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PubMed2001

Ebselen prevents excitotoxicity provoked by glutamate in rat cerebellar granule neurons.

Ebselen is a selenium compound that have glutathione peroxidase-like activity which is neuroprotective in acute stroke ischemia. The efficacy of ebselen to prevent excitotoxicity provoked by glutamate in cerebellar granule neurons was investigated at various time points and concentrations. Simultaneous addition of ebselen with glutamate decreased neuronal death and was completely reversed by 3 microM of ebselen (3 (4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) and propidium iodide assays). However, when 1 microM of ebselen was added with glutamate and remained in the culture medium until 24 or 48 h, the neuronal survival increased to the control. The mechanism proposed for neuroprotection was the ability of ebselen to prevent lipoperoxidation provoked by glutamate. The present findings propose to amplify the use of ebselen in others neurodegenerative disorders involving glutamatergic system.

Animals↗
PubMed1998

ICAM-1 and VCAM-1 expression induced by TNF-alpha are inhibited by a glutathione peroxidase mimic.

Intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) are respectively involved in the endothelial recruitment of neutrophils, and in that of lymphocytes or tumor cells, in response to specific signals. We have used the glutathione peroxidase (GPx) mimic BXT-51072 to assess the possibility that endogenous hydroperoxides play a role in the tumor necrosis factor-alpha (TNFalpha)-induced expression of ICAM-1 and VCAM-1 by monolayers of human endothelial cells. The GPx mimic BXT-51072 strongly inhibits the TNFalpha-induced and cycloheximide-sensitive expression of ICAM-1 and VCAM-1. It also inhibits the TNFalpha-induced reorganization of the actin network and the associated formation of stress fibers. Actin reorganization induced by cytochalasin D treatment did not inhibit ICAM-1 expression. Our results are compatible with specific and synergistic effects of endogenous hydroperoxides on the biosynthesis and processing of cell adhesion molecules and cytoskeleton components.

Actins↗
PubMed1990

Approaches to breast cancer prevention.

It may be possible to delay the step-by-step progression towards frank invasive cancer by avoiding one or more of the well-known clinical risk factors. In addition current clinical trials in the USA and Europe are assessing whether the use of tamoxifen, vitamin analogues or a low-fat diet can delay the appearance of overt disease in women known to be at high risk, but it will be several years before such trials can be evaluated. For women seeking advice on prevention, non-toxic supplements to the diet such as beta-carotene, vitamin A analogues or selenium compounds, and the avoidance of alcohol and obesity, are examples of practical advice which can do no harm yet may help to protect against breast cancer development. In the case of the very anxious first degree relative of a breast cancer patient, the current choice lies essentially between regular monitoring, mastectomy with reconstruction, early termination of ovarian activity and anti-oestrogen therapy. Currently, considerable research is being directed towards identifying oncogenes and growth factors which are involved in the growth of breast cancer. In the meantime, more research needs to be devoted to the effect of various progestagens in counteracting oestrogen support of breast cancer growth, and to biological observations on different formulations and doses of combined oestrogen/progestagen preparations which may reduce breast cancer risk both in pre- and postmenopausal women.

Breast Neoplasms↗
PubMed2003

Design, synthesis and glutathione peroxidase-like properties of ovothiol-derived diselenides.

Eleven imidazole diselenides derived from the naturally occurring family of antioxidants, the ovothiols, were synthetised by cyclisation of selenoamides with trimethylsilyltrifluoromethanesulfonate or refluxing of cyanoamines in a selenium/sodium borohydride mixture. These compounds were assayed for their glutathione peroxidase-like (GSH Px-like) activity and their capacity to be reduced by glutathione. The most active molecules of the series were 4 times more potent in the GSH Px-like test than the widely known reference compound, ebselen. This catalytic activity was mediated by the formation of the antioxidant selenol intermediate upon partial but significant exchange reaction with glutathione.

Animals↗
PubMed2001

SeO(2) induces apoptosis with down-regulation of Bcl-2 and up-regulation of P53 expression in both immortal human hepatic cell line and hepatoma cell line.

