A turn-on and reversible fluorescence sensor for zinc ion.

A simple Schiff base type fluorescent receptor was prepared and evaluated for its fluorescence response to heavy metal ions. Receptor 1 exhibits an "off-on-type" mode with high selectivity in the presence of Zn(2+) ion. The addition of EDTA quenches the fluorescence of receptor 1-Zn(2+) complex, making receptor 1 a reversible chemosensor. The selectivity of 1 for Zn(2+) is the consequence of combined effects of CHEF, C=N isomerization and inhibition of ESIPT.

3,3'-Bis(3-meth-oxy-benz-yl)-1,1'-(ethane-1,2-diyl)-diimidazolium dibromide dihydrate.

In the title compound, C(24)H(28)N(4)O(2) (2+)·2Br(-)·2H(2)O, the diimid-azo-lium cation is located on an inversion center. The imidazole and the benzene rings make a dihedral angle of 68.08 (04)°. In the crystal, O-H⋯Br, C-H⋯O and C-H⋯Br hydrogen bonds link the diimidazolium cations, the bromide anions and the water mol-ecules into a two-dimensional network.

3,3'-Dibenzyl-1,1'-ethyl-enediimidazolium dibromide.

In the title compound, C(22)H(24)N(4) (2+)·2Br(-), the imidazolium dication is located on a crystallographic inversion center. The imidazole and benzene rings make a dihedral angle of 73.1 (9)°. In the crystal, non-classical inter-molecular C-H⋯Br hydrogen bonds link the ion pairs into a two-dimensional network.

Curcumin induces apoptosis through FAS and FADD, in caspase-3-dependent and -independent pathways in the N18 mouse-rat hybrid retina ganglion cells.

Curcumin, a naturally occurring yellow pigment isolated from turmeric, is a well known antioxidant with broad spectrum of anti-tumor activities against many human cancer cells. In this study, curcumin-induced cytotoxic effect of mouse-rat hybrid retina ganglion cells (N18) were investigated. For determining cell viability, the trypan blue exclusion and flow cytometric analysis were used. The curcumin-caused cell cycle arrest in N18 cells was examined by flow cytometry. Curcumin affect on the production of reactive oxygen species and Ca2+ and on the decrease of the level of mitochondria membrane potential (DeltaPsim) were also examined by flow cytometry. Curcumin-induced apoptosis was determined by DAPI staining and Western blotting was used for examining the apoptotic signaling proteins. Cell cycle analysis showed that G2/M phase arrest and sub-G1 occurs in N18 cells following 48 h exposure to curcumin. Curcumin also caused a marked increase in apoptosis, as characterized by DNA fragmentation (sub-G1 phase formation) and DAPI staining, and dysfunction of mitochondria, which was associated with the activation of caspase-8, -9 and -3. Curcumin also promoted the levels of Fas and FADD, Bax, cytochrome c release, but decreased the levels of Bcl-2 causing changes of DeltaPsim. Curcumin also induced endoplasmic reticulum stress in N18 cells which was based on the changes of GADD153 and GRP78 and caused Ca2+ release. Curcumin induced apoptosis through the intrinsic pathway and caspase-3-dependent and -independent pathways in N18 cells.

3,3'-Bis(4-fluoro-benz-yl)-1,1'-ethyl-enediimidazolium tribromidocuprate(I).

The title compound, (C(22)H(22)F(2)N(4))[CuBr(3)], crystallizes with the cation situated on an inversion center and the anion on a twofold rotation axis along one Cu-Br bond. The two imidazole rings are in an anti configuration. The anion has a trigonal planar coordination geometry.

Conformational effect of 2,6-bis(imidazol-1-yl)pyridine on the self-assembly of 1D coordination chains: spontaneous resolution, supramolecular isomerism, and structural transformation.

The achiral 2,6-bis(imidazol-1-yl)pyridine (L) was used as the ditopic organic tecton for the formation of coordination polymers with Zn(II) ions. Hydrothermal reaction between L and ZnX2 (X=Br, Cl) afforded spontaneous resolved double helical motifs in ZnLCl2.0.5H2O (1) and ZnLBr2.0.25H2O (2). In the homochiral crystals of 1a and 2a, the helices are of M-helicity, whereas, in 1b and 2b, they are of P-helicity. In contrast, solvothermal reaction between L and ZnCl2 in dried DMF afforded achiral ZnLCl2 (3a), which exhibits a zigzag polymeric motif. An achiral polymorph 3b which contains 21 helical chains was obtained in wet DMF. The formation of different 1D motifs was related to the conformations of L. All these compounds were characterized by infrared spectroscopy, elemental analyses, and single-crystal X-ray diffraction. As revealed by thermal gravimetric analysis and powder X-ray diffraction study, the homochiral motif in 1 was stable even upon removal of guest water molecules. Contrastingly, structural transformation from 3a or 3b to 1 is possible upon hydration.