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51.
Sadamoto R Niikura K Ueda T Monde K Fukuhara N Nishimura S 《Journal of the American Chemical Society》2004,126(12):3755-3761
UDP-MurNAc-pentapeptide derivative bacterial cell-wall precursors were synthesized as effective tools for surface display on living bacteria. Lactobacilli were incubated in the ketone-modified precursor-containing medium, and the ketone moiety was displayed on the bacterial surface through cell-wall biosynthesis. Oligomannose was coupled with the ketone moiety on the bacterial surface via a aminooxyl linker, thereby displaying this oligosaccharide on the surface of the bacteria. The increase in the adhesion of the sugar-displaying bacteria onto a concanavalin A-attached film compared to that of native bacteria was confirmed by microscopic observation and surface plasmon resonance measurement. The incorporation of the artificial cell-wall precursors was enhanced when incubated with fosfomycin, an inhibitor of cell-wall precursor biosynthesis. 相似文献
52.
[structure: see text] Synthesis and fluorescence properties of pi-conjugated compounds having alternately an aromatic ring such as benzene, pyridine, and thiophene and an enediyne unit in the backbone are described. 相似文献
53.
Friedrich MG Giebeta F Naumann R Knoll W Ataka K Heberle J Hrabakova J Murgida DH Hildebrandt P 《Chemical communications (Cambridge, England)》2004,(21):2376-2377
Membrane-bound cytochrome c oxidase was attached to an electrode via a His-tag linker and studied by surface enhanced resonance Raman spectroscopy, demonstrating intact redox site structures and electron transfer between the electrode and the immobilized enzyme. 相似文献
54.
Photoemission and ionization of He+ under simultaneous irradiation of fundamental laser and high-order harmonic pulses 总被引:1,自引:0,他引:1
Ishikawa K 《Physical review letters》2003,91(4):043002
We theoretically study the response of He+ exposed simultaneously to an intense Ti:sapphire laser and its 27th or 13th harmonic pulses. High-order harmonic emission from He+ is enhanced by many orders of magnitude compared with the case of the fundamental pulse alone. Moreover, while an individual 10 fs laser (wavelength lambda(F)=800 nm) or its 27th harmonic pulse with a peak intensity of 3 x 10(14) and 10(13) W/cm(2), respectively, ionizes no more than 5 x 10(-6) of He+, their combined pulse leads to a surprisingly high He2+ yield of 17%. 相似文献
55.
An efficient method has been developed for the first solid-phase synthesis of HTLV-1 protease inhibitors that contain hydroxyethylamine isostere as a transition-state mimetic. The synthetic procedure was designed to allow the evaluation of stereostructure-activity relationships at the scissile site. All the possible configurations at the hydroxy- and side chain-bearing asymmetric centers of the isostere were constructed by an ester-derived asymmetric aldol reaction. Each inhibitor containing the isostere backbone was synthesized on solid support by using the newly developed succinate ester linker. The configuration at the hydroxy- and side chain-bearing asymmetric center showed remarkable effects on the inhibitory activity; the K(i) value changed with approximately 2 orders of magnitude. The described approach enables an efficient preparation of the inhibitors containing secondary alcohol as a transition-state mimetic. 相似文献
56.
The crystal structure of [{O=VV(salen)}2(mu-F)][VIVO(salen)][BF4].(CH2Cl2)x revealed a hollow cavity with a diameter of 5.3 A that penetrates through the crystal, and a remarkable cyclic chain of the [VO(salen)] unit, a motif that has never been fashioned from oxometal building blocks. These features endow the crystal with a molecular sievelike property for the rapid, reversible, and size-selective absorption of guest CH2Cl2 molecules. 相似文献
57.
