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J Chem Phys. 2014 ;140(21):215101.
Kossack W1, Kipnusu WK1, Dulski M2, Adrjanowicz K3, Madejczyk O2, Kaminska E4, Mapesa EU1, Tress M1, Kaminski K2, Kremer F1.
1Institute of Experimental Physics, University of Leipzig, Linnestr. 5, 04103 Leipzig, Germany.and
2Institute of Physics, University of Silesia, ul. Uniwersytecka 4, 40-007 Katowice, Poland and Silesian Center of Education and Interdisciplinary Research, University of Silesia, 75 Pulku Piechoty 1A, 41-500 Chorzów, Poland.and
3NanoBioMedical Centre, ul. Umultowska 85, 61-614 Poznan, Poland.and
4Department of Pharmacognosy and Phytochemistry, School of Pharmacy with the Division of Laboratory Medicine in Sosnowiec, Medical University of Silesia in Katowice, ul. Jagiellonska 4, 41-200 Sosnowiec, Poland.
Abstract
Fourier Transform Infrared Spectroscopy and Broadband Dielectric Spectroscopy are combined to trace kinetics of mutarotation in L-fucose. After quenching molten samples down to temperatures between T = 313 K and 328 K, the concentrations of two anomeric species change according to a simple exponential time dependence, as seen by an increase in absorbance of specific IR-vibrations. In contrast, the dielectric spectra reveal a slowing down of the structural (α-) relaxation process according to a stretched exponential time dependence (stretching exponent of 1.5 ± 0.2). The rates of change in the IR absorption for α- and β-fucopyranose are (at T = 313 K) nearly one decade faster than that of the intermolecular interactions as measured by the shift of the α-relaxation. This reflects the fact that the α-relaxation monitors the equilibration at a mesoscopic length scale, resulting from fluctuations in the anomeric composition.
