Ruthenium Hexaammine Research Articles

Hydrophobic Interaction of Analytes with Permselective Poly(N-vinyl amide) Films on Electrodes

The synthesis and properties of poly(N-vinyl amide) copolymer films made of N-vinylpyrrolidone (NVP) and N-vinylphthalimide (NVPH) are described. The films are cast as permselective layers with a thickness between 0.18 and 1.5 μm onto spectroscopic graphite electrodes. The permselective properties of films of different thicknesses are investigated with various charged and uncharged hydrophilic and hydrophobic analytes as probes using electrochemical methods. Although the poly(N-vinyl amide) films are uncharged, they show sufficient conductivity for electrochemical measurements such as cyclic voltammetry. The main forces dominating the permselectivity of the copolymer films are hydrophobic interactions, which lead to a preferred preconcentration of neutral, hydrophobic analytes such as catechol in the film. Charged, hydrophilic analytes such as ascorbate or ruthenium hexaammine are rejected by the polymer film, so that their electrochemical signal is substantially attenuated at sufficiently large film thic...

Electrochemistry in microscopic domains. 1. The electrochemical cell and its voltammetric and amperometric response.

Microscopic aqueous sample droplets of nano- and picoliter volumes were formed on the bottom of a polystyrene dish under water-saturated heptane. The electrochemical cell consisted of a beveled carbon fiber microdisk working electrode and a reference electrode with a miniature junction, both inserted into the studied droplet. Both electrodes had a nominal tip diameter of 7.5 microns. Cyclic voltammetry and chronoamperometry in droplets of 3.3 mM ruthenium hexaammine trichloride in 0.1 M KCl solution were performed with this system. The experiments revealed for the first time major deviations in both voltammetric and amperometric microelectrode behavior in picoliter domains as compared to nanoliter volume and bulk solution. The concept and criteria of electrochemical microscopicity of volume is discussed. This work also provides a simple and robust experimental model system to verify electrochemical experiments in restricted domains such as in or near single biological cells or in microscopic tissue cavities. The methodology developed has, however, more general analytical and physicochemical applications as well.

Electroactivity of Redox Probes Encapsulated within Sol-Gel-Derived Silicate Films

The electroactivity of redox probes encapsulated within a silicate film prepared by the sol-gel process has been investigated to provide specific information about dopant stability, entrapment, and activity. Redox probes of different charges and sizes were physically doped into a sol prepared by the acid-catalyzed hydrolysis and condensation of tetramethoxysilane. The doped sols were then spin cast on pretreated glassy carbon electrodes, dried, and placed in a 0.1 M KNO 3 electrolyte solution. The voltammetry of the gel-doped anionic probes (i.e., potassium ferricyanide (Fe(CN) 6 3-/4- ), iridium(IV) chloride (IrCl 6 2-/3- ) , potassium octacyanomolybdate(IV) (Mo(CN) 8 4-/3- )) was stable as the film remained in solution and/or the electrode potential continuously cycled. For the gel-doped cationic or neutral probes (i.e., ruthenium(III) hexaammine (Ru(NH 3 ) 6 3+/2+ ), ruthenium(II) tris(bipyridine) (Ru(bpy) 3 2+/3+ ), ferrocenemethanol (FcCH 2 OH 0/+ )), a significant reduction in the Faradaic current was observed. UV-vis spectroscopy of the electrolyte solution after electrochemical cycling of gel-encapsulated Ru(bpy) 3 2+/3+ confirmed that the dopant leached out of the film. The percentage ofelectroactive reagent was determined for Fe(CN) 6 3-/4- and Ru(bpy) 3 2+ and found to be 3-9% and 5-10%, respectively, consistent with entrapment in a compact, dense matrix. With the exception of the much larger Ru(bpy) 3 2+/3+ , which exhibited peak-shaped voltammetry, the electrochemical behavior of the electroactive fraction of the entrapped redox probes corresponded to a surface-confined process.

