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At least 613 records · Page 34Linked to original sources
PubMed2002

A Raman study of CdSe and ZnSe nanostructures.

Raman studies have been carried out on CdSe nanotubes and ZnSe nanorods produced by surfactant-assisted synthesis. The Raman spectrum of CdSe nanotubes shows modes at 207.5 and 198 cm-1; the former arises from the longitudinal optic phonon mode red-shifted with respect to the bulk mode because of phonon confinement, and the latter is the l = 1 surface phonon. Analysis based on the phonon confinement model demonstrates that the size of the nanoparticle responsible for the red-shift is about 4 nm, close to the estimate from the blue-shift of the photoluminescence. The Raman spectrum of ZnSe nanorods shows modes at 257 and 213 cm-1, assigned to longitudinal and transverse optic phonons, blue-shifted with respect to the bulk ZnSe modes because of compressive strain. The mode at 237 cm-1 is the surface phonon.

Cadmium Compounds↗
PubMed1998

Metal ions suppress the abnormal taste behavior of the Drosophila mutant malvolio.

A mutation in the malvolio (mvl) gene affects taste behavior in Drosophila melanogaster. The malvolio gene encodes a protein (MVL) that exhibits homology to the mammalian natural resistance-associated macrophage proteins. It is also homologous to the Smf1 protein from Saccharomyces cerevisiae, which we have recently demonstrated to function as a Mn2+/Zn2+ transporter. We proposed that the Drosophila and mammalian proteins, like the yeast SMF1 gene product, are metal-ion transporters. To test this hypothesis, malvolio mutant flies were allowed to develop, from egg to adulthood, on a medium containing elevated concentrations of metal ions. Mutant flies that were reared in the presence of 10 mmol l-1 MnCl2 or FeCl2 developed into adults with recovered taste behavior. CaCl2 or MgCl2 had no effect on the mutant's taste perception. ZnCl2 inhibited the effect of MnCl2 when both ions were supplied together. Similar suppression of the abnormal taste behavior was observed when mvl mutants were fed MnCl2 or FeCl2 only at the adult stage. Furthermore, exposure of adult mutant flies to these ions in the testing plate for only 2 h was sufficient to restore normal taste behavior. The suppression of the defective taste behavior suggests that MVL functions as a Mn2+/Fe2+ transporter and that Mn2+ and/or Fe2+ are involved in the signal transduction of taste perception in Drosophila adults.

Animals↗
PubMed2004

[A novel deprotonative functionalization of aromatics with phosphazene base].

A novel type of deprotonative functionalization of aromatics was accomplished with a phosphazene base (t-Bu-P4 base). For various nitrogen heteroaromatics and benzene derivatives, deprotonative 1,2-additions proceeded with the t-Bu-P4 base and ZnI(2) as an additive in the presence of carbonyl compounds. The t-Bu-P4 base has both extremely strong Brønsted basicity and less nucleophilicity due to its huge, widely conjugated structure, and highly chemoselective deprotonations were achieved. In addition the nonmetallic t-Bu-P4 base should not function as a Lewis acid. Therefore the deprotonation with the t-Bu-P4 base is considered to proceed via a different pathway from traditional deprotonative metalation of aromatics with metallic bases. Some reactions with unique regioselectivities were observed.

Benzothiazoles↗
PubMed1992

[Effect of Z-103 on wound healing by dermal incision in guinea pigs].

We investigated the effects of Z-103, ZnSO4, L-carnosine and solcoseryl on wound healing by dermal incision in guinea pigs. The tensile strength, hydroxyproline contents and the value of angiogenesis (carmine contents) at the wounded site of dorsal skin were used as indices of wound healing. Z-103, given daily s.c., increased the tensile strength and hydroxyproline contents on day 4 after operation in a dose-dependent manner; in particular, the effect of 10 mg/kg of Z-103 was nearly equal to that of solcoseryl at 0.5 ml/animal. Moreover, Z-103 10 mg/kg increased the value of angiogenesis on day 3 after the operation. On the other hand, ZnSO4 and L-carnosine, components of Z-103, also similarly increased the tensile strength and hydroxyproline contents. These results suggest that Z-103 possessed an accelerative action on wound healing, and these effects may be due to the activity of its components, ZnSO4 and L-carnosine.

Animals↗
PubMedDate not supplied

[Effect of carbostimulin on acid-base equilibrium of the blood of racing horses during exertion].

The paper deals with possibility to regulate in a proper direction the acid-base state in race horse blood administering carbostimulin at rest and under physical exercises. The preparation is shown to favour an increase in alkaline blood reserves in race hours at rest and to prevent acidotic changes caused by physical exercises. The results obtained show a promising use of carbostimulin for the directed correction of the acid-base state of blood in race horses aimed at increasing the efficiency of the training process.

