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81.
82.
Minjoong Yoon Jae Rim Chang Dongho Kim Yasunao Kuriyama Katsumi Tokumaru 《Photochemistry and photobiology》1991,54(1):75-82
The micellar dependencies of the photophysical properties of benoxaprofen (BXP), a 2-phenyl benzoxazole derivative, have been investigated using fluorescence spectroscopy and laser flash photolysis techniques. The fluorescence of BXP in aqueous solution has been observed to be remarkably quenched upon addition of a surfactant, cetyltrimethyl ammonium bromide (CTAB) or Triton X-100, in contrast to its enhancement in sodium dodecyl sulfate (SDS) micellar solution. Time-resolved fluorescence measurements show that the fluorescence decays biexponentially in the micellar solution, indicating the relaxation of micellar environments surrounding the excited BXP. The major component of fluorescence lifetimes in CTAB or Triton X-100 micellar phase is even shorter (330–427ps) than in SDS micellar phase (731 ps). The nonradiative decay constants are significantly larger (ca 3.0 times 109 s?1) in the CTAB or Triton X-100 micellar phase than in SDS micelles by a factor of ca 10. The major nonradiative decay is interpreted to be the internal conversion due to nuclear geometric change of BXP in the first excited singlet state. This is consistent with the observation that the quantum yields of intersystem crossing are very low (less than 0.01) in the micellar solutions as determined by the laser flash photolysis technique. The laser-induced transient absorption spectrum of BXP in CTAB or Triton X-100 micellar solution shows that the decay kinetics of the transients in CTAB or Triton X-100 are significantly different from first order kinetics in SDS. 相似文献
83.
Myeong Soon Park Koon Ha Park Kun Jun Seung Rim Shin Sea Wha Oh 《Journal of heterocyclic chemistry》2002,39(6):1279-1281
2‐(2‐, 3‐, and 4‐Pyridyl)benzoxazole derivatives were prepared in excellent yields by the oxidative cyclization of phenolic Schiff bases with thianthrene cation radical perchlorate in the presence of 2,6‐di‐tert‐butyl‐4‐methylpyridine. 相似文献
84.
Jong Seung Kim Jeong Ah Rim Ok Jae Shon Kwan Ho Noh Eun-Hee Kim Chaejoon Cheong Jacques Vicens 《Journal of inclusion phenomena and macrocyclic chemistry》2002,43(1-2):51-54
A series of N-pivot calix[4]crown-5-azacrown-5 ethers substituted by 2-picolyl, 3-picolyl and benzyl groups respectively were synthesized. The nitrogen atom of the 2-picolyl group is found to participate in the silver ion complexation through three dimensional encapsulation. 相似文献
85.
Yong‐beom Lim Dr. Somi Park Eunji Lee Ja‐Hyoung Ryu Dr. You‐Rim Yoon Tae‐Hyun Kim Prof. Dr. Myongsoo Lee Prof. Dr. 《化学:亚洲杂志》2007,2(11):1363-1369
We explored a method of controlling bacterial motility and agglutination by using self‐assembled carbohydrate‐coated β‐sheet nanoribbons. To this aim, we synthesized triblock peptides that consist of a carbohydrate, a polyethylene glycol (PEG) spacer, and a β‐sheet‐forming peptide. An investigation into the effect of PEG‐spacer length on the self‐assembly of the triblock peptides showed that the PEG should be of sufficiently length to stabilize the β‐sheet nanoribbon structure. It was found that the stabilization of the nanoribbon led to stronger activity in bacterial motility inhibition and agglutination, thus suggesting that antibacterial activity can be controlled by the stabilization strategy. Furthermore, another level of control over bacterial motility and agglutination was attained by co‐assembly of bacteria‐specific and ‐nonspecific supramolecular building blocks. The nanoribbon specifically detected bacteria after the encapsulation of a fluorescent probe. Moreover, the detection sensitivity was enhanced by the formation of bacterial clusters. All these results suggest that the carbohydrate‐coated β‐sheet nanoribbons can be developed as promising agents for pathogen capture, inactivation, and detection, and that the activity can be controlled at will. 相似文献
86.
The synthesis and reactions of several α,β-unsaturated chloromethyl sulfones is presented, for example [(chloromethyl)sulfonyl]-1,3-propadiene (4), [(chloromethyl)sulfonyl]ethene (5), [(dichloromethyl)sulfonyl]ethene (6) and (E,Z)-1,2-bis[(chloromethyl)sulfonyl]ethene (7). These compounds serve as ‘prepackaged’ Ramberg-Bäcklund reagents, which following an appropriate first step, such as Diels-Alder addition, react with base giving Ramberg-Bäcklund products. 相似文献
87.
