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At least 1,207 records · Page 67Linked to original sources
PubMed2000

Surface-enhanced raman spectra of dyes and organic acids in silver solutions: chloride ion effect.

We have recorded surface-enhanced Raman (SER) spectra of two different classes of compounds, cationic dyes and organic acids, and studied their chloride ion effects on the surface-enhanced Raman scattering (SERS) activities of the silver solution. For the positive charge dyes, rhodamine 6G (R6G) and 1,1'-dimethyl-2,2'-cyanine iodide (DECI), no SERS could be observed without the addition of chloride ions because of lack of the electrostatic interaction between the dye species and the silver particles in the silver solution. The chloride ions served to enlarge silver particles and to contribute the existence of the surface active sites, making the silver solution SERS active to the dye samples. Surface-enhanced resonance Raman scattering (SERRS) intensity of the dye molecules increased with the chloride ion concentration. After reaching a maximum intensity, a Cl- quenching effect on the intensity took place. For the organic acids, benzoic acid and p-aminobenzoic acid (PABA), SERS could be observed without the coexistence of chloride ions. The intensity of the Raman scattering did not vary significantly in the presence of small amount of chloride ion. At high Cl- concentration, quenching SERS intensity began to take effect.

4-Aminobenzoic Acid↗
PubMedDate not supplied

Cytotoxicity of antimicrobial tissue conditioners containing silver-zeolite.

PURPOSE: The purpose of this study was to determine the effects of incorporating antimicrobial silver-zeolite on the in vitro cytotoxicities of five tissue conditioners against the living dermal model, which consisted of normal human dermal fibroblasts in a collagen lattice. MATERIALS AND METHODS: Samples of each tissue conditioner containing silver-zeolite (2 wt% and 5 wt%) were prepared; samples without silver-zeolite were used as a control. Cytotoxicity of each sample against the living dermal model was evaluated by cell viability with MTT assay. RESULTS: Cell viabilities for Visco-Gel, GC Soft-Liner, FITT, and SR-Ivoseal decreased with increasing silver-zeolite content. Cell viability for Shofu Tissue Conditioner showed no significant difference with degree of silver-zeolite incorporation and had higher values than other tissue conditioners. CONCLUSION: Individual compounds eluted from tissue conditioners and silver ions released from silver-zeolite might cause such cytotoxicity. The results suggest that Shofu Tissue Conditioner is a possible candidate for a novel antimicrobial tissue conditioner containing silver-zeolite because it showed the highest cell viability and the smallest influence of incorporating silver-zeolite.

Acrylic Resins↗
PubMed1996

Ant opsins: sequences from the Saharan silver ant and the carpenter ant.

cDNA clones encoding opsins from compound eyes of carpenter ant, Camponotus abdominalis, and Saharan silver ant, Cataglyphis bombycina, were isolated from cDNA libraries. The opsin cDNAs from each species code for deduced proteins with 378 amino acids which are 92% identical. Of the 30 amino acid differences between the two proteins, 13 are non-conservative. Eight of these non-conservative substitutions are within the membrane spanning domain. The presence of a potential Schiff-base counterion in helix III in both species suggests that these opsins are the protein moiety of the visible range pigments. When compared to all known opsins, these opsins are most similar to the opsin from preying mantis (76% identity at the amino acid level). Phyletic comparisons group the two ant opsins with the other arthropod long wavelength opsins.

Amino Acid Sequence↗
PubMed2001

[The enhanced mechanism of Cl- to SERS in silver colloid].

The SERS is enhanced when KCl is added to silver colloid and cation molecule. The hypothesis supposed that Cl- bridged between nano-silver and molecule, as a result the molecule adsorbing on nano-silver surface is promoted and the SERS is therefore enhanced. The CN- and NH3 can be better adsorbed when they are added separately to the nano-silver particles, Cl- and anion molecule. The SERS reduces when CN- and NH3 are added separately to Cl-, anion molecule and silver colloid. The result is that the CN- and NH3 are so strong that they have replaced Cl- and anion molecules. Therefore the SERS reduces. This has proved the bridge role of Cl-.

