Steroid transhydrogenase activity of 3-ketosteroid-Δ1-dehydrogenase from Nocardia corallina

金沢大学自然科学研究科　　金沢大学理工研究域自然システム学系3-Ketosteroid-Δ1-dehydrogenase from Nocardia corallina catalyzes transhydrogenation of 3-keto-4-ene-steroid to 3-keto-1,4-diene-steroid e.g., progesterone to 1,4-androstadiene-3,17-dione. The reaction proceeded linearly at first and then soon slowed down owing to equilibration. The turnover number of this reaction was of the same magnitude as that of the dehydrogenation of 3-keto-4-ene-steroid. The pH optimum was 8.4, which is lower than that of the dehydrogenase reaction. The enzyme has a wide specificity for hydrogen acceptor steroids. The K(m)\u27 and K(max)\u27 values for these steroids and the values of the corresponding 3-keto-4-ene-steroids were compared. Kinetic studies of the steroid transhydrogenase reaction demonstrated a typical ping-pong mechanism. The enzyme oxidized 1,2-tritiated progesterone and transferred the tritium atoms to the reaction product, 4-androstene-3,17-dione, and water. Transhydrogenation in D2O resulted in the incorporation of a deuterium atom into the C2-position of 4-androstene-3,17-dione. The results indicate that the enzyme catalyzes C1,C2-trans axial abstraction of hydrogen atoms from progesterone, transfer of the 1α-hydrogen to the C1-position of 1,4-androstadiene-3,17-dione and release of the 2β-hydrogen to water. Reaction schemes based on the experimental results are proposed. The enzyme also catalyzes the reduction of 3-keto-1,4-diene-steroids with reduced benzoyl viologen

3-keto-5α-steroid-Δ4-dehydrogenase from Nocardia corallina: Purification and characterization

金沢大学自然科学研究科　　金沢大学理工研究域自然システム学系The inducible 3-keto-5α-steroid-Δ4-dehydrogenase of Nocardia corallina was purified to homogeneity using affinity chromatography on 19-nortestosterone-17-acetoxyaminoethyl Sepharose 4B. SDS-polyacrylamide gel electrophoresis, gel filtration and spectral analysis of flavin suggest that the purified dehydrogenase is a monomeric protein of M(r) 60,000 containing one flavin. It has a typical absorption spectrum of flavoprotein with maxima at 457, 375, and 277 nm. The values shifted to 470 and 395 nm on binding of 19-nortestosterone. The enzyme catalyzed the dehydrogenation of 3-keto-5α-steroid at the 4- and 5-position, e.g. the conversion of 5α-androst-1-ene-3,17-dione to 1,4-androstadiene-3,17-dione with the reduction of phenazine methosulfate. The substrate 3-ketosteroid has essentially the 5α-configuration. The enzyme did not reduce potassium ferricyanide but did reduce cytochrome c at a moderate rate, and exhibited only a weak steroid oxidase activity. Stereochemical study demonstrated that the enzyme abstracts the 4β, 5α-hydrogens of the substrate as a hydrogen ion through a protein-based reaction and as a hydride ion by transfer to FAD, respectively. The enzyme oxidizes a wide variety of 3-keto-5α-steroids but not 3β-hydroxysteroid. The dehydrogenase also catalyzed steroid transhydrogenation between 3-keto-5α-steroid and 3-keto-1,4-diene-steroid. The properties of this enzyme are compared with those of 3-keto-steroid-Δ1-dehydrogenase

Reappraisal of Hydatigera taeniaeformis (Batsch, 1786) (Cestoda: Taeniidae) sensu lato with description of Hydatigera kamiyai n. sp.

The common cat tapeworm Hydatigera taeniaeformis is a complex of three morphologically cryptic entities, which can be differentiated genetically. To clarify the biogeography and the host spectrum of the cryptic lineages, 150 specimens of H. taeniaeformis in various definitive and intermediate hosts from Eurasia, Africa and Australia were identified with DNA barcoding using partial mitochondrial cytochrome c oxidase subunit 1 gene sequences and compared with previously published data. Additional phylogenetic analyses of selected isolates were performed using nuclear DNA and mitochondrial genome sequences. Based on molecular data and morphological analysis, Hydatigera kamiyai n. sp. Iwaki is proposed for a cryptic lineage, which is predominantly northern Eurasian and uses mainly arvicoline rodents (voles) and mice of the genus Apodemus as intermediate hosts. Hydatigera taeniaeformis sensu stricto (s.s.) is restricted to murine rodents (rats and mice) as intermediate hosts. It probably originates from Asia but has spread worldwide. Despite remarkable genetic divergence between H. taeniaeformis s.s. and H. kamiyai, interspecific morphological differences are evident only in dimensions of rostellar hooks. The third cryptic lineage is closely related to H. kamiyai, but its taxonomic status remains unresolved due to limited morphological, molecular, biogeographical and ecological data. This Hydatigera sp. is confined to the Mediterranean and its intermediate hosts are unknown. Further studies are needed to classify Hydatigera sp. either as a distinct species or a variant of H. kamiyai. According to previously published limited data, all three entities occur in the Americas, probably due to human-mediated introductions

