Electrolytic process for regenerating nadp from nadph in a polymer matrix-bound form

Regeneration of nicotinamide adenine dinucleotide phosphate (NADP) from its reduced form (NADPH) was performed in a matrix-bound form by an electrolytic method. NADP was immobilized to alginic acid. No significant loss of coenzymic function was induced by the immobilization of NADP on the matrix. Bound NADP was soluble in water. Glucose-6-phosphate dehydrogenase (G-6-PDH) was taken as a model system of coenzyme requiring enzyme. G-6-PDH immobilized on alumina particles was coupled with the soluble form of bound NADP in a fluidized bed type of reactor. The enzymatically reduced coenzyme was electrolytically oxidized in the coenzyme regenerator of NADP from NADPH, which was found to cause no harmful loss of coenzymic function.     

Electrode reactions during electrolytic preparation of nickel hydroxide

We investigate the electrode reactions involved in the electrolytic precipitation of nickel hydroxide from nickel nitrate through quantitative assessment of the reaction products using stainless steel cathode with Ti and Ni anodes. The nitrate ion is reduced at the cathode to form nitrite and ammonium ion, the later being the major product. The production of ammonium ion followed either directly via reduction of nitrate to ammonium ion or in steps via nitrate reduction to nitrite which further reduced to ammonium ion. Finally, we report XRD measurements, tap density, and the discharge capacity performed on the electrolytically precipitated Ni(OH)₂.     

Electron spin resonance studies and theoretical quantum calculations of free radicals generated from anthracenetrione by electrochemical and microsomal reduction

The ESR spectra of radicals obtained by electrolytic reduction of 4,4-dimethylanthracene-1,9,10 (4H)-trione (1) and the regioisomeric quinones 8-acetyloxymethyl-4,4,5-trimethyl- (2), and 5-acetyloxy-methyl-4,4,8-trimethyl-(4H)-1,9,10-anthracenetrione (3) were measured in DMSO and analyzed by quantum chemical calculations. The electrochemistry of these compounds was characterized using cyclic voltammetry, in DMSO and DMF solvents and compared with nifurtimox. The quinones were also reduced by microsomal NADPH-cytochrome P-450 reductase and the corresponding radicals species were also detected by ESR spectroscopy. AMI, INDO, and ADF calculations were performed to obtain the optimized geometries, theoretical hyperfine constants, and spin distributions, respectively. Density functional theory was used to rationalize the reduction potential of these compounds.     

Electro-initiated cationic polymerizations—III: Polymerization of anethole in the presence of tetra-alkylammonium perchlorates

The electro-polymerization of trans-anethole in 1,2-dichloroethane solution with tetraethyland tetrabutylammonium perchlorates as supporting electrolytes was studied: the dependences of polymerization rates and molecular weight on some experimental parameters were determined.To investigate the electrolytic formation of initiating species, the anolyte from the electrolysis of the supporting salt in the absence of monomer was examined; the presence of electrolytically produced perchloric acid was ascertained unequivocally. However, owing to the polarographic behaviour of anethole, which shows an oxidation wave at lower anodic potential than the solvent—salt couple, it was not possible to postulate any reaction mechanism based on a single initiation reaction.The fact that the polymerizations were carried out without control of the anodic potential and some of the kinetic results indicate that two parallel initiation reactions (direct monomer oxidation and protonation by electrolytically formed perchloric acid) can occur.     

Approaches to Artificial Macromolecular Oxygen Carriers

Construction of artificial oxygen carriers by use of iron or cobalt complexes bound to synthetic polymers was attempted. Radical copolymerization of porphyrin vinyl monomers with styrene gave the metalloporphyrins covalently bonded to a polymer chain at low concentration. For these metalloporphyrin polymers, irreversible oxidation via dimerization was prevented in aprotic solvents and reversible oxygenation was observed. The chemical environment around the oxygen-binding site was presumed to play an important role on the stability of oxygenated complex as in the case of the tetraamide groups on the porphyrin plane. When ethylenebis(salicylideniminato)cobalt chelate coordinated to a polymer-ligand, it formed a stable oxygenated complex at room temperature. Rotational motion of the chelate was decreased markedly by the polymer chain to enhance the coordinate bond between the metal ion and the bound oxygen molecule. Furthermore, the iron porphyrin with bulky substituents was oxygenated even in homogeneous aqueous solutions by combining it with the rigid, hydrophobic domain of a water-soluble block copolymer.     

