Remarkably Selective Ag(+) Extraction and Transport by Thiolariat Ethers

Synthesis and metal binding properties of thiolariat ethers, where a sulfide side chain is introduced into a framework of a crown ether, have been performed. Remarkably high Ag(+) selectivity among heavy metal ions was observed in solvent extraction and transport across a liquid membrane using thiolariat ethers with a 15-crown-5 ring as carriers. Thiolariat ethers with a 12-crown-4 or a 18-crown-6 do not exhibit such a high Ag(+) selectivity. The former binds metal ions weakly, and the latter recognizes Pb(2+) as well as Ag(+). The corresponding oxygen analogs, i.e. lariat ethers, do not show Ag(+) selectivity. The Ag(+) binding strength of the sulfoxide and sulfone analogs is much lower than that of thiolariat ethers. Thiolariat ethers with a benzocrown framework containing a sulfide chain at the 4 position of the benzene nucleus showed very low affinity to Ag(+). Extractability and transport ability using various thiolariat ether derivatives strongly suggested that this high Ag(+) selectivity is a result of the synergistic coordination of the ring oxygen and the sulfur atom of the thiolariat ether. NMR chemical shifts of protons and carbons in the proximity of the sulfur atom of the thiolariat ether were changed significantly in accordance with the synergistic coordination described above. 1:1 Complexation between a thiolariat ether and Ag(+) were supported by a Job plot using the chemical shift of the methylene protons adjacent to the sulfur atom.     

Hydrophobic indicators for two-phase titrations and their application to the determination of silver and pentachlorophenol

The hydrophobic dyes tetrabromophenolphthalein ethyl ester and 2,6-dichlorophenolindo-phenol are proposed as visual indicators for two-phase titrations. The aqueous phase is colourless throughout the titration and these indicators make it possible to detect the end-point of the titration by the colour of one or the other phase. The indicators allow the two-phase titration of the silver(I)-1,10-phenanthroline complex with tetraphenylborate and of pentachlorophenol with tetraphenylphosphonium chloride.     

Synthesis of sodium-polystyrenesulfonate-grafted nanoparticles by core-cross-linking of block copolymer micelles

Sodium poly(styrenesulfonate)(polySSNa)-grafted polymer nanoparticles were synthesized by core-cross-linking of block copolymer micelles and subsequent chemical transformation. Block copolymers, poly(p-((1-methyl)silacyclobutyl)styrene-block-poly(neopentyl p-styrenesulfonate)s, polySBS-b-polySSPen, were synthesized by nitroxy-mediated living radical polymerization. The block copolymers formed micelles (R_h=15-23 nm, where R_h represents the hydrodynamic radius) with a polySBS core and polySSPen shell in acetone. The micelle core was cross-linked by ring-opening polymerization of silacyclobutyl groups in polySBS. Hydrolysis of the neopentyl groups provided polySSNa-grafted nanoparticles. The R_h of the particles before the hydrolysis ranged from 12 to 21 nm in acetone, while they varied to the range from 50 to 110 nm in water after the hydrolysis.     

Measurement of the product ion ratio N4+/N3+ in the radiolysis of nitrogen

The ratio of N₄⁺ to N₃⁺ formed in the radiolysis of gaseous nitrogen has been measured to be 4.7 ± 0.4 using a time-resolved atmospheric pressure ionization mass spectrometer. The limit of error has been evaluated from the ion mass discrimination of the apparatus.     

Electrochemical characterization of negative electrodes consisting of surface-modified Zr0.9Ti0.1(Ni1.1Co0.1Mn0.5V0.2Cr0.1)x Laves-phase alloys

Laves-phase hydrogen storage alloy has a high potential for use as negative electrode material as alternative for the misch-metal-based material. In order to improve the energy density and the rate capability of negative electrode, chemical and mechanical modification of Lavesphase alloy with different stoichiometric ratios was carried out. Discharge capacity and high-rate dischargeabilty was evaluated by electrochemical methods and the characterization of Laves-phase alloy was made by X-ray diffraction, SEM observation and PCT measurement. The best result in discharge capacity could be obtained for stoichiometric Laves-phase alloy with a composition of Zr_0.9Ti_0.1Ni_1.1Co_0.1Mn_0.5V_0.2Cr_0.1 by boiling in 10 M KOH solution. On the other hand, the high-rate dischargeability was increased remarkably by introducing mechanical grinding before alkali treatment. The cause for improved performance was discussed on the basis of thermodynamic stability of metal hydride and changes in crystal structure and surface morphology influencing on diffusion coefficient and diffusion path length of hydrogen.     

Synthesis of alanine and leucine by reductive amination of 2-oxoic acid with combination of hydrogenase and dehydrogenase

Alanine synthesis by reductive amination of pyruvate was performed by the combination of NADH regeneration system and alanine dehydrogenase (AlaDH). The conversion of pyruvate to alanine was 99% after 1 h. Leucine synthesis was also carried out by the combination of NADH regeneration system and leucine dehydrogenase (LeuDH). The conversion of 4-methyl-2-oxovalerate to leucine was 60% after 1.5 h.     

Synthesis of [18,19,21,22‐13C4]‐Labeled Tautomycin as an NMR Probe of Protein Phosphatase Inhibitor

We have accomplished the synthesis of ¹³C‐labeled tautomycin at the C18, C19, C21, and C22 positions starting from 100 % [¹³C]triethylphosphonoacetate for the purpose of elucidating the dynamics and conformation of the C17–C26 moiety. NMR spectroscopy of ¹³C‐labeled tautomycin revealed strong binding with protein phosphatase type 1 and new features in the ¹³C NMR spectrum, such as the very small three‐bond coupling constants (²J).