugar. The role of bridging water molecules between two sugar moieties on the distributions of ω torsion angles in oligosaccharides is also explored.
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Affiliation(s)
- Dhilon S Patel
- Department of Pharmaceutical Sciences, University of Maryland , 20 Penn Street HSF II, Baltimore, Maryland 21201, United States
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30
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Patel DS, He X, MacKerell AD. Polarizable empirical force field for hexopyranose monosaccharides based on the classical Drude oscillator. J Phys Chem B 2014; 119:637-52. [PMID: 24564643 PMCID: PMC4143499 DOI: 10.1021/jp412696m] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
A polarizable empirical force field based on the classical Drude oscillator is presented for the hexopyranose form of selected monosaccharides. Parameter optimization targeted quantum mechanical (QM) dipole moments, solute-water interaction energies, vibrational frequencies, and conformational energies. Validation of the model was based on experimental data on crystals, densities of aqueous-sugar solutions, diffusion constants of glucose, and rotational preferences of the exocylic hydroxymethyl of d-glucose and d-galactose in aqueous solution as well as additional QM data. Notably, the final model involves a single electrostatic model for all sixteen diastereomers of the monosaccharides, indicating the transferability of the polarizable model. The presented parameters are anticipated to lay the foundation for a comprehensive polarizable force field for saccharides that will be compatible with the polarizable Drude parameters for lipids and proteins, allowing for simulations of glycolipids and glycoproteins.
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Affiliation(s)
- Dhilon S Patel
- Department of Pharmaceutical Sciences, University of Maryland , 20 Penn Street HSF II, Baltimore, Maryland 21201, United States
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31
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DFT optimization and DFT-MD studies of glucose, ten explicit water molecules enclosed by an implicit solvent, COSMO. COMPUT THEOR CHEM 2014. [DOI: 10.1016/j.comptc.2013.12.007] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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32
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Parella T, Espinosa JF. Long-range proton-carbon coupling constants: NMR methods and applications. PROGRESS IN NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY 2013; 73:17-55. [PMID: 23962883 DOI: 10.1016/j.pnmrs.2013.07.001] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/08/2013] [Revised: 07/03/2013] [Accepted: 07/03/2013] [Indexed: 06/02/2023]
Abstract
A general review of novel NMR methods to measure heteronuclear long-range proton-carbon coupling constants ((n)JCH; n>1) in small molecules is made. NMR experiments are classified in terms of NMR pulse scheme and cross-peak nature. A discussion about simplicity, general applicability and accuracy for each particular NMR experiment is presented and exemplified. Important aspects such as the sign determination and measurement of very small coupling values involving protonated and non-protonated carbons as well as the complementarity between different experiments are also discussed. Finally, a compilation of applications in structural and conformational analysis of different types of molecules since 2000 is surveyed.
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Affiliation(s)
- Teodor Parella
- Servei de Ressonància Magnètica Nuclear, Universitat Autònoma de Barcelona, 08193 Bellaterra, Barcelona, Spain.
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33
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Karabulut S, Leszczynski J. Anomeric and rotameric preferences of glucopyranose in vacuo, water and organic solvents. J Mol Model 2013; 19:3637-45. [DOI: 10.1007/s00894-013-1902-0] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2013] [Accepted: 05/27/2013] [Indexed: 11/28/2022]
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Differently N-protected 3,4,6-tri-O-acetyl-2-amino-2-deoxy-d-glucopyranosyl chlorides and their application in the synthesis of diosgenyl 2-amino-2-deoxy-β-d-glucopyranoside. Carbohydr Res 2013; 367:10-7. [DOI: 10.1016/j.carres.2012.11.020] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2012] [Revised: 11/21/2012] [Accepted: 11/22/2012] [Indexed: 11/21/2022]
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35
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Bestaoui-Berrekhchi-Berrahma N, Derreumaux P, Sekkal-Rahal M, Springborg M, Sayede A, Yousfi N, Kadoun AED. Density functional conformational study of 2-O-sulfated 3,6 anhydro-α-D-galactose and of neo-κ- and ι-carrabiose molecules in gas phase and water. J Mol Model 2012; 19:893-904. [PMID: 23086461 DOI: 10.1007/s00894-012-1621-y] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2012] [Accepted: 10/01/2012] [Indexed: 10/27/2022]
Abstract
We examined the conformational preferences of the 2-O-sulfated-3,6-α-D-anhydrogalactose (compound I) and two 1,3 linked disaccharides constituting-κ or ι-carrageenans using density functional and ab initio methods in gas phase and aqueous solution. Systematic modifications of two torsion angles leading to 324 and 144 starting geometries for the compound I and each disaccharide were used to generate adiabatic maps using B3LYP/6-31G(d). The lower energy conformers were then fully optimized using B3LYP, B3PW91 and MP2 with several basis sets. Overall, we discuss the impact of full relaxation on the energy and structure of the dominant conformations, present the performance comparison with previous molecular mechanics calculations if available, and determine whether our results are impacted, when polarization and diffuse functions are added to the 6-31G(d) basis set, or when the MP2 level of theory is used.
