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991.
Yessi Permana Koji Nakano Dr. Makoto Yamashita Dr. Daisuke Watanabe Kyoko Nozaki Prof. Dr. 《化学:亚洲杂志》2008,3(4):710-718
Four acetyl cobalt complexes, [AcCo(CO)3P(p‐tolyl)3] ( 1 ; p‐tolyl=4‐Me‐C6H4), [AcCo(CO)3P(OPh)3] ( 2 ), [AcCo(CO)3P(NMe2)3] ( 3 ), and [AcCo(CO)2(dppp)] ( 4 ; dppp=1,3‐bis(diphenylphosphanyl)propane), were synthesized, characterized, and examined as catalysts for the unprecedented carbonylative polymerization of oxetanes. Copolymers containing ester (4‐hydroxyalkanoate) and/or ether units were obtained with complexes 1 and 2 , but not with complexes 3 and 4 either in the presence or absence of additional phosphorus ligands. The ester unit/ether unit ratio varied in the range 21:79–63:37, and the highest ester/ether ratio of 63:37 was achieved by using complex 1 in the presence of a further 5 equivalents of P(OPh)3. Although direct carbonylative polymerization is possible, preformation and ring opening of the γ‐lactone is also suggested as an alternative pathway. 相似文献
992.
Nakayama K Tachikawa T Majima T 《Langmuir : the ACS journal of surfaces and colloids》2008,24(13):6425-6428
Protein adsorption and dissociation on cell membrane surfaces is a topic of important study to reveal biological processes including signal transduction and protein trafficking. We demonstrated here the establishment of a mimic model system for the spatial control of protein adsorption/elimination on a lipid bimembrane using a photochemical technique. The novel photoeliminative linker that we synthesized here consists of three distinct components: a substrate (biotin), a photoeliminative group (4-(4-(1-hydroxyethyl)-2-methoxy-5-nitrophenoxy)butanoic acid), and a lipid bimembrane-adsorbent group (farnesyl). The photoeliminative linker was inserted on the entire surface of the lipid bimembrane and two-dimensionally eliminated by spatial UV irradiation onto the membrane to create a biotin pattern. A target protein, streptavidin was selectively immobilized on the patterned biotin, although it was almost not attached on the nonirradiated region. The streptavidin array was selectively dissociated by UV irradiation onto the entire membrane. 相似文献
993.
Sakai H Tanaka K Fukushima H Tsuchiya K Sakai K Kondo T Abe M 《Colloids and surfaces. B, Biointerfaces》2008,66(2):4022-290
Polyurea capsules have been prepared using the electrocapillary emulsification method in order to control the particle size within the submicron range. The polyurea capsules have been synthesized via the interfacial polycondensation between tetraethylenepentamine (TEP) dissolved in an aqueous phase and toluenediisocyanate (TDI) dissolved in a mixture of cyclohexane and chloroform. The oil phase contains a lipophilic nonionic surfactant (sorbitan sesquioleate, SO-15) as an emulsion stabilizer. Scanning electron microscope (SEM) observations reveal that the capsule size is decreased as (i) the amount of the aqueous phase injected into the oil phase is decreased and (ii) the dropping rate of the aqueous phase is decreased. Indeed, the mole ratio of the two monomers makes a significant impact on the capsule size. Under the best experimental condition examined in this study, we obtained polyurea capsules with a diameter of approximately 200 nm, which should be useful in developing bioreactors or carriers. 相似文献
994.
995.
996.
Yasutaka Nagai Daisuke Miyagishi Fujio Ohishi Koji Kobayashi Junji Watanabe 《Polymer Degradation and Stability》2008,93(1):134-138
In order to identify the initiation step in the photodegradation of poly(2,6-butylenenaphthalate)-block-poly(tetramethyleneglycol) (PBN-PTMG), we undertook its photolysis with monochromatic irradiation. We discuss the initiation reaction on the basis of the analytical results for the PBN-PTMG in the presence or absence of 2,2′-dihydroxy-4-methoxybenzophenone as a UV absorber, 2-hydroxy-4-methoxybenzophenone as a UV absorber, β-carotene as a quencher of singlet oxygen or methylene blue as a photosensitiser, respectively.The PBN-PTMG containing 2,2′-dihydroxy-4-methoxybenzophenone exhibits better resistance to the incident light of ca. 370 nm corresponding to the absorption of the n, π* transition of the carbonyl group in the PBN block than the PBN-PTMG containing 2-hydroxy-4-methoxybenzophenone. The PBN-PTMG containing β-carotene shows similar photodegradation tendencies as that of the PBN-PTMG without β-carotene. In contrast, the PBN-PTMG with methylene blue is not degraded by monochromatic radiation in the range λ = 600-690 nm. These facts indicate that singlet oxygen does not participate in the initiation reaction of the photodegradation of the PBN-PTMG. Therefore, we concluded that the photodegradation of the PBN-PTMG is induced through the hydrogen abstraction by carbonyl groups in n, π* excited states. 相似文献
997.
