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French AD. Combining Computational Chemistry and Crystallography for a Better Understanding of the Structure of Cellulose. Adv Carbohydr Chem Biochem 2021; 80:15-93. [PMID: 34872656 DOI: 10.1016/bs.accb.2021.11.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The approaches in this article seek to enhance understanding of cellulose at the molecular level, independent of the source and the particular crystalline form of cellulose. Four main areas of structure research are reviewed. Initially, the molecular shape is inferred from the crystal structures of many small molecules that have β-(1→4) linkages. Then, conformational analyses with potential energy calculations of cellobiose are covered, followed by the use of Atoms-In-Molecules theory to learn about interactions in experimental and theoretical structures. The last section covers models of cellulose nanoparticles. Controversies addressed include the stability of twofold screw-axis conformations, the influence of different computational methods, the predictability of crystalline conformations by studies of isolated molecules, and the twisting of model cellulose crystals.
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Affiliation(s)
- Alfred D French
- Southern Regional Research Center, U.S. Department of Agriculture, New Orleans, Louisiana, USA
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2
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Lin J, Meredith RJ, Oliver AG, Carmichael I, Serianni AS. Two-bond 13C- 13C spin-coupling constants in saccharides: dependencies on exocyclic hydroxyl group conformation. Phys Chem Chem Phys 2021; 23:22912-22922. [PMID: 34617529 DOI: 10.1039/d1cp03320d] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Seven doubly 13C-labeled isotopomers of methyl β-D-glucopyranoside, methyl β-D-xylopyranoside, methyl β-D-galactopyranoside, methyl β-D-galactopyranosyl-(1→4)-β-D-glucopyranoside and methyl β-D-galactopyranosyl-(1→4)-β-D-xylopyranoside were prepared, crystallized, and studied by single-crystal X-ray crystallography and solid-state 13C NMR spectroscopy to determine experimentally the dependence of 2JC1,C3 values in aldopyranosyl rings on the C1-C2-O2-H torsion angle, θ2, involving the C2 carbon of the C1-C2-C3 coupling pathway. Using X-ray crystal structures to determine θ2 in crystalline samples and by selecting compounds that exhibit a relatively wide range of θ2 values in the crystalline state, 2JC1,C3 values measured in crystalline samples were plotted against θ2 and the resulting plot compared to that obtained from density functional theory (DFT) calculations. For θ2 values ranging from ∼90° to ∼240°, very good agreement was observed between the experimental and theoretical plots, providing strong validation of DFT-calculated spin-coupling dependencies on exocyclic C-O bond conformation involving the central carbon of geminal C-C-C coupling pathways. These findings provide new experimental evidence supporting the use of 2JCCC values as non-conventional spin-coupling constraints in MA'AT conformational modeling of saccharides in solution, and the use of NMR spin-couplings not involving coupled hydroxyl hydrogens as indirect probes of C-O bond conformation. Solvomorphism was observed in crystalline βGal-(1→4)-βGlcOCH3 wherein the previously-reported methanol solvate form was found to spontaneously convert to a monohydrate upon air-drying, leading to small but discernible conformational changes in, and a new crystalline form of, this disaccharide.
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Affiliation(s)
- Jieye Lin
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN 46556-5670, USA.
| | - Reagan J Meredith
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN 46556-5670, USA.
| | - Allen G Oliver
- Molecular Structure Facility, University of Notre Dame, Notre Dame, IN 46556-5670, USA
| | - Ian Carmichael
- The Radiation Laboratory, University of Notre Dame, Notre Dame, IN 46556-5670, USA
| | - Anthony S Serianni
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN 46556-5670, USA.