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36
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Taha HA, Richards MR, Lowary TL. Conformational Analysis of Furanoside-Containing Mono- and Oligosaccharides. Chem Rev 2012; 113:1851-76. [DOI: 10.1021/cr300249c] [Citation(s) in RCA: 99] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Affiliation(s)
- Hashem A. Taha
- Alberta Glycomics Centre and Department of Chemistry, Gunning−Lemieux Chemistry Centre, University of Alberta, Edmonton, AB, Canada T6G 2G2
| | - Michele R. Richards
- Alberta Glycomics Centre and Department of Chemistry, Gunning−Lemieux Chemistry Centre, University of Alberta, Edmonton, AB, Canada T6G 2G2
| | - Todd L. Lowary
- Alberta Glycomics Centre and Department of Chemistry, Gunning−Lemieux Chemistry Centre, University of Alberta, Edmonton, AB, Canada T6G 2G2
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37
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Sharma I, Bohé L, Crich D. Influence of protecting groups on the anomeric equilibrium; case of the 4,6-O-benzylidene acetal in the mannopyranose series. Carbohydr Res 2012; 357:126-31. [PMID: 22739244 PMCID: PMC3396728 DOI: 10.1016/j.carres.2012.05.025] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2012] [Revised: 05/25/2012] [Accepted: 05/28/2012] [Indexed: 11/29/2022]
Abstract
It is reported that the replacement of the 4- and 6-O-benzyl ethers in 2,3,4,6-tetra-O-benzyl-α,β-mannopyranose by a 4,6-O-benzylidene acetal results in an increased population of the β-anomer at equilibrium in CDCl(3) solution. The phenomenon is considered to arise from the lower steric bulk of the benzylidene acetal that, through diminished buttressing interactions, reduces steric interactions normally present in the β-anomer.
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Affiliation(s)
- Indrajeet Sharma
- Department of Chemistry, Wayne State University, 5101 Cass Avenue, Detroit, MI 48202, USA
| | - Luis Bohé
- Centre de Recherche de Gif, Institut de Chimie des Substances Naturelles, CNRS, 1 Avenue de la Terrasse, 91190 Gif-sur-Yvette, France
| | - David Crich
- Department of Chemistry, Wayne State University, 5101 Cass Avenue, Detroit, MI 48202, USA
- Centre de Recherche de Gif, Institut de Chimie des Substances Naturelles, CNRS, 1 Avenue de la Terrasse, 91190 Gif-sur-Yvette, France
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38
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Nowacki A, Walczak D, Liberek B. Fully acetylated 1,5-anhydro-2-deoxypent-1-enitols and 1,5-anhydro-2,6-dideoxyhex-1-enitols in DFT level theory conformational studies. Carbohydr Res 2012; 352:177-85. [DOI: 10.1016/j.carres.2012.02.008] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2011] [Revised: 01/16/2012] [Accepted: 02/10/2012] [Indexed: 10/28/2022]
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39
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Sanhueza CA, Dorta RL, Vázquez JT. Stereochemical Properties of Glucosyl Sulfoxides in Solution. J Org Chem 2011; 76:7769-80. [DOI: 10.1021/jo201130x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Carlos A. Sanhueza
- Instituto Universitario de Bio-Orgánica “Antonio González”, Departamento de Química Orgánica, Universidad de La Laguna, 38206 La Laguna, Tenerife, Spain
| | - Rosa L. Dorta
- Instituto Universitario de Bio-Orgánica “Antonio González”, Departamento de Química Orgánica, Universidad de La Laguna, 38206 La Laguna, Tenerife, Spain
| | - Jesús T. Vázquez
- Instituto Universitario de Bio-Orgánica “Antonio González”, Departamento de Química Orgánica, Universidad de La Laguna, 38206 La Laguna, Tenerife, Spain
