Home About us Contact
|
Home About us Contact | ||
|
|
||
Corresponding Ligands (corresponding + ligand)
Selected AbstractsEphrin-A5 regulates the formation of the ascending midbrain dopaminergic pathwaysDEVELOPMENTAL NEUROBIOLOGY, Issue 1 2009Margaret A. Cooper Abstract Dopaminergic neurons from the substantia nigra and the ventral tegmental area of the midbrain project to the caudate/putamen and nucleus accumbens, respectively, establishing the mesostriatal and the mesolimbic pathways. However, the mechanisms underlying the development of these pathways are not well understood. In the current study, the EphA5 receptor and its corresponding ligand, ephrin-A5, were shown to regulate dopaminergic axon outgrowth and influence the formation of the midbrain dopaminergic pathways. Using a strain of mutant mice in which the EphA5 cytoplasmic domain was replaced with ,-galactosidase, EphA5 protein expression was detected in both the ventral tegmental area and the substantia nigra of the midbrain. Ephrin-A5 was found in both the dorsolateral and the ventromedial regions of the striatum, suggesting a role in mediating dopaminergic axon-target interactions. In the presence of ephrin-A5, dopaminergic neurons extended longer neurites in in vitro coculture assays. Furthermore, in mice lacking ephrin-A5, retrograde tracing studies revealed that fewer neurons sent axons to the striatum. These observations indicate that the interactions between ephrin-A ligands and EphA receptors promote growth and targeting of the midbrain dopaminergic axons to the striatum. © 2008 Wiley Periodicals, Inc. Develop Neurobiol, 2009 [source] Tagging (Arene)ruthenium(II) Anticancer Complexes with Fluorescent LabelsEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 18 2007Fabio Zobi Abstract Fluorescent (arene)ruthenium(II) complexes have been prepared by tagging a small fluorogenic reporter onto the chelating ligand of complexes of the type [(,6 -arene)RuCl(Z)]+ (Z = chelating ligand). Complexes [(,6 - p -cym)RuCl(NNO)](Cl) (2), [(,6 - p -cym)RuCl(L3)](Cl) (3) and [(,6 - p -cym)RuCl(L4)](Cl) (4) {p -cym = p- cymene, NNO = 2-[(2-aminoethyl)amino]ethanol, L3 = 2-[(2-aminoethyl)amino]ethyl-2-(methylamino)benzoate and L4 = N -{2-[(2-aminoethyl)amino]ethyl}-2-(methylamino)benzamide} were obtained in good yield from the reaction of the Ru dimer [(,6 - p -cym)RuCl2]2 (1) and the corresponding ligand. The compounds have been fully characterized and their X-ray crystal structures are reported. Compounds 3 and 4 show a photoluminescence response centered at 435 nm with partial fluorescence quenching of the fluorogenic reporters L3 and L4 upon coordination to the metal center. Species 2,4 show good solubility both in water and organic solvents. In water, 2,4 readily hydrolyze to form the aqua complexes. These are stable at acidic pH forming 10,15,% of the corresponding hydroxido complexes in buffered solution (25 mM HEPES) as the pH is raised to a physiological value (pH = 7.44). Under these conditions, 4 (but not 2 or 3) undergoes a fast pH-dependent reversible intramolecular rearrangement. Experimental data and semiempirical calculations indicate that the major species arising from this transformation is a complex with a tridentate chelating ligand following deprotonation at the nitrogen atom of the amide group. Esterase-catalyzed hydrolysis of 3 liberates isatoic acid (MIAH) and generates 2 indicating that the complex is a substrate for the enzyme. Complexes similar to 3 may have potential for esterase-activated Ru-based prodrug delivery systems.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] Pseudo-Octahedral Schiff Base Nickel(II) Complexes: Does Single Oxidation Always Lead to the Nickel(III) Valence Tautomer?EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 27 2008Olaf Rotthaus Abstract With the aim of establishing correlations between the ligand structure and the oxidation site in nickel complexes from Schiff base ligands, five ligands and their nickel complexes have been synthesized. The prototypical asymmetric Schiff base ligand HL1 contains both phenol and pyridine pendant arms with a pivotal imine nitrogen atom. Ligands HL2,5 differ from HL1 by either their phenolate para substituent, the hybridization of the pivotal nitrogen atom, and/or the N-donor properties of the pyridine moiety. The five complexes [Ni(L1,5)2] are obtained by treating the corresponding ligands with 0.5 equiv. of Ni(OAc)2·4H2O in the presence of NEt3. X-ray crystal-structure diffraction studies as well as DFT calculations reveal that [Ni(L1,5)2] involves a high-spin nickel(II) ion within a pseudo-octahedral geometry. The two ligands are arranged in a meridional fashion when the pivotal nitrogen atom is an imine {as in [Ni(L1,2)2] and [Ni(L4,5)2]}, while the fac isomer is preferred in [Ni(L3)2] (amino pivotal nitrogen atom). [Ni(L1)2] is characterized by an oxidation potential at ,0.17 V vs. Fc+/Fc. The one-electron-oxidized species [Ni(L1)2]+ exhibits an EPR signal at g = 2.21 attributed to a phenoxyl radical that is antiferromagnetically coupled to a high-spin NiII ion. [Ni(L2)2] differs from [Ni(L1)2] by the phenolate para substituent (a tert -butyl instead of the methoxyl group) and exhibits an oxidation potential that is ca. 0.16 V higher. Compared to [Ni(L1)2]+ the cation [Ni(L2)2]+ exhibits a SOMO that is more localized on the metal atom. The EPR and electrochemical signatures of [Ni(L3)2]+ are similar to those of [Ni(L1)2]+, thus showing that an imino to amino substitution compensates for a methoxy to tert -butyl one. Replacement of the pyridine by a quinoline group in [Ni(L4,5)2] makes the complexes slightly harder to oxidize. The EPR signatures of the cations [Ni(L4,5)2]+ are roughly similar to those of the pyridine analogs [Ni(L1,2)2]+. The oxidation site is thus not significantly affected by changes in the N-donor properties of the terminal imino nitrogen atom.