Cleavage of nucleotides by Ce4+ and the lanthanide metal complexes

The cleavage of adenosine-5'-monophosphate (5'-AMP) and guanosine-5'-monophosphate (S-GMP) by Ce4+ and lanthanide complex of 2-carboxyethylgermanium sesquioxide (Ge-132) in acidic and near neutral conditions was investigated by NMR, HPLC and measuring the liberated inorganic phosphate at 37 degrees C and 50 degrees C, The results showed that 5'-GMP and 5'-AMP was converted to guanine (G), 5'-monophosphate (depurination of 5'-GMP), ribose (depurination and dephosphorylation of 5'-GMP), phosphate and adenine (A), 5'-monophosphate (depurination of 5'-AMP), ribose (depurination and dephosphorylation of 5'-AMP), phosphate respectively by Ce4+. In presence of lanthanide complexes, 5'-GMP and 5'-AMP were converted to guanosine (Guo) and phosphate and adenosine (Ado) and phosphate respectively. The mechanism of cleaving 5'-GMP and 5'-AMP is hydrolytic scission.

Catalytic oxidization polymerization of aniline in an H2O2-Fe2+ system

Polyaniline is prepared by chemical polymerization of aniline in an acidic solution using H2O2 as an oxidant and ferrous chloride as a catalyst. A wide variety of synthesis parameters are studied, such as the amount of the catalyst, reaction temperature, reaction time, initial molar ratio of oxidant, monomer and catalyst, and aniline and HCl concentrations. The polymerization of aniline can be initiated by a very small amount of catalyst. The yield and the conductivity of product depend on the initial molar ratio of the oxidant and monomer. The polyaniline with a conductivity of about 10 degrees S/cm and a yield of 60% is prepared under optimum conditions. The process of polymerization was studied by in situ ultraviolet-visible spectroscopy and open-circuit potential technology. Compared to the polymerization process in a (NH4)(2)S2O8 system, the features of the H2O2-Fe2+ system are pointed out, and the chain growth mechanism is proposed. (C) 1999 John Wiley & Sons, Inc.

Redox reaction of disulfide polyaniline in aqueous solution

The cleavage and formation of the di sulfide bond of 2,5-dimercapto-1,3,4-thiadiazole (DMcT) were examined in an aqueous solution of pH value from 0 to 14 with and without polyaniline (PAn), The redox reaction of DMcT was accelerated by PAn in acidic condition. The cell using this anodic material was set-up and characterized in aqueous electrolyte.

Studies of methane reforming with carbon dioxide on hexaaluminates

In this paper, a series of Sr1-xLaxNiAl11O19 catalysts were synthesized and their chemical and physical properties were investigated by XRD, UV-DRS, H-2-O-2 titration, TPR and Py-IR techniques. The experimental results show that the Sr1-xLaxNiAl11O19 catalysts have a magnetoplumbite structure and Ni ion is shared between tetrahedral and octahedral sites of the spinel blocks, and the amount of nickel ions in the tetrahedral environment increases with the increase of x value in Sr1-xLaxNiAl11O19. The TPR study revealed that the reducibility of the series of the catalysts depends strongly on the substitution value x, that is, a low temperature peak appears for samples without substitution, in case of samples with x = 1 high temperature peak appears, and for samples with 0acidic sites and amount of the carbon deposition on the catalyst surface. So it is evident that carbon deposition in carbon dioxide reforming of methane can be suppressed by decreasing the acidity of the complex oxides catalysts.

Detection of specific noncovalent protein-fullerenols complexes by matrix-assisted laser desorption ionization mass spectrometry

Matrix-assisted laser desorption ionization (MALDI) mass spectrometry is difficult for the characterization of noncovalent complexes hitherto because of the limitations in acidic matrix, sample preparation, laser-induced polymerization and adduct formation with matrix. Under our experimental conditions, sinapinic acid is used as a matrix, the specific noncovalent interactions of protein with fullerenols were observed by MALDI mass spectrometry. Some mass spectrometric features, such as mass shifts, broad adduct peaks and stoichiometries, showed that the specific non-covalent complexes between protein and fullerenols have been formed at a ratio of 1 : 4 for hemoglobin-fullerenols or 1 : 1 for myoglobin-fullerenols. The results implied that fullereneols could be used to protect partly hemoglobin from decomposition in acidic media, and therefore, it is possible to realize the molecular weight determination of a quaternary protein by MALDI mass spectrometry via the addition of specific organic compound in the matrix.

