Mean square fluctuations of hydrogen atoms and water-biopolymer interactions in hydrated saccharides. |
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| Authors: | M Di Bari F Cavatorta A Deriu G Albanese |
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| Affiliation: | Dipartimento di Fisica, Università di Parma and Istituto Nazionale per la Fisica della Materia, Parco Area delle Scienze 7/A, I-43100, Parma, Italy. |
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| Abstract: | We have used the elastic neutron scattering technique to investigate the dynamics of the two main saccharidic components of starch: amylose and amylopectin. The measurements were carried out in the temperature range of 20 to 320 K and at different hydration levels from the dry state up to 0.47 g saccharide/g D(2)O. In the dry samples, the atomic dynamics is harmonic up to approximately 300 K. In the hydrated samples a "glass-like" transition leading to an anharmonic dynamics is observed. The onset of the anharmonicity occurs at temperatures that increase from approximately 180 K to 260 K upon decreasing hydration from 0.5 to 0.1 g saccharide/g D(2)O. This behavior is qualitatively similar to that observed in hydrated globular proteins, but quantitative differences are present. Assuming a simple asymmetric double-well potential model, the temperature and hydration dependence of the transition have been described in terms of few physical parameters. |
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