Studies on the mechanism maintaining biconcave shape of human erythrocytes.
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Adenosine Triphosphatases↗
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[Drug induced allergic myocardites].
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Acute Disease↗
Characterization of vitamin K from bovine liver.
Concentrated fractions of vitamin K from bovine liver were purified by thin-layer chromatography and fractions were analyzed by UV spectroscopy and mass spectrometry. The chromatographic behavior of the purified vitamins was compared with that of known compounds on thin layers of silica gel, either untreated or impregnated with silver nitrate or paraffin. The principal forms of vitamin K recovered from bovine liver were highly lipophilic. Two fractions were obtained which collectively gave identifiable mass spectra of menaquinone-10, menaquinone-11, and menaquinone-12.
Animals↗
[Amperometric titration of SH groups in milk by means of silver nitrate].
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Animals↗
[The effect of different topical agents on pseudomonas infection of burn wound].
48 Wistar rats were scalded resulting in 15% TBSA full-thickness burn. Pseudomonas aeruginosa (10(9)/ml was inoculated to the wounds. The rats were divided into 6 groups. 5 different topical agents were separately applied to the wounds constituting 5 groups, and no drug was used in control group. Through observing the appearance of wound, the quantity of bacteria in the subeschar tissue and histo-pathological changes, we confirmed that AgSD-ZnSD-A cream was a satisfactory topical agent.
Animals↗
Structure and magnetism of [M3](6/7+) metal chain complexes from density functional theory: analysis for copper and predictions for silver.
The ground-state electronic structure of the trinuclear complex Cu3(dpa)4Cl2 (1), where dpa is the anion of di(2-pyridyl)amine, has been investigated within the framework of density functional theory (DFT) and compared with that obtained for other known M3(dpa)4Cl2 complexes (M = Cr, Co, Ni) and for the still hypothetical Ag3(dpa)4Cl2 compound. Both coinage metal compounds display three singly occupied x2-y2-like (delta) orbitals oriented toward the nitrogen environment of each metal atom, generating antibonding M-(N4) interactions. All other metal orbital combinations are doubly occupied, resulting in no delocalized metal-metal bonding. This is at variance with the other known symmetric M3(dpa)4Cl2 complexes of the first transition series, which all display some delocalized bonding through the metal backbone, with formal bond multiplicity decreasing in the order Cr > Co > Ni. An antiferromagnetic coupling develops between the singly occupied MOs via a superexchange mechanism involving the bridging dpa ligands. This magnetic interaction can be considered as an extension to the three aligned Cu(II) atoms of the well-documented exchange coupling observed in carboxylato-bridged dinuclear copper compounds. Broken-symmetry calculations with approximate spin projection adequately reproduce the coupling constant observed for 1. Oxidation of 1 removes an electron from the magnetic orbital located on the central Cu atom and its ligand environment; 1+ displays a much weaker antiferromagnetic interaction coupling the terminal Cu-N4 moieties via four ligand pathways converging through the x2-y2 orbital of the central metal. The silver homologues of 1 and 1+ display similar electronic ground states, but the calculated magnetic couplings are stronger by factors of about 3 and 4, respectively, resulting from a better overlap between the metal centers and their equatorial ligand environment within the magnetic orbitals.
Copper↗
Characterization of argentosomes, a type of secondary lysosomes, and the sub-organellar distribution of a lysosomotropic basic compound.
Secondary lysosomes (argentosomes) were isolated by centrifugation in a discontinuous sucrose density gradient from livers of rats administered colloidal silver. Compared to the crude homogenate, the purities of the argentosome preparations were 17.4- and 18.5-fold in terms of acid phosphatase and N-acetyl-beta-glucosaminidase activities, respectively. By lipid analysis, the argentosomes were shown to have intermediate properties between normal lysosomes and tritosomes with regard to the contents of triglyceride and cholesterol. The phospholipid content in the argentosomes was also different from that in these two organelles. The cross-point of argentosomes shifted more to the acidic side than that of normal lysosomes. The data on the binding of tritiated p- biphenylmethyl-(dl-tropyl-alpha-tropiniun)bromide [( 3H]BTTB) to argentosomes indicated that the degree of binding and/or incorporation of this basic compound to the organelles was much higher than that to normal lysosomes. These results suggested that the distribution of BTTB on or within argentosomes might be under the control of the surface charge of the argentosomal membranes.
