Novel synthesis of 2,4-diphenylquinolines

2,4-Diphenylquinolines (3) were quantitatively prepared by heating of 3-aryl-4,6-diphenyl-2-oxo-1,3-diazabicyclo[2,2,0]hex-5-enes (2), which were obtained by photochemical electrocyclization of 1-aryl-4,6-diphenyl-2(1H)-pyrimidin-2-ones (1), in benzene at reflux temperature.     

Methylenetetrahydrofolate reductase polymorphism, diet, and breast cancer in Korean women

To evaluate the interactive effect of methylenetetrahydrofolate reductase (MTHFR) genotype and dietary factors on the development of breast cancer, a hospital based case-control study was conducted in South Korean study population consisting of 189 histologically confirmed incident breast cancer cases and their 189 age-matched controls without present or previous history of cancer. A PCR-RFLP method was used for the genotyping of MTHFR (C677T) and statistical evaluations were performed by unconditional logistic regression analysis. Consumption of some dietary factors, such as green vegetables (OR = 0.3, 95% CI: 0.2-0.6), white vegetables (OR = 0.3, 95% CI: 0.1-0.7) mushrooms (OR = 0.4, 95% CI: 0.3-0.7), and meats (OR = 1.7, 95% CI: 1.1-2.8) significantly decreased or increased the risk of breast cancer. Although the breast cancer risk was 1.7-fold (95% CI: 0.8-3.2) increased in women with MTHFR TT genotype, the association was not statistically significant. Women with MTHFR TT genotype and low green vegetable intake increased 5.6-fold (95% CI: 1.2-26.3) risk of breast cancer compared to high green vegetable intake group containing MTHFR CC/CT genotype. However, the interaction was not significant (p for interaction = 0.96). Our findings suggest that MTHFR polymorphism did not influence individual susceptibility to breast cancer. However MTHFR (C667T) genotype and green vegetable intakes appeared to have the interactive effect in breast cancer development.     

Single crystals of amylose V complexes. II. Crystals with 71 helical configuration

It has been shown that lamellar crystals of amylose V complexes with 7₁ helical configuration can be obtained by using complexing agents larger in cross section than n-butanol. The electron diffraction studies indicated a new unit cell for the unheated lamellar crystals which are composed of molecules with 7₁ helical configuration and hold water molecules on the exterior of the helix. Furthermore, from a throughly dried specimen at 100°C. in vacuo we obtained a pattern which showed only three Debye rings. Its spacings were explained by a two-dimensional hexagonal unit cell having a = b = 14.7 A. proposed by Zaslow. It was also found that when the crystals were dispersed in methanol at room temperature, their electron diffraction pattern was the same as that of the anhydrous amylose V complex of n-butanol.     

Characterization of aggregate structures of phospholipid in the process of vesicle solubilization with sodium cholate using laser light scattering method

The aggregate structures formed during vesicle solubilization by sodium cholate, and their properties, were characterized by static laser light scattering (SLS) and electrophoretic light scattering (ELS) methods. The change in dissymmetry value Z₄₅ was observed by examining the regions of vesicles and micelles. The angular light scattering intensity data could be fitted with a modified shell model for the vesicles and a hollow cylinder model for the mixed micelles. In the case of the vesicles, the scattering curves were fitted with a spherical shell model by introducing the interparticle scattering factor S(q) and taking into account the intervesicle positional correlations, which is a function of the fractal dimension (D) and the interparticle correlation length (L). On the basis of the physical meanings of the fractal dimension and interparticle correlation length, the molecular packings of the membrane and the repulsive interaction between the vesicles were analyzed. Furthermore, using electrophoretic light scattering (ELS) the zeta potentials on the mixed vesicles were found to increase with the molar ratio (Re) of sodium cholate to egg yolk phosphatidylcholine (EggPC) in the membrane. It is suggested that the electrostatic properties of the vesicles result in repulsive interaction which is responsible for no fusion of the mixed vesicles. In addition, in the transition from vesicles to micelles, a cylinder-like micelle appeared as an intermediate structure.     

Nonannihilation dynamics in an exothermic reaction-diffusion system with mono-stable excitability

We consider a 2-component excitable and diffusive system which describes a simple exothermic reaction process. In some parameter regime, there are two characteristics of travelling pulses of the system: (i) travelling pulses are planarly unstable; (ii) when two travelling pulses approach closely, they do not annihilate each other and repel like elastic objects. Under this situation, it is shown that ring patterns break down into complex patterns in 2-dimensions, which are totally different from those arising in the well-known excitable and diffusive system with the FitzHugh-Nagumo nonlinearity. (c) 1997 American Institute of Physics.     

