Astellifadiene: Structure Determination by NMR Spectroscopy and Crystalline Sponge Method,and Elucidation of its Biosynthesis

Genome mining of a terpene synthase gene from Emericella variecolor NBRC 32302 and its functional expression in Aspergillus oryzae led to the production of the new sesterterpene hydrocarbon, astellifadiene ( 1 ), having a 6‐8‐6‐5‐fused ring system. The structure of 1 was initially investigated by extensive NMR analyses, and was further confirmed by the crystalline sponge method, which established the absolute structure of 1 and demonstrated the usefulness of the method in the structure determination of complex hydrocarbon natural products. Furthermore, the biosynthesis of 1 was proposed on the basis of isotope‐incorporation experiments performed both in vivo and in vitro. The cyclization of GFPP involves a protonation‐initiated second cyclization sequence, 1,2‐alkyl migration, and 1,5‐hydride shift to generate the novel scaffold of 1 .     

Electronic structures and configurational transformations of some protonated compounds

The equilibrium geometries of HCHOH⁺, CH₃CHOH⁺, (CH₃)₂COH⁺, HCO₂H⁺₂, and CH₃CO₂H⁺₂ were determined by means of the semiempirical INDO—SCF method. The total-energy difference between the protonated isomers was found to be reasonable as compared with that obtained from the NMR observations. The computed barriers of the transformation between the isomers via the pure or distorted rotation or the bending motion were in good agreement with the experimental results.     

Preparation, structure, and magnetic interaction of a Mn(hfac)2-bridged [2-(3-pyridyl)(nitronyl nitroxide)-Mn(hfac)2]2 chain complex

A new one-dimensional chain complex, Mn(hfac)(2)-bridged [2-(3-pyridyl)(nitronyl nitroxide)Mn(hfac)(2)](2), was prepared and its structure and magnetic properties were elucidated; the complex exhibited a large antiferromagnetic interaction of J(1)=-185 K between the three Mn(ii) atoms and the two nitronyl nitroxides to give S=13/2 spin units and a small ferromagnetic interaction of J(3)'=+0.02 K between these spin units at low temperatures (50-1.9 K), compatible with the theoretical analysis for model compounds.     

Measurements of235U/238U isotopic ratio in the photoproduct UF5 by multiphoton ionization and time-of-flight mass spectrometry

A MultiPhoton-Ionization Time-Of-Flight Mass Spectrometry (MPI/TOFMS) apparatus was developed for real-time measurement of the uranium isotopic ratio in nascent UF₅ formed by the 266 nm photolysis of effusive UF₆ ( < 300 K, 1.3 × 10^–4 Pa). The UF₅ was selectively and efficiently multiphoton ionized by 532 nm radiation at appreciably low fluences ( < 10 J/cm²). The main ions observed, U⁺ and U²⁺, were subsequently analyzed with a TOFMS with mass resolution of 1190 to separate²³⁵U ⁿ⁺ and²³⁸U ⁿ⁺ completely. The isotopic ratio measurements showed good precision resulting from the excellent agreement which was observed between the isotopic ratios in UF₅ products and those in a parent UF₆ sample. These results suggested that the MPI/TOFMS method can be applied to the real-time analysis of separation factors in the molecular laser isotope separation of uranium by ionization of UF₅ following the infrared photodissociation of UF₆.     

Phase transition in Pd_(40)Ni_(10)Cu_(30)P_(20) bulk metallic glass under HP & HT

Bulk metallic glass (BMG) can be regarded as a metallic solid with a frozen-in melt structure which lacks atomic periodicity. Generally, BMG is not in an internal equilib- rium state (IES) but may change to the IES when it obtains an appropriate energy to overcome the energy barrier. High pressure and temperature can be a driving force to cause various transitions in amorphous materials, such as a transition from the amor- phous to the crystalline[1―8] or from the crystalline to the amorp…     

Synthesis of saccharide-conjugated polyamides by quasi-living anionic polymerization of a bicyclic lactam

Several well-defined graft copolymers ( 7 ) having a water-soluble natural polysaccharide (dextran) stock and hydrophilic polyamide branches of different molecular weights were synthesized by using a quasi-living anionic polymerization of a bicyclic lactam 1 , namely by the reaction of the acyllactam group in the quasi-living polyamide 2 with the hydroxyl and amino groups in the dextran derivative ( 6 ), of which the reducing end was converted to an amino group. An oligosaccharide-terminated polyamide 3 was also prepared efficiently by similar coupling reaction of the corresponding quasi-living polyamide 2 , with the maltose derivative ( 5 ) having an amino group. © 1994 John Wiley & Sons, Inc.     

Polymerization of Acrylonltrile—Metal Halides Complexes in the Frozen State. I. Radiation-Induced Polymerization of Acrylonltrile—Zinc Chloride Complex in the Frozen State

The radiation-induced polymerization of acrylonitrlle in frozen aqueous zinc chloride solution was carried out at low temperatures. A marked enhancement both in the rate and the degree of polymerization was observed at zinc chloride/acrylonitrile molar ratios above unity, which indicated the importance of formation and stabilization of complexes in the frozen medium. The rate of polymerization R was found to follow the relation, R α [M-ZnCl₂]² I, where I is the dose rate and [M-ZnCl₂] is the concentration of zinc chloride complexed with equimolecu-lar monomer. It is considered that the role of zinc chloride is here dual, both as a reagent for complex formation and also as a source of initiating species on irradiation. The effect of coexisting saturated nitriles were also discussed.     

Intricate Recognition of Glycolipid-Like Compounds by HIV-1 Envelope Proteins Evaluated with Surface Plasmon Resonance Imaging

Fusion of human immunodeficiency virus (HIV) to the cell membrane occurs by the specific binding of an envelope protein of HIV-1 (gp120 and gp160) and a glycosphingolipid of the cell membrane. In this study, quantitative and array-based affinity evaluation of gp120 and gp160 was performed by surface plasmon resonance (SPR) and the SPR imaging technique using a substrate immobilized with glycolipid-like compounds (Gb3, GM3, and Lac). Quantitative affinity evaluation showed that gp160 specifically bound to Gb3 and Lac compared with GM3, whereas gp120 showed lower binding affinity and specificity. Array-based evaluation showed that gp160 binds to Gb3 more favorably than Lac and GM3.     

Deformation Luminescence in gamma-irradiated KCl single crystals

Abstract

Deformation Luminescence(DL) is studied on KCl crystal colored by γ-irradiation. The spectra analysis of DL and thermoluminescence reveals that F-center plays a role as electron donor through the interaction with moving dislocation and V₂-center is a probable luminescence center. A theory is presented for understanding the deformation rate and temperature dependences of DL intensity.