Dielectric relaxation study of the dynamics of monosaccharides: D-ribose and 2-deoxy-D-ribose

• Published in: Journal of physics. Condensed matter Vol. 20; no. 33; pp. 335104 - 335104 (8)
• Main Authors: Kaminski, K, Kaminska, E, Wlodarczyk, P, Paluch, M, Ziolo, J, Ngai, K L
• Format: Journal Article
• Language: English
• Published: Bristol IOP Publishing 20.08.2008; Institute of Physics
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Dielectric loss and relaxation; Dielectric properties of solids and liquids; Dielectrics, piezoelectrics, and ferroelectrics and their properties; Equations of state, phase equilibria, and phase transitions; Exact sciences and technology; Glass transitions; Physics; Specific phase transitions; Glass transition; Pressure effects; Dielectric losses; Property structure relationship; Activation energy; Structure relaxation; Relaxation time; Monosaccharides; Dielectric relaxation
• ISSN: 0953-8984; 1361-648X
• DOI: 10.1088/0953-8984/20/33/335104

The dielectric loss spectra of two closely related monosaccharides, D-ribose and 2-deoxy-D-ribose, measured at ambient and elevated pressures are presented. 2-deoxy-D-ribose and D-ribose are respectively the building blocks of the backbone chains in the nucleic acids DNA (deoxyribonucleic acid) and RNA (ribonucleic acid). Small differences in the structure between D-ribose and 2-deoxy-D-ribose result in changes of the glass transition temperature Tg, as well as the dielectric strength and activation enthalpy of the secondary relaxations. However, the frequency dispersion of the structural alpha-relaxation for the same relaxation time remains practically the same. Two secondary relaxations are present in both sugars. The slower secondary relaxation shifts to lower frequencies with increasing applied pressure, but not the faster one. This pressure dependence indicates that the slower secondary relaxation is the important and 'universal' Johari-Goldstein beta-relaxation of both sugars according to one of the criteria set up to classify secondary relaxations. Additional confirmation of this conclusion comes from good agreement of the observed relaxation time of the slower secondary relaxation with the primitive relaxation time calculated from the coupling model. All the dynamic properties of D-ribose and 2-deoxy-D-ribose are similar to the other monosaccharides, glucose, fructose, galactose and sorbose, except for the much larger relaxation strength of the alpha-relaxation of the former compared to the latter. The difference may distinguish the chemical and biological functions of D-ribose and 2-deoxy-D-ribose from the other monosaccharides.