Animals↗
Post-column addition as a method of controlling triacylglycerol response coefficient of an evaporative light scattering detector in liquid chromatography-evaporative light-scattering detection.
The non-linear response is generally the main limitation to the general quantitative use of evaporative light-scattering detection (ELSD). In the particular case of triacylglycerol (TG) analysis, we present a preliminary paper dealing with the use of post-column additives as a means of monitoring the response of such a detector. As TG can form molecular association complexes (ligand-ligate associations) with either cholesterol, urea or silver nitrate, we report the influence of the concentration of each of these chemical compounds in the liquid phase directed towards the ELSD system. The results show that the response coefficient b of the calibration curve either decreases from 1.25-1.30 to 0.51 or increases from 1.25-1.30 to 1.78 according to the nature and concentration of post-column additive. The use of cholesterol as additive, at a discrete concentration, may lead to a linear response curve (b = 1), i.e. to the direct proportionality of ELSD response versus the TG concentration, making quantitative analysis of such solutes easier. On the other hand, to improve sensitivity, the addition of silver nitrate may be chosen for an increase in b value.
Cholesterol↗
Characteristics of rabbit muscle adenylate kinase inhibition by sulfur and recovery by dithiothreitol.
Structure-function relationships of rabbit muscle adenylate kinase (RMAK) were studied by examining the characteristics of inhibitions by hydrophobic inhibitors and reactivations by sulfhydryl reagents. RMAK is inhibited by 1-butanol,N-ethylmaleimide (NEM) and elemental sulfur (S8) with increasing effectiveness in the order of increasing hydrophobicity. Characteristics of these hydrophobic inhibitors are compared with inhibitors forming covalent bonds or reversible complexes. A mechanism is proposed for hydrophobic inhibitors of RMAK that involves conformational changes promoted by interacting with hydrophobic regions. The reversal of RMAK inhibition by sulfhydryl compounds involves a conformational change that exposes hydrophobic regions and the inhibitor to water. Circular dichroism (CD) data show changes in the secondary structures of RMAK, indicating that the inhibitors and the sulfhydryl compounds promote conformational changes. The results of these studies show that the activity of a small enzyme can be controlled in a manner analogous to the allosteric control of larger enzymes.
Adenosine Triphosphate↗
Solid phase extraction and spectrophotometric determination of silver with 2-(2-quinolylazo)-5-diethylaminophenol as chromogenic reagent.
A new chromogenic reagent, 2-(2-quinolylazo)-5-diethylaminophenol (QADEAP), was synthesized. A sensitive, selective and rapid method has been developed for the determination of microg/L level silver ion based on the rapid reaction of silver(l) with QADEAP and the solid phase extraction of the colored chelate with C18 cartridge. The QADEAP reacts with Ag(l) to form a violet chelate of a molar ratio 1:2 (silver to QADEAP) in pH 3.5-8.0. This chelate was prconcentrated by solid phase extraction with C18 cartridge. An enrichment factor of 100 was achieved. The molar absorptivity of the chelate is 1.30 x 10(5) L mol(-1) cm(-1) at 590 nm in measured solution. Beer's law is obeyed in the range of 0.01-0.6 microg/ml. The relative standard deviation for eleven replicate samples of 0.01 microg/ml is 1.15%. The detection limit is 0.02 microg/L in the original samples. This method was applied to the determination of microg/L level silver ion in water with good results.
Aminophenols↗
Delayed induced responses of birch glandular trichomes and leaf surface lipophilic compounds to mechanical defoliation and simulated winter browsing.