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Lin J, Oliver AG, Serianni AS. Methyl β-lactoside [methyl β-D-galactopyranosyl-(1→4)-β-D-glucopyranoside] monohydrate: a solvomorphism study. ACTA CRYSTALLOGRAPHICA SECTION C-STRUCTURAL CHEMISTRY 2021; 77:668-674. [PMID: 34607990 DOI: 10.1107/s2053229621009499] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/19/2021] [Accepted: 09/11/2021] [Indexed: 11/10/2022]
Abstract
Methyl β-lactoside [methyl β-D-galactopyranosyl-(1→4)-β-D-glucopyranoside] monohydrate, C13H24O11·H2O, (I), was obtained via spontaneous transformation of methyl β-lactoside methanol solvate, (II), during air-drying. Cremer-Pople puckering parameters indicate that the β-D-Galp (β-D-galactopyranosyl) and β-D-Glcp (β-D-glucopyranosyl) rings in (I) adopt slightly distorted 4C1 chair conformations, with the former distorted towards a boat form (BC1,C4) and the latter towards a twist-boat form (O5SC2). Puckering parameters for (I) and (II) indicate that the conformation of the βGalp ring is slightly more affected than the βGlcp ring by the solvomorphism. Conformations of the terminal O-glycosidic linkages in (I) and (II) are virtually identical, whereas those of the internal O-glycosidic linkage show torsion-angle changes of 6° in both C-O bonds. The exocyclic hydroxymethyl group in the βGalp residue adopts a gt conformation (C4' anti to O6') in both (I) and (II), whereas that in the βGlcp residue adopts a gg (gauche-gauche) conformation (H5 anti to O6) in (II) and a gt (gauche-trans) conformation (C4 anti to O6) in (I). The latter conformational change is critical to the solvomorphism in that it allows water to participate in three hydrogen bonds in (I) as opposed to only two hydrogen bonds in (II), potentially producing a more energetically stable structure for (I) than for (II). Visual inspection of the crystalline lattice of (II) reveals channels in which methanol solvent resides and through which solvent might exchange during solvomorphism. These channels are less apparent in the crystalline lattice of (I).
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Affiliation(s)
- Jieye Lin
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN 46556-5670, USA
| | - Allen G Oliver
- Molecular Structure Facility, University of Notre Dame, Notre Dame, IN 46556-5670, USA
| | - Anthony S Serianni
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN 46556-5670, USA
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Lin J, Oliver AG, Meredith RJ, Carmichael I, Serianni AS. Isopropyl 3-deoxy-α-D-ribo-hexopyranoside (isopropyl 3-deoxy-α-D-glucopyranoside): evaluating trends in structural parameters. ACTA CRYSTALLOGRAPHICA SECTION C-STRUCTURAL CHEMISTRY 2021; 77:490-495. [PMID: 34350847 DOI: 10.1107/s205322962100749x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/29/2021] [Accepted: 07/21/2021] [Indexed: 11/10/2022]
Abstract
Isopropyl 3-deoxy-α-D-ribo-hexopyranoside (isopropyl 3-deoxy-α-D-glucopyranoside), C9H18O5, (I), crystallizes from a methanol-ethyl acetate solvent mixture at room temperature in a 4C1 chair conformation that is slightly distorted towards the C5SC1 twist-boat form. A comparison of the structural parameters in (I), methyl α-D-glucopyranoside, (II), α-D-glucopyranosyl-(1→4)-D-glucitol (maltitol), (III), and 3-deoxy-α-D-ribo-hexopyranose (3-deoxy-α-D-glucopyranose), (IV), shows that most endocyclic and exocyclic bond lengths, valence bond angles and torsion angles in the aldohexopyranosyl rings are more affected by anomeric configuration, aglycone structure and/or the conformation of exocyclic substituents, such as hydroxymethyl groups, than by monodeoxygenation at C3. The structural effects observed in the crystal structures of (I)-(IV) were confirmed though density functional theory (DFT) calculations in computed structures (I)c-(IV)c. Exocyclic hydroxymethyl groups adopt the gauche-gauche (gg) conformation (H5 anti to O6) in (I) and (III), and the gauche-trans (gt) conformation (C4 anti to O6) in (II) and (IV). The O-glycoside linkage conformations in (I) and (III) resemble those observed in disaccharides containing β-(1→4) linkages.
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Affiliation(s)
- Jieye Lin
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN 46556-5670, USA
| | - Allen G Oliver
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN 46556-5670, USA
| | - Reagan J Meredith
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN 46556-5670, USA
| | - Ian Carmichael
- Radiation Laboratory, University of Notre Dame, Notre Dame, IN 46556-5670, USA
| | - Anthony S Serianni
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN 46556-5670, USA
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Zhang W, Yoon MK, Meredith RJ, Zajicek J, Oliver AG, Hadad M, Frey MH, Carmichael I, Serianni AS. 13C- 13C spin-coupling constants in crystalline 13C-labeled saccharides: conformational effects interrogated by solid-state 13C NMR spectroscopy. Phys Chem Chem Phys 2019; 21:23576-23588. [PMID: 31621725 DOI: 10.1039/c9cp03228b] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Solid-state 13C NMR spectroscopy has been used in conjunction with selectively 13C-labeled mono- and disaccharides to measure 13C-13C spin-couplings (JCC) in crystalline samples. This experimental approach allows direct correlation of JCC values with specific molecular conformations since, in crystalline samples, molecular conformation is essentially static and can be determined by X-ray crystallography. JCC values measured in the solid-state in known molecular conformations can then be compared to corresponding JCC values calculated in the same conformations using density functional theory (DFT). The latter comparisons provide important validation of DFT-calculated J-couplings, which is not easily obtained by other approaches and is fundamental to obtaining reliable experiment-based conformational models from redundant J-couplings by MA'AT analysis. In this study, representative 1JCC, 2JCCC and 3JCOCC values were studied as either intra-residue couplings in the aldohexopyranosyl rings of monosaccharides or inter-residue (trans-glycoside) couplings in disaccharides. The results demonstrate that (a) accurate JCC values can be measured in crystalline saccharides that have been suitably labeled with 13C, and (b) DFT-calculated JCC values compare favorably with those determined by solid-state 13C NMR when molecular conformation is a constant in both determinations.