Acid-Base Equilibrium↗
PubMed2004

Di-mu-sulfito-bis[(4,4'-dimethyl-2,2'-bipyridine)zinc(II)] dihydrate and poly[[aqua(1,10-phenanthroline)zinc(II)]-mu3-sulfito-zinc(II)-mu3-sulfito].

Two different zinc sulfite compounds have been prepared through the decomposition of pyrosulfite-dithionite ions in aqueous solution, viz. a dimeric complex, di-mu-sulfito-kappa3O,O':O'';kappa3O:O',O''-bis[(4,4'-dimethyl-2,2'-bipyridine-kappa2N,N')zinc(II)] dihydrate, [Zn2(SO3)2(C12H12N2)2].2H2O, (I), which was solved and refined from a twinned sample, and an extended polymer, poly[[aqua(1,10-phenanthroline-kappa2N,N')zinc(II)]-mu3-sulfito-kappa2O:O':O''-zinc(II)-mu3-sulfito-kappa3O:O:O'], [Zn2(SO3)2)(C12H10N2)(H2O)]n, (II). In (I), the dinuclear Zn(II) complex has a center of symmetry. The cation is five-coordinate in a square-pyramidal arrangement, the anion fulfilling a bridging chelating role. Compound (II) comprises two different zinc units, one being five-coordinate (square pyramidal) and the other four-coordinate (trigonal pyramidal), and two independent sulfite groups with different binding modes to the cationic centers.

Journal Article↗
PubMed1996

Inactivation of murine leukemia virus by compounds that react with the zinc finger in the viral nucleocapsid protein.

All retroviral nucleocapsid (NC) proteins, except those of spumaretroviruses, contain one or two copies of the conserved sequence motif C-X2-C-X4-H-X4-C. The conserved cysteine and histidine residues coordinate a zinc ion in each such motif. Rice et al. (W. G. Rice, J. G. Supko, L. Malspeis, R. W. Buckheit, Jr., D. Clanton, M. Bu, L. Graham, C. A. Schaeffer, J. A. Turpin, J. Domagala, R. Gogliotti, J. P. Bader, S. M. Halliday, L. Coren, R. C. Sowder II, L. 0. Arthur, and L. E. Henderson, Science 270:1194-1197, 1995) have described a series of compounds which inactivate human immunodeficiency virus type 1 (HIV-1) particles and oxidize the cysteine thiolates in the NC zinc finger. We have characterized the effects of three such compounds on Moloney murine leukemia virus (MuLV). We find that, as with HIV-1, the compounds inactivate cell-free MuLV particles and induce disulfide cross-linking of NC in these particles. The killed MuLV particles were found to be incapable of synthesizing full-length viral DNA upon infection of a new host cell. When MuLV particles are synthesized in the presence of one of these compounds, the normal maturational cleavage of the Gag polyprotein does not occur. The compounds have no effect on the infectivity of human foamy virus, a spumaretrovirus lacking zinc fingers in its NC protein. The resistance of foamy virus supports the hypothesis that the zinc fingers are the targets for inactivation of MuLV and HIV- I by the compounds. The absolute conservation of the zinc finger motif among oncoretroviruses and lentiviruses and the lethality of all known mutations altering the zinc-binding residues suggest that only the normal, wild-type structure can efficiently perform all of its functions. This possibility would make the zinc finger an ideal target for antiretroviral agents.

3T3 Cells↗
PubMed2005

Development of an automated protein-tyrosine phosphatase 1B inhibition assay and the screening of putative insulin-enhancing vanadium(IV) and zinc(II) complexes.

The inhibition of protein-tyrosine phosphatase 1B (PTP1B) is a potential target for treatment of type 2 diabetes. Vanadium and zinc metal coordinated complexes have insulin-enhancing activities, and while vanadium compounds inhibit PTP1B, little is known on the mode of action of zinc compounds. In this study we developed an automated PTP1B inhibition assay that allows for a rapid assessment of the PTP1B inhibition strength of candidate compounds. Synthetic vanadium(IV) and zinc(II) complexes were evaluated: IC50 values for vanadium complexes ranged from 0.06 to 0.8 microM whereas for zinc compounds, values were above 10 microM. Vanadium sulfate, a non-conjugated inorganic salt, had stronger inhibition activity than any of the conjugated metal complexes.

Dose-Response Relationship, Drug↗
PubMed2000

The function of zinc metallothionein: a link between cellular zinc and redox state.

