Adsorption de l'acide maleique et de l'hydrogene sur le platine-platine en presence de cuivre adsorbe

According to a previous study, the catalytic hydrogenation of maleic acid on platinum catalyst is inhibited by copper adsorption. A copper adatom deactivates five accesible atoms of platinum. A cyclic voltammetry study of hydrogen and maleic acid adsorptions on platinum and on platinum modified by copper adatoms accounts for this result.Indeed a copper adatom inhibits the adsorption of one hydrogen atom on one platinum atom and of one maleic acid molecule on 5 ± 1 platinum atoms.     

Voltammetric behaviour of the copper(II)—thiourea system in sulphuric acid medium at platinum and glassy carbon electrodes

Thiourea, a levelling agent used in copper electrorefining baths, is the focus of a cyclic and rotating disc or ring-disc electrode voltammetric study. Thiourea adsorption, its interaction with Cu²⁺ and formation of Cu(Tu) _n ⁺ complexes are part of the multistep electrode mechanism proposed. Results at platinum and glassy carbon electrodes are applicable to copper electrodes in electrorefining.     

Development of a bath for codeposition of copper and platinum

To improve the mechanical properties of electrodeposited copper, a new bath was developed for the codeposition of copper and platinum. A pyrophosphate bath employing chloroplatinic acid as a source of platinum was investigated at current densities ranging from 1 to 4 A dm⁻² and temperatures from 20 to 60 °C. Bright, shiny and crack-free deposits were obtained at low current densities (i.e., 1–2 A dm⁻²). The amount of platinum observed in the deposits was found to increase with the current density and bath temperature. The Knoop hardness was found to increase with platinum content in the deposits. Corrosion rates measured in solutions of NaCl were found to decrease with platinum content. Deposits containing up to 3.9 wt % of platinum can be obtained by electrodeposition. As compared to electrodeposited copper from the acid bath, the Cu—Pt deposits exhibited a 17% increase in Knoop hardness and a 21% increase in corrosion resistance.     

Dinuclear alkylamine platinum(II) complexes of [1,2-bis(4-fluorophenyl)ethylenediamine]platinum(II): influence of endocytosis and copper and organic cation transport systems on cellular uptake

Various possible pathways for the uptake of cationic alkylamine platinum(II) complexes into the MCF-7 breast cancer cells were studied with di[meso-1,2-bis(4-fluorophenyl)ethylenediamine]di[sulfinylbis(methane)-S][mu-1,6-diaminohexaneN:N']diplatinum(II) disulfate (m-4F-PtDMSO-DAH) as an example. It was demonstrated that m-4F-PtDMSO-DAH competed neither for the copper transporter nor the organic cation transporters (OCT and OATP). Instead, adsorptive endocytosis by macropinocytosis played an essential role. Inhibitors of this processes such as amiloride, N-ethyl-N-isopropylamiloride (EIPA), wortmannin, and cytochalasin D decreased the intracellular uptake of m-4F-PtDMSO-DAH dramatically. These results support the understanding of the pharmacological behavior of this promising drug family, which showed no cross resistance with cisplatin.     

Voltammetry of UPD copper and formic acid as characterization of preferentially oriented polycrystalline platinum surfaces

In order to characterize the surface structure of electrochemically modified polycrystalline platinum, the voltammograms of underpotential deposited copper and of formic acid are studied. The operating conditions are chosen in such a way that a direct comparison to results on single crystal platinum electrodes is possible. It is shown that UPD copper in HF solution and formic acid oxidation are well suited to characterize the modified structure of platinum surfaces.     

Electrochimie dans la cryolithe fondue—II oxydation electrochimique de l'aluminium “dissous”

It is shown by voltammetry that the species often called “dissolved aluminium” which comes from the interaction of aluminium with molten cryolite is electrochemically oxidized at several electrodes (platinum, nickel, copper, graphite, vitrous carbon). The diffusion plateau is used to measure the “solubility” of aluminium as a function of temperature and composition (0·11 weight per cent at 1015°C, is cryolite saturated with alumina). An application to the efficiency of alumina electrolysis is proposed.     

