Effects of solvents on the synthesis of CuInSe2 nanoparticles for thin film solar cells.

Chalcopyrite CuInSe2 (CIS) nanoparticles were synthesized in oleic acid, 1-octadecene, oleyl amine and tetraethylene glycol at temperature above 200 degrees C. Depending on the solvent used and reaction temperature, the obtained nanoparticles had different shapes, sizes, chemical compositions, and crystal and thermal properties. CIS powders synthesized in oleic acid, 1-octadecene and oleyl amine above 200 degrees C exhibited chalcopyrite structure. On the other hand, powders prepared in tetraethylene glycol contained a mixture of CIS and CuSe compounds. The CIS powder obtained in oleyl amine had a high thermal stability over 500 degrees C. CIS thin films prepared from nanoparticles were heat-treated in order to observe changes in their property. After 10 min heat-treatment at 500 degrees C, their crystal structure and chemical composition were slightly changed, and their band gap energies were ca. 1.01 eV except in the case of powders prepared in tetraethylene glycol.

1,3-Bis(6-methyl-pyridin-2-yl)-1H-imidazol-3-ium hexa-fluoro-phosphate.

In the title salt, C17H19N4 (+)·PF6 (-), the two pyridine rings of the cation are inclined to one another by 15.89 (8)°, and inclined to the imidazole ring by 65.05 (10) and 64.07 (10)°. In the crystal, the cations and anions are linked via a series of C-H⋯N and C-H⋯F hydrogen bonds, forming two-dimensional networks lying parallel to (001).

N,N'-Dimethyl-N,N'-bis-(pyridin-2-yl)methane-diamine.

The title compound, C(13)H(16)N(4), consists of two pyridine rings which are linked by an N,N'-dimethyl-methane-amine chain. The pyridine rings adopt a twist conformation and the dihedral angle between them is 60.85 (5)°. The crystal packing is stabilized by weak C-H⋯π inter-actions.

1,3-Bis[(6-methyl-2-pyrid-yl)meth-yl]imidazolium bromide.

The title compound, C(17)H(19)N(4) (+)·Br(-), is built up from 1,3-bis-[(6-methyl-2-pyridin-yl)meth-yl]imidazolium cations and bromide anions. Each of two 6-methyl-2-pyridyl rings is rotated out of the imidazole plane, making dihedral angles of 79.90 (9) and 86.40 (9)°. The packing is consolidated by aromatic π-π inter-actions between the pyridine rings of neighbouring mol-ecules [centroid-centroid distance = 3.554 (2) Å] and by weak C-H⋯N and C-H⋯Br hydrogen bonds.

2-Hydr-oxy-3-nitro-N-phenyl-benzamide.

The asymmetric unit of the title compound, C(13)H(10)N(2)O(4), contains two crystallographically independent mol-ecules. The aromatic rings are oriented at dihedral angles of 24.39 (3) and 7.47 (3)° in the two mol-ecules and intra-molecular N-H⋯O and O-H⋯O hydrogen bonds result in the formation of two planar six-membered rings. In the crystal structure, inter-molecular O-H⋯O and C-H⋯O hydrogen bonds link the mol-ecules into chains, forming R(2) (2)(10) ring motifs. Weak π-π contacts between the benzene and phenyl rings [centroid-centroid distance = 3.955 (3) Å] may further stabilize the structure.

Poly[bis-(N,N-dimethyl-formamide)tris-(µ(4)-trans-stilbene-4,4'-dicarboxyl-ato)-tricadmium(II)]: a two-dimensional network with an unusual 3 topology.

In the title compound, [Cd(3)(C(16)H(10)O(4))(3)(C(3)H(7)NO)(2)](n) or [Cd(3)(SDA)(3)(DMF)(2)](n) (H(2)SDA is trans-stilbene-4,4'-dicarboxylic acid and DMF is dimethyl-formamide), the linear dicarboxylate ligand forms a two-dimensionally layered metal-organic network with the relatively uncommon 3(6) topology. The structure reveals trinuclear secondary building units and has an octa-hedral geometry at a central metal ion (occupying a symmetry site) and tetra-hedral geometries at two surrounding symmetrically equivalent metal ions lying on a threefold axis. The six-connected planar trinuclear Cd(II) centers, Cd(3)(O(2)CR)(6), play a role as potential nodes in generation of the relatively uncommon 3(6) topology. The coordinated DMF unit is disordered around the threefold axis.

Photoinduced cytotoxicity and thioadduct formation by a prodigiosin analogue.

[reaction: see text] The prodigiosin alkaloid 1 and the synthetic analogue 2 show photoinduced cytotoxicity against HL-60 cancer cells. Photoirradiation of 1 and 2 causes photofading, photooxidation, and thioadduct formation. These results provide a model for the redox properties of prodigiosins that play a role in their biological activity and provide a new way to functionalize their pyrromethene entity with water-soluble thiol groups.

Zinc and copper complexes of prodigiosin: implications for copper-mediated double-strand DNA cleavage.