Permselectivities and ion-exchange properties of organically modified sol—gel electrodes

Sol—gel films prepared from organosilanes containing acidic/basic sites have been investigated as permselective and ion-exchange coatings for electroanalytical and bioanalytical investigations. When a glassy carbon electrode was modified with a sol—gel film fabricated from 3-aminopropyl-methyl-diethoxysilane (silane—NH 2), excellent permselectivity and anion-exchange properties were obtained. For a pH 7.4, 1 mM potassium ferricyanide solution, an eight-fold increase in current was observed after the electrode was immersed in solution for 10min whereas complete suppression of the electrochemical response for ruthenium hexaamine and methyl viologen was observed. Sol—gel films fabricated from trimethoxysilylpropyl ethylenediamine triacetic acid (silane—(COOH) 3) exhibited nearly complementary behavior. An approximately 10-fold increase in current was observed for pH 7.4, 1 mM ruthenium hexaammine solutions and complete suppression of the potassium ferricyanide response was observed. These ion-exchange properties can be attributed to the strong electrostatic interactions between the acid/basic functional group in the matrix and the highly charged analyte molecules. When glassy carbon electrodes were modified with diethyl-(triethoxysilypropyl) malonate (silane—(COOEt) 2), the films did not exhibit distinct ion-exchange properties but rather suppressed the reduction of potassium ferricyanide. The observed permselectivity results from the electron dense carbonyl group and/or hydrolyzed ester functionalities in the film.

Control of electron delivery to the oxygen reduction site of cytochrome c oxidase: A role for protons

We have studied the reaction of oxidized "pulsed" cytochrome c oxidase with reduced cytochrome c and with ruthenium(II) hexaammine using stopped-flow mixing. The rate of reduction of Fea3 (the oxygen-binding heme) is not a linear function of the population of reduced Fea (the low-spin heme), as would be expected if electron transfer between these sites is rate-limiting. Instead, the rate can be increased significantly by increasing the driving force of the reductant (lowering of Eh) even after Fea is almost completely reduced. Reduction of Fea3 becomes slower as the pH is raised, and consumption of protons can be seen simultaneously with electron entry into Fea3. Both the reduction of Fea3 and the proton uptake are biphasic. To explain these findings, we propose a model in which (1) intramolecular heme-heme electron transfer is fast, and has an essentially constant rate; (2) when reduction begins, the midpoint potentials of Fea3 and CuB are initially low, and only a small fraction of these centers become reduced; and (3) this reduced population is then stabilized by the uptake of protons. Thus, net reduction of Fea3 and CuB is controlled by the amount of the low-potential population which becomes reduced together with the rate of proton uptake by this reduced low-potential species. Important consequences of this mechanism for the function of the enzyme and for the respiratory chain as a whole are discussed.

Preservation of cartilage matrix proteoglycans using cationic dyes chemically related to ruthenium hexaammine trichloride.

We tested various cationic dyes chemically related to ruthenium hexaammine trichloride (RHT) [i.e., the RHT-cyclohexanedione complex (RHT-CC), pentaamine ruthenium N-dimethylphenylenediimine trichloride (PRT), tris-(bipyridyl)ruthenium (II) chloride (TRC), tris (bipyridyl) iron (II) chloride (TIC), and cobalt hexaammine trichloride (CHT)] for their effectiveness in precipitating cartilage matrix proteoglycans in situ. Dyes were introduced into media at the onset of processing and were present throughout both aldehyde fixation and osmium tetroxide post-fixation. Contrary to expectation, most of the dye-proteoglycan complexes generated and stable under aldehyde fixation conditions were found to be unstable during post-fixation despite the continuing presence of the dye. A similar phenomenon was also found for the cationic dyes commonly used for precipitation of proteoglycans in cartilage tissue sections (such as Acridine Orange, Alcian Blue, Azure A, Methylene Blue, and Ruthenium Red). Only two dyes, i.e., RHT and the newly tested RHT-CC, formed proteoglycan precipitates sufficiently stable to resist disruption and extraction during osmium tetroxide post-fixation. The latter may be particularly useful in semiquantitative analyses of proteoglycan content in unstained tissue sections owing to its intense brown-black color. For applications in which the osmium tetroxide post-fixation step may be omitted, TRC and PRT may also be valuable for semiquantitative histochemistry by virtue of their stable fluorescence and intense violet color signals, respectively.

