A Luminescence Sensor of Inositol 1,4,5-Triphosphate and Its Model Compound by Ruthenium-Templated Assembly of a Bis(Zn 2+ -Cyclen) Complex Having a 2,2′-Bipyridyl Linker (Cyclen ) 1,4,7,10-Tetraazacyclododecane) Shin Aoki,* ,²,‡ Mohd Zulkefeli, § Motoo Shiro, ⊥ Masanori Kohsako, § Kei Takeda, § and Eiichi Kimura | Contribution from the Faculty of Pharmaceutical Sciences and Center for Drug DeliVery Research, Tokyo UniVersity of Science, 2641 Yamazaki, Noda, Chiba, 278-8510 Japan, DiVision of Medicinal Chemistry, Graduate School of Biomedical Sciences, Hiroshima UniVersity, 1-2-3 Kasumi, Minami-ku, Hiroshima, 734-8551 Japan, Rigaku Corporation X-ray Research Laboratory, 3-9-12 Matsubaracho, Akishima, Tokyo, 196-8666 Japan, and Faculty of Integrated Arts and Sciences, Hiroshima UniVersity,1-7-1 Kagamiyama, Higashi-Hiroshima, 739-8521 Japan Received February 10, 2005; E-mail: shinaoki@rs.noda.tus.ac.jp Abstract: A new supramolecular complex (Ru(Zn2L 4 )3) was designed and synthesized as a luminescence sensor for inositol 1,4,5-triphosphate (IP3), which is one of the important second messengers in intracellular signal transduction, and its achiral model compound, cis,cis-1,3,5-cyclohexanetriol triphosphate (CTP3), by a ruthenium(II)-templated assembly of three molecules of a bis(Zn 2+ -cyclen) complex having a 2,2- bipyridyl linker (Zn2L 4 ). Single-crystal X-ray diffraction analysis of a racemic mixture of Ru(Zn2L 4 )3 showed that three of the six Zn 2+ -cyclen units are orientated to face the opposite side of the molecule with three apical ligands (Zn 2+ -bound HO - ) of each of the three Zn 2+ located on the same face. 1 H NMR and UV titrations of Ru(Zn2L 4 )3 with CTP3 indicated that Ru(Zn2L 4 )3 forms a 1:2 complex with CTP3, (Ru(Zn2L 4 )3)- ((CTP3) 6- )2, in aqueous solution at neutral pH. In the absence of guest molecules, Ru(Zn2L 4 )3 (10 µM) has an emission maximum at 610 nm at pH 7.4 (10 mM HEPES with I ) 0.1 (NaNO3)) and 25 °C (excitation at 300 nm). An addition of 2 equiv of CTP3 induced a 4.2-fold enhancement in the emission of Ru(Zn2L 4 )3 at 584 nm. In this article, we describe that Ru(Zn2L 4 )3 is the first chemical sensor that directly responds to CTP3 and IP3 and discriminates these triphosphates from monophosphates and diphosphates. The photodecomposition of Ru(Zn2L 4 )3, which is inhibited upon complexation with CTP3, and the stereoselective complexation of chiral IP3 by Ru(Zn2L 4 )3 are also described. Introduction Inositol 1,4,5-triphosphate (IP 3 ) is one of the important second messengers in intracellular signal transduction. 1 The hydrolysis of phosphatidylinositol 4,5-bisphosphate (PIP 2 ) located in the plasma membrane by a specific phospholipase C (PLC) releases IP 3 , which induces an increase of Ca 2+ concentrations in living cells. To date, a large number of fluorescent probes for Ca 2+ have been developed and used to investigate intracellular events accompanied by the increase in intracellular free Ca 2+ concen- trations. 2,3 Thus far, only a few biological and chemical sensing systems for IP 3 and related phosphates have been developed because IP 3 does not have a chromophore, 4-8 and specific chemical motifs for IP 3 recognition have not been explored. As for biological IP 3 sensors, Hirose and co-workers have developed the green fluorescent protein (GFP)-tagged pleckstrin ² Faculty of Pharmaceutical Sciences, Tokyo University of Science. ‡ Center for Drug Delivery Research, Tokyo University of Science. § Graduate School of Biomedical Sciences, Hiroshima University. ⊥ Rigaku Corporation. | Faculty of Integrated Arts and Sciences, Hiroshima University. (1) (a) Reitz, A. B. Inositol Phosphates and DeriVatiVes; American Chemical Society: Washington, DC, 1991. (b) Berridge, M. J. Nature 1993, 361, 315-325. (c) Potter, B. V. L.; Lampe, D. Angew. Chem., Int. Ed. Engl. 1995, 34, 1933-1972. (d) Taylor, C. W. Biochim. Biophys. Acta 1998, 1436, 19-33. (e) Shears, S. B. Biochim. Biophys. Acta 1998, 1436, 49- 67. (f) Fishman, H. A.; Greenwald, D. R.; Zare, R. N. Annu. ReV. Biophys. Biomol. Struct. 1998, 27, 165-198. (g) Hinterding, K.; Alonso-Dı ´az, D.; Waldmann, H. Angew. Chem., Int. Ed. 1998, 37, 688-749. (h) Taylor, C. W. Biochim. Biophys. Acta 1998, 1436, 19-33. (i) Irvine, R. Curr. Biol. 2001, 11, R172-R174. (j) Taylor, C. W.; Thorn, P. Curr. Biol. 2001, 11, R352-R355. (2) Haugland, R. R. Handbook of Fluorescent Probes and Research Products; Molecular Probes: Eugene, OR, 2002. (3) (a) Grynkiewicz, G.; Poenie, M.; Tsien, R. Y. J. Biol. Chem. 1985, 260, 3440-3450. (b) Minta, A.; Kao, J. P. Y.; Tsien, R. Y. J. Biol. Chem. 1989, 264, 8171-8178. (c) Miyawaki, A.; Griesbeck, O.; Heim, R.; Tsien, R. Y. Proc. Natl. Acad. Sci. U.S.A. 1999, 96, 2135-2140. (4) Hirose, K.; Kadowaki, S.; Tanabe, M.; Takeshima, H.; Iino, M. Science 1999, 284, 1527-1530. Published on Web 06/04/2005 10.1021/ja050876b CCC: $30.25 © 2005 American Chemical Society J. AM. CHEM. SOC. 2005, 127, 9129-9139 9 9129