[reaction: see text] Zinc(II) and copper(II) complexes of prodigiosin (1) have been characterized. All N-atoms of 1 bind Cu(II) to generate 5: the complex exhibits regiospecific oxidation of the C-pyrrole. In contrast, coordination by Zn(II) to 1 produces Zn(1)(2) (8), a 4-coordinate tetrahedral complex. The influence of these binding geometries on Cu-mediated double-strand (ds) DNA cleavage by 1 is discussed.

Photochemically catalyzed reaction of ochratoxin A with D- and L-cysteine.

The photolysis (>300 nm) of ochratoxin A (OTA, N-[[(3R)-5-chloro-8-hydroxy-3-methyl-1-oxo-7-isochromanyl]carbonyl]-3-phenyl-L-alanine, 1) in the presence of excess (2 and 12 molar equiv) cysteine (CySH) has been investigated and found to yield sulfur adducts 5 and 6 that are characterized by liquid chromatography-mass spectrometry and 1H-NMR spectroscopy. The adduct 5 was ascribed to the Michael addition conjugate resulting from covalent attachment of CySH to the ochratoxin quinone (4) generated by photooxidation of OTA. This species was also formed by photolysis of a synthetic sample of the hydroquinone of OTA (ochratoxin hydroquinone, 3) in the presence of 12 equiv L-CySH. The conjugate 5 derived from photolysis of 3 with L-CySH was used for 1H-NMR analysis. The sulfur adduct 6 was the major species detected from covalent attachment of CySH to photoactivated OTA, and it resulted from direct displacement of the OTA Cl atom by CySH. The implications of the cysteinyl adducts to the in vivo toxicity of OTA are discussed, with particular emphasis given to conjugate 5, as products from the photooxidative pathway may be of relevance to the nephrotoxic properties of OTA.

Stoichiometric preference in copper-promoted oxidative DNA damage by ochratoxin A.

The ability of the fungal carcinogen, ochratoxin A (OTA, 1), to facilitate copper-promoted oxidative DNA damage has been assessed using supercoiled plasmid DNA (Form I)-agarose gel electrophoresis and gas chromatography-mass spectrometry with selected-ion monitoring (GC-MS-SIM). OTA is shown to promote oxidative cleavage of Form I DNA with optimal cleavage efficiency occurring under excess Cu(II) conditions. As the concentration of OTA was increased and present in excess of Cu(II) the cleavage was less effective. Parallel findings were found for the ability of the OTA-Cu mixture to facilitate oxidative base damage. Yields (lesions per 10(6) DNA bases) of modified bases upon exposure of calf-thymus DNA (CT-DNA) to OTA-H(2)O(2)-Cu(II) were diminished when the OTA:Cu ratio was increased to 5:1. Electrochemical studies carried out in methanol implicate a ligand-centered 2e oxidation of OTA in the presence of excess Cu(II), while product analyses utilizing electrospray mass spectrometry support the intermediacy of the quinone, OTQ (3), in Cu-promoted oxidation of OTA. The implications of these findings with regard to the mutagenicity of OTA are discussed.

Mutagenicity of ochratoxin A and its hydroquinone metabolite in the SupF gene of the mutation reporter plasmid Ps189.

Ochratoxin A (OTA) is a mycotoxin that enhances renal tumor formation in the outer medulla of male rat kidney. Direct DNA damage and subsequent mutagenicity may contribute to these processes. In this study we have determined whether OTA in the absence or presence of activated rat liver microsomes (RLM) or redox-active transition metals (Fe(III) or Cu(II)) causes promutagenic DNA damage in the supF gene of the mutation reporter plasmid pS189 replicating in human Ad293 cells. In addition, we have assessed the mutagenicity of the hydroquinone metabolite (OTHQ) of OTA in the absence or presence of cysteine without added cofactors. Our results show that oxidation of OTA, either by RLM or by transition metal ions, activates OTA to a directly genotoxic mutagen(s). The Fe(III)/OTA system was the most potent mutagen in our experimental system, causing a 32-fold increase in mutant fraction (MF) above the spontaneous control MF. The Cu(II)/OTA system caused a 9-fold increase in MF, while a 6-10-fold increase in MF was observed for OTA in the presence of RLM. The OTHQ metabolite is also mutagenic, especially in the presence of cysteine, in which a 6-fold increase in MF was observed. Our data provide further insight into OTA bioactivation that may account for its in vivo mutagenicity in male rat kidney.

Detection and characterization of a glutathione conjugate of ochratoxin A.

The ability of the carcinogenic mycotoxin ochratoxin A (OTA) to react with reduced glutathione (GSH) has been assessed using electrospray ionization (ES)-MS techniques. On the basis of the assumption that OTA undergoes biotransformation into the reactive quinone species OTQ (6), a synthetic sample of the reduced form of OTQ (6), hydroquinone OTHQ (5), was prepared and photoreacted with 6 M equiv of GSH to yield an authentic sample of the conjugate 8 that was definitively identified by mass spectrometry, UV-vis spectroscopy and NMR. With the authentic sample of 8 in hand, it was demonstrated that the same conjugate is produced from reaction of 100 microM OTA (1) in the presence of 5 mM GSH following incubation for 1 h with either horseradish peroxidase (HRP)/H(2)O(2), rat liver microsomes (RLM)/NADPH or free Fe(II). In each of these oxidative systems the conjugate 8 was generated in less than 1% yield and the parent OTA molecule is poorly metabolized. Comparison of the peak area ratio of the conjugate 8 to that for the hydroxyOTA metabolite from the RLM/NADPH system implied that the conjugate was produced at a rate of approximately 1-3 pmol min(-)(1) (mg of protein)(-)(1). These studies are the first to demonstrate that OTA undergoes biotransformation to a reactive intermediate [OTQ (6)] that covalently reacts with GSH to yield the conjugate 8. The biological implications of the reactivity of OTA toward GSH are discussed.