Chloroquine-sensitive transplasmalemma electron transport in Tetrahymena pyriformis: a hypothesis for control of parasite protozoa through transmembrane redox

Plasma membrane electron transport was studied in a protozoan cell, Tetrahymena pyriformis, by assaying transmembrane ferricyanide reduction and the reduction of iron compounds. The rates of ferricyanide reduction varied between 0.5 and 2.5 mumol/g dry wt. per min, with a pH optimum at 7.0-7.5. Other active non-permeable electron acceptors, with redox potentials from +360 to -125 mV, were cytochrome c, hexaammine ruthenium chloride, ferric-EDTA, ammonium ferric citrate, and indigo di-, tri- and tetrasulfonates. It was found that Tetrahymena cells can reduce external electron acceptors with redox potentials at pH 7.0 down to -125 mV. Ferricyanide stimulates ciliary action. Transmembrane ferricyanide reduction by Tetrahymena was not inhibited by such mitochondrial inhibitors as antimycin A, 2-n-heptyl-4-hydroxyquinoline N-oxide, or potassium cyanide, but it responded to inhibitors of glycolysis. Transmembrane ferricyanide reduction by Tetrahymena appears to involve a plasma membrane electron transport chain similar to those of other animal cells. As in other cells, the transmembrane electron transport is associated with proton release which may be involved in internal pH control. The transmembrane redox system differs from that of mammalian cells in a 20-fold greater sensitivity to chloroquine and quinacrine. The Tetrahymena ferricyanide reduction is also inhibited by chlorpromazine and suramin. Sensitivity to these drugs indicates that the transplasma membrane electron transport and associated proton pumping may be a target for drugs used against malaria, Trypanosomes and other protozoa.

Bicontinuous microemulsions as media for electrochemical studies

Biocontinuous microemulsions of didodecyldimethylammonium bromide (DDAB)/dodecane/water were explored as media for voltammetric reductions and oxidations of ruthenium(III) hexaammine, ferrocyanide, ferrocene, cob(II)alamin, and several polycyclic aromatic hydrocarbons (PAHs). These clear microemulsions are conductive and are believed to contain a dynamic extended network of interconnected water tubules. Agreement of simulated and experimental voltammetric data shows that electrochemical theory for homogeneous media is followed to a good approximation in DDAB microemulsions. Diffusion of electroactive solutes did not reflect the high bulk viscosities of the microemulsions. Non-polar molecules and ions diffuse as if they were in neat oil or aqueous media, respectively, and voltammograms with good signal to noise ratio are obtained. Reductions of PAHs in the microemulsions occurred by an ECE-type pathway, with nearly reversible one-electron reductions achieved at high scan rates.

The Interactions of Ruthenium Hexaammine with Z-DNA: Crystal Structure of a RU(NH3)+36Salt of d(CGCGCG) at 1.2 Å Resolution

A crystal of d(CGCGCG) in the Z-DNA lattice was soaked with ruthenium(III) hexaammine and its structure refined at 1.2 A resolution. Three unique metal complexes were found absorbed to each hexamer duplex. In addition, two symmetry-related binding sites were located, yielding a total of five ruthenium complexes bound to each d(CGCGCG) duplex. One unique site and its symmetry related site are nearly identical to the binding site of cobalt(III) hexaammine on Z-DNA. At that position, the metal complex bridges the convex surfaces of two adjacent Z-DNA strands by hydrogen bonds to the N7 and O6 functional groups of the guanine bases. The remaining three ruthenium three ruthenium(III) hexaammine binding sites are not present in the cobalt(III) hexaammine Z-DNA structure. Of these, two are related by symmetry and span the gap between the convex outer surface of one Z-DNA strand and the helical groove crevice of a neighboring strand. The third ruthenium site has no symmetry mate and involves interactions with only the deep groove. In this interaction, the metal complex hydrogen bonds to both the phosphate backbone and to a set of primary shell water molecules that extend the hydrogen bonding potential of the deep groove crevice out to the surface of the molecule. Solution studies comparing the circular dichroism spectra of low salt poly(dG-dC).poly(dG-dC) samples in the presence of ruthenium(III) and cobalt(III) hexammine show that the ruthenium complex does stabilize Z-DNA in solution, but not as effectively as the cobalt analogue. This suggests that some of the interactions available for the larger ruthenium complex may not be important for stabilization of the left-handed DNA conformation.

