Quantitative analysis of methylguanidine and guanidine in physiologic fluids by high-performance liquid chromatography-fluorescence detection method.

A rapid and sensitive high-performance liquid chromatographic method has been developed for the quantitative analysis of methylguanidine and guanidine in physiological fluids. These quanidino compounds are separated on a 6 x 0.23 cm cation-exchange column with 0.5 M sodium hydroxide solution. The guanidino compounds are detected with a fluorometer, which monitors the fluorescent guanidine derivatives produced by the reaction of the eluted constituents with 9,10-phenanthrenequinone. Sensitivity to sub-nanomole levels of methylguanidine and guanidine is demonstrated. The method was successfully applied to physiological fluids such as serum and cerebrospinal fluid from uremic patients.     

Selective CO2 reduction into formate using Ln-Ta oxynitrides combined with a binuclear Ru(Ⅱ)complex under visible light

Hybrid materials constructed from a visible-light-absorbing semiconductor and a functional metal complex have attracted attention as efficient photocatalysts for CO₂ reduction with high selectivity to a desired product.In this work,defect fluorite-type Ln-Ta oxynitrides LnTaO_xN_y(Ln=Nd,Sm,Gd,Tb,Dy and Ho)were examined as the semiconductor component in a hybrid photocatalyst system combined with known Ag nanoparticle promoter and binuclear ruthenium(Ⅱ)complex(RuRu’).Among the LnTaO_xN_y examined,TbTaO_xN_y gave the highest performance for CO₂ reduction under visible light(k>400 nm),with a Ru Ru0-based turnover number of 18 and high selectivity to formate(>99%).Physicochemical analyses indicated that high crystallinity and more negative conduction band potential of Ln Ta O_xN_ywith the absence of Ln-4 f states in the band gap structure contributed to higher activity of the hybrid photocatalyst.     

Preparation of Ring and Chain Condensed Oligophosphates

Preparations of small-ring and short-chain condensed phosphates were made by dry and wet processes, respectively. The crystallization of tetra- hexa-, and octaphosphates from the phosphate solution was not easy, and metal salts of these oligophosphates were amorphous and unstable at normal temperature. Guanidine tetraphosphate and ammonium hexaphosphate were crystalline and stable at normal temperature.     

Revisiting the Polymerization of Diphenylacetylenes with Tungsten(VI) Chloride and Tetraphenyltin: An Alternative Mechanism by a Metathesis Catalytic System

An alternative reaction mechanism of the polymerization of diphenylacetylelnes using a catalytic system composed of tungsten(VI) chloride and tetraphenyltin has been proposed through the optimization of reaction conditions and investigation of the effect of the electronic nature of diphenylacetylene monomers on the polymerizability. The detailed structures of the polymers have been suggested by mass spectrometric analysis of the obtained polymers and oligomers, which suggested that a phenyl group of tetraphenyltin has been introduced to an initiating end of the polymer chain. Mass spectrometric analysis also provided information about the termination processes of the polymerization. The experimental results strongly suggested that the polymerization of diphenylacetylenes using tungsten(VI) chloride and tetraphenyltin proceeds through a migratory insertion mechanism rather than the long‐accepted metathesis mechanism.     

Enzymatic degradation of aliphatic polyesters copolymerized with various diamines

Poly(hexamethylene adipate) copolymers with 10–40 mol-% (in feed) of aliphatic diamines of various methylene chain lengths were prepared by melt polycondensation. In vitro degradation was performed in buffer solution at 37°C with a lipase and was evaluated by weight loss of the films. The weight loss increased greatly by the copolymerization and showed a maximum at 10 mol-% of comonomer content. Degradation also increased in a zig-zag fashion with decreasing number of methylene chains in the diamine comonomers. Both effects on the enzymatic degradation are discussed.     

Tolerance,bioaccumulation and biotransformation of arsenic in freshwater prawn (Macrobrachium rosenbergii)

Tolerance bioaccumulation and biotransformation of arsenic compounds by a freshwater prawn (Macrobrachium rosenbergii) were investigated. M. rosenbergii was exposed to 10, 20, 30 and 35 μg As cm⁻³ of disodium arsenate [abbreviated as As(V)], 25, 50, 100 and 120 μg As cm⁻³ of methylarsonic acid (MMAA), or 100,200, 300 and 350 μg As cm⁻³ of dimethylarsinic acid (DMAA). Tolerances (50% lethal concentration: LC₅₀) of the prawn against As(V), MMAA, and DMAA were 30, 100, and 300 μg As cm⁻³, respectively. The prawn accumulated arsenic compounds directly from aqueous phase and biotransformed them in part. Both methylation and demethylation of the arsenicals were observed in vivo. Highly methylated and less toxic arsenicals were less accumulated in M. rosenbergii.