Changes in morphology and chemistry of leaf surface in response to herbivore damage may increase plant resistance to subsequent herbivore attack; however, there is lack of studies on induced responses of glandular trichomes and their exudates in woody plants and on effects of these changes on herbivores. We studied delayed induced responses in leaf surface traits of five clones of silver birch (Betula pendula Roth) subjected to various types of mechanical defoliation and simulated winter browsing. Glandular trichome density and concentrations of the majority of surface lipophilic compounds increased in trees defoliated during the previous summer. This induced response was systemic, since control branches in branch defoliated trees responded to the treatments similarly to defoliated branches, but differently from control trees. In contrast to defoliation treatments, simulated winter browsing reduced glandular trichome density on the following summer and had fewer effects on individual surface lipophilic compounds. Moreover, constitutive density of glandular trichomes was negatively correlated with induced total amount of lipophilic compounds per trichome, indicating a trade-off between constitutive and induced resistance in silver birch. Induced changes in leaf surface traits had no significant effect on leaf damage by chewers, miners and gall mites, but increased susceptibility of birch trees to aphids. However, leaf damage by chewers, miners and gall mites in defoliated (but not in control) trees was correlated with concentrations of some fatty acids and triterpenoids, although the direction of relationships varied among herbivore species. This indicates that induction of surface lipophilic compounds may influence birch resistance to herbivores. Our study thus demonstrated both specificity of elicitation of induced responses of birch leaf surface traits by different types of damage and specificity of the effects of these responses on different types of herbivores.
Animals↗
catena-Poly[[silver(I)-micro-ethane-1,2-diamine-kappa(2)N:N'] 3-fluorobenzoate monohydrate].
The title compound, [[Ag(C2H8N2)](C7H4FO2) x H2O]n, has been synthesized and characterized by elemental analysis and single-crystal X-ray diffraction. The Ag atom is bicoordinated in a linear configuration by two N atoms from two symmetry-related ethylenediamine ligands, giving linear polymeric chains with [-Ag-N-C-C-N-]n backbones running parallel to the b axis. In the crystal packing, these linear chains are interconnected by N-H...O and O-H...O hydrogen bonds, and by weak Ag...OW interactions, forming layers parallel to the ab plane.
Journal Article↗
Synthesis and reactivity of homogeneous and heterogeneous ruthenium-based metathesis catalysts containing electron-withdrawing ligands.
The synthesis and heterogenization of new Grubbs-Hoveyda type metathesis catalysts by chlorine exchange is described. Substitution of one or two chlorine ligands with trifluoroacetate and trifluoromethanesulfonate was accomplished by reaction of [RuCl(2)([double bond]CH-o-iPr-O-C(6)H(4))(IMesH(2))] (IMesH(2) = 1,3-bis(2,4,6-trimethylphenyl)-4,5-dihydroimidazol-2-ylidene) with the silver salts CF(3)COOAg and CF(3)SO(3)Ag, respectively. The resulting compounds, [Ru(CF(3)SO(3))(2)([double bond]CH-o-iPr-O-C(6)H(4))(IMesH(2))] (1), [RuCl(CF(3)SO(3))([double bond]CH-o-iPr-O-C(6)H(4))(IMesH(2))] (2), and [Ru(CF(3)CO(2))(2)([double bond]CH-o-iPr-O-C(6)H(4))(IMesH(2))] (3) were found to be highly active catalysts for ring-closing metathesis (RCM) at elevated temperature (45 degrees C), exceeding known ruthenium-based catalysts in catalytic activity. Turn-over numbers (TONs) up to 1800 were achieved in RCM. Excellent yields were also achieved in enyne metathesis and ring-opening cross metathesis using norborn-5-ene and 7-oxanorborn-5-ene-derivatives. Even more important, 3 was found to be highly active in RCM at room temperature (20 degrees C), allowing TONs up to 1400. Heterogeneous catalysts were synthesized by immobilizing [RuCl(2)([double bond]CH-o-iPr-O-C(6)H(4))(IMesH(2))] on a perfluoroglutaric acid derivatized polystyrene-divinylbenzene (PS-DVB) support (silver form). The resulting supported catalyst [RuCl(polymer-CH(2)-O- CO-CF(2)-CF(2)-CF(2)-COO)([double bond]CH-o-iPr-O-C(6)H(4))(IMesH(2))] (5) showed significantly reduced activities in RCM (TONs = 380) compared with the heterogeneous analogue of 3. The immobilized catalyst, [Ru(polymer-CH(2)-O-CO-CF(2)-CF(2)-CF(2)-COO)(CF(3)CO(2))([double bond]CH-o-iPr-O-C(6)H(4))(IMesH(2))] (4) was obtained by substitution of both Cl ligands of the parent Grubbs-Hoveyda catalyst by addition of CF(3)COOAg to 5. Compound 4 can be prepared in high loadings (160 mg catalyst g(-1) PS-DVB) and possesses excellent activity in RCM with TONs up to 1100 in stirred-batch RCM experiments. Leaching of ruthenium into the reaction mixture was unprecedentedly low, resulting in a ruthenium content <70 ppb (ng g(-1)) in the final RCM-derived products.
