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PubMed1976

[Interaction of electrophilic alkylating agents with nucleophilic sites of mitochondria].

The electrophilic alkylating agents having different numbers of electrophilic groups with nucleophilic sites of mitochondria were studied. Bifunctional compounds were found to modify the structure of mitochondria so that some of the sulfhydryl groups become inaccessible for titrating ions of Ag+. Monofunctional agents caused no changes in the number of determinable sulfhydryl groups and prevented the effect of bifunctional compounds. The linkage formed between the electrophilic residue and the nucleophilic site is stable in the absence of electron transport. During the transport of electrons in the respiratory chain the linkage becomes labile and the electrophilic residue chips off. A scheme of interaction of electrophilic alkylating agents with nucleophilic sites of mitochondria is proposed.

Alkylating Agents↗
PubMed2004

Polymeric silver(I) complexes with pyridyl dithioether ligands: experimental and theoretical investigations on the coordination properties of the ligands.

The reactions of four flexible tetradentate ligands, 1,3-bis(2-pyridylthio)propane (L1), 1,4-bis(2-pyridylthio)butane (L2), 1,5-bis(2-pyridylthio)pentane (L3) and 1,6-bis(2-pyridylthio)hexane (L4) with AgX (X = BF4-, ClO4-, PF6-, or CF3SO3-) lead to the formation of seven new complexes: [AgL1(BF4)]2 (1), [[AgL2](ClO4)]infinity (2), [[AgL2(CH3CN)](PF6)]infinity (3), [[AgL3](BF4)(CHCl3)]2 (4), [[AgL3(CF3SO3)](CH3OH)(0.5)]infinity (5), [[Ag2L4(2)](BF4)2]infinity (6), and [[AgL4](PF6)]infinity (7), which have been characterized by elemental analyses, IR spectroscopy, and X-ray crystallography. Single-crystal X-ray analyses show that complexes 1 and 4 possess dinuclear macrometallacyclic structures, and complexes 2, 3 and 5-7 take chain structures. In all the complexes, the nitrogen atoms of ligands preferentially coordinate to silver atoms to form normal coordination bonds, while the sulfur atoms only show weak interactions with silver atoms and the intermolecular AgS weak contacts connect the low-dimensional complexes into high-dimensional supramolecular networks. Additional weak interactions, such as pi-pi stacking, F...F weak interactions, Ag...O contacts or C-H...O hydrogen bonds, also help to stabilize the crystal structures. It was found that the parity of the -(CH2)n- spacers (n = 3-6) affect the orientation of the two terminal pyridyl rings, thereby significantly influence the framework formations of these complexes. The coordination features of ligands and their conformation changes between free and coordination states have been investigated by DFT calculations.

Crystallography, X-Ray↗
PubMed1995

Zinc sulphadiazines: novel topical antimicrobial agents for burns.

Two new zinc sulphadiazine (Zn(SD)2)-amine complexes, zinc sulphadiazine-methylamine (Zn(SD)2(CH3NH2)2) and zinc sulphadiazine-ethylenediamine (Zn(SD)2(C2H8N2)3.H2O), were prepared and compared with silver sulphadiazine (AgSD). The compounds were readily obtained by reaction of zinc nitrate hexahydrate with sulphadiazine or its salt in methylamine and ethylenediamine, respectively. Structure was established by X-ray crystallography and ultraviolet-visible, infrared and nuclear magnetic resonance spectroscopy. The products were effective, in-vitro, against Gram-positive and Gram-negative bacteria as well as fungus. However, their activity is partially reversed by p-aminobenzoic acid. Further investigations in burned mice revealed that these compounds displayed a potential value in the prevention and treatment of wound healing, and diminution of mortality and weight loss. The toxicity of Zn(SD)2 derivatives was much lower than that of AgSD. The better aqueous solubility and skin permeability may explain the reason for their superiority over AgSD in the efficacy for topical therapy. Zn(SD)2(CH3NH2)2 was consistently more potent and was chosen for further development in clinical uses. The similarity in complexation between Zn(SD)2(CH3NH2)2 and AgSD may be significant to distinguish that from any other Zn(SD)2 derivative in bioactivity.

Animals↗
PubMed2002

[A method for analysis of biochemical phase of anti-HIV antibody and HIV antigen reaction by release of Ag+-sensitive-SH-containing nonprotein compounds].

The phenomenon of release of Ag(+)-sensitive SH containing protein compounds during reaction of serum antibodies to HIV with HIV antigen glycoproteins (AgHIV) (both reagents taken from diagnostic kits) is described. These compounds were detected in nonprotein fractions of serum anti-HIV + AgHIV reaction media and disappeared after dialysis of nonprotein fractions. On the other hand, this phenomenon was not detected during addition of AgHIV to the serum containing no AgHIV. Presumably, the phenomenon should be referred to secondary concomitant reaction, which seems to be mediated by conformational and/or other processes only during highly specific antigen-antibody intermolecular interactions. That is why this phenomenon seems to characterize the biochemical phase of immune reactions, which can be associated with the denaturing processes as well, running in serum anti-HIV + AgHIV reaction media, and it can be used as an additional test in evaluating anti-HIV antibodies.

