| Certain sugars react readily with basic silicic acid to form soluble 2/1 (sugar/silicic acid) silicate complexes. The sugar silicates are chelates: five-membered diolato rings. Only furanose forms react. The reaction appears to involve the anomeric position and its adjacent cis hydroxy group. The appropriate furanose form must have sufficient natural abundance and solubility to provide an observable product, as measured by 29Si and 13C NMR spectroscopy. The high selectivity for formation of sugar silicates may have ramifications in prebiotic chemistry.; Binding of a fluorescent sensor Naphthol AS BIOH with amines was study systematically. The sensor forms solvated ion pairs with amines in the excited state. The sensor selectively binds to aliphatic amines, whereas weakly binding to aromatic amines and nitrogen-containing heterocycles. The basicities of amines are critical for the complex formation. No simple correlation, however, was found between the basicities of the amines and the binding constants, which is a combination of at least three factors: amine basicity, hydrogen bonding, and steric effect. The detection limit of the sensor is 1 muM for aliphatic diamines. |
