Two-step purification of cytochrome P-450 from rat liver microsomes using high-performance liquid chromatography

Cytochrome P-450 from rat liver microsomes treated with phenobarbital (PB) was separated into six fractions, as was cytochrome P-450 treated with 3-methylcholanthrene (MC), by high-performance liquid chromatography (HPLC) with an anion-exchange column. PB and MC induced three forms and one form of cytochrome P-450, respectively. The major forms induced by PB and by MC were further purified to apparent homogeneity based on sodium dodecyl(lauryl)sulphate--polyacrylamide gel electrophoresis by HPLC using a hydroxyapatite column. These new HPLC techniques are simple, rapid and useful for the purification of major forms of cytochrome P-450 from solubilized microsomes.     

Sensitive Electrochemical Detection of Oxalate at a Positively Charged Boron‐Doped Diamond Surface

Allyltriethylammonium bromide (ATAB) was covalently attached to the surface of hydrogen‐terminated boron‐doped diamond (BDD) thin films using a photochemical method to fabricate positively charged electrode surfaces. The anodic current for oxalate oxidation both in cyclic voltammetry and in flow‐injection analysis with amperometry was found to be up to two times larger at ATAB‐modified BDD (ATAB‐BDD) than at an unmodified BDD electrode, which may be based on the electrostatic interaction between the oxalate anion and the electrode surface. In addition, the stability of the electrochemical detection of oxalate was improved at the ATAB‐BDD electrode compared to the unmodified electrode.     

Enhancement effect of organic solvents in inductively coupled plasma atomic emission spectrometry

Summary The enhancement factors of various organic solvents in inductively coupled plasma atomic emission spectrometry (ICP-AES) were measured for diethyldithiocarbamate-cadmium(II) or mercury(II)-solvent systems by comparing the maximum emission intensity of an extract with that of the corresponding aqueous solution. The correlation between the enhancement factors obtained and physical parameters of the solvents were investigated. Among them, the best inverse linear relationship existed between log dielectric constant and log enhancement factor. The plot of log (boiling point x viscosity) vs. log enhancement factor also resulted in a line with a negative slope except water. Carbon tetrachloride, chlorofom and xylene, which gave much larger enhancement factors, were recommended for the use in ICP-AES.

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Verstärkungseffekt durch organische Lösungsmittel in der ICP-AES

     

Nanotube nanoscience: A molecular-dynamics study

Carbon nanotubes, fullerenes, and other nanostructured carbon materials are now the most important material phases in the field of nanoscience and nanotechnology. We study the structural stabilities and the interconversion of carbon nanotubes and various other carbon nanostructured phases at elevated temperatures as well as under high pressure using the molecular dynamics method combined with a newly parametrized transferable tight-binding model. The model can deal with not only sp² and sp³ covalent bonds but also the interaction between sp² layers, which plays an important role in the structural and electronic properties of carbon nanostructured materials. It is found that, during a thermal transformation process of carbon nanotubes with C₆₀ fullerenes trapped inside into double-walled carbon nanotubes, the outer carbon-nanotube wall is chemically active and forms covalent bonds with inner carbon atoms, and that most vacancies on the initially imperfect outer tube wall are eventually filled with atoms migrated from inner fullerenes. It is also found that external pressure of about 20 GPa induces a variety of structural transformations in carbon nanostructures. On the other hand, pressure of 30 GPa or higher usually results in sp³-rich amorphous carbon materials. Finally, the rotational interlayer friction force in double-walled carbon nanotubes is studied for the system of (4,4)@(9,9), and the torque of the friction force per unit area acting on each nanotube of the system is found to be as small as . This small value indicates the importance of carbon nanostuctured materials not only for nanoelectronics but also for nanometer-scale machines in the future.     

