Lewis Acid-Induced Reaction of γ,δ-Epoxy Tin Compounds

γ,δ-Epoxy tin compounds underwent divergent reactions depending upon the substitution pattern of the substrates as well as upon Lewis acids used as the indueer.     

Unique features of animal mitochondrial translation systems: – The non-universal genetic code,unusual features of the translational apparatus and their relevance to human mitochondrial diseases –

In animal mitochondria, several codons are non-universal and their meanings differ depending on the species. In addition, the tRNA structures that decipher codons are sometimes unusually truncated. These features seem to be related to the shortening of mitochondrial (mt) genomes, which occurred during the evolution of mitochondria. These organelles probably originated from the endosymbiosis of an aerobic eubacterium into an ancestral eukaryote. It is plausible that these events brought about the various characteristic features of animal mt translation systems, such as genetic code variations, unusually truncated tRNA and rRNA structures, unilateral tRNA recognition mechanisms by aminoacyl-tRNA synthetases, elongation factors and ribosomes, and compensation for RNA deficits by enlarged proteins. In this article, we discuss molecular mechanisms for these phenomena. Finally, we describe human mt diseases that are caused by modification defects in mt tRNAs.     

Influence of different mixing ratios of Mg and B powder on structural and superconducting properties in MgB2

We fabricated MgB₂ bulks by an in situ Mg diffusive reaction method from compacted B and compacted mixtures of Mg and B respectively. All samples were sintered at 1100 °C for 2 h. MgO impurity phase, density, and critical current density (J_c) were found to be dependent of the starting amount of mixing Mg powder. We also found that the MgO formation in MgB₂ matrix was not mainly attributed to the starting amount of additional Mg powder for Mg diffusive reaction. This indicates that MgO presented in the starting Mg powder is hardly diffused into compacted B.     

Radiation effect on thermoluminescence and electron paramagnetic resonance (EPR) of pink beryl

Morganite, a pink beryl with the chemical formula Be₃Al₂Si₆O₁₈, was investigated in terms of its thermally stimulated luminescence (TL) and electron paramagnetic resonance (EPR) properties due to point defects. Atomic hydrogen H°-centers were induced by γ-radiation and shown to be responsible for a 165°C TL peak. The Fe³⁺-center concentration was found to increase with γ-dose, observed by both TL and EPR measurements, decreasing with thermal treatments beyond 250°C. A mechanism for emission around 315°C is proposed.     

Normal-phase HPLC separation of possible biosynthetic intermediates of pheophytin a and chlorophyll a'.

Normal-phase HPLC conditions have been developed for separating the C17(3) isoprenoid isomers, which are expected to be formed as biosynthetic intermediates of chlorophyll (Chl) a, Chl a' (C13(2)-epimer of Chl a), pheophytin (Pheo) a and protochlorophyll (PChl). The application of these conditions to pigment composition analysis of greening etiolated barley leaves allowed us to detect, for the first time, the C17(3) isomers of Chl a', a possible constituent of the primary electron donor of photosystem (PS) I, P700, and those of Pheo a, the primary electron acceptor of PS II, in the very early stage of greening. The C17(3) isomer distribution patterns were approximately the same between Chl a and Chl a', but significantly different between Pheo a and Chl a', probably reflecting the similarity and difference, respectively, in the biosynthetic pathways of these pigment pairs.     

Enhancement of gamma-ray radiolysis of carbon dioxide with the assistance of solid materials

This work is devoted to enhance gamma-ray radiolysis of CO₂ with the assistance of coexisting metal materials. It is found that lower energy electrons which are generated through interactions of γ-photons with the coexisting metal materials and ejected to CO₂ gas actually enhance decomposition of CO₂ to produce CO. The increment of CO production agrees well with the increment of the deposited energy in CO₂, given by the lower energy electrons emitted from the materials, which is calculated by a numerical simulations code MCNP. It is also suggested that the volumetric decomposition of CO₂ dominates the decomposition at the material’s surface.