Molecular Regulation of Copper Homeostasis in the Male Gonad during the Process of Spermatogenesis

Owing to its redox properties, copper is a cofactor of enzymes that catalyze reactions in fundamental metabolic processes. However, copper–oxygen interaction, which is a source of toxic oxygen radicals generated by the Fenton reaction, makes copper a doubled-edged-sword in an oxygen environment. Among the microelements influencing male fertility, copper plays a special role because both copper deficiency and overload in the gonads worsen spermatozoa quality and disturb reproductive function in mammals. Male gametes are produced during spermatogenesis, a multi-step process that consumes large amounts of oxygen. Germ cells containing a high amount of unsaturated fatty acids in their membranes are particularly vulnerable to excess copper-mediated oxidative stress. In addition, an appropriate copper level is necessary to initiate meiosis in premeiotic germ cells. The balance between essential and toxic copper concentrations in germ cells at different stages of spermatogenesis and in Sertoli cells that support their development is handled by a network of copper importers, chaperones, recipient proteins, and exporters. Here, we describe coordinated regulation/functioning of copper-binding proteins expressed in germ and Sertoli cells with special emphasis on copper transporters, copper transporting ATPases, and SOD1, a copper-dependent antioxidant enzyme. These and other proteins assure copper bioavailability in germ cells and protection against copper toxicity.     

Multispecificity of drug transporters: probing inhibitor selectivity for the human drug efflux transporters ABCB1 and ABCG2

Multidrug resistance transporters P-glycoprotein/ABCB1 and ABCG2 limit the effect of a large number of cytostatic and cytotoxic drugs by energy-dependent efflux. In experimental models, pump inhibitors reestablish sensitivity towards these drugs. Both transporters demonstrate remarkably broad and partly overlapping substrate specificity. Propafenone analogues are inhibitors of a large number of drug efflux pumps including P-glycoprotein and ABCG2 as well as the microbial pumps. Here the two human ABC transporters ABCB1 and ABCG2 have been studied with respect to interaction with this class of compounds. Data indicate that within the same chemical scaffold, selectivity indices span three orders of magnitude. Compounds with the highest selectivity indices contain a non-ionizable nitrogen atom. Qualitative and quantitative pharmacophore models indicate that hydrophobicity, the number of rotatable bonds, and the number of H-bond acceptors are key features for both activity and selectivity.     

NO reduction by isobutene, in the presence of oxygen, on platinum and copper, a comparative study

The reaction of NO, oxygen and isobutene was studied under conditions close to stoichiometric, on a platinum and on a copper disk in order to better understand the role of each metal, free of any support and dispersion effects. The products of the reaction were analysed by mass spectrometry and an XPS characterization of the surface was carried out at different stages of the reaction. A correlation between the catalytic activity for NO conversion and the presence of adsorbed intermediates has been clearly demonstrated on platinum. On copper, a redox cycle of the metal is necessary to activate the catalyst. On platinum, oxygen is necessary to initiate the reaction, clean the surface and form reactive intermediates; the reaction is strongly sensitive to oxygen concentration, whereas on copper, oxygen does not directly participate in the reaction mechanism.     

Conjugation of Cisplatin Analogues and Cyclooxygenase Inhibitors to Overcome Cisplatin Resistance

Cyclooxygenase (COX) is an enzyme involved in tumorigenesis and is associated with tumor cell resistance against platinum‐based antitumor drugs. Cisplatin analogues were conjugated with COX inhibitors (indomethacin, ibuprofen) to study the synergistic effects that were previously observed in combination treatments. The conjugates ensure concerted transport of both drugs into cells, and subsequent intracellular cleavage enables a dual‐action mode. Whereas the platinum(II) complexes showed cytotoxicities similar to those of cisplatin, the platinum(IV) conjugates revealed highly increased cytotoxic activities and were able to completely overcome cisplatin‐related resistance. Although some of the complexes are potent COX inhibitors, the conjugates appear to execute their cytotoxic action via COX‐independent mechanisms. Instead, the increased lipophilicity and kinetic inertness of the conjugates seem to facilitate cellular accumulation of the platinum drugs and thus improve the efficacy of the antitumor agents. These conjugates are important tools for the elucidation of the direct influence of COX inhibitors on platinum‐based anticancer drugs in tumor cells.     

铂类抗癌药物生产污水的处理探讨

为了更好地处理铂类抗癌药物生产过程中产生的污水,同时有效回收贵金属,通过对生产工艺的分析,提出了用三个工艺方法来处理铂类抗癌药物生产工程中的污水。可以解决铂类抗癌药物生产过程中的污水处理问题。     

Copper deposition and its replacement by platinum on a gold electrode

The decoration of single crystal gold electrodes with platinum using underpotential deposited copper as an intermediate has been studied in detail. It was found that a significant fraction of the copper is lost in the transfer process from the upd cell to the exchange cell. In addition the surface of the gold is not covered uniformly by the platinum. Nevertheless, acceleration of the electroreduction of oxygen was observed with a loading of 0.14 μg cm⁻². The structure of the decorating layer was studied by scanning electron microscopy and atomic force microscopy.     