Antigen-Antibody Reactions↗
PubMed1992

Neuropathological effects of triphenyl phosphite on the central nervous system of the hen (Gallus domesticus).

The neurotoxic effects of single subcutaneous injections of 1000 mg triphenyl phosphite (TPP)/kg body weight were investigated in White Leghorn hens. At 7 days postexposure, birds began to show signs of mild to moderate ataxia that progressed to severe ataxia and paralysis at 21 days. Inhibition of whole brain neuropathy target esterase was 85% at 48 hr and 73% by 21 days postexposure. After postexposure periods of 7, 14, and 21 days, hens were killed and their brains and spinal cords were examined for degenerating axons and terminals using the Fink-Heimer silver impregnation method. A small amount of degeneration was noted at 7 days. By 21 days, dense degeneration was noted in the spinal gray matter and funiculi. Degeneration was also present in the granular cell layer of cerebellar folia I-VI and in nuclei and fiber tracts of the medulla. Moderate to dense degeneration was also seen in several forebrain and midbrain areas including the paleostriatum, ansa lenticularis, the dorso-intermediate thalamic nucleus, lateral spiriform, pedunculopontine tegmental, and lateral mesencephalic nuclei and in the deeper layers of the optic tectum. These results indicate that, in addition to affecting the spinal cord and brainstem, exposure to TPP also damages higher order centers responsible for processing and integrating sensorimotor, visual, and auditory information.

Animals↗
PubMed2005

[Study and spectrophotometric determination of trace silver with iodide-Victoria Pure Blue BO system].

Analytical properties and spectra of naphthyl diphenymethane basic dyes and associated complexes of dye with [AgI2]- was studied. A new method for the spectrophotometric determination of trace amount of silver was developed. The method was based on the Victoria Pure Blue BO reacted with [AgI2]- to form blue associated complex in the buffer medium of H3PO4 -NaH2PO4. The spectrophotometric measurements were directly carried out at 574 nm, the apparent molar absorptivity of associated complex was 7.25 x 10(4) L x mol(-1) x cm(-1). The Beer's law was obeyed in the range of 4-250 microg x L(-1). The recoveries were in the range of 97.0%-98.3%. RSD was 2.7%. The method has been used to determination of trace silver in river water with satisfactory results.

Fresh Water↗
PubMed2004

Factors affecting the sorption of model environmental pollutants onto silver polydimethylsiloxane nanocomposite Raman substrates.

The presence of aromatic compounds in water is an important topic in environmental sciences. Silver-polydimethylsiloxane nanocomposites (Ag-PDMS) have recently been demonstrated as promising substrates for the detection of model environmental pollutants via surface-enhanced Raman spectroscopy (SERS). This work discusses how different variables such as pH and matrix composition can affect the sorption and SERS activity of these chemicals. The results show that the conjugate base of weak acids can interact more efficiently with the substrate, leading to an increased signal at higher pH, while amino-aromatic compounds interact more efficiently at a lower pH. The sorption of these chemicals is an essential step in the process and has been attributed to the absorption of the analyte into the PDMS followed by its adsorption to the metallic surface. In addition, the presence of moderate concentrations (1 x 10(-4) M) of a supporting electrolyte such as nitrate or fluoride can improve the sorption of 4-hydroxybenzoic acid to the Ag-PDMS nanoparticles. Other ions such as phosphate and chloride cause rapid oxidation of the substrates even at concentrations as low as 1 x 10(-5) M. The effect of these variables in the analysis of real samples is presented. The potential use of liquid chromatography for isolating the model pollutants from detrimental matrix components in nat- ural waters is also shown.

Adsorption↗
PubMed1995

Triphenyl phosphite-induced neuropathy in the avian forebrain: a silver impregnation study of the visual and auditory systems of the Japanese quail.

Single subcutaneous injections of triphenyl phosphite (TPP) (62.5-500 mg/kg body weight) were made in the Japanese quail (Coturnix coturnix japonica). The extent and density of resultant central nervous system degeneration were mapped by using the Fink-Heimer silver impregnation method to selectively impregnate degenerating axons and terminals. In addition to resulting in degeneration in the medulla and cerebellum, exposure to TPP also resulted in axonal and terminal degeneration in specific midbrain and forebrain nuclei and tracts related to the auditory and visual systems. Auditory system nuclei containing axonal and terminal degeneration included the lateral mesencephalic nucleus, pars dorsalis, the nucleus ovoidalis, and area L of Rose in the caudal neostriatum. Anterograde degeneration was also noted in nuclei and tracts related to the visual tectofugal system-the brachium of the superior colliculus, nucleus rotundus, pretectal nuclei, and the ectostriatum. Additional degeneration was noted in the paleostriatum primitivum, dorso-intermediate posterior thalamic nucleus, lateral spiriform nucleus, and the pedunculopontine tegmental nucleus, all of which are related to visuomotor control. These results indicate that in the Japanese quail, exposure to TPP yields anterograde degeneration in nuclei and tracts involved with the transmission and processing of higher order visuomotor, visual sensory, and auditory sensory information.