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Affiliation(s)
- Wenhui Zhang
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN 46556-5670, USA.
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Turney T, Pan Q, Zhang W, Oliver AG, Serianni AS. O-Benzoyl side-chain conformations in 2,3,4,6-tetra-O-benzoyl-β-D-galactopyranosyl-(1→4)-1,2,6-tri-O-benzoyl-β-D-glucopyranose (ethyl acetate solvate) and 1,2,4,6-tetra-O-benzoyl-β-D-glucopyranose (acetone solvate). ACTA CRYSTALLOGRAPHICA SECTION C-STRUCTURAL CHEMISTRY 2019; 75:161-167. [DOI: 10.1107/s2053229619000822] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/26/2018] [Accepted: 01/17/2019] [Indexed: 05/30/2023]
Abstract
The crystal structures of 2,3,4,6-tetra-O-benzoyl-β-D-galactopyranosyl-(1→4)-1,2,6-tri-O-benzoyl-β-D-glucopyranose ethyl acetate hemisolvate, C61H50O18·0.5C4H8O2, and 1,2,4,6-tetra-O-benzoyl-β-D-glucopyranose acetone monosolvate, C34H28O10·C3H6O, were determined and compared to those of methyl β-D-galactopyranosyl-(1→4)-β-D-glucopyranoside (methyl β-lactoside) and methyl β-D-glucopyranoside hemihydrate, C7H14O6·0.5H2O, to evaluate the effects of O-benzoylation on bond lengths, bond angles and torsion angles. In general, O-benzoylation exerts little effect on exo- and endocyclic C—C and endocyclic C—O bond lengths, but exocyclic C—O bonds involved in O-benzoylation are lengthened by 0.02–0.04 Å depending on the site of substitution. The conformation of the O-benzoyl side-chains is highly conserved, with the carbonyl O atom either eclipsing the H atom attached to a 2°-alcoholic C atom or bisecting the H—C—H bond angle of an 1°-alcoholic C atom. Of the three bonds that determine the side-chain geometry, the C—O bond involving the alcoholic C atom exhibits greater rotational variability than the remaining C—O and C—C bonds involving the carbonyl C atom. These findings are in good agreement with recent solution NMR studies of the O-acetyl side-chain conformation in saccharides.
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Zhang W, Turney T, Meredith R, Pan Q, Sernau L, Wang X, Hu X, Woods RJ, Carmichael I, Serianni AS. Conformational Populations of β-(1→4) O-Glycosidic Linkages Using Redundant NMR J-Couplings and Circular Statistics. J Phys Chem B 2017; 121:3042-3058. [PMID: 28296420 DOI: 10.1021/acs.jpcb.7b02252] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Twelve disaccharides containing β-(1→4) linkages and displaying systematic structural variations in the vicinity of these linkages were selectively labeled with 13C to facilitate measurements of multiple NMR spin-spin (scalar; J) coupling constants (JCH and JCC values) across their O-glycosidic linkages. Ensembles of spin-couplings (2JCOC, 3JCOCH, 3JCOCC) sensitive to the two linkage torsion angles, phi (ϕ) and psi (ψ), were analyzed by using parametrized equations obtained from density functional theory (DFT) calculations, Fredholm theory, and circular statistics to calculate experiment-based rotamer populations for ϕ and ψ in each disaccharide. With the statistical program MA'AT, torsion angles ϕ and ψ were modeled as a single von Mises distribution, which yielded two parameters, the mean position and the circular standard deviation (CSD) for each angle. The NMR-derived rotamer populations were compared to those obtained from 1 μs aqueous molecular dynamics (MD) simulations and crystallographic database statistical analyses. Conformer populations obtained exclusively from the MA'AT treatment of redundant J-couplings were in very good agreement with those obtained from the MD simulations, providing evidence that conformational populations can be determined by NMR for mobile molecular elements such as O-glycosidic linkages with minimal input from theory. The approach also provides an experimental means to validate the conformational preferences predicted from MD simulations. The conformational behaviors of ϕ in the 12 disaccharides were very similar, but those of ψ varied significantly, allowing a classification of the 12 disaccharides based on preferred linkage conformation in solution.