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40
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Hricovíni M. Effect of Solvent and Counterions upon Structure and NMR Spin−Spin Coupling Constants in Heparin Disaccharide. J Phys Chem B 2011; 115:1503-11. [DOI: 10.1021/jp1098552] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Affiliation(s)
- Miloš Hricovíni
- Institute of Chemistry, Slovak Academy of Sciences, 845 38 Bratislava, Slovakia
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41
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Cézard C, Trivelli X, Aubry F, Djedaïni-Pilard F, Dupradeau FY. Molecular dynamics studies of native and substituted cyclodextrins in different media: 1. Charge derivation and force field performances. Phys Chem Chem Phys 2011; 13:15103-21. [DOI: 10.1039/c1cp20854c] [Citation(s) in RCA: 87] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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42
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Hansen HS, Hünenberger PH. A reoptimized GROMOS force field for hexopyranose-based carbohydrates accounting for the relative free energies of ring conformers, anomers, epimers, hydroxymethyl rotamers, and glycosidic linkage conformers. J Comput Chem 2010; 32:998-1032. [PMID: 21387332 DOI: 10.1002/jcc.21675] [Citation(s) in RCA: 125] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2010] [Revised: 08/12/2010] [Accepted: 08/17/2010] [Indexed: 11/07/2022]
Abstract
This article presents a reoptimization of the GROMOS 53A6 force field for hexopyranose-based carbohydrates (nearly equivalent to 45A4 for pure carbohydrate systems) into a new version 56A(CARBO) (nearly equivalent to 53A6 for non-carbohydrate systems). This reoptimization was found necessary to repair a number of shortcomings of the 53A6 (45A4) parameter set and to extend the scope of the force field to properties that had not been included previously into the parameterization procedure. The new 56A(CARBO) force field is characterized by: (i) the formulation of systematic build-up rules for the automatic generation of force-field topologies over a large class of compounds including (but not restricted to) unfunctionalized polyhexopyranoses with arbritrary connectivities; (ii) the systematic use of enhanced sampling methods for inclusion of experimental thermodynamic data concerning slow or unphysical processes into the parameterization procedure; and (iii) an extensive validation against available experimental data in solution and, to a limited extent, theoretical (quantum-mechanical) data in the gas phase. At present, the 56A(CARBO) force field is restricted to compounds of the elements C, O, and H presenting single bonds only, no oxygen functions other than alcohol, ether, hemiacetal, or acetal, and no cyclic segments other than six-membered rings (separated by at least one intermediate atom). After calibration, this force field is shown to reproduce well the relative free energies of ring conformers, anomers, epimers, hydroxymethyl rotamers, and glycosidic linkage conformers. As a result, the 56A(CARBO) force field should be suitable for: (i) the characterization of the dynamics of pyranose ring conformational transitions (in simulations on the microsecond timescale); (ii) the investigation of systems where alternative ring conformations become significantly populated; (iii) the investigation of anomerization or epimerization in terms of free-energy differences; and (iv) the design of simulation approaches accelerating the anomerization process along an unphysical pathway.
