Structural studies of carbohydrates by deuterium NMR:  sucrose

Tyrell, P. M.; Prestegard, James H.

doi:10.1021/ja00274a023

Cited by 17 publications

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“…The intermolecular nature of the relaxation fits into the category of the so-called Johari−Goldstein β-relaxation according to the classification of secondary relaxations given by ref . Sucrose was the object of very intensive theoretical studies, , and the NMR measurements with particular consideration of its structure and rigidity. ,− Unfortunately, a clear picture has not emerged from these studies. Some authors claimed that sucrose is a rigid molecule and thus motion around the glycosidic bond is blocked, ,, whereas others proved that rotation of the monosugar rings via glycosidic bond is limited but possible. , The relative rigidity of the sucrose in comparison to the other disaccharides is surely a result of the internal hydrogen bond (or bonds) between glucopyranosyl and fructofuranosyl rings.…”

Section: Discussion and Resultsmentioning

confidence: 99%

Dielectric Studies on Mobility of the Glycosidic Linkage in Seven Disaccharides

et al. 2008

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Isobaric dielectric relaxation measurements were performed on seven chosen disaccharides. For five of them, i.e., sucrose, maltose, trehalose, lactulose, and leucrose, we were able to observe the temperature evolution of the structural relaxation process. In the case of the other disaccharides studied (lactose and cellobiose), it was impossible to obtain such information because of the large contribution of the dc conductivity and polarization of the capacitor plates to the imaginary and real part of the complex permittivity, respectively. On the other hand, in the glassy state, two secondary relaxations have been identified in the dielectric spectra of all investigated carbohydrates. The faster one (gamma) is a common characteristic feature of the entire sugar family (mono-, di-, oligo-, and polysaccharide). The molecular origin of this process is still not unambiguously identified but is expected to involve intramolecular degrees of freedom as inferred from insensitivity of its relaxation time to pressure found in some monosaccharides (fructose and ribose). The slower one (labeled beta) was recently identified to be intermolecular in origin (i.e., a Johari-Goldstein (JG) beta-relaxation), involving twisting motion of the monosugar rings around the glycosidic bond. The activation energies and dielectric strengths for the beta-relaxation determined herein provide us valuable information about the flexibility of the glycosidic bond and the mobility of this particular linkage in the disaccharides studied. In turn, this information is essential for the control of the diffusivity of drugs or water entrapped in the sugar matrix.

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Section: Discussion and Resultsmentioning

confidence: 99%

Dielectric Studies on Mobility of the Glycosidic Linkage in Seven Disaccharides

et al. 2008

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“…A simple model permits us to calculate the orientation of the rotation axis of the polar head group from the measured four hydroxyl doublets. A similar procedure was used by Prestegard et al [7,8]. This procedure, as applied to our case, is now described.…”

Section: Hydroxyl Quadrupolar Splittingsmentioning

confidence: 88%

Deuterium NMR studies ofn-octyl α andβ–glucopyranoside liquid-crystalline systems

Loewenstein

Igner

1991

Liquid Crystals

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Deuterium NMR measurements have been performed on mixtures of n-octyla-D-glucopyranoside (aOG) and n-octyl-B-D-glucopyranoside (BOG) with deuteriated water or benzene. The phase diagrams, at high crOG concentrations (lamellar phases), are similar to those reported previously for the B anomer.Deuterium NMR measurements of D,O in mixtures with aOG or BOG at lower concentrations show the existence of additional hexagonal and isotropic (including possibly cubic) phases. Some differences were noted between the phase diagrams of u and BOG at these concentrations. The sign of the diamagnetic anisotropy, Ax, of the S, lamellar phase of aOG/D,O and aOG/C,D, was found to be negative. Slow exchange between the sugar hydroxyl deuterons and water in aOG enabled us to measure their quadrupolar splittings at different temperatures. Using a simple model, where rotation of the polar head as a rigid unit around a single axis is assumed, we have calculated the direction of this axis relative to a molecular axis. The results show that this axis is approximately parallel to the C,-C, axis.

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“…Already during the 1980s, Prestegard and co-workers were exploring orientational and conformational preferences of mono- and disaccharides in membranelike environments using either potassium laurate micelle systems or the more bilayerlike cesium perfluorooctanoate micelles. − In particular, NMR deuterium quadrupolar splittings of labeled carbohydrates were used to interpret experimental observations; both molecular orientation and conformation were adjusted in the search procedure. For organic molecules in general and carbohydrates in particular, RDCs are a source of additional NMR observables that add knowledge about various conformational processes occurring in solution. − …”

Section: Introductionmentioning

confidence: 99%

Molecular Conformations in the Pentasaccharide LNF-1 Derived from NMR Spectroscopy and Molecular Dynamics Simulations

et al. 2011

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The conformational dynamics of the human milk oligosaccharide lacto-N-fucopentaose (LNF-1), α-L-Fucp-(1 → 2)-β-D-Galp-(1 → 3)-β-D-GlcpNAc-(1 → 3)-β-D-Galp-(1 → 4)-D-Glcp, has been analyzed using NMR spectroscopy and molecular dynamics (MD) computer simulations. Employing the Hadamard (13)C-excitation technique and the J-HMBC experiment, (1)H,(13)C trans-glycosidic J coupling constants were obtained, and from one- and two-dimensional (1)H,(1)H T-ROESY experiments, proton-proton cross-relaxation rates were determined in isotropic D(2)O solution. In the lyotropic liquid-crystalline medium consisting of ditetradecylphosphatidylcholine, dihexylphosphatidylcholine, N-cetyl-N,N,N-trimethylammonium bromide, and D(2)O, (1)H, (1)H and one-bond (1)H, (13)C residual dipolar couplings (RDCs), as well as relative sign information on homonuclear RDCs, were determined for the pentasaccharide. Molecular dynamics simulations with explicit water were carried out from which the internal isomerization relaxation time constant, τ(N), was calculated for transitions at the ψ torsion angle of the β-(1 → 3) linkage to the lactosyl group in LNF-1. Compared to the global reorientation time, τ(M), of ∼0.6 ns determined experimentally in D(2)O solution, the time constant for the isomerization relaxation process, τ(N(scaled)), is about one-third as large. The NMR parameters derived from the isotropic solution show very good agreement with those calculated from the MD simulations. The only notable difference occurs at the reducing end, which should be more flexible than observed by the molecular simulation, a conclusion in complete agreement with previous (13)C NMR relaxation data. A hydrogen-bond analysis of the MD simulation revealed that inter-residue hydrogen bonds on the order of ∼30% were present across the glycosidic linkages to sugar ring oxygens. This finding highlights that intramolecular hydrogen bonds might be important in preserving well-defined structures in otherwise flexible molecules. An analysis including generalized order parameters obtained from nuclear spin relaxation experiments was performed and successfully shown to limit the conformational space accessible to the molecule when the number of experimental data are too scarce for a complete conformational analysis.

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Structural studies of carbohydrates by deuterium NMR: sucrose

Cited by 17 publications

References 0 publications

Dielectric Studies on Mobility of the Glycosidic Linkage in Seven Disaccharides

Dielectric Studies on Mobility of the Glycosidic Linkage in Seven Disaccharides

Deuterium NMR studies ofn-octyl α andβ–glucopyranoside liquid-crystalline systems

Molecular Conformations in the Pentasaccharide LNF-1 Derived from NMR Spectroscopy and Molecular Dynamics Simulations

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