Electrochemically distinguishable states of ferricytochrome c and their transition with changes in temperature and pH

The biphasic behavior of the formal potential (E^o') of cytochrome c with variations of pH (2.5–9) and temperature (4–52° C) is discussed. From an analysis of the dependence of E^o' on pH and temperature it was found that the biphasic behavior of E^o' is due to ferricytochrome c and not ferrocytochrome c. Four conformational states in ferricytochrome c have been identified from the electrochemical measurements. The linear change in E^o' of the individual states with pH and temperature was explained by a simple equation of the electrode reaction with an apparent protonation number. A pH versus temperature diagram which shows the stable regions of the four states has been obtained. These four states correspond to states that have been suggested by other methods such as spectrophotometry and resonance Raman spectroscopy. Since the biphasic changes of E^o' with pH and temperature were very sharp, a conformational transition instead of a change by an equilibrium reaction was introduced to explaine this feature. The high temperature dependence of E^o' (2 mV K⁻¹) of some states has been explained partly by the concentration dependent effect of protons on the entropy change of the electrode reaction.     

Distribution of metal chelates between aqueous and surfactant phases separated from a micellar solution of a nonionic surfactant

A dilute micellar solution of poly(oxyethylene) 4-nonylphenyl ether with oxyethylene units 7.5 (PONPE-7.5) was separated into two phases (aqueous and surfactant phases) at room temperature. The partition constants of several chelating reagents and their metal chelates between the two phases were determined at 293 K and ionic strength 0.1 (NaClO₄). The partition constants of the neutral metal chelates depend on the kind of metal ions and were considerably smaller than those expected from the regular solution theory. These facts suggested that the chelates were incorporated into a hydrocarbon environment in the surfactant phase, whereas the chelating reagents were distributed in the poly(oxyethylene) part of PONPE-7.5. A brief review was also presented on the analytical applications to the extraction of metal ions and organic compounds.     

Nickel-catalyzed cross-coupling of silyl enol ethers with grignard reagents. Regio- and stereocontrolled synthesis of olefins

The substitution of the siloxy group in silyl enol ethers with Grignard reagents to form olefins is accomplished by use of nickel acetylacetonate or phosphine-nickel complexes as catalysts, the stereo- and regiochemistry of coupled olefins depending upon the nature of the catalyst and reaction conditions employed.     

Micelle-mediated extraction

The extraction technique based on phase separation in aqueous micellar solutions is reviewed. The technique has now been utilized for separation and preconcentration of metal chelates, organic compounds, and proteins. Additionally, the phase behavior of the micellar solutions and recent advances in the phase separation technique are also described. In the extraction of metal chelates, distribution equilibria are considered. In contrast to conventional solvent extraction, the distribution of metal chelates into a condensed surfactant phase (surfactant-rich phase) was dependent on metal ions. Proteins were extractable into the surfactant-rich phase according to their hydrophobicity. The recent use of affinity ligands and water-soluble polymers for controlling extractability of proteins are also introduced.     

A new entry of nucleophiles in rhodium-catalyzed asymmetric 1,4-addition reactions: addition of organozinc reagents for the synthesis of 2-aryl-4-piperidones

A rhodium-catalyzed asymmetric 1,4-addition reaction has been applied to the synthesis of 2-aryl-4-piperidones. While other conventional nucleophiles fail, organozinc reagents have been successfully utilized for the construction of these useful compounds in very good yield and enantiomeric excess.     

Use of cholate derivatives with submicellar concentration for controlling selectivity of proteins in hydrophobic interaction chromatography

Hydrophobic interaction chromatography (HIC) of proteins using a phenyl column has been performed in the presence of various surfactants with micellar and submicellar concentration ranges. Most surfactants were effective for a decrease in the retention of proteins in both concentration ranges. However, the use of anionic cholate derivatives increased the retention of the proteins with high isoelectric point, such as lysozyme, cytochrome c, and trypsin, in submicellar concentration range, and then decreased it above the critical micellar concentration, while the retention of the other proteins was monotonously decreased. The results of frontal chromatographic analysis of the surfactant and capillary electrophoresis for the proteins in the presence of surfactant show that in the submicellar concentration range, cholate derivatives allowed to be adsorbed on the stationary phase, while they exhibited no interactions with the proteins. Thus, it appeared that the increase in the retention of basic proteins was due to the electrostatic attraction between the proteins and cholate-modified stationary phase. We have applied the unique property of cholate to the separation of ovalbumin and lysozyme in egg white sample using hydrophobic chromatography.     

Cografting kinetics of styrene and ethyl acrylate onto polyethylene

Kinetic studies of cografting reactions of styrene (St) and ethyl acrylate (EA) onto preirradiated polyethylene (PE) have been investigated by means of bromine labeling and infrared spectroscopy. Kinetic data obtained from these methods, that is, the percent grafting, the number of graft chains, and growing rates, were obtained at temperatures of 0, 20, 40, and 50°C. The graft percent was virtually influenced by the degree of swelling. At 0°C, the mixing ratio of ethyl acrylate and styrene monomer before the beginning of the reaction was equal to the existence ratio in the graft chains after the reaction. Therefore, this reaction is considered to be diffusion-controlled. On the contrary, at 20 and 40°C, the existence ratio in graft chains after the reaction. Therefore, this reaction is considered to be diffusion-controlled. On the contrary, at 20 and 40°C, the existence ratio in graft chains agreed with the theoretical curve calculated from monomer reactivity ratio. The number of active graft chains for given times were 3～5 × 10^?7 mole/g PE and it decreased with temperature; 0 > 20 > 50°C. While the total number of graft chains is 5～15 × 10^?7 mole/g PE and it increased with temperature; 0 < 20 < 50°C. The growing rate were 1～5 monomer/site/sec for 0°C, 2～15 for 20°C.     

Catalytic asymmetric hydrosilylation of ketones: I. Chiral phosphine-platinum(II) complex-catalyzed hydrosilylation.

Dichlorobis(dimethylphenylphosphine)di-μ-chlorodiplatinum(II) was found to be an effective catalyst for the hydrosilylation of alkyl phenyl ketones with methyldichlorosilane to give the corresponding silyl ethers of 1-phenylalkanols. In the case of dialkyl ketones, the reaction was accompanied by formation of silyl enol ethers in considerable amounts. Asymmetric hydrosilylation of a series of alkyl phenyl ketones catalyzed by chiral phosphine- platinum(II) complexes was undertaken. The products were readily converted into partially active 1-phenylalkanols.     

Iron-catalyzed oxidative homo-coupling of aryl Grignard reagents

[reaction: see text] Iron-catalyzed homo-coupling of aryl Grignard reagents was successfully developed. A variety of aryl Grignard reagents were efficiently converted into the corresponding symmetrical biaryls in the presence of 1-5 mol % FeCl3 and a stoichiometric amount of 1,2-dichloroethane.     

Mechanism of stereoregular polymerization of butadiene by homogeneous Ziegler-Natta catalysts. II. Effects of the nature of bases and halogens

The effects of the addition of various bases to metal acetylacetonate–diethylaluminum chloride catalyst systems were investigated. Generally speaking, the cis content of polybutadiene decreases as the basicity of bases in a homologous series increases. The effects were more prominent for the cobalt and the titanium catalysts than for the nickel and the vanadium catalysts. The effects of the species of halogens on the microstructure of polybutadiene were also discussed. In conclusion, the decrease of the cis content was ascribed to the decrease of the electron density of dπ orbitals of the transition metal atoms.