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Affiliation(s)
- Wenhui Zhang
- Department of Chemistry and Biochemistry, University of Notre Dame , Notre Dame, Indiana 46556-5670, United States
| | - Toby Turney
- Department of Chemistry and Biochemistry, University of Notre Dame , Notre Dame, Indiana 46556-5670, United States
| | - Reagan Meredith
- Department of Chemistry and Biochemistry, University of Notre Dame , Notre Dame, Indiana 46556-5670, United States
| | - Qingfeng Pan
- Omicron Biochemicals Inc. , South Bend, Indiana 46617-2701, United States
| | - Luke Sernau
- Department of Chemistry and Biochemistry, University of Notre Dame , Notre Dame, Indiana 46556-5670, United States
| | - Xiaocong Wang
- Complex Carbohydrate Research Center, University of Georgia , Athens, Georgia 30602, United States
| | - Xiaosong Hu
- Department of Chemistry, Wuhan University of Technology , Wuhan 430070, China
| | - Robert J Woods
- Complex Carbohydrate Research Center, University of Georgia , Athens, Georgia 30602, United States
| | - Ian Carmichael
- Radiation Laboratory, University of Notre Dame , Notre Dame, Indiana 46556-5670, United States
| | - Anthony S Serianni
- Department of Chemistry and Biochemistry, University of Notre Dame , Notre Dame, Indiana 46556-5670, United States
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Klepach T, Zhao H, Hu X, Zhang W, Stenutz R, Hadad MJ, Carmichael I, Serianni AS. Informing saccharide structural NMR studies with density functional theory calculations. Methods Mol Biol 2015; 1273:289-331. [PMID: 25753718 DOI: 10.1007/978-1-4939-2343-4_20] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Density functional theory (DFT) is a powerful computational tool to enable structural interpretations of NMR spin-spin coupling constants ( J-couplings) in saccharides, including the abundant (1)H-(1)H ( JHH), (13)C-(1)H ( JCH), and (13)C-(13)C ( JCC) values that exist for coupling pathways comprised of 1-4 bonds. The multiple hydroxyl groups in saccharides, with their attendant lone-pair orbitals, exert significant effects on J-couplings that can be difficult to decipher and quantify without input from theory. Oxygen substituent effects are configurational and conformational in origin (e.g., axial/equatorial orientation of an OH group in an aldopyranosyl ring; C-O bond conformation involving an exocyclic OH group). DFT studies shed light on these effects, and if conducted properly, yield quantitative relationships between a specific J-coupling and one or more conformational elements in the target molecule. These relationships assist studies of saccharide structure and conformation in solution, which are often challenged by the presence of conformational averaging. Redundant J-couplings, defined as an ensemble of J-couplings sensitive to the same conformational element, are particularly helpful when the element is flexible in solution (i.e., samples multiple conformational states on the NMR time scale), provided that algorithms are available to convert redundant J-values into meaningful conformational models. If the latter conversion is achievable, the data can serve as a means of testing, validating, and refining theoretical methods like molecular dynamics (MD) simulations, which are currently relied upon heavily to assign conformational models of saccharides in solution despite a paucity of experimental data needed to independently validate the method.
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Affiliation(s)
- Thomas Klepach
- Department of Chemistry and Biochemistry, University of Notre Dame, 251 Nieuwland Science Hall, Notre Dame, IN, 46556-5670, USA
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Zhang W, Oliver AG, Vu HM, Duman JG, Serianni AS. Methyl 4-O-β-D-xylopyranosyl β-D-mannopyranoside, a core disaccharide of an antifreeze glycolipid. Acta Crystallogr C 2013; 69:1047-50. [DOI: 10.1107/s0108270113019021] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2013] [Accepted: 07/09/2013] [Indexed: 11/10/2022] Open
Abstract
Methyl β-D-xylopyranosyl-(1→4)-β-D-mannopyranoside, C12<!?tlsb=-0.02pt>H22O10, crystallized as colorless block-like needles from methanol–water solvent. Comparisons to the internal linkage conformations in the two crystallographic forms of the structurally related disaccharide methyl β-D-mannopyranosyl-(1→4)-β-D-xylopyranoside are discussed. Intramolecular inter-residue hydrogen bonding is observed between one mannopyranosyl hydroxy O atom and the ring O atom of the xylopyranosyl residue. Intermolecular hydrogen bonding yields a bilayered two-dimensional sheet of molecules that are located parallel to thebcplane.