An immortal human hepatic cell line HL-7702 and human hepatoma cell line SMMC-7721 were treated with 3-30 microM SeO(2). SeO(2) at 30 microM markedly inhibited cell proliferation and viability, and prompted apoptosis of both normal hepatic and hepatoma cells after 48h treatment. SeO(2) could also down-regulate the Bcl-2 level, greatly in HL-7702 and slightly in SMMC-7721 cells, but up-regulate wild type P53 level a little in HL-7702 and significantly in SMMC-7721 cells. The Bcl-2/P53 value was closely correlated with the apoptotic rate as well as SeO(2) concentrations.

Apoptosis↗
PubMed2006

The potential of nuts in the prevention of cancer.

Cancer is a disease that is characterized by the loss of genetic control over cell growth and proliferation, mainly as a result of the exposure to environmental factors. Cessation of smoking and a high consumption of fruits and vegetables are the most important means of reducing the risk of cancer in our society. Like fruits and vegetables, nuts are a source of vegetable protein, monounsaturated fatty acids, vitamin E, phenolic compounds, selenium, vegetable fibre, folic acid and phytoestrogens. There are numerous mechanisms of action by which these components can intervene in the prevention of cancer, although they have not been fully elucidated. There are very few epidemiological studies analyzing the relationship between nuts consumption and risk of cancer. One of the greatest difficulties in interpreting the results is that the consumption of nuts, seeds and legumes are often presented together. The most commonly studied location is the colon/rectum, an organ in which the effect of nuts is biologically plausible. Although the results are not conclusive, a protective effect on colon and rectum cancer is possible. Likewise, some studies show a possible protective effect on prostate cancer, but there is insufficient data on other tumour locations. New epidemiological studies are required to clarify the possible effects of nuts on cancer, particularly prospective studies that make reliable and complete estimations of their consumption and which make it possible to analyse their effects independently of the consumption of legumes and seeds.

Female↗
PubMed2004

Vapor generation by UV irradiation for sample introduction with atomic spectrometry.

Volatile species of the conventional hydride-forming elements (As, Bi, Sb, Se, Sn, Pb, Cd, Te), Hg, transition metals (Ni, Co, Cu, Fe), noble metals (Ag, Au, Rh, Pd, Pt), and nonmetals (I, S) were generated following UV irradiation of their aqueous solutions to which low molecular weight carboxylic acids (formic, acetic, propionic) had been added. Free radicals arising from photodissociation of the latter provide a new and useful alternative to the common methods of chemical/electrochemical vapor generation techniques for the determination of these analytes by atomic spectrometry. Quantitative estimates of the efficiencies of these generation processes were not undertaken, although calculated signal-to-background ratios (>1500 for 5 ng/mL As, Sb, Bi, Se, and Te; 20 for 10 ng/mL Sn, Cu, Rh, Au, Pd, Pt, and Cd; 2400 for 1 ng/mL Hg; and 1000 for Co using ICP-TOF-MS detection) do provide clear evidence of the efficacy of this approach for sample introduction. In the case of Ni and Se, the tetracarbonyl and alkylated selenium compounds have been identified, respectively.

Journal Article↗
PubMed1993

Mutagenesis of structural half-cystine residues in human thioredoxin and effects on the regulation of activity by selenodiglutathione.

A human thioredoxin cDNA was modified to optimize Escherichia coli expression and subcloned into the plasmid pACA, a vector for T7 RNA polymerase-directed expression. The substitution of structural (noncatalytic) half-cystines in human thioredoxin (hTrx) was made by site-directed mutagenesis. The recombinant wild-type (wt) hTrx and its mutant C61S, C72S, and C61S/C72S were expressed and purified to homogeneity. Characterization of the wt and mutant hTrx was done with respect to redox activity with thioredoxin reductase (TR), tryptophan fluorescence, and effects of incubation with GS-Se-SG, which is believed to be the major metabolite of inorganic selenium compounds in mammalian tissues. The Km and kcat of wild-type hTrx for human placenta thioredoxin reductase (HP-TR) at pH 7.0 were 2.0 microM and 2800 min-1, respectively. The mutant proteins C61S, C72S, and C61S/C72S had Km and kcat values similar to those of the wt thioredoxin. Tryptophan fluorescence measurements showed that the wt and mutant proteins had similar stability to a denaturing agent. Incubation of fully reduced thioredoxin with 0.1 molar equivalent of GS-Se-SG resulted in continued oxidation of SH groups. After 3.5 h only 0.5 of initially 4.6 SH groups/thioredoxin remained. With the oxidized protein, a pronounced lag phase in thioredoxin reductase-dependent insulin disulfide reduction was present. Disulfide-linked dimers of the protein were present. The results clearly showed that noncatalytic cysteine residues in hTrx were oxidized accompanied by dimerization and inactivation. The activities of the mutant proteins C72S and C61S/C72S were unchanged after 3 h of incubation with GS-Se-SG. No dimer appeared of the C72S thioredoxin.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed2001

