Dielectric Studies on Mobility of the Glycosidic Linkage in Seven Disaccharides
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 studi...
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| Published in: | The journal of physical chemistry. B Vol. 112; no. 40; pp. 12816 - 12823 |
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| Main Authors: | , , , , , , , , , |
| Format: | Journal Article |
| Language: | English |
| Published: |
United States
American Chemical Society
09-10-2008
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| Subjects: | |
| Online Access: | Get full text |
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| Summary: | 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 (γ) 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 β) was recently identified to be intermolecular in origin (i.e., a Johari−Goldstein (JG) β-relaxation), involving twisting motion of the monosugar rings around the glycosidic bond. The activation energies and dielectric strengths for the β-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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| Bibliography: | ark:/67375/TPS-G0X869QR-R istex:B64A25211C6AB6BE3B0A64FC0240629A1E36B3C9 ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 |
| ISSN: | 1520-6106 1520-5207 |
| DOI: | 10.1021/jp804240a |