Structural approach to nanoscience: a case study of complex and cluster formation in ZnBr2–ZnCl2 melts

Although the melt structure of glass-forming ZnCl₂ has so far been well studied, there exists quite little information on the structural change due to anion-substitution. In the present work, the short-range structure of ZnCl₂–ZnBr₂ mixture melts was analyzed systematically by time-of-flight pulsed neutron diffraction techniques, Raman spectroscopy, molecular orbital calculations, and molecular dynamics simulations. According to radial distribution analysis, it was found that there were tetrahedral structural units of ligand-substituted [ZnCl_nBr_4−n]²⁻ (n=0–4) in these melts, not implying the simple mixing of [ZnCl₄]²⁻ and [ZnBr₄]²⁻ units. Further detailed estimation indicated that the ligand-substituted complex anions were linked with each other by sharing a common anion.     

Surface Analysis of Cr2O3‐, CoO‐, and Al2O3‐Doped Iron–Phosphate Glasses at High Temperature

Surface structures of iron–phosphate glasses were examined using X‐ray photoelectron spectroscopy (XPS). Cr₂O₃, CoO, and Al₂O₃ were introduced to the glass by the replacement of a part of Fe₂O₃, and the simulated fission products are also added. The obtained glasses showed high chemical durabilities by MCC‐1 test. In situ high‐temperature and room‐temperature XPS measurements were conducted on the polished sample surfaces and also those after 1‐week chemical durability test. Unique trends were observed in XPS spectra on heating and after the chemical durability test, respectively. Nature of the glass surface of iron–phosphate glasses was explained from the point of view of surface energy, and the origin of high chemical durability and the effect of chromium ions were discussed based on the changes on surface composition and valence states of transition‐metal ions.     

Reductive activation of dioxygen: A new concept for the catalytic oxidation

Transition metal–dioxygen complexes, which have been studied intensively in relevance to the active species of oxygenation with dioxygen molecule, are classified according to the extent of electron transfer from the metal center(s) to the O₂ ligand. A new O₂-activation method via a higher valent bis(μ-oxo) dimetal species resulting from extensive electron transfer is proposed on the basis of the results of our bioinorganic studies on the dioxygen complexes supported by the hydrotris(3,5-diisopropylpyrazolyl)borate ligand (Tp^iPr).     

Effect of lecithin on the release of 5′-nucleotidase from liver plasma membrane of rat by bile acids

Bile acids solubilize proteins from liver plasma membrane both in vivo and in vitro. The ability to solubilize the proteins is dependent on the species of bile acid. In this paper, the effect of phospholipid on the solubilization of a membrane-bound enzyme by bile acids was investigated in vitro. Taurocholate (TC) and tauroursodeoxycholate (TUDC) solubilized the enzyme, 5′-nucleotidase, from the liver plasma membrane of the rat in a concentration-dependent manner, although there was a great difference in their effect; at 40 mM, TC solubilized 55.4% of the original 5′-nucleotidase activity of the membrane, but TUDC only 5.7%. While lecithin alone had no solubilizing effect, its addition to the bile acids provoked a 10-fold increase in the solubilizing effect of TUDC, but virtually no change for TC, essentially equalizing the solubilizing effect of the two. Both TC-rich and TUDC-rich bile were obtained from rats infused with the respective bile acids via the jugular vein after their endogenous bile acid pool had been depleted. The solubilization effect of these biles was quite similar to the bile acid-lecithin mixtures. These findings demonstrate that lecithin enhances the ability of the bile acids to solubilize the membrane protein and eliminates the difference in the two bile acid species in their solubilizing ability.     