Precise coulometric determination of iron in iron ores with electrogenerated manganese(III) fluoride

Iron in Mohr's salt, electrolytic iron and iron ores has been determined by precision coulometric titration with electrolytically generated manganese (III) fluoride, with biamperometric end-point detection. The titration curve indicated the irreversibility of the electrode reaction of manganese(III) fluoride. Total iron in several standard samples of iron ores was determined with standard deviations of about 0.012%.     

Coulometric determination of uranium and iron or plutonium in a single aliquot using platinum working electrode

A controlled potential coulometric method developed earlier for the determination of uranium in the presence of iron or plutonium using platinum working electrode was extended for individual determination of uranium and iron or plutonium in single aliquot. After uranium determination, Fe(III) or Pu(IV) in the aliquot is reduced electrolytically to Fe(II) or Pu(III) and subsequently determined by electrolytic oxidation to Fe(III) or Pu(IV), respectively. Analysis of synthetic solutions indicated that the values for uranium, iron and plutonium obtained by this method are reproducible within±0.2% and are in good agreement with values obtained using conventional redox methods 1, 2.     

Effect of associating polymer on the viscosity behavior of suspensions consisting of particles with different surface properties

Associating polymers which consist of water-soluble long-chain molecules containing a small fraction of hydrophobic groups (hydrophobes) behave as flocculants in aqueous suspensions. The effects of associating polymers on the rheological behavior are studied for single suspensions of particles with hydrophilic and hydrophobic surfaces, and their mixtures. For particles with hydrophilic surfaces, the suspensions are highly flocculated by a bridging mechanism, because the water-soluble chains adsorb onto hydrophilic surfaces. On the other hand, the particles with hydrophobic surfaces cannot be dispersed in water without polymer and the additions of a small amount of polymer are required for preparation of homogeneous suspensions. The associating polymer acts as a dispersant at low concentrations. However, further additions of polymer lead to a drastic increase in viscosity. Since the hydrophobes on one end of molecules adsorb onto hydrophobic surfaces and other hydrophobes tending from the particles can form micelles, the particles are connected by linkage of interchain associations. By mixing two suspensions of particles with hydrophilic and hydrophobic surfaces, the viscosity is substantially reduced and the flow becomes nearly Newtonian. The associating polymer in complex suspensions acts as a binder between the hydrophilic and hydrophobic surfaces. The hetero-flocculation which leads to the formation of composite particles may be responsible for the viscosity reduction of complex suspensions.     

Planarizing surface topography by polymer adhesion to water-soluble templates with replicated null pattern

Water-soluble polymer templates are replicated from flat master surface patterns by spin-casting a poly(vinyl alcohol) film-forming solution that solidifies at standard ambient conditions in less than 1 min. The fabricated water-soluble templates are coupled to substrates with surface topography by polymer adhesion with an intervening reactive or photocurable liquid layer. After curing, the resulting two-layer solid structure is subjected to water thereby dissolving the soluble template to expose the underlying polymer adhesive layer with flat surface topography. The results demonstrate a reduction of surface topography from several micrometers to less than 100 nm. The chemical interactions involved in bonding the soluble template to the polymer adhesive and then dissolving are measured by Raman spectroscopy to demonstrate that the constituents comprising the water-soluble template are absent from the surface of the planarization material.     

Coupled Electron‐Proton Transport in Electropolymerized Methylene Blue and the Influences of Its Protonation Level on the Rate of Electron Exchange with β‐Nicotinamide Adenine Dinucleotide

This paper describes electrochemical characteristics of poly(methylene blue) electrolytically deposited on glassy carbon and examines the electrocatalytic activity of the polymer toward oxidation of the coenzyme NADH. Redox‐active properties of the cationic polyelectrolyte arose from both electron self‐exchange between electroactive sites and a high ionic film‐conductivity. The diffusion coefficient of charge carriers in the film increased with decreasing solution pH, indicating the pH dependence of the electron diffusion coefficient. The electrocatalytic oxidation of NADH at the polymer‐modified electrode proceeded via an intermediate charge‐transfer complex of the reduced polymer with the oxidized coenzyme. The complex dissociated more rapidly into the oxidation products as the reduced polymer protonated. Thus, the rate constant for the cross‐exchange reaction rose with a decrease in pH. For NADH oxidation, the polyelectrolyte exhibited an electrocatalytic activity higher than the monomeric dye because of a stronger oxidizing power of the second oxidized form of the polymer.     

Electrochemically induced growth of zinc oxide.

