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81.
Mamoru Yasui Toshifumi Shiroya Keiji Fujimoto Haruma Kawaguchi 《Colloids and surfaces. B, Biointerfaces》1997,8(6):267-319
Poly(N-isopropylacrylamide)s (PNIPAMs) carboxylated at one chain end or both ends were prepared by polymerization using 4,4-azobis(N,N,-cyanopentanoic acid) (V-501) as an initiator and β-mercaptopropionic acid (MPA) as a chain transfer reagent. One end group of PNIPAM carboxylated at both ends was conjugated with latex particles, and another with trypsin using carbodiimide. Differential scanning calorimetry (DSC) revealed that PNIPAM on the particles exhibited a drastic phase transition, and that the transition temperature was largely elevated when the enzyme was immobilized at the chain end. Therefore, PNIPAM on the particles showed two phase transitions because of the coexistence of the enzyme-conjugated and non-conjugated PNIPAMs. The activity of trypsin immobilized on the particles with the PNIPAM spacer showed significant temperature dependence. The apparent relative activity increased above the transition temperature of non enzyme-conjugated PNIPAM on the particles. One of the reasons for this is that the diffusion of the substrate changed discontinuously around the transition temperature. Therefore, the temperature dependence of the enzymatic activity was significantly affected by the molecular size of the substrates. The enzymatic activity was also influenced by the surface density of trypsin and PNIPAM on the particle, and the molecular weight of the PNIPAM spacer. 相似文献
82.
The ether extract of the females of white-spotted longicorn beetle Anoplophora malasiaca showed activity as contact sex pheromone to males. The extract was fractionated, and a pheromonal activity was revealed only when three fractions; n-hexane, n-hexane/EtOAc 9:1, and EtOAc were blended. The relative structures of gomadalactone A, B, and C, three active components isolated from the EtOAc fraction, were determined by spectroscopic studies to be (1S∗,4R∗,5S∗)-5-hydroxy-4-[(E)-7-hydroxy-4-methylhept-3-enyl]-4,8-dimethyl-3-oxabicyclo[3.3.0]octan-7-en-2,6-dione, (1R∗,4R∗,5R∗)-5-hydroxy-4-[(E)-7-hydroxy-4-methylhept-3-enyl]-4,8-dimethyl-3-oxabicyclo[3.3.0]octan-7-en-2,6-dione, and (1S∗,4R∗,5S∗,8S∗)-5-hydroxy-4-[(E)-7-hydroxy-4-methylhept-3-enyl]-4,8-dimethyl-3-oxabicyclo[3.3.0]octan-2,6-dione, respectively. 相似文献
83.
We apply an orbital phase theory to the torquoselectivity of the electrocyclic reactions of 3-substituted (X) cyclobutenes. The torquoselectivity is shown to be controlled by the orbital-phase relation of the reacting pi(CC) and sigma(CC) bonds with the sigma(CX) bond geminal to the sigma(CC) bond to be cleaved. The inward rotation of electron-donating sigma(CX) bonds and outward rotation of electron-withdrawing sigma(CX) bonds have been deduced from the orbital-phase theory. Enhancement of the inward rotation by the electron-donating capability of the sigma(CX) bonds is confirmed by the correlation between the torquoselectivity and sigma(CX) orbital energy. The orbital overlaps between the geminal sigma(CX) (sigma(CH)) and sigma(CC) bonds are found to be important as well. Unsaturated substituents with low-lying unoccupied pi orbitals also promote the inward rotation. 相似文献
84.
Fukuzumi S Satoh N Okamoto T Yasui K Suenobu T Seko Y Fujitsuka M Ito O 《Journal of the American Chemical Society》2001,123(32):7756-7766
The lowest excited state of aromatic carbonyl compounds (naphthaldehydes, acetonaphthones, and 10-methylacridone) is changed from the n,pi triplet to the pi,pi singlet which becomes lower in energy than the n,pi triplet by the complexation with metal ions such as Mg(ClO(4))(2) and Sc(OTf)(3) (OTf = triflate), which act as Lewis acids. Remarkable positive shifts of the one-electron reduction potentials of the singlet excited states of the Lewis acid-carbonyl complexes (e.g., 1.3 V for the 1-naphthaldehyde-Sc(OTf)(3) complex) as compared to those of the triplet excited states of uncomplexed carbonyl compounds result in a significant increase in the redox reactivity of the Lewis acid complexes vs uncomplexed carbonyl compounds in the photoinduced electron-transfer reactions. Such enhancement of the redox reactivity of the Lewis acid complexes leads to the efficient C-C bond formation between benzyltrimethylsilane and aromatic carbonyl compounds via the Lewis-acid-promoted photoinduced electron transfer. The quantum yield determinations, the fluorescence quenching, and direct detection of the reaction intermediates by means of laser flash photolysis experiments indicate that the Lewis acid-catalyzed photoaddition reactions proceed via photoinduced electron transfer from benzyltrimethylsilane to the singlet excited states of Lewis acid-carbonyl complexes. 相似文献
85.