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Gubica T, Stępień DK, Pisklak DM, Ostrowski A, Cyrański MK. Single-crystal and powder X-ray diffraction, 13C CP/MAS NMR, and DFT-GIAO calculations of methyl 3,4,6-tri-O-acetyl-2-O-(2,3,4,6-tetra-O-acetyl-β-d-galactopyranosyl)-α-d-glucopyranoside and methyl 2,4,6-tri-O-acetyl-3-O-(2,3,4,6-tetra-O-acetyl-β-d-galactopyranosyl)-α-d-glucopyranoside. J Mol Struct 2013. [DOI: 10.1016/j.molstruc.2012.12.012] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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Zhang W, Oliver AG, Vu HM, Duman JG, Serianni AS. Methyl 4-O-β-D-mannopyranosyl β-D-xylopyranoside. Acta Crystallogr C 2012; 68:o502-6. [DOI: 10.1107/s0108270112046689] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2012] [Accepted: 11/12/2012] [Indexed: 11/10/2022] Open
Abstract
Methyl β-D-mannopyranosyl-(1→4)-β-D-xylopyranoside, C12H22O10, (I), crystallizes as colorless needles from water, with two crystallographically independent molecules, (IA) and (IB), comprising the asymmetric unit. The internal glycosidic linkage conformation in molecule (IA) is characterized by a φ′ torsion angle (O5′Man—C1′Man—O1′Man—C4Xyl; Man is mannose and Xyl is xylose) of −88.38 (17)° and a ψ′ torsion angle (C1′Man—O1′Man—C4Xyl—C5Xyl) of −149.22 (15)°, whereas the corresponding torsion angles in molecule (IB) are −89.82 (17) and −159.98 (14)°, respectively. Ring atom numbering conforms to the convention in which C1 denotes the anomeric C atom, and C5 and C6 denote the hydroxymethyl (–CH2OH) C atom in the β-Xylpand β-Manpresidues, respectively. By comparison, the internal glycosidic linkage in the major disorder component of the structurally related disaccharide, methyl β-D-galactopyranosyl-(1→4)-β-D-xylopyranoside), (II) [Zhang, Oliver & Serriani (2012).Acta Cryst.C68, o7–o11], is characterized by φ′ = −85.7 (6)° and ψ′ = −141.6 (8)°. Inter-residue hydrogen bonding is observed between atoms O3Xyland O5′Manin both (IA) and (IB) [O3Xyl...O5′Maninternuclear distances = 2.7268 (16) and 2.6920 (17) Å, respectively], analogous to the inter-residue hydrogen bond detected between atoms O3Xyland O5′Galin (II). Exocyclic hydroxymethyl group conformation in the β-Manpresidue of (IA) isgauche–gauche, whereas that in the β-Manpresidue of (IB) isgauche–trans.