Animals↗
PubMed2005

Solvent control on the selective, nonselective, and absent response of a partially substituted lower rim calix(4)arene derivative for soft metal cations (mercury(II) and silver(I)). Structural and thermodynamic studies.

The solvent control on the ability of a partially substituted lower rim calix(4)arene derivative 5,11,17,23,tetra-tert-butyl[25,27-bis(hydroxy)-26,28-bis(ethylthioethoxy)]-calix(4)arene, 1 to host soft metal cations (Hg(II) and Ag(I)) is demonstrated through 1H NMR, electrochemical (conductance measurements), and thermodynamic characterization of the complexation process in a wide variety of solvents. Solvent-ligand interactions were assessed from 1H NMR measurements involving 1 and various solvents in CDCl3. Thus, the formation of a 1:1 1-CH3CN adduct is reported. As far as metal cations are concerned, depending on the medium their complexation with 1 was only observed for Hg(II) and Ag(I). Thus, in acetonitrile, 1 is more selective for Hg(II) relative to Ag(I) by a factor of 2.2 x 10(3). In methanol the selectivity is reversed to an extent that the affinity of 1 for Ag(I) is 1.4 x 10(3) higher than that for Hg(II). However, 1 is unable to recognize selectively these cations in N,N-dimethylformamide while in propylene carbonate the ability of 1 to interact with these cations is lost. An outstanding feature of thermodynamics emerges when an assessment is made of the ligand effect on the complexation of these cations and analogues calix(4)arene derivatives. Thus, in acetonitrile the thermodynamics of cation complexation by the hydrophilic cavity of a calix(4)arene containing mixed pendant groups is built up from thermodynamic data for the same process involving derivatives with common functionalities at the narrow rim. This is a unique example of the additive contribution of pendant arms in the field of thermodynamics of calixarene chemistry.

Acetonitriles↗
PubMed1997

Using microcontact printing to pattern the attachment of mammalian cells to self-assembled monolayers of alkanethiolates on transparent films of gold and silver.

This paper describes a convenient methodology for patterning substrates for cell culture that allows the positions and dimensions of attached cells to be controlled. The method uses self-assembled monolayers (SAMs) of terminally substituted alkanethiolates (R(CH2)11-15S-) adsorbed on optically transparent films of gold or silver to control the properties of the substrates. SAMs terminated in methyl groups adsorb protein and SAMs terminated in oligo(ethylene glycol) groups resist entirely the adsorption of protein. This methodology uses microcontact printing (microCP)-an experimentally simple, nonphotolithographic process-to pattern the formation of SAMs at the micrometer scale; microCP uses an elastomeric stamp having at its surface a pattern in relief to transfer an alkanethiol to a surface of gold or silver in the same pattern. Patterned SAMs having hydrophobic, methyl-terminated lines 10, 30, 60, and 90 microm in width and separated by protein-resistant regions 120 microm in width were prepared and coated with fibronectin; the protein adsorbed only to the methyl-terminated regions. Bovine capillary endothelial cells attached only to the fibronectin-coated, methyl-terminated regions of the patterned SAMs. The cells remained attached to the SAMs and confined to the pattern of underlying SAMs for at least 5-7 days. Because the substrates are optically transparent, cells could be visualized by inverted microscopy and by fluorescence microscopy after fixing and staining with fluorescein-labeled phalloidin.

Actin Cytoskeleton↗
PubMed1999

Giant platinum clusters: 2-nm covalent metal cluster labels.

A new class of covalently linkable platinum cluster reagents with core diameters close to 2 nm has been prepared. The new label offers the performance advantages and versatility of the 1.4-nm Nanogold in a larger label which is more clearly visualized against electron-dense regions of a specimen. Large platinum clusters were prepared by the reduction of platinum(II) acetate in the presence of 1,10-phenanthroline ligands which had been synthetically modified to include solubilizing and reactive cross-linkable functional groups. These were then conjugated site-specifically to antibody IgG molecules and to Fab' fragments and visualized by scanning transmission electron microscopy. The resulting conjugates may be autometallographically enhanced and show sensitivity similar to that of Nanogold conjugates in immunoblotting experiments. In preliminary experiments, they have also exhibited labeling of tissue antigens and penetrate to access nuclear targets.

Affinity Labels↗
PubMed1993

Prolonged exercise reduces Ca2+ release in rat skeletal muscle sarcoplasmic reticulum.

Prolonged exercise decreased the rate of Ca+ release in sarcoplasmic reticulum (SR) vesicles isolated from rat muscle by 20-30% when release was initiated by 5, 10, and 20 microM AgNO3 [3H]Ryanodine binding was also depressed by 20% in SR vesicles isolated from the exercised animals. In contrast, the maximum amount of Ca2+ release in the presence of ruthenium red, a known inhibitor of the Ca2+ release mechanism, was not affected by prolonged exercise. These results suggest that exercise depressed Ca2+ release from SR by directly modifying the Ca2+ release channel.

Animals↗