The total space of the spinor bundle on the four-dimensional sphere S4 is a quaternionic line bundle that admits a metric of Spin(7) holonomy. We consider octonionic Yang–Mills instanton on this eight-dimensional gravitational instanton. This is a higher dimensional generalization of (anti-) self-dual instanton on the Eguchi-Hanson space. We propose an ansatz for Spin(7) Yang–Mills field and derive a system of non-linear ordinary differential equations. The solutions are classified according to the asymptotic behavior at infinity. We give a complete solution when the gauge group is reduced to a product of SU(2) subalgebras in Spin(7). The existence of more general Spin(7) valued solutions can be seen by making an asymptotic expansion. 相似文献
86.
Shinro Yasui Kosei Shioji Munekazu Tsujimoto Atsuyoshi Ohno 《Heteroatom Chemistry》2000,11(2):152-157
The reaction of methylviologen (MV2+) with tributylphosphine ( 1p ) and diethylphenylphosphine ( 1q ) in the presence of an alkyl-substituted pyridine ( 2 ) was found to take place through a single-electron transfer (SET) from 1 to MV2+ followed by nucleophilic attack by 2 on the resulting phosphine radical cation 1 •+. Kinetic examination showed that, in the transition state for the reaction of 1 •+ with 2 , an unpaired electron is largely delocalized to the pyridine moiety. © 2000 John Wiley & Sons, Inc. Heteroatom Chem 11:152–157, 2000 相似文献
87.
Takayuki Nishiguchi Yamashita Masayuki Yoshikawa Yutaka Yasui Hiroyuki 《Crystallography Reports》2019,64(7):1099-1102
Crystallography Reports - Zn(II) complexes with 2-ethyl-3-hydroxy-4H-pyran-4-thione, [Zn(ehpt)2], and 2-ethyl-3-hydroxy-4H-pyran-4-selenone, [Zn(ehps)2], were synthesized and characterized by... 相似文献
88.
X. Ding Y. Yasui Y. Kawaguchi H. Niino A. Yabe 《Applied Physics A: Materials Science & Processing》2002,75(3):437-440
The laser-induced back-side wet etching of fused silica with aqueous solutions of pyranine (8-hydroxy-1,3,6-pyrenetrisulfonic
acid trisodium salt) is reported. KrF and XeF excimer lasers were employed as light sources. Well-defined line-and-space and
grid micropatterns, free of debris and microcracks, were obtained. Compared with other organic solutions, the aqueous pyranine
etching medium etches more slowly but produces a higher quality etched surface. With the KrF laser, the etch rate ranged from
0.02 to 0.12 nm pulse-1, depending on the dye concentration and the fluence of the laser. The etch rate decreased dramatically when the XeF laser
was employed, which was partially attributed to the lower absorption efficiency of the aqueous pyranine solution at the XeF
laser wavelength.
Received: 20 November 2001 / Accepted: 21 November 2001 / Published online: 2 May 2002 相似文献
89.
Su Houng Lee Shigehiro Yasui Wei Liu Che Ming Ko 《The European Physical Journal C - Particles and Fields》2008,54(2):259-265
Based on the color–spin interaction in diquarks, we argue that charmed multiquark hadrons are likely to exist. Because of
the appreciable number of charm quarks produced in central nucleus–nucleus collisions at ultrarelativistic energies, the production
of charmed multiquark hadrons is expected to be enhanced in these collisions. Using both the quark coalescence model and the
statistical hadronization model, we estimate the yield of charmed tetraquark mesons, Tcc, and pentaquark baryons, Θcs, in heavy ion collisions at RHIC and LHC. We further discuss the decay modes of these charmed exotic hadrons in order to
facilitate their detections in experiments.
PACS 25.75.Dw; 14.20.Lq; 14.40.Lb 相似文献
90.
Effect of particle addition on sonochemical reaction 总被引:1,自引:0,他引:1
Enhancement of chemical reaction with a photocatalyst of titanium dioxide (TiO(2)) by ultrasonic irradiation is studied through the absorbance measurements for liberation of iodine from a KI aqueous solution as an index of oxidation reaction. It is well known as a synergetic effect that the addition of TiO(2) fine particles under UV has an ability to enhance the yield in chemical reaction with OH-radical from hot spot at violent collapse of cavitation bubbles with intense ultrasound. In this study, the absorbance is measured after simultaneous irradiation of ultrasound and UV with the addition of TiO(2) much less than the usual concentration by two orders of content. It is shown that, even in case of quite a little TiO(2) addition where the photocatalytic effect is less, the yield is enhanced obviously in comparison with the summation in yield of independent procedure of ultrasound without TiO(2) and UV with TiO(2). The absorbance-peak deviation to the shorter wavelength implies the generation of titanium peroxide (TiO(3)). The effect of particle addition is due to the chemically activated particle surface on the TiO(2) and probably to the increase in the cavitation bubbles that results in promoting a transfer of OH-radical and other oxidants to bulk liquid region at the collapse. 相似文献