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French AD. Combining computational chemistry and crystallography for a better understanding of the structure of cellulose. Adv Carbohydr Chem Biochem 2012; 67:19-93. [PMID: 22794182 DOI: 10.1016/b978-0-12-396527-1.00002-4] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
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Zhang W, Oliver AG, Serianni AS. Disorder and conformational analysis of methyl β-D-galactopyranosyl-(1→4)-β-D-xylopyranoside. Acta Crystallogr C 2011; 68:o7-11. [DOI: 10.1107/s0108270111048347] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2011] [Accepted: 11/14/2011] [Indexed: 11/10/2022] Open
Abstract
Methyl β-D-galactopyranosyl-(1→4)-β-D-xylopyranoside, C12H22O10, (II), crystallizes as colorless needles from water with positional disorder in the xylopyranosyl (Xyl) ring and no water molecules in the unit cell. The internal glycosidic linkage conformation in (II) is characterized by a ϕ′ torsion angle (C2′Gal—C1′Gal—O1′Gal—C4Xyl) of 156.4 (5)° and a ψ′ torsion angle (C1′Gal—O1′Gal—C4Xyl—C3Xyl) of 94.0 (11)°, where the ring atom numbering conforms to the convention in which C1 denotes the anomeric C atom, and C5 and C6 denote the hydroxymethyl (–CH2OH) C atoms in the β-Xyl and β-Gal residues, respectively. By comparison, the internal linkage conformation in the crystal structure of the structurally related disaccharide, methyl β-lactoside [methyl β-D-galactopyranosyl-(1→4)-β-D-glucopyranoside], (III) [Stenutz, Shang & Serianni (1999).Acta Cryst.C55, 1719–1721], is characterized by ϕ′ = 153.8 (2)° and ψ′ = 78.4 (2)°. A comparison of β-(1→4)-linked disaccharides shows considerable variability in both ϕ′ and ψ′, with the range in the latter (∼38°) greater than that in the former (∼28°). Inter-residue hydrogen bonding is observed between atoms O3Xyland O5′Galin the crystal structure of (II), analogous to the inter-residue hydrogen bond detected between atoms O3Glcand O5′Galin (III). The exocyclic hydroxymethyl conformations in the Gal residues of (II) and (III) are identical (gauche–transconformer).
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Zhang W, Oliver AG, Serianni AS. Methyl β-D-galactopyranosyl-(1→4)-β-D-allopyranoside tetrahydrate. Acta Crystallogr C 2010; 66:o484-7. [DOI: 10.1107/s0108270110029471] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2010] [Accepted: 07/23/2010] [Indexed: 11/10/2022] Open
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Zhang W, Zhao H, Carmichael I, Serianni AS. An NMR investigation of putative interresidue H-bonding in methyl alpha-cellobioside in solution. Carbohydr Res 2009; 344:1582-7. [PMID: 19632671 DOI: 10.1016/j.carres.2009.06.007] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2009] [Revised: 06/02/2009] [Accepted: 06/03/2009] [Indexed: 11/28/2022]
Abstract
Methyl alpha-cellobioside (methyl beta-D-glucopyranosyl-(1-->4)-alpha-D-glucopyranoside) was labeled with (13)C at C4' for use in NMR studies in DMSO-d(6) solvent to attempt the detection of a trans-H-bond J-coupling ((3h)J(CCOH)) between C4' and OH3. Analysis of the OH3 signal at 600 MHz revealed only the presence of two homonuclear J-couplings: (3)J(H3,OH3) and a smaller, longer range J(HH). No evidence for (3h)J(C4',OH3) was found. The longer range J(HH) was traced to (4)J(H4,OH3) based on 2D (1)H-(1)H COSY data and inspection of the H2 and H4 signal lineshapes. A limited set of DFT calculations was performed on a methyl cellobioside mimic to evaluate the structural dependencies of (4)J(H2,O3H) and (4)J(H4,O3H) on the H3-C3-O3-H torsion angle. Computed couplings range from about -0.7 to about +1.1 Hz, with maximal values observed when the C-H and O-H bonds are roughly diaxial.
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Affiliation(s)
- Wenhui Zhang
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN 46556, United States
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Jockusch RA, Kroemer RT, Talbot FO, Snoek LC, Carçabal P, Simons JP, Havenith M, Bakker JM, Compagnon I, Meijer G, von Helden G. Probing the Glycosidic Linkage: UV and IR Ion-Dip Spectroscopy of a Lactoside. J Am Chem Soc 2004; 126:5709-14. [PMID: 15125663 DOI: 10.1021/ja031679k] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The beta(1-->4) glycosidic linkage found in lactose is a prevalent structural motif in many carbohydrates and glycoconjugates. Using UV and IR ion-dip spectroscopies to probe benzyl lactoside isolated in the gas phase, we find that the disaccharide unit adopts only a single, rigid structure. Its fully resolved infrared ion-dip spectrum is in excellent agreement with that of the global minimum structure computed ab initio. This has glycosidic torsion angles of phi(H) (H1-C1-O-C4') approximately 180 degrees and psi(H) (C1-O-C4'-H4') approximately 0 degrees which correspond to a rotation of approximately 150 degrees about the glycosidic bond compared to the accepted solution-phase conformation. We discuss the biological implications of this discovery and the generality of the strategies employed in making it.
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Affiliation(s)
- Rebecca A Jockusch
- Department of Chemistry, Physical and Theoretical Chemistry Laboratory, Oxford University, Oxford OX1 3QZ, United Kingdom
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