A chemical and biochemical mechanism of action of the metallothionein (MT)/thionein (T) couple has been proposed. The mechanism emphasizes the importance of zinc/sulfur cluster bonding in MT and the significance of the two cluster networks as redox units that confer mobility on otherwise tightly bound and redox-inert zinc in MT. In this article, it is further explored how this redox mechanism controls the metabolically active cellular zinc pool. The low redox potential of the sulfur donor atoms in the clusters readily allows oxidation by mild cellular oxidants with concomitant release of zinc. Such a release by oxidants and the preservation of zinc binding by antioxidants place MT under the control of the cellular redox state and, consequently, energy metabolism. The binding of effectors, e.g., ATP, elicits conformational changes and alters zinc binding in MT. The glutathione/glutathione disulfide redox couple as well as selenium compounds effect zinc delivery from MT to the apoforms of zinc enzymes. This novel action of selenium on zinc/sulfur coordination sites has significant implications for the interaction between these essential elements. Tight binding and kinetic lability, modulation of MT by cellular ligands and the redox state, control of MT gene expression by zinc and many other inducers all support a critical function of the MT/T system in cellular homeostasis and distribution of zinc.

Adenosine Triphosphate↗
PubMed2004

The role of hydrogen bonding in the crystal structures of zinc phosphate hydrates.

The compounds alpha- and beta-hopeite have been synthesised by hydrothermal crystallisation from aqueous solution at 90 degrees C and 20 degrees C, respectively. The crystal structures of these polymorphic forms of zinc phosphate tetrahydrate (ZPT), Zn(3)(PO(4))(2).4 H(2)O, have been resolved. Single-crystal analysis proves that the main difference between the alpha and beta forms of ZPT is caused by the difference in orientation of one of the water molecules in the ZnO(6) octahedral network, indicating two different hydrogen-bonding patterns. A previously unknown hopeite, Zn(3)(HPO(4))(3).3 H(2)O (ZHPT), has been isolated and analysed. This helps to achieve a better understanding of the mechanism of formation of zinc phosphate compounds. Unambiguous identification of each phase is established by analysis of their unique thermal behaviour and thermodynamic interrelationship.

Crystallization↗
PubMed2004

Evaluation of metal-conjugated compounds as inhibitors of 3CL protease of SARS-CoV.

3C-like (3CL) protease is essential for the life cycle of severe acute respiratory syndrome-coronavirus (SARS-CoV) and therefore represents a key anti-viral target. A compound library consisting of 960 commercially available drugs and biologically active substances was screened for inhibition of SARS-CoV 3CL protease. Potent inhibition was achieved using the mercury-containing compounds thimerosal and phenylmercuric acetate, as well as hexachlorophene. As well, 1-10 microM of each compound inhibited viral replication in Vero E6 cell culture. Detailed mechanism studies using a fluorescence-based protease assay demonstrated that the three compounds acted as competitive inhibitors (Ki=0.7, 2.4, and 13.7 microM for phenylmercuric acetate, thimerosal, and hexachlorophene, respectively). A panel of metal ions including Zn2+ and its conjugates were then evaluated for their anti-3CL protease activities. Inhibition was more pronounced using a zinc-conjugated compound (1-hydroxypyridine-2-thione zinc; Ki=0.17 microM) than using the ion alone (Ki=1.1 microM).

Amino Acid Sequence↗
PubMed1994

Interaction of phthalocyanines with lipid membranes: a spectroscopic and functional study on isolated rat liver mitochondria.

Absorption and emission spectroscopic studies on Zn(II)-phthalocyanine (ZnPc) incorporated into unilamellar liposomes of dipalmitoylphosphatidylcholine, sometimes added with cholesterol or cardiolipin, and released to rat liver mitochondria via the three types of liposomal vesicles indicated that: (a) ZnPc predominantly dissolves in all lipid domains of biological membranes with the exception of cardiolipin-containing regions; a partial localization of ZnPc in protein binding sites is also postulated; (b) the spectroscopic properties of ZnPc, although mainly determined by the aggregation state of the dye, are somewhat influenced by the physico-chemical characteristics of the lipid environment; (c) ZnPc-binding lipid domains in mitochondria are mainly localized in the outer membrane; this conclusion is clearly deduced from the trends of Arrhenius plots of the ZnPc fluorescence quantum yield in whole mitochondria and isolated inner or outer membrane in the temperature range -10 degrees C-(+)45 degrees C; (d) the nature of the ZnPc-binding site in mitochondria is not dependent on the chemical composition of the liposome carrier, contrary to what observed for other hydrophobic dyes, such as porphyrins. This has been also confirmed by photosensitization experiments. Actually, illumination of ZnPc-loaded mitochondria by 600-700 nm light causes a decline of the respiratory control ratio, which is essentially dependent on the amount of incorporated photosensitizer, irrespective of the composition of the carrier.

