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PubMed2001

Effects of metal salts on the oral production of volatile sulfur-containing compounds (VSC).

BACKGROUND/AIM: Halitosis, mainly caused by bacteria located on the posterior dorsum of the tongue and in periodontal pockets, is due to formation of volatile sulfur compounds (VSC). The hypothesis to be tested was that the affinity of a metal for sulfur determines its anti-VSC activity. METHOD: Clinical tests were carried out on 12 subjects who rinsed with cysteine to induce halitosis (baseline) before rinsing with 7.34 mM ZnCl2, SnF2 and CuCl2. Mouth air VSC analyses were repeated following cysteine rinses at 1 h, 2 h and 3 h using a gas chromatograph. In vitro experiments tested toxic metals Hg2+, Pb2+ and Cd2+. 10-microl aliquots of metal salts were added to 1-ml aliquots of human whole saliva from 30 subjects. Samples were incubated overnight at 37oC and saliva headspace was analyzed for VSC in a gas chromatograph. CLINICAL RESULTS: Cu2+>Sn2+>Zn2+ (supports hypothesis). Zn2+ had significantly less anti-VSC effect compared with Cu2+ and Sn2+ at 1, 2 and 3 h. In vitro results indicated that Hg2+, Cu2+ and Cd2+ had close to 100% anti-VSC effect, and that Pb2+ was less effective and Cd2+ more effective than expected in inhibiting VSC. CONCLUSIONS: Apart from Hg2+ and Cu2+, the metals had a significantly greater effect on H2S than on CH3SH. Cu2+ and Hg2+ have well-known antibacterial activity and may presumably also operate by this mechanism.

Adult↗
PubMed2004

Semiconductor quantum dots and free radical induced DNA nicking.

There is a growing interest in the use of semiconductor quantum dots as fluorescent markers in biological applications. However, there are concerns regarding the potential environmental impact and toxic nature of these nanomaterials. In this study, we have investigated the interaction of water-soluble semiconductor quantum dots with supercoiled DNA.

Biosensing Techniques↗
PubMed2006

Mono- vs. bi-metallic assembly on a bulky bis(imino)terpyridine framework: a combined experimental and theoretical study.

The bis(imino)terpyridine ligands, 6,6''-{(2,6-i-Pr2C6H3)N=CR}2-2,2':6',2''-C15H9N3 (R = H L1, Me L2), have been prepared in high yield from the condensation reaction of the corresponding carbonyl compound with two equivalents of 2,6-diisopropylaniline. The molecular structure of L2 reveals a transoid relationship between the imino and pyridyl nitrogen groups throughout the ligand framework. Treatment of aldimine-containing L1 with one equivalent or an excess of MX2 in n-BuOH at 110 degrees C gives the mononuclear five-coordinate complexes, [(L1)MX2] (M = Fe, X = Cl 1a; M = Ni, X = Br 1b; M = Zn, X = Cl 1c), in which the metal centre occupies the terpyridine cavity and the imino groups pendant. Conversely, reaction of ketimine-containing L2 with excess MX2 in n-BuOH at 110 degrees C affords the binuclear complexes, [(L2)M2X4] (M = Fe, X = Cl 3a; M = Ni, X = Br 3b; M = Zn, X = Cl 3c), in which one metal centre occupies a bidentate pyridylimine cavity while the other a tridentate bipyridylimine cavity. 1H NMR studies on diamagnetic 3c suggests a fluxional process is operational at ambient temperature in which the central pyridine ring undergoes an exchange between metal coordination. Under less forcing conditions (room temperature in dichloromethane), the monometallic counterpart of 1b [(L2)NiBr2] (2b) has been isolated which can be converted to 3b by addition of one equivalent of (DME)NiBr2 (DME = 1,2-dimethoxyethane) in n-BuOH at 110 degrees C. Quantum mechanical calculations (DFT) have been performed on [(L1)ZnCl2] and [(L2)ZnCl2] for different monometallic conformations and show that 1a is the energetically preferred structure for L1 while there is evidence for dynamic behaviour in L2-containing species leading to bimetallic formation. Single-crystal X-ray diffraction studies have been performed on 1a, 1b, 1c, 2b, 3a, 3b(H2O) and 3c.

Aniline Compounds↗
PubMed1995

Thymidine free radicals generated during metallo-phthalocyanine photosensitization: a comparison with gamma-radiation.

In order to obtain information concerning the mechanism(s) of metallo-phthalocyanine (MePcS4) photosensitized damage of DNA constituents, the EPR-spin trapping method in conjunction with liquid chromatography was used to study thymidine (dThd) free radicals formed during photosensitization or exposure to gamma-radiation in solution. Under specified conditions two dThd free radical species, 5-hydroxy-5,6-dihydrothymidine-6-yl and 6-hydroxy-5,6-dihydrothymidine-5-yl, were formed both during exposure to ionizing radiation and photosensitization. These results imply that identical reactive intermediates (*OH radicals) are involved in the radiolytic and photosensitized oxidation of dThd. A light-dependent, Fenton-type mechanism is proposed to explain the generation of hydroxyl radicals during MePcS4 photosensitization.

