Five‐Membered Cyclitol Phosphate Formation by a myo‐Inositol Phosphate Synthase Orthologue in the Biosynthesis of the Carbocyclic Nucleoside Antibiotic Aristeromycin

Aristeromycin is a unique carbocyclic nucleoside antibiotic produced by Streptomyces citricolor. In order to elucidate its intriguing carbocyclic formation, we used a genome‐mining approach to identify the responsible enzyme. In silico screening with known cyclitol synthases involved in primary metabolism, such as myo‐inositol‐1‐phosphate synthase (MIPS) and dehydroqunate synthase (DHQS), identified a unique MIPS orthologue (Ari2) encoded in the genome of S. citricolor. Heterologous expression of the gene cluster containing ari2 with a cosmid vector in Streptomyces albus resulted in the production of aristeromycin, thus indicating that the cloned DNA region (37.5 kb) with 33 open reading frames contains its biosynthetic gene cluster. We verified that Ari2 catalyzes the formation of a novel five‐membered cyclitol phosphate from d ‐fructose 6‐phosphate (F6P) with NAD⁺ as a cofactor. This provides insight into cyclitol phosphate synthase as a member of the MIPS family of enzymes. A biosynthetic pathway to aristeromycin is proposed based on bioinformatics analysis of the gene cluster.     

Carbonization of pitches—IV: Carbonization of polycyclic aromatic hydrocarbons under the presence of aluminum chloride catalyst

Using aluminum chloride as a catalyst, polycyclic aromatic hydrocarbons were converted into carbons of two different structures, although at the early stage all carbonization processes proceeded via molten phase. The structures were examined with an optical microscope under crossed nicois. The first type of structure was a flow pattern with large oriented needle like domains observed for carbons obtained from naphthalene, chrysene, and anthracene, whereas the second one was a mosaic structure for carbon from pyrene. A significant subsequent graphitization at 2500°C (as expressed by L_c) took place for both types regardless of the different size of oriented domains. The orientation of domains depends on the rate of carbonization controlled by the holding temperature, time and quantity of the catalyst. Appropriate conditions of carbonization suppressing too fast generation of nuclei so as to permit the formation of ordered arrangement of condensed molecules were found to yield a needle-like coke also from pyrene, thus showing that the passing through a molten phase is not a sufficient condition for formation of a needle-like structure.     

High-Pressure Hot Isostatic Pressing of Synthetic Mica

Powder compacts of synthetic mica (fluorphlogopite) encapsulated in a boro-silicate glass tube were isostatically hot-pressed using high-pressure-high-temperature hot isostatic pressing equipment with Ar gas and a Mo heater. Synthetic mica was isostatically hot-pressed, while retaining the composition and structure of the starting material, to 96.8% of theoretical density without additives at 500 MPa and 700°C for 3 h.     

Modifying carbonization properties of pitches. 1. Conversion of benzene-insoluble matter of coal-tar pitch into graphitizable carbon

Reactivities of benzene-insoluble/quinoline-soluble matter (QS—BI) and quinoline insolubles (QI) of coal-tar pitch in reductive alkylation and hydrogenation with the aid of alkali metals were investigated, to obtain basic information on the possibility of changing their graphitizability and the orientation of their cokes. Alkylation increased the solubility in benzene of both components; however only the soluble fraction of QS—BI was fusible. In contrast, the soluble fractions produced by hydrogenation from both QS—BI and QI were fusible giving a flow-pattern structure and graphitizable carbon. Fusibility of pitches in the early stage of carbonization is discussed from the viewpoints of graphitization and orientation of cokes obtained by subsequent heat treatment.     

A study on locational configuration of distributed generators under uncertain demand growth

The distributed generator (DG) has several advantages over the large‐scale power plant and is expected to complement the power system. In this paper, we focus on the locational flexibility and short lead time as advantages of DG, and examine the influence of uncertainty of demand growth on the optimal locational configuration of DGs in the transmission network and on the amount of installed DG. The results indicate that the total capacity of installed DGs is greater under uncertain demand growth than under certain growth. It is also indicated that under uncertainty, the installed DG capacity is distributed generally in proportion to the growth of the local loads. The latter finding suggests that the expected load growth at each point could be a useful indicator for screening candidate locational configurations of DGs. © 2000 Scripta Technica, Elect Eng Jpn, 133(4): 53–62, 2000     

Studies on the Accessibility of Starch by Deuteration

Cellulose and the various starches were dried in vacuum line apparatus, deuterated in liquid deuterium oxide, and dried in the same apparatus. Their accessibility was determined by measurement of the maximum absorbance (a) and the integral absorbance (b) at the wave number of each OH and OD group band on the infrared spectra, and crystallinity was calculated from accessibility. Crystallinity of cellulose showed the reasonable values of 0.66 for (a) and 0.71 for (b). Crystallinity of starches was considerable lower than those by means of the X-ray diffraction. There are inaccessible regions (so called crystalline fractions) in the starch granules which are not able to be deuterated and, moreover, neither to contain nor to absorb moisture inside. The reason why crystallinity was so low might be attributed to dehydration in the amorphous region at high vacuum.     

Indolepyruvate ferredoxin oxidoreductase: An oxygen-sensitive iron-sulfur enzyme from the hyperthermophilic archaeon Thermococcus profundus

Thermococcus profundus is a strictly anaerobic sulfur-dependent archaeon that grows optimally at 80°C by peptide fermentation. Indolepyruvate ferredoxin oxidoreductase (IOR), an enzyme involved in the peptide fermentation pathway, was purified to homogeneity from the archaeon under strictly anaerobic conditions. The maximal activity was?obtained above the boiling temperature of water (105°C), with a half-life of 62min at 100°C and 20min at 105°C. IOR was oxygen-sensitive with a half-life of 7h at 25°C under aerobic conditions. The specific activity of T.?profundus IOR was found to be dependent on the number of [4Fe-4S] clusters in the enzyme.     

Effect of gate insulating layer on organic static induction transistor characteristics

Organic static induction transistors, which have relatively short vertical channels, are attractive devices for their low operating voltage and high operating speed. However, a gate voltage larger than the Schottky barrier potential usually leads to a large gate leakage current and thus poor device performance. To limit the gate leakage current, we considered adding insulating layers around the gate electrode. The oxidization of aluminum during a physical vapor deposition process was used to form insulating layers around the gate electrode. The results demonstrate that by appending gate insulating layers, gate leakage currents can be effectively reduced and device characteristics, especially the on/off ratio, can be improved.     

A comparative study of DFT and XPS with reference to the adsorption of caesium ions in smectites

Chemical states of Cs ion adsorbed on dioctahedral smectites were studied using X-ray photoelectron spectroscopy (XPS) and molecular orbital calculations based on the density functional theory (DFT). Smectites investigated were montmorillonite, montmorillonite–beidellite, Fe–montmorillonite, and nontronite. It was found that montmorillonite samples kept approximately 50% of adsorbed Cs ions after a treatment by BaCl₂ aqueous solution, which were the highest values among the smectite samples. Cs(4d) binding energy was slightly shifted towards a lower energy by 0.2–0.8 eV after a BaCl₂ treatment, which suggests that plural adsorption sites exist on the smectite surface. Stable Cs adsorption sites and the adsorption energies were determined by DFT calculations. As a result, Cs ion is adsorbed strongly on a basal oxygen hexagonal hole. The chemical shift of the calculated Cs(4d) peak gave the same tendency as shown in the XPS measurements.