Syntheses and characterization of the metal maleonitrilediselenolates [K([2.2.2]-cryptand)]2[M(Se2C2(CN)2)2] (M = Ni, Pd, Pt) and [Ni(dmf)(5)Cl]2[Ni(Se2C2(CN)2)2].

Reaction of KNH(2), K(2)Se, Se, [2.2.2]-cryptand, and a metal source yields the metal bis(maleonitrilediselenolates) [K([2.2.2]-cryptand)](2)[M(Se(2)C(2)(CN)(2))(2)] (M = Ni, 1; Pd, 2, Pt, 3). These compounds are isostructural and crystallize with four formula units in the monoclinic space group P2(1)/c in cells at T = 153 K with parameters (a (A), b (A), c (A), beta (deg), V (A(3))) of 12.220(1), 15.860(2), 15.306(1), 107.64(2), 2827(1) for 1; 12.291(1), 15.669(1), 15.548(1), 108.55(1), 2839(1) for 2; and 12.292(3), 15.671(3), 15.569(3), 108.59(3), 2842(1) for 3. The cation of 1 has been substituted to yield [Ni(dmf)(5)Cl](2)[Ni(Se(2)C(2)(CN)(2))(2)] (4). [Ni(dmf)(5)Cl](2)[Ni(Se(2)C(2)(CN)(2))(2)] (4) crystallizes with one molecule in the triclinic space group P1 in a cell with parameters (T = 153 K) of a = 8.842(2) A, b =13.161(3) A, c = 13.831(3) A, alpha = 110.08(3) degrees, beta = 95.23(3) degrees, gamma = 93.72(3) degrees, V = 1484(1) A(3). The electronic absorption and infrared spectra are characteristic of metal maleonitrilediselenolates. Cyclic voltammetry shows that the maleonitrilediselenolate (mns) complexes are more easily oxidized than their maleonitriledithiolate (mnt) analogues.

Maleates↗
PubMed2006

Construction of new heteroselenometallic clusters: formation of crownlike [Et4N]4[(mu5-WSe4)(CuI)5(mu-I)2] and octahedral polymeric [(mu6-WSe4)Cu6I4(py)4]n from planar [Et4N]4[(mu4-WSe4)Cu4I6] with additional faces.

The coplanar cluster compound [Et4N]4[(mu4-WSe4)Cu4I6] (1) was prepared from reaction of [Et4N]2[WSe4] with 4 equiv of CuI in N,N-dimethylformamide (DMF) solution in the presence of [Et(4)N]I. Treatment of 1 with pyridine (py) in dry MeCN gave the neutral cluster [(mu4-WSe4)Cu4(py)6I2] (2) in good yield. Recrystallization of 1 from py/i-PrOH resulted in the reorganization of the coplanar WSe4Cu4 core and the formation of a neutral polymeric cluster [(mu3-WOSe3)Cu3(py)3(mu-I)]n (3) containing a nest-shaped OWSe3Cu3 core and a terminal W=O bond. The interaction of cluster 1 with excess PPh3 in CH3Cl3 gave [(mu3-WSe4)Cu3(PPh3)3(mu3-I)] (4) which has a cubanelike SeWSe3Cu3I core. Treatment of 1 with 1 equiv of CuI in dimethyl sulfoxide (DMSO) yielded [Et4N]4[(mu5-WSe4)(CuI)5(mu-I)2] (5) which has a crown-like core structure. Treatment of 1 in DMF with 2 equiv of CuI in the presence of py resulted in the formation of a two-dimensional polymeric cluster, [(mu6-WSe4)Cu6I4(py)4]n (6), consisting of an octahedral WSe4Cu6 repeating unit. The solid-state structures of clusters 3, 5, and 6 have been further established by X-ray crystallography. The nonlinear optical properties of 6 have been also investigated. Cluster 6 was found to exhibit good photostability and a large optical limiting effect with the limiting threshold being ca. 0.3 J cm(-2).