Electron Spin Resonance Spectroscopy↗
PubMed2004

Heptaaquatetra-mu3-hydroxy-hexa-mu2-L-leucine-(L-leucine)tetraytterbium(III) tetrachlorozinc(II) trichlorohydroxyzinc(II) tetrachloride octahydrate.

The title bimetallic compound, [Yb4(mu3-OH)4(C6H13NO2)7(H2O)7][ZnCl4][ZnCl3(OH)]Cl4.8H2O, was synthesized at near physiological pH (6.0). The compound exhibits some novel structural features, including an asymmetric [Yb4(mu3-OH)4(L-leucine)7(H2O)7]8+ complex cation in which four OH groups act as bridging ligands, linking four Yb3+ cations into a Yb4O4 structural unit. Each pair of adjacent Yb3+ ions is further bridged by one carboxy group from a leucine ligand. Water molecules and a monodentate leucine ligand also coordinate to Yb3+ ions, completing their eight-coordinate square-antiprismatic coordination. The Yb4(mu3-OH)4(L-leucine)7(H2O)7]8+ cation, the [ZnCl4]2-, [ZnCl3OH]2- and Cl- anions, and the lattice water molecules are linked via hydrogen bonds.

Crystallography, X-Ray↗
PubMed2002

[Polaprezinc].

Explore the source record for details and available documents.

2-Pyridinylmethylsulfinylbenzimidazoles↗
PubMed2006

Caspase-2: a possible trigger of apoptosis induced in A-549 tumor cells by ZnPc photodynamic treatment.

Photodynamic therapy applied to cell cultures represents a widely accepted experimental method to investigate molecular mechanisms that lead to apoptotic cell death. In this context the subcellular localization of photosensitizers seems to be a significant factor in order to determine the apoptotic pathway that could be activated. We have characterized the experimental conditions that induce apoptotic cell death in A-549 cells incubated with ZnPc and irrradiated with red light. Previously we have found that in this cell line the drug is localized in the Golgi apparatus after 3-h incubation. Indirect immunofluorescence analysis of the events that lead to apoptosis made possible the detection of caspase-2 activation in the Golgi region immediately after photodynamic treatments. A few minutes later, the morphology of this organelle starts to disrupt and just 6 h after treatment the nuclei appear affected showing the fragmented appearance typical of apoptotic cell death. From this results we assume that following the photodynamic treatment of A-549 cells with ZnPc, the activation of caspase-2 in the Golgi apparatus could begin to initiate immediately the apoptotic process.

Adenocarcinoma↗
PubMed1997

Reflections on antireflection films.

BACKGROUND: The development of antireflection films 50 years ago was based on interference of light waves. Antireflection films have broad ophthalmic applications by increasing transmittance and decreasing reflection as a function of wavelength and polarization. Design considerations of thin films are enormous, as are the rigors of successful film production. METHODS: A computer search of optometric and ophthalmologic databases produced very few pertinent references. Discussions with optical engineers led to extensive publications in optical engineering journals and texts. RESULTS: Literature search and interviews with optical engineers provided the historical development, design, and production considerations of optical antireflection coatings. CONCLUSIONS: Ophthalmic thin-film antireflection coatings have a long but unknown development. Many design and production parameters must be considered in producing effective, long-lived ophthalmic coatings, which do offer significant improvement in optical performance.

Eyeglasses↗
PubMed2006

Methoxy-substituted TQEN family of fluorescent zinc sensors.

Two methoxy-substituted TQEN (N,N,N',N'-tetrakis(2-quinolylmethyl)ethylenediamine) derivatives, T(MQ)EN (N,N,N',N'-tetrakis(6-methoxy-2-quinolylmethyl)ethylenediamine) and T(TMQ)EN (N,N,N',N'-tetrakis(5,6,7-trimethoxy-2-quinolylmethyl)ethylenediamine), have been prepared, and their fluorescence properties with respect to Zn2+ coordination were investigated. Introduction of a methoxy substituent at 6-position of the quinoline ring enhances the fluorescence intensity by 10-fold, and the three methoxy substituents in the 5,6,7-positions afford significant enhancement of the long-wavelength component of the fluorescence of zinc complex. The substituents did not alter the binding affinity of these compounds toward zinc ion significantly. T(MQ)EN was proved to be effective in detection of zinc ion in cells by fluorescent microscopy.

Animals↗
PubMed2000

A donor-acceptor compound composed of a dinuclear zinc(II) complex of a robson macrocycle with 8-methylquinoline

A donor-acceptor compound, diaqua-1kappaO,2kappaO-[&mgr;-11, 23-dimethyl-3,7,15,19-tetraazatricyclo[19.3.1.1(9,13)]hexacosa-1(25), 2,7,9,11,13(26),14,19,21,23-decaene-25,26-diolato-1kappa(4)N(3),N(7), O(25),O(26):2kappa(4)N(15),N(19),O(25),O(26)]dizinc(II) diperchlorate bis(8-methylquinoline) ethanol disolvate, [Zn(2)(C(24)H(26)N(4)O(2))(H(2)O)(2)](ClO(4))(2).2C(10)H(9)N. 2C(2)H(6)O, obtained by the reaction of a dinuclear zinc(II) complex of a Robson macrocycle (acceptor) and 8-methylquinoline (donor), lies about an inversion centre and the coordination about the unique Zn atom is a distorted square pyramid. The fifth coordination site is occupied by the water molecule, Zn-O = 2.016 (2) A, and the average macrocyclic Zn-O and Zn-N distances are 2.059 (6) and 2.059 (3) A, respectively.

