| Popis: |
The main objective of the work presented in this thesis was to develop new methods for sugar sensing as well as sugar analysis. Boronic acids were chosen as sugar binding motif because of their affinity to sugars. For this purpose a novel type of boronic acid, 3-Pyridinylboronic acid (3pa), was developed. This boronic acid was identified as a key sensing element for reversible sugar complexation in an aqueous solution at physiological pH. In terms of sugar sensing, 3pba was successfully applied to develop a surface-enhanced Raman glucose sensor. In this study, indirect detection of glucose was demonstrated for the first time by using surface-enhanced Raman spectroscopy. Then, taking advantage of the high binding constant of 3pba with sugars, colorimetric detections of monosaccharides were done using absorption spectroscopy in the visible region. The mechanism of the high diol/triol binding of 3pba in a neutral pH was discussed based on the 1H, 13C, and 11B NMR spectroscopic studies. Monosaccharides as well as disaccharides were explored and K constants were verified by the NMR spectroscopy technique. In terms of sugar analysis, 3pba was used to develop an effective ionization agent for ESI-MS analysis of sugars. It was demonstrated that the dynamic covalent supramolecular binding, between the arylboronic acid and sugars allowed convenient in situ derivatization of the sugar analytes. The zwitterionic nature of 3pba allowed intense ion signals of both the corresponding cations and anions to be observed by a simple switching of the ESI-MS polarity. Isomeric monosaccharides, such as fructose, glucose, and galactose, and isomeric disaccharides, such as lactose and sucrose, were ionized and distinguished by a simple ESI-MS2 experiment. Moreover, zwitterionic aryl boronic acid allowed the facile formations of structurally well-defined gas phase ions with inert charge sites on trisaccharides. As a consequence, successful demonstration of sequencing of a trisaccharide was achieved. |