Adsorption↗
PubMed1977

Topical chemotherapy for burns using cerium salts and silver sulfadiazine.

These experimental data indicate that cerium compounds exert a measurable antimicrobial action in vitro. In vivo the simultaneous use of cerium sulfadiazine and silver sulfadiazine was more effective than silver sulfadiazine alone or the combination of cerous nitrate and silver sulfadiazine. When cerous nitrate was used clically, gram-positive bacteria predominated. In contrast, wounds exposed to silver salts alone harbor a predominately gram-negative flora. The combination of cerous nitrate and silver sulfadiazine appears to provide a broad spectrum inhibitory to both types of organisms. It is apparent that a sampling problem exists in any attempt to monitor wounds that may exceed a square meter in extent. These bacteriologic data pertain only to the surface flora. The need to culture tissue samples of burn wounds has been emphasized. Our experience, however, is that invasion of deep tissue without dense surface colonization, greater than 10(5), is infrequent. Furthermore, fragments of eschar were submitted regularly for culture; those results confirmed the surface culture findins. The characteristic yellow-green color of cerium nitrate treated eschars may results from oxidation of trivalent cerium to yellow ceric ions. Free silver and sulfadiazine ions are available also in small amounts because of limited ionization of the highly insoluble silver sulfadiazine. This might promote the in vivo formation of cerous sulfadiazine and would provide a continuous source of ionic cerium for microbial inhibition. The modification of silver sulfadiazine cream by incorporating cerous nitrate into it strikingly enhances its topical antiseptic effect in burn wounds without increasing toxicity.

Administration, Topical↗
PubMed1998

Action of gold chloride ("gold toning") on silver-enhanced 1 nm gold markers.

In conventional immunoelectron microscopy (IEM), very small colloidal gold particles (0.8-3 nm), or the gold compound Nanogold (1.4 nm) are silver-enhanced for easy detection. However, silver enhancement has drawbacks. First, the silver layer is dissolved during fixation with osmium tetroxide, even if the concentration and incubation time are strongly reduced during pre-embedding labeling experiments in transmission electron microscopic (TEM) and scanning electron microscopic (SEM) studies. Second, after exposure to the electron beam the silver layer may migrate on the section or the whole particles may disappear. Sometimes silver migration can be observed even without irradiation. This effect strongly hampers reinvestigation of previously inspected areas, after some time of storage. In both cases, gold chloride treatment after silver enhancement is sufficient to completely protect the silver-enhanced 1 nm gold markers. Gold chloride treatment is part of the so-called "gold toning" procedure, which is a method used to substitute and/or cover the silver by a layer of gold. It can be applied in TEM and SEM experiments. As a serious drawback, gold chloride treatment slightly reduces the size of both unenhanced and silver-enhanced gold particles and can lead to disintegrated silver/gold particles. Therefore, this technique is useful for pre-embedding IEM, on-(resin)section, and ultrathin cryosection labeling experiments. However, it appears to be unsuitable for double-labeling studies using different gold sizes, for quantitation experiments, and in SEM.

Cryoultramicrotomy↗
PubMed2003

A standard for silver CP/MAS experiments.

Silver methanesulfonate, AgSO3CH3, is a photo-stable, commercially available compound which is a superior 109Ag standard for setting up CP/MAS experiments. The 109Ag CP/MAS spectrum at moderate sample spinning speeds easily yields a single, relatively narrow peak with a single transient. The 109Ag chemical shift of solid AgSO3CH3 is 87.2 ppm with respect to a 9 M aqueous solution of AgNO3. The static spectrum yields chemical shift tensor components delta11=191 ppm, delta22=63 ppm and delta33=8 ppm. Therefore the span, Omega, is 183 ppm and the skew, kappa, is -0.39. These values are in accord with the known crystal structure.

Calibration↗
PubMed2006

CH...pi interaction for rhenium-based rectangles: an interaction that is rarely designed into a host-guest pair.

