Search

Streptomyces coelicolorA3(2) possesses nine genes for family 18 chitinases and two for family 19, showing high multiplicity. By hybridization analyses, distribution of those chitinase genes was investigated in six other Streptomycesspecies covering the whole phylogenetic range based on 16S rDNA sequences. All strains showed high-multiplicity of chitinase genes, like S. coelicolorA3(2). The phylogeny and gene organization of the family 18 chitinase genes cloned from Streptomycesspecies so far were then analyzed to investigate the gene evolution. It was concluded that Streptomycesalready possessed a variety of chitinase genes prior to branching into many species, and that the ancestral genes of chiAand chiBhave been generated by gene-duplication. In the course of the analyses, evidence that the chi30and chi40genes of S. thermoviolaceuswere derived from their corresponding original chitinase genes by losing gene parts for substrate-binding domains and fibronectin type III-like domains was obtained. It was thus shown that gene-duplication and domain-deletion were implicated in generating the high diversity and multiplicity of chitinase genes in Streptomycesspecies.

The first total synthesis of a marine-derived potent antitumor antibiotic, (±)-spiroxin C, was achieved via a TBAF-activated Suzuki−Miyaura cross-coupling reaction as a key step, which was also shown to be useful for the synthesis of sterically hindered binaphthyl derivatives.

In order to monitor the crustal deformation in the area of eastern Kanto, central Japan, Ibaraki University has started the high precision geodetic studies with GPS measurements in collaboration with Geographical Survey Institute of Japan (GSI). The first measurements were taken in 1991 with a small network of 8 sites. Four more sites were included since 1998 for a better coverage in the region. In the present study, we analyzed the data collected since 1998 by using the GAMIT/GLOBK software for estimating the displacement vectors in the ITRF96 reference frame. The data from the continuous GPS network of GSI and the GPS sites of IGS close to the studied region (Tsukuba and Usuda) were included for obtaining the primary solutions. The initial results by constraining the co-ordinates of the IGS stations nearest to the network confirmed the repeatability of the baseline components. The results presented here were obtained by assuming the 4 fiducial stations around the network, namely, Irkutsks (IRKT), Fairbanks (FAIR), Sheshan (SHAO) and Dededo (GUAM). The average uncertainties of the horizontal velocities from three consecutive campaigns, each separated by six months, were estimated to be ±4.6 mm/yr and ±3.5 mm/yr for the northward and eastward components, respectively.

Diastereoselective reduction of 6-bromo-6-substituted penicillanate esters has been achieved by treatment with tributylphosphine to give 6-substituted penicillanate esters. This reaction would appear to proceed through a phosphonium β-lactam enolate species, followed by a diastereoselective protonation. This method has the advantage of being simple to carry out and it is mild, gives high diastereoselectivity, and should tolerate a number of functional groups in the substrates. Implications of these observations are discussed.

Lithium ion secondary batteries are currently the best portable energy storage device for the consumer electronics market. The recent development of the lithium ion secondary batteries has been achieved by the use of selected carbon and graphite materials as an anode. The performance of lithium ion secondary batteries, such as the charge/discharge capacity, voltage profile and cyclic stability, depend strongly on the microstructure of the anode materials made of carbon and graphite. Due to the contribution of the carbon materials used in the anode in last five years, the capacity of the typical Li ion battery has been improved 1.7 times. However, there are still active investigations to identify the key parameters of carbons that provide the improved anode properties, as carbon and graphite materials have large varieties in the microstructure, texture, crystallinity and morphology, depending on their preparation processes and precursor materials, as well as various forms such as powder, fibers and spherule. In the present article, we describe the correlation between the microstructural parameters and electrochemical properties of conventional and novel types of carbon materials for Li ion batteries, namely, graphitizable carbons such as milled mesophase pitch-based carbon fibers, polyparaphenylene-based carbon heat-treated at low temperatures and boron-doped graphitized materials, by connecting with the market demand and the trends in Li ion secondary batteries. The basic scientific theory can contribute to further developments of the Li ion batteries such as polymer batteries for consumer electronics, multimedia technology and future hybrid and electric vehicles.

