title: A tong-like fluorescence sensor for metal ions: perfect conformational switch of hinge sugar by pyrene stacking.
abstract: Carbohydrates are among the potential materials for molecular devices, since they are abundant natural resources. However, their rigidity has restricted their use for movable devices. Hinge sugars, 2,4-diamino-2,4-dideoxy-xylopyranosides, shed light on the use of carbohydrates as movable components, as demonstrated by the motion by which all four equatorial substituents can change to an axial orientation in synchronization with a chelation-driven 4C1-1C4 ring flip. In this study, we synthesized a tong-like metal ion sensor, 1,3-di-O-pyrenylmethylated hinge sugar (1), and its model compound, methyl 2,4-di-O-pyrenecarbonyl-xylopyranoside (2), to extend the abilities of hinge sugars as molecular components. From observations of the solvent-dependent conformational and fluorescent behavior of 2, we found that the pyrene stacking assists the 1C4 formation of xylopyranoside by 1.7 kcal mol(-1). We also found that compound 1 produced excimer fluorescence by chelation to Pt2+, Zn2+, Cd2+, Mg2+ or Mn2+, and unexpectedly by addition of acids. 1H NMR measurements ascribed this behavior to the 4C1-1C4 ring flip of hinge sugar in response to chelation or protonation at N2, and revealed rapid and perfect 1C4 formation in the case of Zn2+. These findings will extend the scope of hinge sugars as movable components.
authors.affiliation: Department of Life Science, Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, 4259 B3 Nagatsutacho, Midoriku, Yokohama, 226-8501, Japan. hyuasa@bio.titech.ac.jp
authors.forename: Hideya
authors.initials: H
authors.lastname: Yuasa
authors.forename: Naofusa
authors.initials: N
authors.lastname: Miyagawa
authors.forename: Masatoshi
authors.initials: M
authors.lastname: Nakatani
authors.forename: Masayuki
authors.initials: M
authors.lastname: Izumi
authors.forename: Hironobu
authors.initials: H
authors.lastname: Hashimoto
mesh_terms: D015374:Biosensing Techniques / Q000379:methods*; D002241:Carbohydrates / Q000138:chemical synthesis* / Q000737:chemistry; D005453:Fluorescence; D008670:Metals / Q000737:chemistry*; D008968:Molecular Conformation; D011721:Pyrenes / Q000138:chemical synthesis* / Q000737:chemistry
chemical_list: D002241:Carbohydrates; D008670:Metals; D011721:Pyrenes