Journal Article↗
Fluorescent coordination networks of 2,3,6,7,10,11-hexakis(phenylthio)triphenylene and silver(I) triflate.
The polycyclic aromatic ligand 2,3,6,7,10,11-hexakis(phenylthio)triphenylene (HPhTT) coordinates with AgTf (Tf = trifluoromethylsulfonate) to form 1D networks with various solvent molecules included. In particular, the crystal structures and photoluminescent properties of compound 1 (formula = 2HPhTT.3AgTf.3toluene) and compound 2 (formula = 2HPhTT.3AgTf.2THF) are described. Both 1 and 2 feature similar network connectivity as well as similar local coordination environments around the silver(I) atoms. The organizations of the guest molecules in the two structures are, however, quite different: In 1, the toluene molecules are enclathrated in isolated cavities by the host network; in 2, the THF molecules are confined in continuous 1D channels. Because of the large aromatic system of the triphenylene moiety, strong fluorescent bands (room temperature) are observed for HPhTT, 1 and 2, with lambda(F,max) = 447 nm for HPhTT and lambda(F,max) = 440 nm for both 1 and 2.
Journal Article↗
Microwave-Accelerated Metal-Enhanced Fluorescence (MAMEF) with silver colloids in 96-well plates: Application to ultra fast and sensitive immunoassays, High Throughput Screening and drug discovery.
Fluorescence detection is the basis of most assays used in drug discovery and High Throughput Screening (HTS) today. In all of these assays, assay rapidity and sensitivity is a primary concern, the sensitivity determined by both the quantum yield of the fluorophores and efficiency of the detection system, while rapidity is determined by the physical and biophysical parameters of temperature, concentration, assay bioaffinity, etc. In this paper we describe a platform technology that promises to fundamentally address these two physical constraints of sensitivity and rapidity. By combining the use of Metal-Enhanced Fluorescence (MEF), a near-field effect that can significantly enhance fluorescence signatures, with low power microwave heating, we can significantly increase the sensitivity of surface assays as well as >95% kinetically complete the assay within a few seconds. In addition, the metallic nanostructures used to facilitate MEF appear to be preferentially heated as compared to the surface assay fluid, advantageously localizing the MEF and heating around the nanostructures. To demonstrate proof of principle, a 96-well plate has been functionalized with silver nanostructures, and a model protein avidin-biotin assay studied. In our findings, a greater than 5-fold fluorescence enhancement coupled with a approximately 90-fold increase in assay kinetics was observed, but with no assay washing steps needed due to the silver-enhanced evanescent field mode of excitation. These findings promise to strongly facilitate high throughput fluorescence-based processes, such as in biology, drug discovery and general compound screening.
Colloids↗
Analysis of the purity of cetrimide by titrations.