On factor states of -algebras and their extensions

We obtain some results on the unique extension of (factor) states of -algebras which complement various existing results. Our results also lead to a class of -algebras whose states are -convex sums of factor states.

     

Surface structure of silica gel reacted with 3-mercaptopropyltriethoxysilane and 3-aminopropyltriethoxysilane: formation of the S–S bridge structure and its characterization by Raman scattering and diffuse reflectance Fourier transform spectroscopic studies

 Silica gel samples, modified with 3-mercaptopropyltriethoxysilane, and their S–S-bridged samples have been prepared. In order to characterize the microstructure of the surface of these silica gel samples, Raman scattering and diffuse reflectance Fourier transform IR spectra of these samples have been examined by comparison with Raman spectra of various n-alkyl disulfides and their related silane polymers. The S–S and C–S stretch modes characteristic of the CH₂SSCH₂ segment, in addition to the SH and C–S stretch modes of the CH₂SH segment, have been assigned for these silica gel samples. It has been found that, even on the surface of the silica gel, a specific conformer is stabilized about the CH₂SSCH₂ segment. Received: 1 May 2001 Accepted: 16 June 2001     

Preparation of Phosphinated Polymer‐Incarcerated Palladium and Its Application to C?N and C?C Bond‐Forming Reactions

Phosphinated polymer‐incarcerated (PI) Pd catalysts were prepared by immobilization of palladium with phosphinated polymers by using the PI method. The phosphinated PI Pd catalysts showed good catalytic activity without externally added phosphine ligands in the amination of aryl halides for C N bond‐forming reactions, as well as in Suzuki–Miyaura and Sonogashira coupling. No leaching of palladium from the immobilized Pd was observed by fluorescence X‐ray analysis. Furthermore, it was found that immobilization of Pd by the PI process facilitated the suppression of poisoning of the metal by amines. These effects can be ascribed to stabilization of the catalyst by both the phosphine moieties and the benzene rings in the swollen polymer support. The phosphinated PI Pd catalysts could also be recovered by simple filtration and reused several times without leaching of palladium in both the amination and Suzuki–Miyaura coupling reactions.     

MNDO MO theoretical study of electronic structure and homolytic dissociation of perfluoroalkanoyl peroxides

The MNDO molecular orbital method was applied to alkanoyl peroxides and the effect of fluorination on the electronic structure and the rate of the homolytic 0-0 cleavage of alkanoyl peroxides were analyzed. The fluorine atom introduced at the carbon atom makes the peroxy 0-0 bond long and the dihedral angle between two COO planes large. The analysis of two-atom energy and its components energies has shown that the rate of the 0-0 cleavage correlates well with the destabilization of the resonance energy of the 0-0 bond and not with the electrostatic energy. The effect of elongation of the perfluoroalkyl group is also well elucidated by the two-atom energy. The perfluoroalkyl group lowers the σ*(0-0) anti-bonding orbital considerably, and this fully explains the observed rate of induced decomposition of perfluoroalkanoyl peroxides with benzene.     

Coordinated design of cofactor and active site structures in development of new protein catalysts

New methods for the synthesis of artificial metalloenzymes are important for the construction of novel biocatalysts and biomaterials. Recently, we reported new methodology for the synthesis of artificial metalloenzymes by reconstituting apo-myoglobin with metal complexes (Ohashi, M. et al., Angew Chem., Int. Ed. 2003, 42, 1005-1008). However, it has been difficult to improve their reactivity, since their crystal structures were not available. In this article, we report the crystal structures of M(III)(Schiff base).apo-A71GMbs (M = Cr and Mn). The structures suggest that the position of the metal complex in apo-Mb is regulated by (i) noncovalent interaction between the ligand and surrounding peptides and (ii) the ligation of the metal ion to proximal histidine (His93). In addition, it is proposed that specific interactions of Ile107 with 3- and 3'-substituent groups on the salen ligand control the location of the Schiff base ligand in the active site. On the basis of these results, we have successfully controlled the enantioselectivity in the sulfoxidation of thioanisole by changing the size of substituents at the 3 and 3' positions. This is the first example of an enantioselective enzymatic reaction regulated by the design of metal complex in the protein active site.