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] Nickel Complexes and Cobalt Coordination Polymers with Organochalcogen (S, Se) Ligands Bearing an N -Methylimidazole Moiety: Syntheses, Structures, and Properties,EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 26 2008Wei-Guo Jia Abstract The organochalcogen ligands (S, Se) derived from 3-methylimidazole-2-thione/selone groups mbit (2a), mbis (2b), ebit (2c), and ebis (2d) [mbit = 1,1,-methylenebis(1,3-dihydro-3-methyl-2H -imidazole-2-thione), mbis = 1,1,-methylenebis(1,3-dihydro-3-methyl-2H -imidazole-2-selone), ebit = 1,1,-(1,2-ethanediyl)bis(1,3-dihydro-3-methyl-1H -imidazole-2-thione), ebis = 1,1,-(1,2-ethanediyl)bis(1,3-dihydro-3-methyl-1H -imidazole-2-selone)] were synthesized and characterized. Mononuclear NiII complexes NiBr2mbit (3a), NiBr2mbis (3b), NiBr2ebit (3c), and NiBr2ebis (3d) were obtained by the reactions of Ni(PPh3)2Br2 with 2a, 2b, 2c, and 2d, respectively. However, when the corresponding ligands 2a, 2b, 2c, and 2d were treated with CoCl2 in thf solution CoII 1D coordination polymers (CoCl2mbit)n (4a), (CoCl2mbis)n (4b), (CoCl2ebit)n (4c), and (CoCl2ebis)n (4d) were obtained. All compounds were fully characterized by IR spectroscopy and elemental analysis. The crystal structures of 2c, 3a, 3b, 3c, 4a, 4b, and 4c were determined by X-ray crystallography. The local geometry around the nickel atom in complexes 3a,c was distorted tetrahedron with coordinated S(Se) and two Br atoms, and the organochalcogen ligands form an eight- or a nine-membered ring with the nickel atom included. The cobalt atom coordination polymers 4a and 4b coexist as left-handed and right-handed helical chains, but 4c formed a zigzag chain with a CH3CN solvent molecule taken up in the channel structure. After activation with methylaluminoxane (MAO), the nickel complexes exhibited high activities for addition polymerization of norbornene (1.42,×,108 g,PNBmol,1,Nih,1 for 3a). The effects of the Al/Ni ratio, reaction temperature, and reaction time to norbornene polymerization were also investigated.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] Syntheses, Characterization, and Luminescent Properties of Monoethylzinc Complexes with Anilido,Imine LigandsEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 26 2007Qing Su Abstract The syntheses of three anilido,imine ligands of the general formula ortho -C6H4(NHAr,)(CH=NAr, [Ar, = 7-(2,4-Me2)C9H4N, Ar, = 2,6-Me2C6H3 (2a); Ar, = 7-(2,4-Me2)C9H4N, Ar,= 2,6-Et2C6H3 (2b); Ar, = 7-(2,4-Me2)C9H4N, Ar,= 2,6- iPr2C6H3 (2c)] and four zinc(II) complexes of the general formula [ortho -C6H4(NHAr,)(CH=NAr,)]ZnEt [Ar, = 7-(2,4-Me2)C9H4N, Ar,= 2,6-Me2C6H3 (3a); Ar, = 7-(2,4-Me2)C9H4N, Ar,= 2,6-Et2C6H3 (3b); Ar, = 7-(2,4-Me2)C9H4N, Ar, = 2,6- iPr2C6H3 (3c); Ar, = 2,6-Me2C6H3, Ar, = 2,6- iPr2C6H3 (3d)] are described. The complexes were synthesized from the reaction of ZnEt2 with corresponding ligands 2 by alkane elimination. All compounds were characterized by elemental analysis and 1H and 13C NMR spectroscopy. The molecular structures of compounds 2a, 2b, 3b, and 3c were determined by single-crystal X-ray crystallography. The X-ray analysis reveals that complexes 3b and 3c exist in the dimeric form with the N atom in the quinolyl ring coordinating to the other Zn atom to make the Zn atoms four coordinate. Luminescent properties of ligands 2a,2d and complexes 3a,3d in both solution and the solid state were studied. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] A simple and convenient approach for evaluation of the parameters of ligand,receptor interaction.JOURNAL OF MOLECULAR RECOGNITION, Issue 2 2008Receptor blocking index, its application Abstract A new approach for determination of the parameters for ligand-receptor interaction, which is based on so-called dilution coordinates, was developed earlier. Equations that allow evaluation of not only the affinity of ligand-receptor interaction but also of the amount of free (or occupied by corresponding ligand) receptors were suggested. The most important advantage of this approach as compared with well-known methods is the ability to determine the binding parameters for ligand-receptor interaction even for the cases in which ligand and receptor are already present in a mixture and separation of counterparts from each other is technically difficult or even impossible. Due to this reason, the proposed approach can be especially useful for studying interactions between highly-labile biological receptors and corresponding ligands as found in vivo. In the present paper I continue to consider how to determine the binding parameters for a given ligand-receptor interaction if the value of receptor blocking index is determined experimentally. Copyright © 2008 John Wiley & Sons, Ltd. [source] | ||||||||||