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PubMed2003

Bis(2-aminopyridine-kappaN(1))(benzoato-kappaO)silver(I).

In the title compound, [Ag(C(7)H(5)O(2))(C(5)H(6)N(2))(2)], the Ag(I) atom is tricoordinated by two independent pyridine N atoms and one benzoate O atom in a nearly planar geometry. An intramolecular N-H.O hydrogen bond forms an S(8) graph ring. The packing is built from molecular layers stabilized by two types of N-H.O hydrogen bond. Intermolecular Ag.N and intramolecular Ag.O contacts were also observed, together with three weak intermolecular C-H.pi interactions.

Journal Article↗
PubMed2006

Gamma-modification of poly[(N,N-diethyldithiocarbamato)silver(I)].

In the title compound, catena-poly[[trisilver(I)-tri-mu3-N,N-diethyldithiocarbamato-3'kappaS:1kappaS':2kappaS;1kappaS:2kappaS':3kappaS;2kappaS:3kappa2S,S':1'kappaS'], [Ag3(C5H10NS2)3]n, the trigonally and tetrahedrally coordinated Ag atoms are mu3-bridged by kappa3- and kappa4-S2CNEt2 ligands to form a ribbon structure along the c axis. There is a twofold axis parallel to the b axis and passing through the tetrahedrally coordinated Ag atom. The S2CNEt2 ligands coordinate the Ag atoms in eta1,eta2- and eta2,eta2-fashions, depending on the bridging S atoms. The distances between the trigonal Ag and S atoms are 2.4915 (11)-2.6205 (11) A, while those between the tetrahedral Ag and S atoms are 2.5457 (11) and 2.7145 (10) A. The shortest Ag...Ag distance between trigonal Ag atoms is 2.8336 (7) A, which indicates a weak Ag...Ag interaction, whereas the shortest distance between trigonal and tetrahedral Ag atoms is 3.463 (6) A, which is considered as non-bonding.

Journal Article↗
PubMed1997

Nitrosating agents: is peroxynitrite a likely candidate?

The reagents capable of effecting electrophilic and free radical nitrosation are briefly reviewed, together with the appropriate mechanisms, and in the light of these findings the possibilities of peroxynitrite/peroxynitrous acid acting as a nitrosating species are considered. The conclusion is that it is not to be expected that conventional direct nitrosation would occur. However, the very low yields of some nitrosation products can be accounted for in terms of nitrosation via the nitrogen oxide decomposition products of peroxynitrite. Thus NO could react with a radical substrate, or be converted to N2O3 (a well-known nitrosating species), whereas NO2 if formed can nitrosate via N2O4. A short post-script is added reviewing the Cu+-mediated reaction of S-nitrosothiols, generating (at low [thiol]) nitric oxide.

Copper↗
PubMed1998

Separation of cellular iron containing compounds by electrophoresis.

High resolution separation of metalloproteins and other iron compounds based on native gel electrophoresis followed by 59Fe autoradiography is described. Lysates of mouse spleen erythroid cells metabolically labeled with 59Fe-transferrin were separated on 3-20% polyacrylamide gradient gels in the presence of Triton X100 and detected by autoradiography. In addition to ferritin and hemoglobin, several compounds characterized by their binding of iron under different conditions were described. Iron chelatable by desferrioxamine migrated in the region where several high-molecular weight compounds were detected by silver staining. The technique is nondissociative, allowing identification of iron compounds with the use of specific antibodies. Cellular iron transport and the action of iron chelators on specific cellular targets can be investigated in many small biological samples in parallel.

Animals↗
PubMed2004

A scanning electron microscope examination of silver cones removed from endodontically treated teeth. 1972.

Twenty-five silver cones were removed from teeth which had been treated endodontically from 3 months to 20 years previously. Examination by the scanning electron microscope revealed that these cones were moderately to severely corroded. The corrosion patterns were described as ranging from pitting to deep crater formation with globular or spherical agglomerations. Examinations with the electron probe showed sulfur peaks on the corroded portions of the cones. X-ray diffraction analyses indicated that the chemical compounds formed were silver sulfides, silver sulfates, silver carbonates, and silver amine sulfate amide hydrates. Tissue culture studies indicated that the corrosion products were highly cytotoxic. The mechanisms for the formation of the corrosion products have been postulated as being due to plastic deformations and metal transfer to the silver cones, plus contact of the silver with tissue fluids.

Corrosion↗
PubMed2002

Molecular weight distributions of heavy aromatic petroleum fractions by Ag+ electrospray ionization mass spectrometry.