Photocalorimetry. 4. Enthalpies of substitution reactions of rhodium(III) and iridium(III) pentaammine halides and of ruthenium(II) hexaammine

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTPhotocalorimetry. 4. Enthalpies of substitution reactions of rhodium(III) and iridium(III) pentaammine halides and of ruthenium(II) hexaammineYaacov Harel and Arthur W. AdamsonCite this: J. Phys. Chem. 1986, 90, 25, 6690–6693Publication Date (Print):December 1, 1986Publication History Published online1 May 2002Published inissue 1 December 1986https://doi.org/10.1021/j100283a020RIGHTS & PERMISSIONSArticle Views54Altmetric-Citations13LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (536 KB) Get e-Alerts

Modification of transmembrane electron transport activity in plasma membranes of Simian virus 40 transformed pineal cells

Changes have been found in the plasma membrane enzyme system which carries out transmembrane electron transport and associated proton transport in Simian virus 40 (SV40) temperature-sensitive A ( tsA) mutant-transformed rat pineal cell line, RPN209-1. This cell line was temperature-sensitive for the maintenance of transformation. RPN209-1 cells expressed the transformed phenotype (rapid growth, high cell density, and cloning in soft agar) at the permissive temperature (33°C) and the nontransformed phenotype (slower growth, lower saturation density, and lower cloning efficiency in soft agar) at the nonpermissive temperature (40°C). The reduction of external ferricyanide, hexaammine ruthenium and diferric transferrin was used to measure the transmembrane redox activity. The transformed RPN209-1 cells expressed a lower transmembrane redox activity, which is more sensitive to the antitumor drug adriamycin, when compared to the cells with a nontransformed phenotype. The lower transmembrane redox activity is associated with a decrease in the affinity for ferricyanide and a change in V max of the enzyme. Since the transformed cells have 25% lower concentation of NADH, the decrease in V max may be partly based on substrate limitation. Ionic strength variation in the assay media shows that the change in activity with transformation is not based on change in cell-surface change. Treatment with neuraminidase, however, indicates that sialic acid is important for enzyme activity, consistent with previous proposals that the transmembrane enzyme is a glycoprotein. The proton extrusion associated with transplasma membrane electron transport is increased in transformed cells relative to the rate of ferricyanide reduction. A relation between proton pumping transplasma membrane electron transport and growth stimulation by external oxidants is discussed.

NMR study of the nature of the second coordination sphere in aqueous solutions of ruthenium(III) hexaammine

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTNMR study of the nature of the second coordination sphere in aqueous solutions of ruthenium(III) hexaammineDaniel Waysbort and Gil NavonCite this: J. Phys. Chem. 1980, 84, 6, 674–678Publication Date (Print):March 1, 1980Publication History Published online1 May 2002Published inissue 1 March 1980https://doi.org/10.1021/j100443a021RIGHTS & PERMISSIONSArticle Views59Altmetric-Citations7LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (764 KB) Get e-Alerts

Acid ionization constant and the base-catalyzed hydrolysis of ruthenium(III) hexaammine ion

Acid ionization constant and the base-catalyzed hydrolysis of ruthenium(III) hexaammine ion

Mechanism of reduction of cobalt(III) and ruthenium(III) hexaammine complexes by several aliphatic radicals

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTMechanism of reduction of cobalt(III) and ruthenium(III) hexaammine complexes by several aliphatic radicalsH. Cohen and D. MeyersteinCite this: J. Am. Chem. Soc. 1972, 94, 20, 6944–6948Publication Date (Print):October 1, 1972Publication History Published online1 May 2002Published inissue 1 October 1972https://doi.org/10.1021/ja00775a014RIGHTS & PERMISSIONSArticle Views188Altmetric-Citations36LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (1 MB) Get e-Alerts Get e-Alerts

Deprotonated ruthenium(III) hexa-ammine and its role in aquation and proton exchange reactions

The deprotonated ruthenium(III) hexa-ammine complex is characterized by its absorption spectrum; its formation equilibrium constant is reported and its role in aquation and proton transfer reactions is discussed.

Reduction of ruthenium(III) hexaammine by hydrogen atoms and monovalent zinc, cadmium, and nickel ions in aqueous solutions

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTReduction of ruthenium(III) hexaammine by hydrogen atoms and monovalent zinc, cadmium, and nickel ions in aqueous solutionsGil Navon and D. MeyersteinCite this: J. Phys. Chem. 1970, 74, 23, 4067–4070Publication Date (Print):November 1, 1970Publication History Published online1 May 2002Published inissue 1 November 1970https://doi.org/10.1021/j100717a011RIGHTS & PERMISSIONSArticle Views209Altmetric-Citations20LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (528 KB) Get e-Alerts