Yasuda K 《Journal of computational chemistry》2008,29(3):334-342
We propose the algorithm to evaluate the Coulomb potential in the ab initio density functional calculation on the graphics processor unit (GPU). The numerical accuracy required for the algorithm is investigated in detail. It is shown that GPU, which supports only the single-precision floating number natively, can take part in the major computational tasks. Because of the limited size of the working memory, the Gauss-Rys quadrature to evaluate the electron repulsion integrals (ERIs) is investigated in detail. The error analysis of the quadrature is performed. New interpolation formula of the roots and weights is presented, which is suitable for the processor of the single-instruction multiple-data type. It is proposed to calculate only small ERIs on GPU. ERIs can be classified efficiently with the upper-bound formula. The algorithm is implemented on NVIDIA GeForce 8800 GTX and the Gaussian 03 program suite. It is applied to the test molecules Taxol and Valinomycin. The total energies calculated are essentially the same as the reference ones. The preliminary results show the considerable speedup over the commodity microprocessor. 相似文献
998.
Yamaguchi S Matsumoto S Ishizuka K Iko Y Tabata KV Arata HF Fujita H Noji H Hamachi I 《Chemistry (Weinheim an der Bergstrasse, Germany)》2008,14(6):1891-1896
The artificial regulation of protein functions is essential for the realization of protein-based soft devices, because of their unique functions conducted within a nano-sized molecular space. We report that self-assembled nanomeshes comprising heat-responsive supramolecular hydrogel fibers can control the rotary motion of an enzyme-based biomotor (F(1)-ATPase) in an on/off manner at the single-molecule level. Direct observation of the interaction of the supramolecular fibers with a microbead unit tethered to the F(1)-ATPase and the clear threshold in the size of the bead required to stop ATPase rotation indicates that the bead was physically blocked so as to stop the rotary motion of ATPase. The temperature-induced formation and collapse of the supramolecular nanomesh can produce or destroy, respectively, the physical obstacle for ATPase so as to control the ATPase motion in an off/on manner. Furthermore, this switching of the F(1)-ATPase motion could be spatially restricted by using a microheating device. The integration of biomolecules and hard materials, interfaced with intelligent soft materials such as supramolecular hydrogels, is promising for the development of novel semi-synthetic nano-biodevices. 相似文献
999.
Yoshida K Yamaguchi T Kittaka S Bellissent-Funel MC Fouquet P 《The Journal of chemical physics》2008,129(5):054702
Thermodynamic, structural, and dynamic properties of heavy water (D(2)O) confined in mesoporous silica glass MCM-41 C10, C12, and C14 were investigated by differential scanning calorimetry, neutron diffraction, and neutron spin echo (NSE) measurements, respectively. The DSC data showed that no crystallization of D(2)O confined in C10 occurs in a temperature range between 298 and 180 K, and that crystalline ice is formed at 204 and 221 K for C12 and C14, respectively. For C10, the neutron radial distribution functions of confined D(2)O suggested a structural change in the supercooled state between 223 and 173 K. For C10 sample, it has been found that the tetrahedral-like water structure is partially enhanced in the central part of pores at 173 K. For all the samples, the intermediate scattering functions from the NSE measurements are fitted by the Kohlrausch-Williams-Watts stretched exponential function which implies that confined supercooled D(2)O exhibits a wide distribution of relaxation times. For C10, C12, and C14 samples, between 298 and 240 K, the relaxation times of supercooled D(2)O follow remarkably well the Vogel-Fulcher-Tamman equation; for C10 sample, below 240 K, the relaxation times of nonfreezing D(2)O show an Arrhenius type behavior. From the present experimental results on calorimetric, structural, and dynamic properties, it has been concluded that supercooled D(2)O confined in MCM-41 C10 experiences a transition from high-density to low-density hydrogen-bonded structure at around 229 K. 相似文献
1000.
Nakamura E Koshino M Tanaka T Niimi Y Harano K Nakamura Y Isobe H 《Journal of the American Chemical Society》2008,130(25):7808-7809
A diamide molecule bearing a biotin terminus was bonded via an amide linkage to the surface of an aminated single-walled carbon nanotube and examined by a high-resolution transmission electron microscope. The still and movie images allowed us to study not only the conformation of the molecule but also its time evolution. An iterative sequence of modeling and simulation allowed us to assign one plausible conformation out of >10(8) possibilities. The images also provide direct support for the accepted wisdom that the curved regions of pristine carbon nanotubes are chemically reactive. 相似文献