The ability of electrospray ionization mass spectrometry (ESI MS) to analyze heavy aromatic petroleum fractions using silver nitrate as a reagent compound to form characteristic adduct ions has been examined. The complexation of aromatic compounds containing long alkyl substituents with the silver ion leads to the formation of abundant adduct ions such as [M + Ag]+ and [2M + Ag]+. The concentration of the [2M + Ag]+ ions can be reduced by increasing the sampling cone voltage. Molecular ions and other adduct ions may also be formed depending on the structure of the aromatic molecule. Results obtained from the analysis of representative heavy petroleum fractions and vacuum residues by the Ag+ ESI MS method and conventional ionization methods were in good agreement. The current method extends the applicability of electrospray ionization to the analysis of neutral hydrocarbons in heavy aromatic petroleum fractions. It is simple and compatible with widely available LC/MS instrumentation. The extreme complexity of the Ag

Journal Article↗
PubMed1997

Effect of treatment with the neuroactive peptide posatirelin on microanatomical changes of frontal cortex and hippocampus caused by lesions of the locus coeruleus.

The influence of monolateral and bilateral lesions of the Locus coeruleus (LC) on the number of nerve cell and glial fibrillary acidic protein (GFAP)-immunoreactive astrocyte profiles, on silver-gold impregnated fibres and on tyrosine hydroxylase (TH) immunoreactivity was assessed in the rat frontal cortex and hippocampus. The influence of treatment for 4 and 8 weeks with a 10 mg/kg/day dose of the neuroactive peptide posatirelin on the above parameters was also investigated. Lesions of the LC decreased the number of nerve cell profiles in the frontal cortex 8 weeks after lesioning and were without effect on nerve cell profiles in the frontal cortex 4 weeks after lesioning and in the hippocampus at both 4 and 8 weeks after LC lesioning. Glial fibrillary acidic protein (GFAP)-immunoreactive astrocytes were not affected by lesions of LC. Silver-gold impregnated fibres were decreased in the frontal cortex but not in the hippocampus of LC-lesioned rats at 8 weeks after lesioning. TH immunoreactivity, which was localized in nerve fibre-like structures both in the frontal cortex and in the hippocampus was decreased in the frontal cortex and in the hippocampus from the 4th week after LC lesioning. Treatment with posatirelin was without effect on the number of nerve cell and of GFAP-immunoreactive astrocyte profiles at both 4 and 8 weeks after LC lesioning, with the exception of nerve cells of the frontal cortex in monolaterally-lesioned rats which were increased 8 weeks after lesioning. The compound increased silver-gold impregnated fibres in the frontal cortex of monolaterally lesioned rats after 8 weeks of treatment, but did not affect TH immunoreactivity both in the frontal cortex or in the hippocampus. The above results suggest that treatment with posatirelin exerts a neuroprotective effect on the frontal cortex consisting of the partial restoration of some microanatomical changes caused by lesions of LC. The possible significance of this effect is discussed.

Animals↗
PubMed2005

Monoclinic and triclinic concomitant polymorphs of di-mu-pyridazine-1kappa(2)N:2kappa(2)N'-bis[(saccharinato)silver(I)].

Crystallization of the title compound, di-mu-pyridazine-1kappa(2)N:2kappa(2)N'-bis[(2,3-dihydro-3-oxobenzisosulfonazolato-kappaN)silver(I)], [Ag2(C7H4NO3S)2(C4H4N2)2], from acetonitrile yields both monoclinic, (I), and triclinic, (II), polymorphs. In both forms, the silver(I) ions have a slightly distorted trigonal AgN(3) coordination geometry and are doubly bridged by two neutral pyridazine (pydz) ligands, generating a centrosymmetric dimeric structure. The saccharinate (sac) ligands are N-coordinated. The dihedral angles between the sac and pydz rings are 8.43 (7) and 7.94 (8) degrees in (I) and (II), respectively, suggesting that the dimeric molecule is nearly flat. The bond geometry is similar in both polymorphs. In (I), the dimers interact with each other via aromatic pi(sac)-pi(pydz) stacking interactions, forming two-dimensional layers, which are further crosslinked by weak C-H...O interactions. Compound (II) exhibits similar C-H...O and pi-pi interactions, but additional C-H...pi and pi...Ag interactions help to stabilize the packing of the dimers.

Journal Article↗
PubMed1985

Ultrastructural autometallography: a method for silver amplification of catalytic metals.

The autometallographic technique involves application of a silver bromide-containing emulsion on the surface of ultrathin sections placed on grids that are subsequently exposed to a photographic developer. In tissue sections from animals treated intravitally with gold, silver, or mercury compounds, accumulations of the metals are visualized by autometallography and can be used for quantitative studies. After amplification, sections can be stained with lead citrate and uranyl acetate. Using autometallography, particles of colloidal gold dispersed in a film of gelatin showed a time-dependent growth and were gradually amplified up to 3.5-fold after 15 min of development. Hence the method may prove useful tracing colloidal gold particles in sections with low particle density, and be a powerful tool for revealing metals in biological tissues.