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Affiliation(s)
- Halvor S Hansen
- Laboratorium für Physikalische Chemie, ETH Zürich, CH-8093 Zürich, Switzerland
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43
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Perić-Hassler L, Hansen HS, Baron R, Hünenberger PH. Conformational properties of glucose-based disaccharides investigated using molecular dynamics simulations with local elevation umbrella sampling. Carbohydr Res 2010; 345:1781-801. [PMID: 20576257 DOI: 10.1016/j.carres.2010.05.026] [Citation(s) in RCA: 107] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2010] [Revised: 05/20/2010] [Accepted: 05/22/2010] [Indexed: 10/19/2022]
Abstract
Explicit-solvent molecular dynamics (MD) simulations of the 11 glucose-based disaccharides in water at 300K and 1bar are reported. The simulations were carried out with the GROMOS 45A4 force-field and the sampling along the glycosidic dihedral angles phi and psi was artificially enhanced using the local elevation umbrella sampling (LEUS) method. The trajectories are analyzed in terms of free-energy maps, stable and metastable conformational states (relative free energies and estimated transition timescales), intramolecular H-bonds, single molecule configurational entropies, and agreement with experimental data. All disaccharides considered are found to be characterized either by a single stable (overwhelmingly populated) state ((1-->n)-linked disaccharides with n=1, 2, 3, or 4) or by two stable (comparably populated and differing in the third glycosidic dihedral angle omega ; gg or gt) states with a low interconversion barrier ((1-->6)-linked disaccharides). Metastable (anti-phi or anti-psi) states are also identified with relative free energies in the range of 8-22 kJ mol(-1). The 11 compounds can be classified into four families: (i) the alpha(1-->1)alpha-linked disaccharide trehalose (axial-axial linkage) presents no metastable state, the lowest configurational entropy, and no intramolecular H-bonds; (ii) the four alpha(1-->n)-linked disaccharides (n=1, 2, 3, or 4; axial-equatorial linkage) present one metastable (anti-psi) state, an intermediate configurational entropy, and two alternative intramolecular H-bonds; (iii) the four beta(1-->n)-linked disaccharides (n=1, 2, 3, or 4; equatorial-equatorial linkage) present two metastable (anti-phi and anti-psi) states, an intermediate configurational entropy, and one intramolecular H-bond; (iv) the two (1-->6)-linked disaccharides (additional glycosidic dihedral angle) present no (isomaltose) or a pair of (gentiobiose) metastable (anti-phi) states, the highest configurational entropy, and no intramolecular H-bonds. The observed conformational preferences appear to be dictated by four main driving forces (ring conformational preferences, exo-anomeric effect, steric constraints, and possible presence of a third glycosidic dihedral angle), leaving a secondary role to intramolecular H-bonding and specific solvation effects. In spite of the weak conformational driving force attributed to solvent-exposed H-bonds in water (highly polar protic solvent), intramolecular H-bonds may still have a significant influence on the physico-chemical properties of the disaccharide by decreasing its hydrophilicity. Along with previous work, the results also complete the suggestion of a spectrum of approximate transition timescales for carbohydrates up to the disaccharide level, namely: approximately 30 ps (hydroxyl groups), approximately 1 ns (free lactol group, free hydroxymethyl groups, glycosidic dihedral angleomega in (1-->6)-linked disaccharides), approximately 10 ns to 2 micros (ring conformation, glycosidic dihedral angles phi and psi). The calculated average values of the glycosidic torsional angles agree well with the available experimental data, providing validation for the force-field and simulation methodology employed.