Electroreduction of nitrate ions on Pt(1 1 1) electrodes modified by copper adatoms

Kinetics and mechanism of nitrate ion reduction on Pt(1 1 1) and Cu-modified Pt(1 1 1) electrodes have been studied by means of cyclic voltammetry, potentiostatic current transient technique and in situ FTIRS in solutions of perchloric and sulphuric acids to elucidate the role of the background anion. Modification of platinum surface with copper adatoms or small amount of 3D-Cu crystallites was performed using potential cycling between 0.05 and 0.3 V in solutions with low concentration of copper ions, this allowed us to vary coverage θ_Cu smoothly. Following desorption of copper during the potential sweep from 0.3 to 1.0 V allowed us to estimate actual coverage of Pt surface with Cu adatoms. Another manner of the modification was also applied: copper was electrochemically deposited at several constant potentials in solutions containing 10⁻⁵ or 10⁻⁴ M Cu²⁺ and 5 mM NaNO₃ with registration of current transients of copper deposition and nitrate reduction.It has been found that nitrate reduction at the Pt(1 1 1) surface modified by copper adatoms in sulphuric acid solutions is hindered as compared to pure platinum due to induced sulphate adsorption at E < 0.3 V. Sulphate blocks the adsorption sites on the platinum surface and/or islands of epitaxial Cu(1 × 1) monolayer thus hindering the adsorption of nitrate anions and their reduction. The extent of inhibition weakly depends on the copper adatom coverage. Deposition of a small amount of bulk copper does not affect noticeably the rate of nitrate reduction.Nitrate reduction on copper-modified Pt(1 1 1) electrodes in perchloric acid solutions occurs much faster as compared to pure platinum. The steady-state currents are higher by 4 and 2 orders of magnitude at the potentials of 0.12 and 0.3 V, respectively. The catalytic effect of copper adatoms is largely caused by the facilitation of nitrate adsorption on the platinum surface near Cu_ad and/or on the islands of the Cu(1 × 1) monolayer (induced nitrate adsorption).Hydrogen adatoms block the adsorption sites on platinum for NO₃⁻ anion adsorption and inhibit reactions of nitrate reduction even at moderate surface coverage.The products of nitrate reduction in sulphuric and perchloric acids are essentially the same (NO and ammonia) irrespective of the presence or absence of Cu on the platinum surface.     

Preparation of Highly Dispersive Platinum Catalysts Impregnated on Titania-Incorporated Silica Support

Highly dispersive silica-impregnated platinum catalysts were prepared by incorporating titania to the surface of silica support and by treating the impregnated platinum precursor with hydrogen peroxide. High dispersion of platinum on the titania-incorporated silica support was confirmed by XRD, TEM, EXAFS, and X-ray photoelectron spectroscopy (XPS) techniques. The platinum particles dispersed on silica ranged from 1 to 2 nm in size, although the loading amount of platinum was as high as 4 wt.%. The strong interaction between platinum and titania suppressed the migration and aggregation of the platinum particles on the surface, retaining a high dispersion of platinum. The platinum catalysts impregnated on the titania-incorporated silica showed higher catalytic activities in the combustion of methane than the platinum catalysts impregnated on the silica, while their catalytic activities were poor in the hydrogenation of nitrobenzene. Platinum dispersions and catalytic activities of the platinum catalysts on the silica support were discussed in relation to the strong interaction between platinum and titania.     

Polymers with platinum drugs and other macromolecular metal complexes for cancer treatment

Metal-based anticancer drugs, in particular platinum-drugs, have been investigated for the treatment of cancer for the last 40 years. A small set of platinum-based drugs have meanwhile received FDA approval for the treatment of various cancer. Cisplatin and its relatives are currently one of the most widely used anticancer drugs. The use is however associated with significant side effects and rising drug resistance. To combat these problems, drug delivery carriers have been developed to increase the protection of the drug and increase efficacy. Metal-based drugs represent a rather unique drug delivery challenge. Most anticancer drugs are either physically encapsulated into a polymer matrix or they can be conjugated to the polymer via a degradable linker. While both pathways are possible for metal-based drugs, the conjugation to the polymer can be carried via labile or permanent ligands. In addition, the prodrug strategy using the drug in the higher oxidation state is a common approach that has been widely tested for platinum drug. The delivery of platinum drugs is now a mature field and the various conjugation techniques have been combined with a range of drug carriers including dendrimers, micelles and solid polymer nanoparticles. Hybrids of macromolecular metal complexes with inorganic nanoparticles have been tested in recent years to combine the ability to deliver the drug with imaging properties. An emerging trend is the surface decoration of the polymeric nanoparticles with targeting ligands such as folates. The advanced state of this field is evident by the fact that some macromolecular platinum drugs even advanced to the clinic. While the delivery of platinum drugs has been well explored, the delivery of other metal-based drugs based on gold, ruthenium or cobalt is still in their infancy.     