The purity of cetrimide, trimethyl tetradecyl ammonium bromide (TTAB), which is an important preservative of many cosmetic and pharmaceutical products, was determined by three independent methods of titration. Traditionally, cetrimide was analysed by an assay method of the European Pharmacopoeia, which showed consistently a low purity of cetrimide with associated large standard deviations, however. A systematic 3% bias of the European Pharmacopoeia assay method was identified by comparing the result with results of two alternative methods of titration that exhibited high precision and high accuracy. Titration by perchloric acid showed a 99.69% +/- 0.05% purity of cetrimide, and titration by silver nitrate showed a 99.85% +/- 0.05% purity, while the traditional assay method predicted a purity of only 97.1% +/- 0.4%. It was found that the discrepancy could be identified as differences in selectivity during the extraction step of the European Pharmacopoeia assay method. The distribution coefficients between chloroform and water of cetrimide and the corresponding iodide species (TTAI) were thus determined as 2150 +/- 50 M(-1) and 68000 +/- 4000 M(-1), respectively.
Cetrimonium↗
[Specific inhibition of nuclear DNA synthesis with carcinogens (autoradiography studies of a short-term test)].
Six suckling growing CBA mice 14 days old (5-6 g of body weight) of the same litter served as test animals in each experiment. 0.1 ml of the dissolved chemicals (15-30 per cent of the LD50 were applied by i.p. injection to 3 animals each (experiment) and an equal number of mice was treated with the solvent only (control). 15 hours later the animals were given a single i.p. injection of 3H thymidine (2 microCi/g body weight) and 50 min afterwards they were sacrificed for autopsy and preparation of autoradiographs. Autoradiographs of nuclei of renal tubular epithelia and of liver epithelium were examined by visual silver grain counting (150 nuclei in each experiment and the same number in the corresponding control). We could demonstrate that carcinogenic compounds of different chemical classes partially inhibit the nuclear incorporation of thymidine in a significant manner over a time period longer than 24 hours. This inhibition may be due as a consequence of a prolonged S phase, expressed as a decrease of the mean of silver grain number per nucleus in comparison with the unaltered control. This decrease is used as a criterion for the suppressive effect of carcinogenic substances on the nuclear DNA synthesis rate. Noncarcinogenic compounds did not show this effect.
Animals↗
Biosynthesis and degradation of nodule-specific Rhizobium loti compounds in Lotus nodules.
Two nodule-specific Rhizobium loti compounds were identified in Lotus tenuis and Lotus pedunculatus nodules induced by strain NZP2037. One, a silver nitrate-positive cation called rhizolotine, has been characterized as the riboside of a novel alpha-hydroxyimino acid containing a 1,4,5,6-tetrahydropyrimidine ring (G. J. Shaw, R. D. Wilson, G. A. Lane, L. D. Kennedy, D. B. Scott, and G. J. Gainsford, J. Chem. Soc. Chem. Commun., p. 180-181, 1986), and the other, yellow-1, stains yellow with ninhydrin. Both compounds were degraded by R. loti NZP2037 but not by strains of Rhizobium meliloti, Rhizobium trifolii, or Agrobacterium tumefaciens. Under the conditions tested neither compound was able to serve as a sole source of C or N for growth of R. loti NZP2037. Rhizolotine and yellow-1 were found in nodules from a range of different legumes inoculated with NZP2037, suggesting that the Rhizobium and not the host plant determines their synthesis. Neither compound was found in nodulelike structures of L. pedunculatus induced by transposon Tn5-induced noninfectious (Inf-) mutants of NZP2037 or in similar structures induced by a transconjugant of NZP2037 containing the symbiotic (Sym) cointegrate plasmid pPN1 of R. trifolii. Both compounds were also absent in the ineffective nodules induced by the bacterial-release-negative (Bar-) mutant, strain PN239. However, both compounds were present in nodules induced by the fixation-negative (Fix-) mutant PN235 and in Fix+ nodules formed by a plasmid-cured derivative of NZP2037. These results would suggest that infection and bacterial release from the infection thread are necessary for nodule (symbiotic) synthesis of these compounds.
Bacterial Proteins↗