Purification, crystallization and preliminary X-ray analysis of a deletion mutant of a major buckwheat allergen

A 16 kDa buckwheat protein (BWp16) is a major allergen responsible for immediate hypersensitivity reactions including anaphylaxis. An immunologically active mutant of BWp16 was prepared and a three-wavelength MAD data set was collected from a crystal of selenomethionine-labelled mutant protein

The electron-capture origin of supernova 2018zd

In the transitional mass range ($\sim$ 8-10 solar masses) between white dwarf formation and iron core-collapse supernovae, stars are expected to produce an electron-capture supernova. Theoretically, these progenitors are thought to be super-asymptotic giant branch stars with a degenerate O+Ne+Mg core, and electron capture onto Ne and Mg nuclei should initiate core collapse. However, no supernovae have unequivocally been identified from an electron-capture origin, partly because of uncertainty in theoretical predictions. Here we present six indicators of electron-capture supernovae and show that supernova 2018zd is the only known supernova having strong evidence for or consistent with all six: progenitor identification, circumstellar material, chemical composition, explosion energy, light curve, and nucleosynthesis. For supernova 2018zd, we infer a super-asymptotic giant branch progenitor based on the faint candidate in the pre-explosion images and the chemically-enriched circumstellar material revealed by the early ultraviolet colours and flash spectroscopy. The light-curve morphology and nebular emission lines can be explained with the low explosion energy and neutron-rich nucleosynthesis produced in an electron-capture supernova. This identification provides insights into the complex stellar evolution, supernova physics, cosmic nucleosynthesis, and remnant populations in the transitional mass range.Comment: Author version of the published letter in Nature Astronomy, 28 June 202

The electron-capture origin of supernova 2018zd

In the transitional mass range (~8–10 solar masses) between white dwarf formation and iron core-collapse supernovae, stars are expected to produce an electron-capture supernova. Theoretically, these progenitors are thought to be super-asymptotic giant branch stars with a degenerate O + Ne + Mg core, and electron capture onto Ne and Mg nuclei should initiate core collapse1–4. However, no supernovae have unequivocally been identified from an electron-capture origin, partly because of uncertainty in theoretical predictions. Here we present six indicators of electron-capture supernovae and show that supernova 2018zd is the only known supernova with strong evidence for or consistent with all six: progenitor identification, circumstellar material, chemical composition5–7, explosion energy, light curve and nucleosynthesis8–12. For supernova 2018zd, we infer a super-asymptotic giant branch progenitor based on the faint candidate in the pre-explosion images and the chemically enriched circumstellar material revealed by the early ultraviolet colours and flash spectroscopy. The light-curve morphology and nebular emission lines can be explained by the low explosion energy and neutron-rich nucleosynthesis produced in an electron-capture supernova. This identification provides insights into the complex stellar evolution, supernova physics, cosmic nucleosynthesis and remnant populations in the transitional mass range. Electron-capture supernovae are thought to come from progenitors with a narrow range of masses, and thus they are rare. Here the authors present six indicators of an electron-capture supernova origin, and find that supernova 2018zd fulfils all six criteria.Instituto de Astrofísica de La PlataFacultad de Ciencias Astronómicas y Geofísica

Research and Design of a Routing Protocol in Large-Scale Wireless Sensor Networks

无线传感器网络，作为全球未来十大技术之一，集成了传感器技术、嵌入式计算技术、分布式信息处理和自组织网技术，可实时感知、采集、处理、传输网络分布区域内的各种信息数据，在军事国防、生物医疗、环境监测、抢险救灾、防恐反恐、危险区域远程控制等领域具有十分广阔的应用前景。 本文研究分析了无线传感器网络的已有路由协议，并针对大规模的无线传感器网络设计了一种树状路由协议，它根据节点地址信息来形成路由，从而简化了复杂繁冗的路由表查找和维护，节省了不必要的开销，提高了路由效率，实现了快速有效的数据传输。 为支持此路由协议本文提出了一种自适应动态地址分配算——ADAR（AdaptiveDynamicAddre...As one of the ten high technologies in the future, wireless sensor network, which is the integration of micro-sensors, embedded computing, modern network and Ad Hoc technologies, can apperceive, collect, process and transmit various information data within the region. It can be used in military defense, biomedical, environmental monitoring, disaster relief, counter-terrorism, remote control of haz...学位：工学硕士院系专业：信息科学与技术学院通信工程系_通信与信息系统学号：2332007115216