Influence of the a-ring on the proton affinity and anticancer properties of the prodigiosins.

Prodigiosin (Prod, 1) is the parent member of a class of polypyrrole natural products that exhibit promising immunosuppressive and anticancer activities. They are known to act as H+/Cl- symporters possibly through electrostatic binding to Cl- that facilitates proton-coupled transmembrane transport of halides. This activity has been ascribed to their promotion of apoptosis by acidification of the intracellular pH (pHi). Since the protonated pyrromethene chromophore of Prod (1) is expected to play a critical role in pHi regulation, and the A-pyrrole ring is known to be important for anticancer activity, we prepared several Prod analogues with various A-ring systems to determine their proton affinity in 1:1 (v/v) acetonitrile (MeCN)/H(2)O and anticancer properties against HL-60 cancer cells. Our studies show that the A-ring strongly influences the proton affinity of the pyrromethene entity. Replacement of the C-2 methoxy group in 2,4-dimethoxy-pyrromethene 3 (apparent pK(a) = 4.95) with the A-pyrrole ring to generate the Prod analogue 5 raised the apparent pK(a) to 7.54 (increase by 2.59 pK units) and caused a 76 nm red shift in the UV-vis absorbance of the protonated species (AH+). The A-pyrrole NH atom plays an important role in stabilization of AH+, as its replacement with O or S atoms decreases the apparent pK(a) by 0.79 and 1.07 pK units, respectively. A 4-substituted phenyl series of Prod analogues 8-14 exhibited a linear correlation with the Hammett sigma(p) values. Within the phenyl series, two Prod analogues were found to inhibit colony formation of HL-60 cancer cells, although the inhibition did not correlate with the proton affinity of the pyrromethene entity. The implications of these findings with regard to the anticancer activities of the prodigiosins are discussed.

Molecular aspects of the transport and toxicity of ochratoxin a.

Ochratoxins are a class of naturally occurring compounds produced by several fungi. The most toxic is ochratoxin A (OTA), and occurrence of some human nephropathies and tumors correlate with enhanced OTA exposure. In this Account, the following areas are examined: molecular details of the binding of OTA to human serum albumin (HSA), the influences of binding to HSA on the trans-port of OTA across epithelial cell membranes by organic anion transport proteins, the oxidative activation of OTA, and the formation of OTA adducts with biological molecules. These studies are beginning to provide a detailed chemical model for the trans-port, accumulation, and genotoxic and carcinogenic effects of OTA.

Nickel(II), copper(II) and zinc(II) binding properties and cytotoxicity of tripodal, hexadentate tris(ethylenediamine)--analogue chelators.

Three tripodal hexamine chelators based on cis,cis-1,3,5-triaminocyclohexane (tach) have been synthesized and their aqueous coordination chemistry with Ni(II), Cu(II) and Zn(II) is reported. The chelators have a 2-aminoethyl pendant arm attached to each nitrogen of tach, specifically 'tachen'(N,N',N''-tris(2-aminoethyl)cyclohexane-cis,cis-1,3,5-triamine), and two with S,S,S-chiral pendant arms, 'tachpn'(N,N',N''-tris(2-aminopropyl)cyclohexane-cis,cis-1,3,5-triamine) and 'tachbn'(N,N',N''-tris(2-amino-3-phenylpropyl)cyclohexane-cis,cis-1,3,5-triamine. These chelators complex Ni(II), Cu(II) and Zn(II) in aqueous or aqueous/methanolic medium. The crystalline products [M(II)L](X)2 are isolated, where M = Ni(II), Cu(II) or Zn(II), L = tachen, tachpn or tachbn, and X = ClO4-. Crystallographic study of selected tachpn and tachbn complexes shows the chelate arms are constrained in a Lambda(deltadeltadelta) configuration about M(II), which is attributed to their chirality. Solution UV-vis spectroscopy of the Ni(II) and Cu(II) complexes indicates six-coordination and little effect of the pendant arm substitution on ligand-field strength. The single exception is [Cu(tachbn)]2+, whose spectrum is consistent with five-coordination in solution. The cytotoxicities of tachen, tachpn and tachbn toward cultured cancer cells is in the order tachen < tachpn < tachbn < tachpyr, where tachpyr is the aminopyridyl chelator N,N',N''-tris(2-pyridylmethyl)cyclohexane-cis,cis-1,3,5-triamine. The cytotoxicity difference is attributed to an order of increasing lipophilicity, tachen < tachpn < tachbn.