Fourier transform infrared spectroscopic study of water-in-supercritical CO2 microemulsion as a function of water content

Fourier transform infrared (FT-IR) spectrum of water-in-supercritical CO(2) microemulsion was measured at 60 degrees C and 30.0 MPa over a wide range of water/CO(2) ratio from 0.0 to 1.2 wt % to study the distribution of water into CO(2), interfacial area around surfactant headgroup, and core water pool. The microemulsion was stabilized by sodium bis(1H,1H,2H, 2H-heptadecafluorodecyl)-2-sulfosuccinate [8FS(EO)(2)] equimolarly mixed with sodium 1-oxo-1-[4-(tridecafluorohexyl)phenyl]-2-hexanesulfonate [FC6HC4] or with poly(ethylene glycol) 2,6,8-trimethyl-4-nonyl ether [TMN-6]. The signal area of the O-H stretching band of water suggested that the number of water molecules in the microemulsion increases linearly with the water/CO(2) ratio, except for a slow initial increase below 0.4 wt % due to a part of water dissolved in CO(2). The amount of water in CO(2) was evaluated by decomposing the bending band of water into two components, one at lower frequency ascribed to water in CO(2) and the other at higher frequency to water in the microemulsion. The decomposition confirmed that CO(2) is saturated with water at the water content of 0.4 wt %. It was also revealed, from the symmetric SO stretching frequency of the surfactant, that the sulfonate headgroup is completely hydrated at the water/CO(2) ratio of 0.4-0.5 wt %. The results demonstrated that water is introduced preferentially into CO(2) and the interfacial area at small water content, and then is loaded into the micelle core after the saturation of CO(2) with water and the full hydration of the surfactant headgroup.     

Enantioselective hydrogenation of α-phenylcinnamic acids over cinchonidine-modified Pd/C commercial catalysts

Enantioselective hydrogenation of α-phenylcinnamic acid (PCA) and p,p′-dimethoxyphenylcinnamic acid (DMPCA) was studied over a variety of commercial 5 % Pd/C catalysts to reveal catalyst properties suitable for obtaining high enantioselectivity. The catalysts were characterized by CO adsorption, X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM). It is confirmed that pretreatment at 353 K under atmospheric pressure of H₂ before modification with cinchonidine is very effective for all the Pd/C catalysts used here to improve the selectivity and reaction rate. It is suggested that the distribution of Pd metal particles is crucial to attain high selectivity (ee% = 79 ± 1 for PCA, 89 ± 2 for DMPCA): a uniform or eggshell-type distribution of Pd is more suitable than an egg-white or egg-yolk-type distribution. It is also suggested that the dispersion of Pd metal particles controls the enantioselectivity over cinchonidine (CD)-modified Pd/C catalysts. XPS techniques are proposed to provide a convenient method to find desirable catalysts. The choice of such Pd/C catalysts could facilitate high-throughput guided study on highly enantioselective hydrogenation of α,β-unsaturated carboxylic acids.     

Quantum treatment of hydrogen nuclei in primary kinetic isotope effects in a thermal [1,5]-sigmatropic hydrogen (or deuterium) shift from (Z)-1,3-pentadiene

The geometric and kinetic isotope effects (GIE and KIE) for thermal [1,5]-sigmatropic H and D shifts of (Z)-1,3-pentadiene were studied by including the direct quantum effect of the migrating H or D nucleus in the multi-component molecular orbital-Hartree-Fock (MC_MO-HF) method. Based on the results, the C(1)-D bond lengths are 0.007 Angstrom shorter than the C1-H bond lengths in both the reactant (A) and the transition states (TS), whereas other bond lengths resemble those between H and D. The ratio of the rate constant (k(H)/k(D)) of the reaction for the thermal [1,5]-H and D shifts determined using the MC_MO-HF method (8.28) is closer to the experimental value (12.2) than that determined using either the conventional restricted Hartree-Fock (4.10) or restricted M?ller-Plesset second-order perturbation (3.79) methods.     

Minimum spanning acycle and lifetime of persistent homology in the Linial–Meshulam process

This paper studies a higher dimensional generalization of Frieze's ‐limit theorem on the d‐Linial–Meshulam process. First, we define spanning acycles as a higher dimensional analogue of spanning trees, and connect its minimum weight to persistent homology. Then, our main result shows that the expected weight of the minimum spanning acycle behaves in . © 2017 Wiley Periodicals, Inc. Random Struct. Alg., 51, 315–340, 2017