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961.
Metal ion induced FRET OFF-ON in tren/dansyl-appended rhodamine 总被引:1,自引:0,他引:1
A series of new fluorescent probes bearing tren-spaced rhodamine B and dansyl groups have been synthesized. Compound 1 exhibits selective changes in the absorption and the emission spectra toward Cu2+ ion over miscellaneous metal cations. Among 1-3, 1 shows the best FRET efficiency through dansyl emission to rhodamine absorption for the Cu2+ ion. 相似文献
962.
New electrochromic systems based on bis-isophthalates were designed and prepared. They showed electrochromism behavior by two-electron reduction. The displayed colors showed greatly enhanced bistability and were dependent on the length of the conjugated bridge between the two isophthalate groups. We believe that the connection of two electrochromic systems with a conjugated bridge is a good basic strategy to obtain new bistable electrochromic systems. 相似文献
963.
Tributyltin hydride-mediated radical reactions of organic halides were successfully carried out in a continuous flow system using a microreactor. The reactions proceeded within a very short period of time, coupled with quickly decomposing radical initiators such as V-65 and V-70. The continuous flow reaction system was applied to gram scale synthesis of a key intermediate for furofuran lignans. 相似文献
964.
Tin-free Giese reaction and the related radical carbonylation process proceeded efficiently in the presence of sodium cyanoborohydride and tetrabutylammonium cyanoborohydride. The reaction took place chemoselectively at the carbon-iodine bond but not at the carbon-bromine and carbon-chlorine bonds. The iodine atom transfer followed by hydride reduction of the resulting carbon-iodine bond is proposed as a possible mechanism. 相似文献
965.
Ilhyong Ryu Hiroshi Matsubara Hiroyuki Nakamura Dennis P. Curran 《Chemical record (New York, N.Y.)》2008,8(6):351-363
The phase‐vanishing (PV) method is based on spontaneous reaction controlled by diffusion of reagents into fluorous media, such as perfluorohexanes (FC‐72) and polyperfluoroethers. Thus, the original PV reaction utilizes a triphasic test tube method composed of a bottom reagent phase, a middle fluorous phase, and a top substrate phase. In such a triphasic system, the fluorous phase acts as a liquid membrane to transport the bottom reagents to the top organic phase containing substrates. In the end, the bottom layer disappears and two phases remain. Since the first demonstration of the PV method by bromination of alkenes with molecular bromine, a number of applications have been developed thus far. These include halogenation of alcohols with SOBr2 and PBr3, demethylation of methoxyarenes with BBr3, cyclopropanation of alkenes by CH2I2‐AlEt3, and Friedel–Crafts acylation of aromatic compounds with SnCl4. A fluorous triphasic U‐tube method is effective for chlorination of alcohols based on lighter (less dense) reagents such as SOCl2 and PCl3. A system using a solution containing reagents as a bottom phase is useful for oxidation with m‐CPBA, which may be defined as a new category for the “extractive PV” method. Recent advances include a “quadraphasic” PV method, in which an aqueous “scavenger” phase is added to the original triphasic PV method to remove acidic by‐products. © 2008 The Japan Chemical Journal Forum and Wiley Periodicals, Inc. Chem Rec 8: 351–363; 2008: Published online in Wiley InterScience ( www.interscience.wiley.com ) DOI 10.1002/tcr.20161 相似文献
966.
Yutao Yang Ming Ma Lei Shen Jusung An Eunji Kim Hongmei Liu Ming Jin Shuxiang Wang Jinchao Zhang Prof. Jong Seung Kim Prof. Caixia Yin 《Angewandte Chemie (International ed. in English)》2023,62(40):e202310408
Cerebral ischemia-reperfusion injury (CIRI) is intimately associated with the redox regulation of biothiol, a crucial antioxidant marker that precludes the onset of ROS. We designed a novel fluorescent probe, DCI-Ac-Py , showing various physicochemical properties, such as high selectivity, exceptional signal-to-noise ratio, near-infrared (NIR) optical window, and blood–brain barrier (BBB) penetrability, for detecting biothiols in the brain. The picolinate serves as a specific recognition group that is rapidly activated by biothiol and undergoes nucleophilic substitution with the adjacent acrylic ester to yield the desired NIR probe. Additionally, the probe's lipid solubility is improved through the inclusion of halogen atoms, which aids in penetrating the BBB. Using DCI-Ac-Py , we investigated changes of biothiols in vivo in the brains of mice during CIRI. We found that biothiol-mediated NF-kB classical (P65-related) and nonclassical (RelB-related) pathways contribute to abundant ROS production induced by CIRI and that biothiols are involved in redox regulation. These findings provide new insights into the study of CIRI and shed light on the physiological and pathological mechanisms of biothiols in the brain. 相似文献
967.
Jahng KC Kim SI Kim DH Seo CS Son JK Lee SH Lee ES Jahng Y 《Chemical & pharmaceutical bulletin》2008,56(4):607-609
One-pot synthesis of various 2,3-polymethylene-4(3H)-quinazolinones from anthranilic acid, corresponding lactam and SOCl(2) is described, which can be applicable to the synthesis of simple 4(3H)-quinazolinone-derived alkaloids, such as luotonin A, tryptanthrin, and rutaecarpine. 相似文献
968.
Seung Ho Yang Michael Nosonovsky Huan Zhang Koo-Hyun Chung 《Chemical physics letters》2008,463(1-3):286-287
In this response to the comment by Caupin et al. [1] on our earlier paper, we explain why negative pressure in nanoscale water capillary bridges in AFM experiments is lower than the pressure reported in macroscale and microscale experiments. An estimate shows that for the tip radius of 10 nm, the bridge foundation area (A) is on the order of A = 10−16 m2, and the typical experimental value of the capillary force (Fad) on the order of Fcap = 10 nN corresponds to the negative pressure P = −Fcap/A = −100 MPa. 相似文献
969.
Muramatsu H Yamamoto Y Shigeno M Shirakawabe Y Inoue A Kim WS Kim SJ Chang SM Kim JM 《Analytica chimica acta》2008,611(2):233-238
We have fabricated polymer tips for atomic force microscopy in order to elucidate the effects of tip length and shape on cantilever vibration damping in liquids. The vibration damping is investigated by measuring the vibration amplitude of cantilevers as a function of tip-sample distance. The cantilever with a short tip provides a higher damping effect over long tip-sample distances. When the vibration amplitude was rescaled to show the effect of the cantilever width on oscillation damping, the vibration amplitude of cantilevers with various tip lengths was similarly obtained in a long distance range over 50 μm. This similarity is explained by an acoustic damping model in which an acoustic wave is generated by the cantilever. Finally, the results indicate a cantilever with a sufficiently long tip compared to the cantilever width can dramatically reduce the long-range damping effect in a liquid environment. 相似文献
970.
Sun Young Kim Yun Seon Yeon Seung Min Park Jeong Hyun Kim Jae Kyu Song 《Chemical physics letters》2008,462(1-3):100-103
Photoluminescence (PL) of zinc oxide (ZnO) nanorods with an average thickness of 5 nm and a length of 30 nm is blue-shifted compared to the bulk due to quantum confinement effects. The exciton states remain relatively stable at a high carrier density due to a smaller exciton size and an enhanced exciton binding energy in the quantum confined nanorods, whereas the electron-hole plasma states are formed in the bulk at the similar carrier density. A linear dependence of the PL intensity on the excitation intensity also corroborates the assumption that the stable exciton states are responsible for the undisturbed emission at a high carrier density. 相似文献