Copper delivery by metallochaperone proteins

Copper is an essential element in all living organisms, serving as a cofactor for many important proteins and enzymes. Metallochaperone proteins deliver copper ions to specific physiological partners by direct protein-protein interactions. The Atx1-like chaperones transfer copper to intracellular copper transporters, and the CCS chaperones shuttle copper to copper,zinc superoxide dismutase. Crystallographic studies of these two copper chaperone families have provided insights into metal binding and target recognition by metallochaperones and have led to detailed molecular models for the copper transfer mechanism.     

Electrical Insulating Properties of Porcelain Enamels on Copper

The electrical properties of copper oxide-bearing porcelain enamels fired on sheet platinum and of the clear base porcelain enamel fired on sheet copper were measured. The dielectric constant, dissipation factor, and resistivity of the coatings were determined from room temperature to 700°F., and at frequencies varying from 0.1 to 100 kc. per second. The effect of firing time, firing temperature, and coating thickness on the copper ion content resulting in the coatings fired on copper was investigated. The copper ion concentration of the porcelain enamels fired on cop per was determined by X-ray fluorescence analysis. Electrical measurements of coatings fired on platinum and on copper were correlated with the copper ion concentration of the coating. At concentrations in the coating below 5% CuO, some marked changes occurred in the electrical characteristics of the coatings as a function of CuO content. These changes were even more accentuated at elevated temperatures. At concentrations varying from 5% CuO to the saturation point of CuO in the coating (about 20% CuO for coatings fired at 1600°F.), the electrical properties of these coatings at room temperature were nearly unchanged throughout this range, whereas at elevated temperatures the general effect was that of a decrease in dielectric constant and dissipation factor as the CuO content was increased.     

Voltammetric study of the influence of benzotriazole on copper deposition from a sulphuric plating bath

Copper electrodeposition on to a platinum substrate from an acid sulphate plating bath was investigated with and without the additive benzotriazole (BTAH). In voltammetric experiments, the deposition process is shifted to more negative potentials in the presence of BTAH than in its absence from the bath. Moreover, the current density of the deposition process was higher in the presence of this additive than in its absence. With or without the additive, copper deposition showed features of nucleation in the voltammetric curves. Scanning electronic microscopy (SEM) images showed that copper deposits laid down in the presence of BTAH, for any potential and charge density studied, were smoother than in the absence of this additive. X-ray spectra indicated that the electrodeposits produced in the absence or presence of BTAH were composed of a mixture of copper, copper oxide and platinum oxide and also indicated that in the presence of BTAH, the deposit was less crystalline than in its absence.     

Morphological selection of electroless metal deposits on silicon in aqueous fluoride solution

Well-defined silver and gold dendrites are prepared on silicon substrates in aqueous fluoride acid solution containing AgNO₃ and KAuCl₄, respectively. In cases of electroless platinum and copper deposition in fluoride acid solution, no corresponding metal dendrites but platinum microcrystallines and copper granular-crystallines are formed. Our experiments found that the morphological selection of electroless metal deposits is related to the microstructure of etched silicon. A possible template mechanism and affecting factors for the morphological selection of electroless metal deposits are discussed.     

Synthesis of nanoporous platinum thin films and application as hydrogen sensor

A nanoporous platinum (np-Pt) thin film based hydrogen sensor was fabricated and studied. The np-Pt thin films were fabricated through a method of chemical dealloying and coarsening starting from a CuPt alloy. The alloy thin films of Cu_xPt_1?x were deposited by sputtering copper and platinum at the same time. The dealloying process completely removed the copper from the film. We demonstrate a method to control the porosity of np-Pt by a method of coarsening. Scanning electron microscopy confirmed the presence of porosity with size ranging from a few nanometers to tens of nanometers. A sensor device with four electrodes was fabricated on the np-Pt thin films using a stainless steel mask and by sputtering copper. The electrical characteristics of the sensor exhibit marked sensitivity or current changes in the presence of hydrogen. The results demonstrate that np-Pt thin films configured as a gas sensor have high sensitivity to hydrogen.