Animals↗
PubMed1994

The assessment of the HO. scavenging action of therapeutic agents.

A new method is reported for the assessment of the HO. scavenging action of therapeutic agents. It is based on the photolysis of zinc oxide and has a detection limit of 3.3%. The scavenging order of the compounds tested was penicillamine > rentiapril > ascorbic acid > cysteine > glutathione > thiomalic acid > N-acetylcysteine > myocrysin > methionine. None were as effective as DMSO. It is argued that these compounds can have an in vivo protective effect where HO. is produced from oxidant producing cells, thus limiting radical induced damage.

Azo Compounds↗
PubMed1996

Apoptosis of mouse MS-2 fibrosarcoma cells induced by photodynamic therapy with Zn (II)-phthalocyanine.

The destructive process of mouse MS-2 fibrosarcoma induced by photodynamic therapy (PDT) with liposome-administered Zn(II)-phthalocyanine (ZnPc) was studied by electron microscopy. Pronounced ultrastructural changes characteristic of apoptosis were observed for several tumour cells, including early occurrence of condensation and margination of chromatin, disappearance of nuclear pores, karyopyknosis, karyorrhexis, protuberance formation at the cell surface and cell fragmentation. The findings indicate that apoptosis was involved in the process of tumour cell death induced by ZnPc-PDT. The detailed mechanism and pathways controlling this phenomenon need to be elucidated further.

Animals↗
PubMed2004

In vitro neuronal cytotoxicity of latex and nonlatex orthodontic elastics.

Although the toxicity of many dental materials has been thoroughly investigated, the toxicity of orthodontic elastic materials has not been extensively tested. We evaluated the neurotoxicity of 3 latex and 3 nonlatex orthodontic elastics in murine cerebral cortical cell cultures. Standard-sized pieces of each material from 3 manufacturers (American, Masel, and GAC) were placed on culture well inserts, allowing the material to be exposed to the culture bathing media without causing physical disruption of the cells. Cell death was quantified by assaying the release of the cytosolic enzyme lactate dehydrogenase. Exposure of cortical cultures to the nonlatex elastics did not cause significant neuronal death, but exposure to each of the latex elastics resulted in significant neuronal death. The neuronal death induced by each of the latex elastics was blocked by adding the metal chelator, EDTA (calcium disodium ethylenediaminetetraacetate). Because many latexes use zinc-containing compounds in the prevulcanization process, and the death induced had characteristics similar to zinc-induced neuronal death, it seems likely that the toxicity of latex elastics was mediated by zinc release. Because ingestion of zinc is not a health risk, the results suggest that, in spite of the finding that latex elastics have higher in vitro cytotoxicity than nonlatex elastics, the use of latex elastics in orthodontics is acceptable.

Analysis of Variance↗
PubMed2005

Stability and quantum yield effects of small molecule additives on solutions of semiconductor nanoparticles.

The effect of additives on the photostability of semiconductor nanoparticles was studied using CdSe, CdSe/ZnSe and CdSe/ZnS particles of various sizes and composition. The additives included phosphine oxides, amines, and antioxidants. Strong initial enhancement of band edge emission by hexadecylamine was observed for the uncoated particles but stability over a week period in light and air was shown to be poor. Inorganic coatings rendered the nanoparticles initially insensitive to additive but provided little extra stability in terms of photoluminescence. Antioxidant was shown to be effective at reducing the rate of photooxidative degradation for all particles in chloroform but not in toluene.

Adsorption↗
PubMed2004

Near-complete suppression of quantum dot blinking in ambient conditions.

Colloidal semiconductor quantum dots are attractive fluorophores for multicolor imaging because of broad absorption and narrow emission spectra, and they are brighter and far more photostable than organic dyes. However, severe intermittence in emission (also known as blinking) has been universally observed from single dots and has been considered an intrinsic limitation difficult to overcome. This is unfortunate because growing applications in spectroscopy of single biological molecules and quantum information processing using single photon sources could greatly benefit from long-lasting and nonblinking single-molecule emitters. For instance, in a recent application of single-dot imaging, the tracking of membrane receptors was interrupted frequently due to the stroboscopic nature of recording. Blinking can also reduce the brightness in ensemble imaging via signal saturation. Here we show that the quantum dot blinking can be suppressed with the emission duty cycle approaching 100% while maintaining biocompatibility.

Biocompatible Materials↗