Journal Article↗
PubMed2005

Fluorescent nanocrystals as colloidal probes in complex fluids measured by fluorescence correlation spectroscopy.

The diffusion properties of fluorescent colloidal CdSe and CdSe/ZnS nanocrystals (QDs) with different hydrophilic coatings were characterized in complex fluids such as actin solutions using fluorescence correlation spectroscopy (FCS). The hydrodynamic radii of the QDs were determined both in organic solvents and water. Attention was given to the potential artifacts arising from the fluorescence properties of the QDs. With increasing excitation intensities, the apparent particle concentration and diffusion times are overestimated if using a simple diffusion model. This can be explained by a numerical simulation. The diffusion behavior of QDs in actin networks of different concentrations was determined to demonstrate the potential use of nanocrystals as probes in soft biological matter. The decreasing diffusion coefficient of the nanocrystals with increasing actin concentration results in an intrinsic polymer viscosity of 0.12+/-0.02 ml mg(-1), in accordance with literature values.

Actins↗
PubMed1993

New drugs and future developments in photodynamic therapy.

New photosensitizing drugs are becoming available which should improve on some of the disadvantages of haematoporphyrin derivates for photodynamic therapy (PDT). The main features are shorter duration of systemic photosensitisation, activation by longer and more penetrating light and better tumour to normal tissue drug uptake ratios. These drugs together with better understanding of in vivo light dosimetry promise to improve both results and clinical acceptability for PDT in future studies.

Aminolevulinic Acid↗
PubMed2004

Biocompatible fluorescent nanocrystals for immunolabeling of membrane proteins and cells.

A methodology for simple convenient preparation of bright, negatively or positively charged, water-soluble CdSe/ZnS core/shell nanocrystals (NCs) and their stabilization in aqueous solution is described. Single NCs can be detected using a standard epifluorescent microscope, ensuring a detection limit of one molecule coupled with an NC. NCs solubilized in water by DL-Cys were stabilized, to avoid aggregation, by poly(allylamine) and conjugated with polyclonal anti-mouse antibodies (Abs). NC-Abs conjugates were tested in dot-blots and exhibited retention of binding capacity within several nanograms of antigen detected. We further demonstrated the advantages of NC-Abs conjugates in the immunofluorescent detection and three-dimensional (3D) confocal analysis of p-glycoprotein (p-gp), one of the main mediators of the MDR phenotype, overexpressed in the membrane of MCF7r breast adenocarcinoma cells. Immunolabeling of p-gp with NC-Abs conjugates was 4200-, 2600-, and 420-fold more resistant to photobleaching than its labeling with fluorescein isothiocyanate-Abs, R-phycoerythrin-Abs, and AlexaFluor488-Abs, respectively. The labeling of p-gp with NC-Abs conjugates was highly specific, and the data were used for confocal reconstruction of 3D images of the p-gp distribution in the MCF7r cell membrane. Finally, we demonstrated the applicability of NC-Abs conjugates obtained by the method described to specific detection of antigens in paraffin-embedded formaldehyde-fixed cancer tissue specimens, using immunostaining of cytokeratin in skin basal carcinoma as an example. We conclude that the NC-Abs conjugates may serve as easy-to-do, highly sensitive, photostable labels for immunofluorescent analysis, immunohistochemical detection, and 3D confocal studies of membrane proteins and cells.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed2005

The inhibition of osteogenesis with human bone marrow mesenchymal stem cells by CdSe/ZnS quantum dot labels.

CdSe/ZnS quantum dots (QDs) have recently been used as cell tracers for long term imaging of live cells. A number of studies indicate that introduction of quantum dots to cells have no apparent deleterious effects on the morphology or growth of cells. In the present study, the human bone marrow mesenchymal stem cells (hBMSCs) were used as a model to examine the effects of QDs on the growth and osteogenic differentiation of the cells. The CdSe/ZnS QDs were delivered into hBMSCs by liposome-mediated transfection with high efficiency; analysis by transmission electron microscopy revealed that the internalized QDs could be located in the endosome-like vesicles. Uptake of QDs into hBMSCs did not affect the proliferation and cell cycle distribution of the cells. When induced to differentiate along the osteogenic lineage, the QD-containing-hBMSCs were shown to have mineral deposition on the extracellular matrix. However, the cells displayed lower alkaline phosphatase activity as compared to those without QDs. Analysis by reverse transcriptase polymerase chain reaction further demonstrated that the expression of two osteogenic markers, osteopontin and osteocalcin, was significantly inhibited. Together our results show that the presence of QDs in hBMSCs prevents the full response of the cells to induced osteogenic differentiation.

Bone Marrow Cells↗