QUANTITATIVE AND QUALITATIVE ESI-TOF STUDY OF METAL CARBOXYLATE RICH LIGAND COMPLEXES INTERACTION WITH CARBOHYDRATES

摘要

Sugar and metal ion interactions have important implications in a variety of biological systems such as supporting in membrane systems, cell-cell adhesion, intercellular recognition, signal transduction, fertilization, and as targets of bacterial or viral infections of cells.[1-3] A structural and functional model of carboxylate rich ligand metal complexes have been developed by Musie et al.[1] This model specifically mimics the active site of the xylose/glucose isomerase coordination. Titrations with different concentration of carbohydrates with iron (III), zinc (II) and copper (II) carboxylate rich ligand complexes using UV-Vis spectroscopy has shown that moderate interaction. Furthermore, NMR studies have shown that the sugars are coordinated to the metal centers through the oxygen at the anomeric carbon. Although NMR was found to be a very helpful tool in getting insight into specific binding to the metal centers, determination of binding constants is found to be difficult. In this study, with the power of a time-of-flight mass spectrometer, a method of online monitoring of the sugar-metal complex formation with identification and quantitation simultaneously has been applied. This MS method can also be applied to complexes which cannot be measured using UV-Vis spectroscopy because of a lack of the necessary chromophore. The characterizations, mode of sugar binding and the apparent binding constants calculated using TOF-MS will be discussed.