The electrolytically induced precipitation of zinc oxide from zinc nitrate solution on gold surfaces in the presence of water-soluble polymers was examined for reaction times between 0.5 and 600 seconds. Regardless of the additive, polycrystalline films of zinc oxide have formed after 30 seconds, but polymeric additives dramatically change the morphology of the ZnO films. Amperometric analysis and fitting the diffusion reduced the current density-time curve according to Avrami kinetics and it reveals that polymers bearing methacrylic acid groups result in spherical growth whereas such with sulfonic acid groups lead to a platelike growth of crystallites. Without additive prisms grow predominantly in one dimension. These findings are confirmed also by scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis.     

Effect of grinding with hydroxypropyl cellulose on the dissolution and particle size of a poorly water-soluble drug.

A new benzofuroquinoline derivative, 3,9-bis(N,N-dimethylcarbamoyloxy)-5H-benzofuro[3,2-c]quinoli ne-6-one (KCA-098), shows poor oral absorption due to practical insolubility in water. In this study, a co-grinding technique employing a water-soluble polymer was used for improvement of the dissolution rate of KCA-098. Powder X-ray diffraction patterns and IR spectra of KCA-098 showed the conversion of the drug from a crystal state to an amorphous state by grinding with a polymer such as hydroxypropyl cellulose (HPC-SL) or polyvinylpyrrolidone (PVP K30). The particle size of KCA-098 was remarkably reduced to a submicron size by grinding with HPC-SL. The co-ground mixture with HPC-SL showed a rapid dissolution rate and maintained supersaturation for more than 1 h. On the other hand, the co-ground mixture with PVP K30 showed rapid dissolution and supersaturation for a shorter period. These data suggest that the rapid dissolution rate was obtained by the conversion of the drug particles from a crystal to amorphous state by grinding with water-soluble polymers and that a reduction in particle size to the submicron level led to the maintenance of supersaturation due to good dispersion.     

Electrical conductivity in vinyl chloride during polymerization

Vinyl chloride of good polymerization quality showed a measurable electrical conductivity. The ionic strength of redistilled VCM appeared to be independent of temperature in the range from 20 to 50°C, and to decrease at higher temperatures. Conductivity measurements during bulk polymerization of VCM showed that the conductivity decreased with conversion. Other results indicated that electrolytically active species, formed during the polymerization, were trapped in the polymer matrix.     

Synthesis and characterization of amino-terminated telechelic polybutadiene

Butadiene was polymerized with water-soluble 4,4′-azobis(amidinopropane)dihydrochloride initiator in an ethanol-water medium at 60°C. Important variables, such as the initiator concentration, monomer concentration, solvency, and polymerization time and temperature were studied. ¹³C-NMR studies showed that no observable chain transfer to ethanol occurred during the polymerization. The conversion of monomer to polymer was significantly increased while maintaining a relatively narrow molecular weight distribution by intermittent feed of the initiator. The amidino end-groups of the polymer were transformed into amino groups by reduction using lithium aluminum hydride in THF, so that amine-terminated polybutadiene was obtained. The amino functionality of the polybutadiene was determined by titration to be 2.0. © 1995 John Wiley & Sons, Inc.     

Enzymatic synthesis of caged NADP cofactors: aqueous NADP photorelease and optical properties

The synthesis of caged NADP analogues 18, 19, and 20 has been accomplished by utilizing the transglycosidase activity of solubilized NAD glycohydrolase (porcine brain) to incorporate caged nicotinamides 2, 3, and 4 into NADP. The synthesis of several nicotinamides modified at the carboxamide with o-nitrobenzyl photolabile groups is demonstrated as well as their potential for enzymatic transglycosidation. These results further demonstrate the feasibility of direct enzymatic transglycosidation of sterically hindered substrates into NAD(P), although high nicotinamide analogue water solubility was found to be a necessary trait for yield enhancement with certain analogues. Caged analogues were surveyed under aqueous conditions for net NADP photorelease, while the UV and fluorescent properties of both analogues and their photobyproducts were assessed for compatibility with systems that rely on optical monitoring of enzyme activity. A highly water-soluble alpha-methyl-o-nitrobenzyl group 8 was developed for the synthesis of 20 in order to enhance net NADP photorelease. Compound 20 demonstrated a high 75% net NADP photoreleased without substantial UV optical blackening or fluorescent byproducts. Analogues 18 and 19 were shown by ESI/MALDI-MS to photogenerate primarily adducts of NADP with deleterious UV and fluorescent properties. Our work stresses the superior release properties conferred by alpha-methyl substitution on aqueous carboxamide photorelease from o-nitrobenzyl compounds.     