Alkoxy- and thiolato-bridged Re(I) molecular rectangles [{(CO)3Re(mu-ER)2Re(CO)3}2(mu-bpy)2] (ER = SC4H9, 1a; SC8H17, 1b; OC4H9, 2a; OC12H25, 2b; bpy = 4,4'-bipyridine) exhibit strong interactions with several planar aromatic molecules. The nature of their binding was studied by spectral techniques and verified by X-ray diffraction analysis. Standard absorption and fluorescence titrations showed that a relatively strong 1:1 interaction occurs between aromatic guests such as pyrene and these rectangles. The results of a single-crystal X-ray diffraction analysis show that the recognition of 1 with a pyrene molecule is mainly due to CH...pi interactions and the face of the guest pyrene is located over the edges of the bpy linkers of 1. This is a fairly novel example of an interaction that is rarely designed into a host-guest pair. Furthermore, the interaction of 1 with Ag+ results in the self-organization of supramolecular arrays, as revealed by solid-state data.

Crystallography, X-Ray↗
PubMed2006

Dimetallo[3.3]para- and metacyclophanes by self-assembly of pyridylmethyl armed-monoazatrithia- and monoazadithiaoxa-12-crown-4 ethers with Ag+ ions.

New pyridylmethyl armed-monoazadithiaoxa- and monoazatrithia-12-crown-4 have been prepared. The structures of the Ag+ complexes of the new ligands were investigated by X-ray crystallography, 1H NMR titrations, and FAB-MS measurements. In all cases, the Ag+ complexes form dimetallo[3.3]para- or metacyclophane structures depending on the position of the N atom of the pyridine rings.

Crown Ethers↗
PubMed2002

Effects of ligand-bound silver on Ceriodaphnia dubia.

In aqueous media, ionic silver concentrations are low and transport occurs in the colloidal phase. In the aquatic environment, silver forms 1:1 complexes with thiol-containing compounds such as cysteine and glutathione. In order to quantitatively characterize the risk associated with silver in aquatic ecosystems, the bioavailabilities and toxicities of silver cysteinate and silver glutathionate were characterized. Static renewal bioassays were conducted with Ceriodaphnia dubia to estimate chronic toxicity, using mortality and reproduction as endpoints. Silver nitrate was the most lethal compound, with a median lethal concentration (8-d LC50) of 0.32 microg Ag/L (95% confidence interval [CI] = 0.19-0.54). The 48-h LC50 for AgNO3 was 0.5 microg/L and did not change significantly through 8 d. The presence of food in the bioassay did not change the 48-h LC50 for AgNO3. Silver glutathionate (AgGSH) and silver cysteinate (AgCys) induced less mortality during the 8-d bioassay. Silver cysteinate appeared to have the greatest effect on fecundity, with a no-observable-effect concentration (NOEC) less than 0.001 microg/L. Silver nitrate and AgGSH had lowest-observable-effect concentration (LOEC) values (nominal concentrations) of 0.01 and 0.6 microg/L, respectively. Results indicate that the ligand-bound silver in these laboratory studies is bioavailable and impairs reproduction of C. dubia at low aqueous concentrations.

Animals↗
PubMed2004

Solid-state 109Ag CP/MAS NMR spectroscopy of some diammine silver(I) complexes.

Solid-state cross-polarization magic-angle spinning (CP/MAS) NMR spectra were recorded for the compounds [Ag(NH3)2]2SO4, [Ag(NH3)2]2SeO4 and [Ag(NH3))]NO3, all of which contain the linear or nearly linear two-coordinate [Ag(NH3)2]+ ion. The 109Ag CP/MAS NMR spectra show centrebands and associated spinning sideband manifolds typical for systems with moderately large shielding anisotropy, and splittings due to indirect 1J(109Ag,14N) spin-spin coupling. Spinning sideband analysis was used to determine the 109Ag shielding anisotropy and asymmetry parameters Deltasigma and eta from these spectra, yielding anisotropies in the range 1500-1600 ppm and asymmetry parameters in the range 0-0.3. Spectra were also recorded for 15N and (for the selenate) 77Se. In all cases the number of resonances observed is as expected for the crystallographic asymmetric units. The crystal structure of the selenate is reported for the first time. One-bond (107, 109Ag,15N) coupling constants are found to have magnitudes in the range 60-65 Hz. Density functional calculations of the Ag shielding tensor for model systems yield results that are in good agreement with the experimentally determined shielding parameters, and suggest that in the solid compounds Deltasigma and eta are reduced and increased, respectively, from the values calculated for the free [Ag(NH3)2]+ ion (1920 ppm and 0, respectively), primarily as a result of cation-cation interactions, for which there is evidence from the presence of metal-over-metal stacks of [Ag(NH3)2]+ ions in the solid-state structures of these compounds.