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Affiliation(s)
- Lovorka Perić-Hassler
- Laboratory of Physical Chemistry, ETH Zürich, ETH Hönggerberg, HCI, CH-8093 Zürich, Switzerland
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44
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Schnupf U, Willett J, Momany F. DFTMD studies of glucose and epimers: anomeric ratios, rotamer populations, and hydration energies. Carbohydr Res 2010; 345:503-11. [DOI: 10.1016/j.carres.2009.12.001] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2009] [Revised: 11/24/2009] [Accepted: 12/07/2009] [Indexed: 10/20/2022]
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45
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Kövér KE, Szilágyi L, Batta G, Uhrín D, Jiménez-Barbero J. Biomolecular Recognition by Oligosaccharides and Glycopeptides: The NMR Point of View. COMPREHENSIVE NATURAL PRODUCTS II 2010:197-246. [DOI: 10.1016/b978-008045382-8.00193-3] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/27/2023]
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46
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Spiwok V, Tvaroska I. Conformational free energy surface of alpha-N-acetylneuraminic acid: an interplay between hydrogen bonding and solvation. J Phys Chem B 2009; 113:9589-94. [PMID: 19374421 DOI: 10.1021/jp8113495] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The conformational free energy surface of alpha-N-acetylneuraminic acid (Neu5Ac, sialic acid) in the space of ring-puckering coordinates was calculated using the metadynamics method. Free energy surfaces in vacuum and with an explicit solvent were calculated in GLYCAM 06 force field. In vacuum three structures are almost equivalently populated, namely, the (2)C(5) chair and the B(3,6)/(2)S(6) and (O)S(3) boat/skew-boat conformations. The B(3,6)/(2)S(6) structure is stabilized by an ionic hydrogen bond between the amide N-H bond and the carboxylic group. However, this structure is unfavorable in a water environment in which the experimentally observed (2)C(5) chair conformation is predicted to be more stable than the other structures. These results indicate that environment significantly influences conformation of Neu5Ac and that Neu5Ac-processing enzymes might modify a conformation of their substrates solely by a changing polarity of the environment. The structure of Neu5Ac bound in influenza neuraminidase ((4)S(2)/B(2,5)) belongs to conformations preferred in a water environment. The free energy penalty of this conformational change was calculated (relative to (2)C(5)) as 10.2 +/- 2.0 and 17.3 +/- 2.0 kJ/mol for (4,O)B/(O)S(3) and (4)S(2), respectively. This result indicates that mimicking of the enzyme-bound conformation is likely to be a viable strategy for the design of neuraminidase inhibitors.
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Affiliation(s)
- Vojtech Spiwok
- Department of Structure and Function of Saccharides, Centre for Glycomics, Slovak Academy of Sciences, 84538 Bratislava, Slovak Republic.
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47
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Computational studies of the role of glycopyranosyl oxacarbenium ions in glycobiology and glycochemistry. Adv Carbohydr Chem Biochem 2009; 62:83-159. [PMID: 19501705 DOI: 10.1016/s0065-2318(09)00004-3] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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48
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The (α-1,6) glycosidic bond of isomaltose: a tricky system for theoretical conformational studies. Carbohydr Res 2009; 344:1235-47. [DOI: 10.1016/j.carres.2009.04.022] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2009] [Revised: 04/19/2009] [Accepted: 04/21/2009] [Indexed: 11/23/2022]
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49
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Spiwok V, Tvaroska I. Metadynamics modelling of the solvent effect on primary hydroxyl rotamer equilibria in hexopyranosides. Carbohydr Res 2009; 344:1575-81. [PMID: 19539272 DOI: 10.1016/j.carres.2009.05.019] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2009] [Revised: 04/29/2009] [Accepted: 05/13/2009] [Indexed: 11/16/2022]
Abstract
Accurate modelling of rotamer equilibria for the primary hydroxyl groups of monosaccharides continues to be a great challenge of computational glycochemistry. The metadynamics technique was applied to study the conformational free energy surfaces of methyl alpha-D-glucopyranoside and methyl alpha-D-galactopyranoside, employing the GLYCAM06 force field. For both molecules, seven to eight conformational free-energy minima, differing in the omega (O-5-C-5-C-6-O-6) and chi (C-3-C-4-O-4-HO-4) dihedral angles, were identified in vacuum or in a water environment. The calculated rotamer equilibrium of the primary hydroxyl group is significantly different in vacuum than in water. The major effect of a water environment is the destabilisation of a hydrogen bond between O-4-HO-4 and O-6-HO-6 groups. It was possible to calculate the free-energy differences of individual rotamers with an accuracy of better than 2 kJ/mol. The calculated gg, gt and tg rotamer populations in water are in close agreement with experimental measurements, and therefore support the theoretical background of metadynamics.
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Affiliation(s)
- Vojtech Spiwok
- Department of Biochemistry and Microbiology, Institute of Chemical Technology in Prague, Technická 3, 166 28 Prague 6, Czech Republic.
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50
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Methyl 6-deoxy-6-iodo-α-d-glucopyranoside: crystal structure and high-resolution NMR spectroscopy. Carbohydr Res 2009; 344:830-3. [PMID: 19268282 DOI: 10.1016/j.carres.2009.02.004] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2008] [Revised: 02/05/2009] [Accepted: 02/05/2009] [Indexed: 11/20/2022]
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