Electrochemistry of vanadium hexacyanoferrate film

Two stable redox couples, accompanying clear color switches between yellow green and blue, can be observed when the VHCF-coated film platinum electrodes are cyclic potential scanned in 3.6 M H2SO4 and 0.2 M K2SO4 electrolyte solution. Electrochemical results and in situ Fourier transfer infrared (FT-IR) spectroscopy demonstrate that the redox reaction of the electroactive iron sites is related to the first redox couple (E-1/2 = 0.81 V) while the second redox couple (E-1/2 = 1.01 V) is due to the redox reactions of the electroactive vanadyl ions. Under the proper conditions, such as in high acidic solutions or thin films (deposition time is less than 2 min) and so on, the third redox couple (E-1/2 = 0.89-0.94 V) can be observed on the cyclic voltammograms, which originates from the redox reactions of the interstitial vanadyl ions. This electrochemical reaction mechanism is investigated by in situ probe beam deflection technique, exchange of K+ ions accompanies with redox reaction of the iron sites, but for redox reaction of the vanadyl ions, both H+ ions, K+ ions and water molecules are involved.

Self-assembled monolayers of thiols on gold electrodes for bioelectrochemistry and biosensors

Monolayers of biological compounds including redox proteins and enzymes, and phospholipids have been immobilized on a gold electrode surface through self-assembling. These proteins and enzymes, such as cytochrome c, cytochrome c oxidase and horseradish peroxidase (HRP), immobilized covalently to the self-assembled monolayers (SAMs) of 3-mercaptopropionic acid on a gold electrode, communicate directly electrons with the electrode surface without mediators and keep their physiological activities. The electron transfer of HRP with the gold electrode can also be mediated by the alkanethiol SAMs with electroactive group viologens on the gold electrode surface. All these direct electrochemistries of proteins and enzymes might offer an opportunity to build a third generation of biosensors without mediators for analytes, such as H2O2, glucose and cholesterol. Monensin and valinomycin have been incorporated into the bilayers on the gold electrode consisting of the SAMs of alkanethiol and a lipid monolayer, which have high selectivity for monovalent ions, and the resulting Na+ or K+ sensor has a wide linear range and high stability. These self-assembly systems provide a good mimetic model for studying the physiological function of a membrane and its associated enzyme. (C) 1997 Elsevier Science S.A.

Research on modified electrode of conducting polymer .2. Characteristics of polypyrrole film doped with heteropolyanions

Polypyrrole film electrode with Co(W2O7)(6)(10-) and CuW12O406- ions were synthesised in aqueous solutions, The electrode possesses a good stability and cyclic voltammetric behavior in weakly acidic or near neutral solutions, The redox of CuW12O406- ion can be catalysed by the polypyrrole film, The ESR measurement of the polypyrrole film with Co(W2O7)(6)(10-) and CuW12O406- ions indicates that the heteropolyanions not only play the role of neutralizing electricity in the polypyrrole film, contrasted with the film containing NO3-, but also Interact with the polypyrrole molecular chain to form some additive compound, The additive compound affects the electric structure elf the polypyrrole film and is unstable at more positive or more negative potentials.

Heterogenization of heteropolyacids: A general discussion on the preparation of supported acid catalysts

Heteropolyacids (HPAs) possess both acidic and redox catalytic properties and held extensive promise of practical application. These type of compound display a great potential of specific synthesis reactions for replacing sulfuric acid to satisfy the requirements of environmental protection. Heterogenizing HPAs would not only make them more useful in liquid phase oxidation with oxygen and in acid-catalyzed reaction, as the catalyst is often difficult to separate from the reaction products, but also create favorable factors for realizing heterogenization of homogeneous reaction and even utilizing new technology of catalytic distillation. In this paper, different kinds of porous materials which are well characterized, including oxides such as Al2O3, SiO2, TiO2, diatomite, bentonite, and active carbon of different sources, were used as support for heterogenizing HPAs (in different media), and the obtained results, the intrinsic characters of supports which may influence both the nature of the interaction between HPAs and supports in the heterogenization and the activity in the catalytic reaction, are explored. It is expected that these can provide a referential model for preparing supported acid catalyst used in liquid phase.

Probe beam deflection study of the ion exchange between Prussian blue film or indium hexacyanoferrate film and electrolyte solutions

Probe beam deflection(PBD) technique together with electrochemical techniques such as cyclic voltammetry was used to study the ion exchange in prussian blue(PB) film and its analogue indium hexacyanoferrate (InHCF) chemically modified electrodes, The ion exchange mechanism of PB was verified as following: K2Fe2+FeI(CN)(6)(-e--K+)reversible arrow(+e-+K+)KFe(3+)Fe(I)(CN)(6)(-xe--xK+)reversible arrow(+xe-+xK+) [Fe3+FeI(CN)(6)](x)[KFe3+FeI(CN)(6)](1-x) where on reduction in contact with an acidic KCl electrolyte, H+ enter PB film before K+. Both the cations and anions participate concurrently in the redox process of InHCF, meanwhile K+ ion plays a major role in the whole charge transfer process of this film with increasing radii of anions.

