311 research outputs found
キイロショウジョウバエ由来のチオレドキシン還元酵素のC未端テトラペプチド配列は、ヒト肺由来のチオレドキシン還元酵素では酸化還元活性を示さない
The isozymes of mammalian thioredoxin reductase (TrxR) contain the penultimate selenocysteineresidue (SeCys) in the redox-active C-terminal tetrapeptide, -Gly-Cys-SeCys-Gly (end). Amutant form of the mammalian enzyme TrxR-X498C in which SeCys is replaced with Cys showsa dramatically decreased catalytic activity, suggesting that SeCys residue plays an integral role inthe catalysis. In contrast, TrxR of the fruit fly, Drosophila melanogaster, has no selenium in the corresponding C-terminal redox sequence, which instead of SeCys has flanking serine residues in the terminal sequence, -Ser-Cys-Cys-Ser (end). Because the catalytic activity of Dm-TrxR is comparable to that of the mammalian selenoenzyme, we introduced the serine residues at the corresponding positions of the recombinant TrxR-X498C and mimicked the redox center of the fruit fly TrxR. However, the catalysis remained as low as the Cys mutant of the selenoenzyme,
suggesting that the additional structural features are still required for the tetrapeptide to function as a redox center. MOPAC calculation suggested that the complete motif might involve the hexapeptide sequence, which includes a proline residue, -Pro-X-Ser-Cys-Cys-Ser (end). The proline-containing motif is conserved among other insect TrxRs such as those of honeybee and fruit fly.ほ乳類チオレドキシン還元酵素はC末端配列-Gly-Cys-SeCys-Gly(end)の後ろから2番目にセレノシステイン(SeCys)残基を持つ.SeCys をシステインに変換すると酵素の活性は大きく低下するので,SeCys 残基が触媒活性に必須であることが分かる.これに対してキイロショウジョウバエのチオレドキシン還元酵素(Dm-TrxR)のC末端配列にはセレンが含まれず,システイン残基の対が2つのセリンに挟まれた配列-Ser-Cys-Cys-Ser (end)を持つ.それでも Dm-TrxR はほ乳類のセレン含有酵素と同程度の触媒能を示す.われわれはヒト肺チオレドキシン還元酵素に Dm-TrxR のC末端テトラペプチド配列を導入してその効果を調べた.しかし,酵素活性はまったく上昇せず,Dm-TrxR のC末端のテトラペプチド配列-Ser-Cys-Cys-Ser だけでは Cys 残基のチオール基を活性化する効果はなかった.そこで,分子軌道計算 MOPAC を用いて酸化還元機能を担うためのC末端配列モチーフを探索した.その結果,テトラペプチドにさらに2つ先のプロリンまでを含めた Pro-X-Ser-Cys-Cys-Ser(end)により初めて酸化還元モチーフとして機能する可能性が示唆された.Pro を含むこの配列モチーフはミツバチや蚊などほかの昆虫の TrxR でも保存されてい
Iron-catalysed cross-coupling of halohydrins with aryl aluminium reagents: a protecting-group-free strategy attaining remarkable rate enhancement and diastereoinduction.
Non-protected halohydrins are cross-coupled with aryl aluminium reagents to produce aryl alkanols in the presence of the iron-bisphosphine catalysts. Remarkable reaction rate enhancement and diastereoinduction are realized by the in situ generated aluminium alkoxides, offering a new method for the reactivity and selectivity control of the iron-catalysed cross-coupling reaction
On representation matrices of boundary conditions in gauge theories compactified on two-dimensional orbifolds
We study the existence of diagonal representatives in each equivalence class
of representation matrices of boundary conditions in gauge theories
compactified on the orbifolds (). Using
constraints, unitary transformations and gauge transformations, we examine
whether the representation matrices can simultaneously become diagonal or not.
We show that at least one diagonal representative necessarily exists in each
equivalence class on and , but the
representation matrices on and can
contain not only diagonal matrices but also non-diagonal ones and
non-diagonal and ones, respectively, as a member of
block-diagonal submatrices. These non-diagonal matrices have discrete
parameters, which means that the rank-reducing symmetry breaking can be caused
by the discrete Wilson line phases.Comment: 44 page
Development of a frequency-detuned interferometer as a prototype experiment for next-generation gravitational-wave detectors
We report on our prototype experiment that uses a 4-m detuned resonant sideband extraction interferometer with suspended mirrors, which has almost the same configuration as the next-generation, gravitational-wave detectors. We have developed a new control scheme and have succeeded in the operation of such an interferometer with suspended mirrors for the first time ever as far as we know. We believe that this is the first such instrument that can see the radiation pressure signal enhancement, which can improve the sensitivity of next-generation gravitational-wave detectors
Interferometers for Displacement-Noise-Free Gravitational-Wave Detection
We propose a class of displacement- and laser-noise free
gravitational-wave-interferometer configurations, which does not sense
non-geodesic mirror motions and laser noises, but provides non-vanishing
gravitational-wave signal. Our interferometer consists of 4 mirrors and 2
beamsplitters, which form 4 Mach-Zehnder interferometers. By contrast to
previous works, no composite mirrors are required. Each mirror in our
configuration is sensed redundantly, by at least two pairs of incident and
reflected beams. Displacement- and laser-noise free detection is achieved when
output signals from these 4 interferometers are combined appropriately. Our
3-dimensional interferometer configuration has a low-frequency response
proportional to f^2, which is better than the f^3 achievable by previous
2-dimensional configurations.Comment: 5 pages, 4 figure
Preparation of BaTiO3 nanotube arrays, CoFe2O4 nanoparticles and their composite
Multiferroic nanocomposites which possess both ferroelectric and ferromagnetic properties are attracting much attention because of their scientific interest and significant technological promise in the novel multifunctional devices. Gas-phase syntheses have been typically used to fabricate multiferroic nanocomposites [1]; however, high production cost has been hindering further expansion of the research field. In this research, the components of multiferroic nanocomposites are fabricated by anodization and hydrothermal treatment which were then used to fabricate multiferroic nanocomposites through electrophoretic deposition (EPD) as cheaper alternatives to the costly gas-phase processes.
TiO2 nanotubes arrays were firstly formed on Ti metal foils by anodization in an electrolyte containing ethylene glycol, dimethyl sulfoxide, ammonium fluoride and water. Then, BaTiO3 nanotube arrays were obtained by hydrothermal treatment of TiO2 nanotube arrays using Ba-containing aqueous solution. The morphologies and crystal structure of BaTiO3 nanotube arrays were analyzed by a scanning electron microscope (SEM) and an X-ray diffractometer (XRD).
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