Determination of water-soluble vitamins using a colorimetric microbial viability assay based on the reduction of water-soluble tetrazolium salts

A method for the determination of water-soluble vitamins using a colorimetric microbial viability assay based on the reduction of the tetrazolium salt {2-(2-methoxy-4-nitrophenyl)-3-(4-nitrophenyl)-5-(2,4-disulfophenyl)-2H-tetrazolium, monosodium salt (WST-8)} via 2-methyl-1,4-napthoquinone (NQ) was developed. Measurement conditions were optimized for the microbiological determination of water-soluble vitamins, such as vitamin B₆, biotin, folic acid, niacin, and pantothenic acid, using microorganisms that have a water-soluble vitamin requirement. A linear relationship between absorbance and water-soluble vitamin concentration was obtained. The proposed method was applied to determine the concentration of vitamin B₆ in various foodstuffs. There was good agreement between vitamin B₆ concentrations determined after 24 h using the WST-8 colorimetric method and those obtained after 48 h using a conventional method. The results suggest that the WST-8 colorimetric assay is a useful method for the rapid determination of water-soluble vitamins in a 96-well microtiter plate.     

Bio-inorganic approach to hydrocarbon oxidation

Oxidation reactions mimicking the biological oxidative processes are summarized. A dioxygen molecule can be activated by way of reductive activation within a coordination sphere of transition metal complexes, and the resulting electrophilic oxo species, which can also be generated by treatment with an oxo transfer reagent (so-called “shunt path”), exhibit oxidizing ability just like an oxene species.     

PCR-based identification of pathogenic Candida species using primer mixes specific to Candida DNA topoisomerase II genes

For rapid identification of Candida to the species level, degenerated primers and specific primers based on the genomic sequences of DNA topoisomerase II of C. albicans, C. dubliniensis, C. tropicalis (genotypes I and II), C. parapsilosis (genotypes I and II), C. krusei, C. kefyr, C. guilliermondii, C. glabrata, C. lusitaniae and Y. lipolytica were designed and their specificities tested in PCR-based identifications. Each of the specific primers selectively and exclusively amplified its own DNA fragment, not only from the corresponding genomic DNA of the Candida sp. but also from DNA mixtures containing other DNAs from several fungal species. For a simpler PCR-based identification, the specific primers were divided into three groups (PsI, PsII and PsIII), each of which contained four specific primer pairs. PCR with the primer mixes yielded four different sizes of PCR product, corresponding to each Candida sp. in the sample DNA. To obtain higher sensitivity of PCR amplification, sample DNAs were preamplified by the degenerated primer pair (CDF28/CDR148), followed by the main amplification using the primer mixes. By including this nested PCR step, 40 fg yeast genomic DNA was detected in the sample. Furthermore, we applied this nested PCR to a clinical diagnosis, using splenic tissues from experimentally infected mice and several clinical materials from patients. In all cases, the nested PCR amplifications detected proper DNA fragments of Candida spp., which were also identified by the standard identification tests. These results suggest that nested PCR, using primer mixes of the Candida DNA topoisomerase II genes, is simple and feasible for the rapid detection/identification of Candida to species level in clinical materials.     

Trifluoromethylation by Visible-Light-Driven Photoredox Catalysis

The trifluoromethyl group widely prevails in pharmaceutical and agrochemical compounds, while accompanying by the development of new methodologies for trifluoromethylation. Recently, the radical trifluoromethylation by photoredox catalysis has emerged. This Article describes several pioneering works and their representative mechanisms via generation of the trifluoromethyl radical based on photoredox processes.     

Electronic coupling in dimetallic complexes with pi-conjugated bridge

Compound 2, [(eta5-C5Me5) Fe(dppe)]2(mu-C[triple bond]C-CH==CH-C[triple bond]C), was prepared by the reaction of compound 1, [eta5-C5Me5) Fe(dppe)]2+ (mu2-C==CH-CH=CH-HC=C).(PF6)2-, with KOBu(t). Compound 2 showed two quasi-reversible one-electron oxidations at -0.674 and -0.253 V, respectively. The comproportionation constant, Kc, was calculated from these measurements. The mixed-valence(MV) radical cation 2+ showed an absorption peak at 1586 nm, which was assigned to the MV pi-pi band of the delocalized complex (Robin-Day Mixed-valence Class III) and the effective coupling parameter, Hab, is consistent with the presence of electronic delocalization.