Mean square fluctuations of hydrogen atoms and water-biopolymer interactions in hydrated saccharides.
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.
Di Bari
M
M
Dipartimento di Fisica, Università di Parma and Istituto Nazionale per la Fisica della Materia, Parco Area delle Scienze 7/A, I-43100, Parma, Italy.
Cavatorta
F
F
Deriu
A
A
Albanese
G
G
D000687:Amylopectin / Q000737:chemistry / Q000378:metabolism*; D000688:Amylose / Q000737:chemistry / Q000378:metabolism*; D001704:Biopolymers / Q000737:chemistry / Q000378:metabolism*; D004548:Elasticity; D006859:Hydrogen / Q000378:metabolism*; D009502:Neutrons; D012542:Scattering, Radiation; D013696:Temperature; D013816:Thermodynamics; D014867:Water / Q000378:metabolism*
D001704:Biopolymers; D014867:Water; D006859:Hydrogen; D000688:Amylose; D000687:Amylopectin