Investigating the Aqueous Behavior Of D-Glucose, D-Fructose And D-Allulose By Molecular Dynamics (MD) Simulations And Nuclear Magnetic Resonance (NMR) Relaxometry

Balabanlı, Zinnur Yağmur
D-Glucose, D-Fructose and D-Allulose are isomeric monosaccharides, specifically D-allulose and D-fructose are carbon-3 epimers of each other. Although they are very similar in structural properties, physical properties of their solutions and food formulations are observed to be different. This thesis focuses on uncovering the aqueous behavior of these three monosaccharides, by investigating their 10, 20 and 40% (w/w) solutions at the molecular level by molecular dynamics (MD) simulations and NMR relaxometry. Number and occurrence frequency of hydrogen bonds (HB) between sugar-sugar, sugar-water, water-water, radial distribution functions (RDF) of water oxygens around monosaccharide oxygens, and bound water ratio were calculated by MD simulations. Diffusion coefficients of three selected monosaccharides were calculated and measured by both MD and NMR methods. Results showed that, glucose and fructose molecules were not tendent to form both intra and intermolecular HBs with itself or each other at the studied concentrations, allulose was also not tendent to form intermolecular HBs with sugar molecules, but intramolecular bonding was observed to be frequent especially in pyranose forms. For all sugars, sugar-water HBs were present in 100% of trajectory, and glucose was found to be the most successful to cluster water molecules around and form HBs, while allulose was the one with the least water clustering and HB abilities. It was revealed that, epimerization of fructose into allulose improved the intramolecular HB forming tendency of allulose, especially of pyranose forms. RDF results showed that, ring hydroxyl and hydroxyethyl oxygens were better at clustering the water molecules at 0.28nm, than the ring oxygens of all ring forms. β form of glucose was the best to cluster water molecules among all tautomers of all sugars. Configurational changes between fructose and allulose significantly affect the water interaction ability of allulose pyranoses, mainly, O1, O3 and O5 were found to be responsible for the decrease in number of sugar-water interactions. In the case of allulose, frequent occurrence of furanose form in aqueous media and improved intramolecular HB of pyranose form supports the findings. For diffusion coefficients, sugar and water diffusion coefficients were in a decrease with respect to increasing concentration, being in good agreement with the increase in the ratio of bound water molecules with increasing concentration. Also, NMR measurements were sharing the same decreasing trend with calculated values.


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Citation Formats
Z. Y. Balabanlı, “Investigating the Aqueous Behavior Of D-Glucose, D-Fructose And D-Allulose By Molecular Dynamics (MD) Simulations And Nuclear Magnetic Resonance (NMR) Relaxometry,” M.S. - Master of Science, Middle East Technical University, 2022.