Photoinduced reaction in relations to water photolysis was studied on Pt- or other catalysts-supported TiO2 (P-25) particles. It was found that stoichiometric H2 and O2 formation does not take place with the photocatalyst, and only H2 production was observed. A long-term water photolysis was carried out by Pt-supported TiO2 (TiO2/Pt) to produce H2, in which H2 formation stopped almost after 600 h irradiation. After recovering the TiO2/Pt particles used in the long-term reaction, they were reused in a photocatalytic H⁺ reduction by adding methanol as an electron donor, but no H2 production was observed showing that the TiO2/Pt particles have lost their photocatalytic activity after the long-term reaction. These results suggest that TiO2 itself works as an electron donor to produce H2. Structural change of the TiO2/Pt have been studied by both X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) before and after the photoreaction. In both the XRD and XPS, the structure of the original TiO2 almost disappeared after the photoreaction and new structures appeared, showing that Ti⁴⁺ changed irreversibly to a higher valance state (Ti⁵⁺) after producing H2.

Polyurethane/polypeptide block copolymers were synthesized. Infrared spectroscopy and differential scanning calorimetry revealed that in the block copolymers both segments undergo phase-mixing, while in polyurethane/polypeptide blend both components undergo phase-separation. Contact angle measurement showed that in the block copolymers polyurethane segments tended to appear on the membrane surface, whereas in polyurethane/polypeptide blend polypeptide components appeared on the membrane surface. In vitro nonthrombogenicity of the block copolymers was similar to that of homopolymers or polymer blends, though adhesion and deformation of platelets were suppressed on the block copolymer membranes.

In the treatment and therapy of patients suffering a stroke, it is very important to predict whether viable neurones, even those of poor function, remain intact in the lesions of the brain. To determine whether viable neurones of low functional activity are represented in in vivoneuroreceptor imaging, we undertook experiments in gerbils with cerebral infarction, in which we examined histological changes and the results of dual-tracer in vivoautoradiography of glucose utilization with 14C-labelled deoxyglu-cose and benzodiazepine receptor binding with 123I-labelled Ro 16–0154. The unrelated findings of cerebral glucose metabolism and benzodiazepine receptor binding were observed in the primary infarct lesion and in remote areas, including the ipsilateral striatum and thalamus.

Iomazenil is a specific ligand for central-type benzodiazepine receptors (BZR). In order to determine the clinical significance of the findings of 123I-iomazenil single photon emission tomography (SPET) in cerebrovascular disease (CVD), we compared the cerebral uptake of 123I-iomazenil with oxygen metabolism measured by positron emission tomography (PET). Depending on the severity of the haemodynamic and/or metabolic impairment based on our institutional criteria [a reduction of < 30.6 ml 100 g-1min-1in cerebral blood flow (CBF) and an increase of > 0.52 in the oxygen extraction fraction (OEF)], the cortical areas were classified into four groups as follows: Group I, normal CBF and OEF; Group II, normal CBF and increased OEF; Group III, reduced CBF and normal OEF; Group IV, reduced CBF and increased OEF. Seven patients (mean age 65 ± 7 years) with CVD underwent both PET and 123I-iomazenil SPET within 8 days. The ratios of the mean counts in 14 regions of interest in the cerebral cortices to those in the cerebellar cortices (R/C ratios) were compared with the cerebral metabolic rate of oxygen (CMRO2). The R/C ratios of Group IV were lower than those of Group I (P< 0.005). The R/C ratios correlated with CMRO2in Group III (r= 0.577, P< 0.01) and in Group IV (r= 0.707, P< 0.005), but not in Groups I or II. These results suggests that reduced uptake in 123I-iomazenil SPET reflects oxidative hypometabolism causing neuronal damage in haemodynamically and metabolically impaired areas in patients with CVD. This information may be valuable when deciding therapeutic approaches.