A flow system with an electrochemical reduction cell for spectrophotometric determinations of major constituents in Fe/V alloys

Insertion of an electrochemical cell in a flow injection system to evaluate the on-line reduction of ionic species is presented. The cell comprised Pt electrodes installed in two sections separated by a Nafion membrane. The sample was injected into an acidic carrier stream and passed through the cathode compartment of the electrolytic chamber where the species were reduced as consequence of an applied DC voltage. The sample solution leaving the cell received a confluent reagent stream (1,10-phenanthroline buffered at pH 4.7) and the reacted products were dropped off in an open tube for gas/liquid separation. Efficiency of the Fe(3+) to Fe(2+) reduction in acidic medium was evaluated in the presence of strongly reducing species of V and Mo by monitoring the Fe(II) colored complex. Interferences from Pb(2+), Co(2+), Ni(2+), Zn(2+), Cu(2+), V(5+) and Mo(6+) were evaluated. Production of strongly reducing species of V at the electrolytic cell presented higher efficiency for Fe reduction than the electrolytic chamber itself. Total reduction of Fe(3+) in solutions containing up to 10 mg l(-1) Fe plus 100 mg l(-1) V or 100 mg l(-1) of Mo was achieved by the electrolytic process at 2 A. The quantitative determination of Fe and V in low silicon Fe/V alloys was achieved. Accuracy was assessed with the certified Euro-standard 577-1 ferrovanadium alloy produced by the Bureau of Analysed Samples Limited and no difference at the 95% confident level was found.     

DTNB电化学行为的探讨

应用电解还原, 紫外和红外光谱及循环伏安等方法, 研究了DTNB在水溶液中和汞电极上的电化学行为。借助于电解还原和ESR技术, 首次检测到在DTNB电解还原中产生的自由基讯号。研究了该自由基的性质和动力学衰变规律。     

Turbulent drag reduction characteristics of poly(acrylamide-co-acrylic acid) in a rotating disk apparatus

The effects of experimental parameters such as temperature, polymer concentration, and rotational speed of the disk on drag reduction properties of water-soluble copolymer of poly(acrylamide-co-acrylic acid) in a turbulent flow were examined. Drag reduction (DR) efficacy up to 45% was found to be dependent on its medium temperature in a rotating disk apparatus. When the temperature was increased, the copolymer was found to be much susceptible to mechanical degradation, indicating that polymer chain scission becomes more severe at elevated temperatures. In addition, the optimum copolymer concentration for high DR efficacy was also observed.     

Synthesis of soluble electron‐donating polymers containing vinylogous TTF by oxidative dimerization of 1,4‐bisdithiafulvenyl‐2,5‐dialkoxybenzene

A new electron‐donating polymer composed of a vinylogous tetrathiafulvalene (TTF) unit was prepared by the oxidative dimerization of 1,4‐bisdithiafulvenyl‐2,5‐didodecyloxybenzene using iodine. The polymer was soluble in common organic solvents such as CHCl₃ and toluene. The number‐average molecular weight of the polymer with dodecyloxy group was 24,900 determined from GPC. The UV–vis spectrum of the polymer showed the absorption maxima at 587, 712, and 803 nm, which are due to a cation radical of the vinylogous TTF unit in the polymer. The reduction of the polymer to its neutral state was performed using sodium hydrogen sulfite. The structure of the polymer was confirmed by ¹H NMR and UV–vis spectra compared with that of a dimer model compound prepared by oxidation of 1‐dithiafulvenyl‐2,5‐didodecyloxybenzene using iodine. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4600–4608, 2005     

对硝基苯酚在质子惰性溶剂中的氧化还原机理

利用现场红外光谱电化学法、红外光谱循环伏吸法(CVA)和导数循环伏吸法(DCVA)研究了对硝基苯酚(PNP)在乙腈中的氧化还原机理,并结合B3LYP方法在6-311++G*水平上计算得出反应中自由基阴离子和二聚体可能的结构.通过循环伏安曲线(CV)和快速扫描红外光谱验证了在电化学还原过程中PNP在乙腈溶剂中发生较复杂的自质子化反应,并且PNP的电化学行为受其浓度的影响.当PNP浓度较高时,PNP在还原成自由基阴离子后发生自质子化作用,然后自由基阴离子与质子化产物得到电子发生二聚反应,随后PNP阴离子还原成二价阴离子;当PNP浓度较低时,电化学还原机理会发生改变,二聚现象消失,阴离子自由基继续还原.