Oh CR Choo DJ Shim WH Lee DH Roh EJ Lee SG Song CE 《Chemical communications (Cambridge, England)》2003,(9):1100-1101
In the chiral Co(III)(salen)-catalysed HKR of racemic epoxides, in the presence of ionic liquids, Co(II)(salen) complex is oxidised without acetic acid to catalytically active Co(III)(salen) complex during reaction and, moreover, this oxidation state is stabilised against reduction to Co(II) complex which enables the reuse of the recovered catalyst for consecutive reactions without extra reoxidation. 相似文献
88.
Lee SR Yoon DK Park SH Lee EH Kim YH Stenger P Zasadzinski JA Jung HT 《Langmuir : the ACS journal of surfaces and colloids》2005,21(11):4989-4995
We have investigated the surface ordering of a synthetic, asymmetric, fan-shaped dendrimer containing a carboxyl core and perfluorinated tails which was obtained by the esterification of the intermediary. X-ray diffraction patterns and transmission electron microscopy (TEM) images show the molecules self-assemble into a hexagonal, cylindrical mesophase. Surface pressure-area isotherms and Brewster angle microscopy measurements show the molecule forms a stable monolayer at the air-water interface with a single phase transition. As a condensed monolayer, the perfluorinated tails are well-packed with hexagonal symmetry with (10) spacing of approximately 0.5 nm from molecular-scale atomic force microscopy (AFM) images. Such dense molecular-scale packing has not been observed in other dendritic molecules thus far. Compared to the case of conventional dendritic molecules with alkyl tails, these molecules occupy a much smaller molecular area due to the strong microphase separation between the carboxylic core and perfluorinated tails at the air-water interface. After monolayer collapse, the irregular islands with terrace morphology are observed in contrast with conventional alkyl-terminated self-assembled dendritic molecules where irregular islands do not appear. The interfacial and internal structure of every terrace shows planar columnar morphology from AFM and TEM imaging. From these results, we discuss the stability of perfluorinated, self-assembled dendrimers on water, as well as how to generate planar morphology on a hydrophilic surface. 相似文献
89.
Poly(l‐Lactic Acid)/Gelatin Fibrous Scaffold Loaded with Simvastatin/Beta‐Cyclodextrin‐Modified Hydroxyapatite Inclusion Complex for Bone Tissue Regeneration 下载免费PDF全文
Jung Bok Lee Ji Eun Kim Daniel A. Balikov Min Soo Bae Dong Nyoung Heo Donghyun Lee Hyun Joon Rim Deok‐Won Lee Hak‐Joon Sung Il Keun Kwon 《Macromolecular bioscience》2016,16(7):1027-1038
Recently, the application of nanostructured materials in the field of tissue engineering has garnered attention to mediate treatment and regeneration of bone defects. In this study, poly(l ‐lactic acid) (PLLA)/gelatin (PG) fibrous scaffolds are fabricated and β‐cyclodextrin (βCD) grafted nano‐hydroxyapatite (HAp) is coated onto the fibrous scaffold surface via an interaction between βCD and adamantane. Simvastatin (SIM), which is known to promote osteoblast viability and differentiation, is loaded into the remaining βCD. The specimen morphologies are characterized by scanning electron microscopy. The release profile of SIM from the drug loaded scaffold is also evaluated. In vitro proliferation and osteogenic differentiation of human adipose derived stem cells on SIM/HAp coated PG composite scaffolds is characterized by alkaline phosphatase (ALP) activity, mineralization (Alizarin Red S staining), and real time Polymerase chain reaction (PCR). The scaffolds are then implanted into rabbit calvarial defects and analyzed by microcomputed tomography for bone formation after four and eight weeks. These results demonstrate that SIM loaded PLLA/gelatin/HAp‐(βCD) scaffolds promote significantly higher ALP activity, mineralization, osteogenic gene expression, and bone regeneration than control scaffolds. This suggests the potential application of this material toward bone tissue engineering.
90.
As one of the measures to improve the environment in an automobile, malodor caused by the automobile air-conditioning system evaporator was evaluated and analyzed using laboratory-scale test cooling bench. The odor was simulated with an evaporator test cooling bench equipped with an airflow controller, air temperature and relative humidity controller. To simulate the same odor characteristics that occur from automobiles, one previously used automobile air conditioner evaporator associated with unpleasant odors was selected. The odor was evaluated by trained panels and collected with aluminum polyester bags. Collected samples were analyzed by thermal desorption into a cryotrap and subsequent gas chromatographic separation, followed by simultaneous olfactometry, flame ionization detector and identified by atomic emission detection and mass spectrometry. Compounds such as alcohols, aldehydes, and organic acids were identified as responsible odor-active compounds. Gas chromatography/flame ionization detection/olfactometry combined sensory method with instrumental analysis was very effective as an odor evaluation method in an automobile air-conditioning system evaporator. 相似文献