Animals↗
PubMed1986

Purification, biochemical properties and active sites of N-acetyl-beta-D-hexosaminidases from human seminal plasma.

Two isoenzymes of N-acetyl-beta-D-glucosaminidase (EC 3.2.1.30) (Hex A and Hex B) from human seminal plasma were purified to homogeneity with specific activities of 26 and 60 units/mg of protein respectively. N-Acetyl-beta-D-glucosaminidase activity was inseparable from N-acetyl-beta-D-galactosaminidase activity in both Hex A and Hex B by various conventional chromatographic procedures. Although Km values of N-acetyl-beta-glucosaminidase activity of Hex A and Hex B were similar (1.33 mM), those of N-acetyl-beta-galactosaminidase activity were 0.14 mM for Hex A and 0.40 mM for Hex B. However, pH optima and temperature optima were identical for N-acetyl-beta-glucosaminidase and N-acetyl-beta-galactosaminidase activities of both isoenzymes; Hex A was far more heat-sensitive than Hex B. Thiol-reactive compounds such as silver salts, mercuric salts, p-chloromercuribenzoate and thimerosal strongly inhibited the N-acetyl-beta-glucosaminidase activities of both isoenzymes. GSH protected the enzyme activities from inactivation caused by these reagents, confirming the presence of thiol groups at the active centres. Inhibitions of N-acetyl-beta-glucosaminidase activities of both isoenzymes by metal salts and organic anions were comparable; acetate and arsenite were effective inhibitors for both isoenzymes. In contrast, inhibitions of N-acetyl-beta-glucosaminidase activities of the two isoenzymes by iodoacetic acid, iodoacetamide and ethylmaleimide were not comparable; Hex B was more susceptible to inhibition by these agents at 20 mM concentration. The N-acetyl-beta-glucosaminidase activities of both isoenzymes are strongly inhibited, in decreasing order, by N-acetyl-galactosamine, mannosamine, disaccharic acid lactone, N-acetylglucosamine and gluconolactone. The Ki values of the N-acetyl-beta-glucosaminidase and N-acetyl-beta-galactosaminidase activities for N-acetylhexosamines and results from mixed-substrate kinetics indicated that the activities for the two substrates are located at different sites in Hex A and at the same site in Hex B. The Mr values of Hex A and Hex B were determined to be 195,000 and 210,000 respectively by gel filtration through Sephadex G-200. SDS/polyacrylamide-gel electrophoresis revealed that Hex A and Hex B are each composed of four subunits corresponding to Mr about 50,000 each. No further polypeptide chain was obtained after reduction and alkylation of Hex A and Hex B with 10 mM-dithiothreitol and 10 mM-iodoacetamide.

Binding Sites↗
PubMed2000

Self-assembly and structure of interconverting multinuclear inorganic arrays: a.

Coordination of the pentatopic ligand 3 with AgI leads to the simultaneous self-assembly of two polynuclear architectures: a [4 x 5] grid-type species 10 and a quadruple-helicate 11, which contain twenty and ten silver ions. respectively. Their structures have been established by X-ray diffraction analysis of the crystals obtained as a mixture on crystallisation. Complex 10 contains two [2 x 5]-AgI10 rectangular subgrids located on opposite sides of an array of parallel ligands of 3 that are twisted into a transoid N=C-C=N arrangement around the central C-C bond; it may thus be formulated as a grid of grids: [2 x (2 x 5)]. Complex 11 is an inorganic quadruple helicate that consists of two sets of two parallel ligands of 3 connected by an array of ten silver ions. Both compounds 10 and 11 are novel types of polynuclear complexes that are composed of two subunits. Their formation points to the possibility of generating specific arrays of metal ions by self-assembly, involving, in particular, a combination of subunits within the overall entity. They represent organised patterns of ion dots of special significance in view of their formal relationship to quantum dots.

Journal Article↗
PubMed2006

Associative visual learning, color discrimination, and chromatic adaptation in the harnessed honeybee Apis mellifera L.

We studied associative visual learning in harnessed honeybees trained with monochromatic lights associated with a reward of sucrose solution delivered to the antennae and proboscis, to elicit the proboscis extension reflex (PER). We demonstrated five properties of visual learning under these conditions. First, antennae deprivation significantly increased visual acquisition, suggesting that sensory input from the antennae interferes with visual learning. Second, covering the compound eyes with silver paste significantly decreased visual acquisition, while covering the ocelli did not. Third, there was no significant difference in the visual acquisition between nurse bees, guard bees, and foragers. Fourth, bees conditioned with a 540-nm light stimulus exhibited light-induced PER with a 618-nm, but not with a 439-nm light stimulus. Finally, bees conditioned with a 540-nm light stimulus exhibited PER immediately after the 439-nm light was turned off, suggesting that the bees reacted to an afterimage induced by prior adaptation to the 439-nm light that might be similar to the 540-nm light.

Acclimatization↗