Kenichi Futamura 《Annals of Operations Research》2000,93(1-4):71-90
Traditionally, studies on tandem queueing networks concentrate on systems with infinite buffers, exponential service times, and/or single servers where solutions are more tractable. Less research can be found on more general, less tractable systems. We examine multipleserver systems with finite buffers and nonexponential service times, studying the effects of coefficient of variation (cv) of the servicetime distribution on the throughput of these systems, where cv differs among stations.Starting with the single station, we examine the effects of cv and the number of servers at the station on the distribution of interdeparture times. This insight helps explain the differences in throughput seen in the single (fast) server vs. multiple (slow) server problem. These results, in turn, shed light on the server allocation problem when cv differs among stations. We present some observations, as well as the intuition behind them. 相似文献
58.
Bastakoti BP Guragain S Yokoyama Y Yusa S Nakashima K 《Langmuir : the ACS journal of surfaces and colloids》2011,27(1):379-384
An asymmetric triblock copolymer, poly(styrene-b-acrylic acid-b-ethylene glycol) (PS-b-PAA-b-PEG), was synthesized via reversible addition-fragmentation chain transfer controlled radical polymerization. Micelles of PS-b-PAA-b-PEG with PS core, PAA shell, and PEG corona were then prepared in aqueous solutions, followed by extensive characterization based on dynamic light scattering, zeta-potential, and transmission electron microscopy (TEM) measurements. The well-characterized micelles were used to fabricate hollow nanospheres of CaCO(3) as a template. It was elucidated from TEM measurements that the hollow nanospheres have a uniform size with cavity diameters of ca. 20 nm. The X-ray diffraction analysis revealed a high purity and crystallinity of the hollow nanospheres. The hollow CaCO(3) nanospheres thus obtained have been used for the controlled release of an anti-inflammatory drug, naproxen. The significance of this study is that we have overcome a previous difficulty in the synthesis of hollow CaCO(3) nanospheres. After mixing of Ca(2+) and CO(3)(2-) ions, the growth of CaCO(3) is generally quite rapid to induce large crystal, which prevented us from obtaining hollow CaCO(3) nanospheres with controlled structure. However, we could solve this issue by using micelles of PS-b-PAA-b-PEG as a template. The PS core acts as a template that can be removed to form a cavity of hollow CaCO(3) nanospheres, the PAA shell is beneficial for arresting Ca(2+) ions to produce CaCO(3), and the PEG corona stabilizes the CaCO(3)/micelle nanocomposite to prevent secondary aggregate formation. 相似文献
59.
Hamada T Sato YT Yoshikawa K Nagasaki T 《Langmuir : the ACS journal of surfaces and colloids》2005,21(17):7626-7628
A photosensitive amphiphilic molecule can switch the shape of an assembled vesicle as determined by microscopic observation. Photoisomerization induces a change in membrane fluctuation behavior or a morphological transition between ellipsoid and bud shapes, depending on the asymmetrical degree of the initial shape. The mechanism of this reversible photoswitching in the vesicle morphology is interpreted in terms of a change in the effective cross-sectional area of the photosensitive molecule. 相似文献
60.
Dova E Peschar R Sakata M Kato K Schenk H 《Chemistry (Weinheim an der Bergstrasse, Germany)》2006,12(19):5043-5052
The spin-crossover complex [Fe(teec)(6)](ClO(4))(2) (teec = chloroethyltetrazole) exhibits a 50 % incomplete spin crossover in the temperature range 300-30 K. Time-resolved synchrotron powder diffraction experiments have been carried out to elucidate its structural behavior. We report crystal structure models of this material at 300 K (high spin) and 90 K (low spin), as solved from synchrotron powder diffraction data by using Genetic Algorithm and Parallel Tempering techniques and refined with Rietveld refinement. During short synchrotron powder diffraction experiments (five minutes duration) two distinguishable lattices were observed the quantities of which vary with temperature. The implication of this phenomenon, that is interpreted as a structural phase transition associated with the high-to-low spin crossover, and the structural characteristics of the high-spin and low-spin models are discussed in relation to other compounds showing a similar type of spin-crossover behavior. 相似文献