Anions↗
PubMed2006

Mononuclear Ni(III) complexes [NiIII(L)(P(C6H3-3-SiMe3-2-S)3)]0/1- (L = thiolate, selenolate, CH2CN, Cl, PPh3): relevance to the nickel site of [NiFe] hydrogenases.

The stable mononuclear Ni(III)-thiolate complexes [NiIII(L)(P(C6H3-3-SiMe3-2-S)3)]- (L = SePh (2), Cl (3), SEt (4), 2-S-C4H3S (5), CH2CN (7)) were isolated and characterized by UV-vis, EPR, IR, SQUID, CV, 1H NMR, and single-crystal X-ray diffraction. The increased basicity (electronic density) of the nickel center of complexes [NiIII(L)(P(C6H3-3-SiMe3-2-S)3)]- modulated by the monodentate ligand L and the substituted groups of the phenylthiolate rings promotes the stability and reactivity. In contrast to the irreversible reduction at -1.17 V (vs Cp2Fe/Cp2Fe+) for complex 3, the cyclic voltammograms of complexes [NiIII(SePh)(P(o-C6H4S)3)]-, 2, 4, and 7 display reversible NiIII/II redox processes with E(1/2) = -1.20, -1.26, -1.32, and -1.34 V (vs Cp2Fe/Cp2Fe+), respectively. Compared to complex 2 containing a phenylselenolate-coordinated ligand, complex 4 with a stronger electron-donating ethylthiolate coordinated to the Ni(III) promotes dechlorination of CH2Cl2 to yield complex 3 (kobs = (6.01 +/- 0.03) x 10-4 s-1 for conversion of complex 4 into 3 vs kobs = (4.78 +/- 0.02) x 10-5 s-1 for conversion of complex 2 into 3). Interestingly, addition of CH3CN into complex 3 in the presence of sodium hydride yielded the stable Ni(III)-cyanomethanide complex 7 with a NiIII-CH2CN bond distance of 2.037(3) A. The NiIII-SEt bond length of 2.273(1) A in complex 4 is at the upper end of the 2.12-2.28 A range for the NiIII-S bond lengths of the oxidized-form [NiFe] hydrogenases. In contrast to the inertness of complexes 3 and 7 under CO atmosphere, carbon monoxide triggers the reductive elimination of the monodentate chalcogenolate ligand of complexes 2, 4, and 5 to produce the trigonal bipyramidal complex [NiII(CO)(P(C6H3-3-SiMe3-2-S)3]- (6).

Chlorine↗
PubMed2002

Preparation of cadmium selenide-polyolefin composites from functional phosphine oxides and ruthenium-based metathesis.

Cadmium selenide nanoparticles, prepared by known methods, were stabilized with functional phosphine oxide 1, then used to support the polymerization of cyclic olefins radially outward from the surface by ruthenium-catalyzed ring-opening metathesis polymerization (ROMP). The conversion of compound 1 into the new metathesis catalyst 3 by carbene exchange and the subsequent polymerization of cyclic olefins were observed spectroscopically by (1)H NMR to afford for example CdSe-polycyclooctene composite 6. Transmission electron micrographs on thin films of these composites showed good nanoparticle dispersion. This is in stark contrast to the substantial nanoparticle aggregation observed when similar polymerizations were performed in the presence of conventional TOPO-covered nanoparticles. The methods reported here to prepare composite product 6 are applicable to other cyclic olefins, and suggest that this chemistry will be useful for incorporating CdSe nanoparticles into a wide variety of polymer matrices.

Alkenes↗
PubMed2004

Biomimetic studies on anti-thyroid drugs and thyroid hormone synthesis.

The selenium analogues of anti-thyroid drugs exhibit their anti-thyroid action by a mechanism different from that of MMI. The selenium analogue of MMI and related selenium compounds exhibit high GPx activity, providing a novel method for the reversible inhibition of thyroid hormone biosynthesis.

Antithyroid Agents↗
PubMed2005

Light-controlled molecular switches modulate nanocrystal fluorescence.

