The crystal and molecular structure of a trisaccharide, β-cellotriose undecaacetate: 1,2,3,6-tetra-O-acetyl-4-O-[2,3,6-tri-O-acetyl-4-O-(2,3,4,6-tetra-O-acetyl-β-<scp>D</scp>-glucopyranosyl)-β-<scp>D</scp>-glucopyranosyl]-β-<scp>D</scp>-glucopyranose

Pérez, Serge; Brisse, F.

doi:10.1107/s0567740877008942

Cited by 36 publications

(3 citation statements)

References 7 publications

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“…The side-chain torsional angles in all calculated structures close to the energy minima represented by p{-108} and a{-107} also agree well with the respective values of the unprimed and primed residues in the peracetylated trimer structure. 30 The main-chain torsional angles and between the unprimed and primed pyranose ring in the trimer are -98°and -143°, respectively, in our notation. These values diverge only slightly from those in the lowenergy structures computed here, although there is no 2-fold helix constraint in the low molecular mass analogues of CTA.…”

Section: Resultsmentioning

confidence: 99%

“…The structural features Geometry of the pyranose ring of the monomer unit (taken from the X-ray structure of the central unit of cellotriose undecaacetate). 30 Bond lengths (large numerals) are in angstroms; bond angles (smaller italic numerals) are in degrees. in Figure 5 were obtained by averaging the bond lengths and bond angles of all acetates (including the terminal ones) in the dimer and the trimer model compounds.…”

Section: Methodsmentioning

confidence: 99%

“…Figure4. Geometry of the pyranose ring of the monomer unit (taken from the X-ray structure of the central unit of cellotriose undecaacetate) 30. Bond lengths (large numerals) are in angstroms; bond angles (smaller italic numerals) are in degrees.…”

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Computation of low-energy crystalline arrangements of cellulose triacetate

Wolf¹,

Francotte²,

Glasser³

et al. 1992

Macromolecules

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Low-energy crystal packings of cellulose triacetate (CTA) have been computed, based on a "two-dimers" unit cell as suggested for CTA I. In addition to the different packing arrangements, parallel versus antiparallel, the effect of changes in the main-chain conformation on the crystal packing was investigated.Minor alterations of the main-chain torsional angles were sometimes found to induce significant changes of unit-cell parameters, although yielding structures with comparable energies. Since small changes of the main-chain conformation do not involve large energy barriers, it is therefore assumed that, in crystalline CTA, local transitions between unit cells with slightly different parameters are possible. Even highly ordered CTA samples might thus consist of a distribution of marginally differing crystalline domains. The resulting imperfections at the interfaces of slightly different unit cells, conceivable on the basis of the computed structures, might explain the problems encountered in the experimental elucidation of the crystal structures in both CTA morphologies, CTA I and CTA II.

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Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

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Computation of low-energy crystalline arrangements of cellulose triacetate

Wolf¹,

Francotte²,

Glasser³

et al. 1992

Macromolecules

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Oligosaccharide Conformations by Diffraction Methods

Pérez

Gautier

Ernst

et al. 2000

Carbohydrates in Chemistry and Biology

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Diffraction by single crystals is by far the most powerful experimental method for the characterization of the atomic arrangements in molecules. X-ray and neutron, are used since their wavelengths are of the same order of magnitude as the interatomic distances, typically around an Angstrom unit. The electron and nuclei are the scatterers of the X ray and neutron incident radiation, respectively. The single crystals are usually grown by slow evaporation of saturated solution under controlled environments. Ideally their dimensions should be in the order of 0.2 to 0.5 mm and over 1.0 mm, in the respective case of studies from X-ray and neutron diffraction. Irradiation of the crystal by a monochromatic beam leads to constructive interferences, known as diffraction, of the scattered waves in specific directions. The diffraction patterns, that are recorded on electronic devices, consist of a series of Bragg reflections. Their positions and intensities, respectively, contain the details on the unit cell dimensions, space group symmetry, and atomic positions. Unit cells are the building block of the crystals. In order to determine the crystal structure, both the amplitude and phase of the diffracted wave in every Bragg reflection are required. While the measured intensities are proportional to the square of the amplitude, the phase of the reflection relative to that of the incident beam is unknown as it cannot be recorded experimentally. There are several ways to calculate the phases of some important reflections, among them direct methods which are now used routinely to solve crystal structures. Using Fourier transform, the amplitude and phase information is used to synthesized electron density maps that reveal the atomic content of the unit cell. Least square refinement methods are then used to minimize the discrepancy between the measured and calculated structure amplitudes. From a knowledge of the final atomic coordinates, the molecular shape is revealed and such structural features as bond lengths, bond angles, torsion angles, hydrogen bonds, intermolecular distances are directly computed.

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Conformational features of oligocellulose acetates in the solid state and their implications for the structures of cellulose triacetate

Pérez

Brisse

1978

Biopolymers

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SynopsisThe crystal data on cellobiose octaacetate and cellotriose undecaacetate are compared in an effort to analyze what information available from crystal structures of oligosaccharides can be used to arrive at the three-dimensional structure of the related polysaccharides. This comparison points out the remarkable behavior of the reducing end of both molecules. The glycosidic torsion angles (4, $) around the reducing and the middle residues in the disaccharide and in the trisaccharide have values around 45" and 14O, while the conformational angles about the nonreducing residues in cellotriose acetate are 24" and -20". The conformations of the primary acetate groups on the two nonreducing residues are similar, but they differ from those observed for the acetate groups belonging to the reducing residues. The possibility of a 21 symmetry axis between contiguous triacetate residues within the oligosaccharide is examined, along with a comparison of the molecular packing found in the oligomer structures. Conformational energy calculations have been performed on two dimeric entities derived from cellotriose acetate. The isoenergy maps show the drastic influence of the relative orientations of the primary acetate groups. It is proposed that the nonreducing dimer, as found in the crystal structure of cellotriose acetate, most nearly expresses the "polymer averaged" interactions for contiguous residues in cellulose triacetate.

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The crystal and molecular structure of a trisaccharide, β-cellotriose undecaacetate: 1,2,3,6-tetra-O-acetyl-4-O-[2,3,6-tri-O-acetyl-4-O-(2,3,4,6-tetra-O-acetyl-β-D-glucopyranosyl)-β-D-glucopyranosyl]-β-D-glucopyranose

Cited by 36 publications

References 7 publications

Computation of low-energy crystalline arrangements of cellulose triacetate

Computation of low-energy crystalline arrangements of cellulose triacetate

Oligosaccharide Conformations by Diffraction Methods

Conformational features of oligocellulose acetates in the solid state and their implications for the structures of cellulose triacetate

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