Algorithms↗
PubMed2006

Synthesis from caffeine of a mixed N-heterocyclic carbene-silver acetate complex active against resistant respiratory pathogens.

The bis(N-heterocyclic carbene) (NHC) silver complex, 3, with a methyl carbonate anion was formed from the reaction of the iodide salt of methylated caffeine, 1, with silver (I) oxide in methanol. Attempts to crystallize this complex from a mixture of common alcohols and ethyl acetate led to the formation of an NHC-silver acetate complex, 4. The more direct synthesis of 4 was accomplished by the in-situ deprotonation of 1 by silver acetate in methanol. Complex 4 demonstrated antimicrobial activity against numerous resistant respiratory pathogens from the lungs of cystic fibrosis (CF) patients including members of the Burkholderia cepacia complex that cause a high rate of mortality in patients with cystic fibrosis (CF). Application of this NHC silver complex to primary cultures of murine respiratory epithelial cells followed by microarray analysis showed minimal gene expression changes at the concentrations effective against respiratory pathogens. Furthermore, methylated caffeine without silver showed some antibacterial and antifungal activity.

Acetates↗
PubMed2003

Studies in polyphenol chemistry and bioactivity. 4.(1) Synthesis of trimeric, tetrameric, pentameric, and higher oligomeric epicatechin-derived procyanidins having all-4beta,8-interflavan connectivity and their inhibition of cancer cell growth through cell cycle arrest.

We report an improved synthesis of bis(5,7,3',4'-tetra-O-benzyl)epicatechin 4beta,8-dimer (3) from 5,7,3',4'-tetra-O-benzylepicatechin (1) and 5,7,3',4'-tetra-O-benzyl-4-(2-hydroxyethoxy)epicatechin (2) by replacing the previously employed Lewis acid, titanium tetrachloride, with the clay mineral Bentonite K-10. Under the same conditions, the benzyl-protected all-4beta,8-trimer, -tetramer, and -pentamer were obtained regioselectively from their lower homologues, albeit in rapidly decreasing yields. Reaction of 2 with an organoaluminum thiolate generated from 2-mercaptobenzothiazole and trimethylaluminum followed by acetylation produced 3-O-acetyl-4-[(2-benzothiazolyl)thio]-5,7,3',4'-tetra-O-benzylepicatechin (12). Medium-sized protected oligomers with 4beta,8-interflavan linkages are obtained in improved yields by using this compound as the electrophile and silver tetrafluoroborate as activator and are isolated by reversed-phase HPLC. Their deprotection by ester saponification followed by hydrogenolysis yielded the free procyanidins, which were characterized as their peracetates. The synthetic procyanidins are identical by normal-phase HPLC with fractions isolated from cocoa. The principle of chain extension by two members was demonstrated using a dimeric electrophile obtained by self-condensation of compound 12. Both the synthetic and natural pentamer 32 inhibit the growth of several breast cancer cell lines. Using the MDA MB 231 line, it was established that this outcome is based on the induction of cell cycle arrest in the G0/G1 phase. Subsequent cell death is more likely necrotic rather than apoptotic. Control experiments demonstrate that the polyphenol itself, rather than hydrogen peroxide potentially formed by its autoxidation, is the causative agent.

Antineoplastic Agents↗