Spiropyran dyes were attached to fluorescent core-shell CdSe/ZnS nanocrystals via thiol-containing linkers. Photoisomerization of the dye to its merocyanine form by UV irradiation caused a dramatic loss in the intrinsic nanoparticle fluorescence, which was regained upon reversing the isomerization with visible light. The fluorescence quenching efficiency increased with increasing spectral overlap of fluorescence emission and merocyanine adsorption bands, consistent with FRET as the quenching mechanism. Typically, complete quenching required at least 80 bound dye molecules per particle.

Benzopyrans↗
PubMed2004

Self-organized, highly luminescent CdSe nanorod-DNA complexes.

DNA molecules are useful building blocks and nanotemplates for controllable fabrication of various bioinorganic nanostructures due to their unique physical-chemical properties and recognition capabilities and the synthetic availability of desired nucleotide sequences and length. We have synthesized novel DNA complexes with positively charged, highly luminescent CdSe nanorods that can be self-organized into filamentary, netlike, or spheroidal nanostructures. DNA-CdSe-nanorod filaments possess strongly linearly polarized photoluminescence due to the unidirectional orientation of nanorods along the filaments.

Cadmium Compounds↗
PubMed2006

Recognition-directed orthogonal self-assembly of polymers and nanoparticles on patterned surfaces.

We demonstrate the patterning of silica substrates with thymine (Thy-PS) and positively charged N-methylpyridinium (PVMP) polymers using photolithography and the subsequent orthogonal modification of these surfaces using diaminopyridine-functionalized polystyrene (DAP-PS) and carboxylate-derivatized CdSe/ZnS core-shell nanoparticles (COO-NP) through diamidopyridine-thymine three-point hydrogen bonding and pyridinium-carboxylate electrostatic interactions, respectively. This two-component orthogonal surface modification was accomplished in a self-sorting, single-step fashion, providing a versatile tool for the rapid and efficient creation of complex materials.

Cadmium Compounds↗
PubMed2006

Edge-bridged Mo2Fe6S8 to pN-type Mo2Fe6S9 cluster conversion: structural fate of the attacking sulfide/selenide nucleophile.

Reaction of the edge-bridged double cubane cluster [(Tp)(2)M(2)Fe(6)S(8)(PEt(3))(4)] (1; Tp = hydrotris(pyrazolyl)borate(1-)) with hydrosulfide affords the clusters [(Tp)(2)M(2)Fe(6)S(9)(SH)(2)](3)(-)(,4)(-) (M = Mo (2), V), which have been established as the first structural (topological) analogues of the P(N) cluster of nitrogenase. The synthetic reaction is an example of core conversion, resulting in the transformation M(2)Fe(6)(mu(3)-S)(6)(mu(4)-S)(2) (C(i)) --> M(2)Fe(6)(mu(2)-S)(2)(mu(3)-S)(6)(mu(6)-S) (C(2)(v)), the reaction pathway of which is unknown. The most prominent structural feature of P(N)-type clusters is the mu(6)-S atom, which bridges six iron atoms in two MFe(3)S(3) cuboidal halves of the cluster. The initial issue in core conversion is the origin of the mu(6)-S atom. Utilizing SeH(-) as a surrogate reactant for SH(-) in the system 1/SeH(-)/L(-) in acetonitrile, a series of selenide clusters [(Tp)(2)Mo(2)Fe(6)S(8)SeL(2)](3)(-) (L(-) = SH(-) (4), SeH(-) (5), EtS(-) (6), CN(-) (7)) was prepared. The electrospray mass spectra of 4 and 6 revealed inclusion of one Se atom in each cluster, and (1)H NMR spectra and crystallographic refinements of 4-7 indicated that this atom was disordered over the two mu(2)-S/Se positions. The clusters {[(Tp)(2)Mo(2)Fe(6)S(9)](mu(2)-S)}(2)(5)(-) (8) and {[(Tp)(2)Mo(2)Fe(6)S(8)Se](mu(2)-Se)}(2)(5)(-) (9) were prepared from 2 and 5, respectively, and shown to be isostructural. They consist of two P(N)-type cluster units bridged by two mu(2)-S or mu(2)-Se atoms. It is concluded that, in the preparation of 2, the probable structural fate of the attacking nucleophile is as a mu(2)-S atom, and that the mu(3)-S and mu(6)-S atoms of the product cluster derive from precursor cluster 1. Cluster fragmentation during P(N)-type cluster synthesis is unlikely.

Crystallography, X-Ray↗