Electrochemical study of isopoly- and heteropoly-oxometallates film modified microelectrodes .6. Preparation and redox properties of 12-molybdophosphoric acid and 12-molybdosilicic acid modified carbon fiber microelectrodes

The redox behaviours of 12-molybdophosphoric acid (12-MPA) and 12-molybdosilicic acid (12-MSA) in aqueous acid media are characterized at the carbon fiber (CF) microelectrode. The preparation of CF microelectrode modified with 12-MPA or 12-MSA monolayer and the oxidation-reduction properties of the modified electrode in aqueous acid media or 50% (v/v) water-organic media containing some inorganic acids are studied by cyclic voltammetry. 12-MPA or 12-MSA monolayer modified CF microelectrode with high stability and redox reversibility in aqueous acidic media can be prepared by simple dip coating. The cyclic voltammograms of 12-MPA and 12-MSA and their modified CF microelectrodes in aqueous acid solution exhibit three two-electron reversible waves with the same half-wave potentials, which defines that the species adsorbed on the CF electrode surface are 12-MPA and 12-MSA themselves. The acidity of electrolyte solution, the organic solvents in the electrolyte solution, and the scanning potential range strongly influence on the redox behaviours and stability of 12-MPA or 12-MSA monolayer modified electrodes. On the other hand, the catalytic effects of the 12-MPA and 12-MSA and chlorate anions in aqueous acidic solution on the electrode reaction processes of 12-MPA or 12-MSA are described.

SYNTHESIS AND PHASE-BEHAVIOR STUDIES OF 2 NEW CHIRAL LIQUID-CRYSTALS OF SCHIFF-BASE - THE INFLUENCE OF INTRAMOLECULAR HYDROGEN-BOND ON THE PHASE-BEHAVIOR

Two new chiral liquid crystals of schiff-base type have been synthesized. This series of compounds contain a-chloro acidic ester chain prepared from commercially available L-valine. Both of the compounds exhibit tilted smectic phases; their phase transitions were studied using DSC and polarized optical microscopy; the influence of intramolecular hydrogen bonds on the phase behavior was studied as well.

INTERACTIONS OF RARE-EARTH LENS WITH BOVINE BLOOD CU(ZN)-SUPEROXIDE DISMUTASE

The interactions of lanthanium trichloride and terbium trichloride with bovine blood Cu (Zn)-superoxide dismutase [Cu(Zn)-SOD] in the aqueous solution of hexamethylenetetrarnine buffer (pH = 6.3) have been studied by using fluorescece, CD and ESR spectra. The results indicated that rare earth ions were coordinated to the carboxyl groups of acidic amino acid residues which were far from active center of the Cu(Zn)-SOD molecule and only lightly disturbed the secondary structure of the enzyme protien, and made the coordination structure of enzyme-bound CU2+ come from the rhombchedron to the axial shape at 77 K and the activity of Cu(Zn)-SOD enzyme was not nearly changed at room temperature.

APPLICATION OF POLYBUTADIENE-BASED POLYMERIC SURFACTANTS IN LIQUID MEMBRANE SEPARATION

New polybutadiene-based surfactants (LYF) were synthesized by sulfonation of liquid polybutadiene with acetal sulfate at an elevated temperature, and their properties in a liquid surfactant membrane (LSM) separation process were examined by comparison with the two polyisobutylene-based surfactants ECA4360 and EM301. It was found that LYF surfactants had satisfactory overall properties as regards stability, swelling, and demulsification Of the W/O emulsion in the cases of both acidic and caustic internal aqueous phases.

EFFECTS OF METAL-IONS ON THE CONFORMATION OF POLAR HEADGROUP OF SPHINGOMYELIN BILAYER

With the wide application of rare earth in agriculture, medicament, especially the application of Gd-DTPA as nuclear magnetic resonance image reagent in clinical practice([1]), the studies on the toxicology in biological body, as well as the study on the use as informative probes instead of divalent calcium ion in biological and biochemical research have attracted intensive concern([2]). Phospholipids bilayers have served as a model of biomembrane in the last two decades. The effects of metal ions on the conformation of polar headgroup of dipalmitoylphosphatidylcholine (DPPC) bilayers have been reported([3]). Sphingomyelin is major component of several biological tissues such as brain and nerve cells and has identical polar headgroup to DPPC. The interaction of metal ions with sphingomyelin bilayer remains nonrevealed. This note presents the results of the study on this aspect.