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991.
Suh YG Lee YS Kim SH Jung JK Yun H Jang J Kim NJ Jung JW 《Organic & biomolecular chemistry》2012,10(3):561-568
A novel and stereo-controlled method for the preparation of functionalized macrolactams was developed. The process involves stereoselective enol ether formation, followed by an azacyclic ring expansion via an aza-Claisen rearrangement. Herewith, we describe a systematic investigation of an aza-Claisen rearrangement-induced ring expansion of azacycles prepared by appending E/Z-enol ethers to the medium-sized lactams as well as the stereochemical outcome. In addition, the strategy was successfully applied to the total synthesis of fluvirucinine A(1) and 3-epi-fluvirucinine A(1). This method offers an attractive alternative to the intramolecular amide-aldol reaction for the elaboration of β-alkoxy-α-substituted motifs. 相似文献
992.
Lee R Kim J Kim SY Jang SM Lee SM Choi IH Park SW Shin JS Yoo KH 《Lab on a chip》2012,12(13):2377-2384
Label-free cell-based assays have emerged as a promising means for high-throughput screening. Most label-free sensors are based on impedance measurements that reflect the passive electrical properties of cells. Here we introduce a capacitance-based assay that measures the dielectric constant (capacitance) of biological cells, and demonstrate the feasibility of analyzing endocytosis and screening chemotherapeutic agents with this assay. Endocytosis induces a change in the zeta potential, leading to a change in the dielectric constant which enables real-time endocytosis monitoring using the capacitance sensor. Additionally, since the dielectric constant is proportional to cell radius and cell volume, cell viability can be estimated from the change in capacitance. Therefore, the capacitance sensor array can also be used for cytotoxicity testing for large-scale chemotherapeutic screening. 相似文献
993.
Lee YR Kim IY Kim TW Lee JM Hwang SJ 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(8):2263-2271
Homogeneously mixed colloidal suspensions of reduced graphene oxide, or RGO, and layered manganate nanosheets have been synthesized by a simple addition of the exfoliated colloid of RGO into that of layered MnO(2). The obtained mixed colloidal suspensions with the RGO/MnO(2) ratio of ≤0.3 show good colloidal stability without any phase separation and a negatively charged state with a zeta (ζ) potential of -30 to -40?mV. The flocculation of these mixed colloidal suspensions with lithium cations yields porous nanocomposites of Li/RGO-layered MnO(2) with high electrochemical activity and a markedly expanded surface area of around 70-100?m(2) g(-1). Relative to the Li/RGO and Li/layered MnO(2) nanocomposites (≈116 and ≈167?F?g(-1)), the obtained Li/RGO-layered MnO(2) nanocomposites deliver a larger capacitance of approximately 210?F?g(-1) with good cyclability of around 95-97?% up to the 1000th cycle, thus indicating the positive effect of hybridization on the electrode performances of RGO and lithium manganate. Also, an electrophoretic deposition of the mixed colloidal suspensions makes it possible to easily fabricate uniform hybrid films composed of graphene and manganese oxide. The obtained films show a distinct electrochemical activity and a homogeneous distribution of RGO and MnO(2). The present experimental findings clearly demonstrate that the utilization of the mixed colloidal suspensions as precursors provides a facile and universal methodology to synthesize various types of graphene/metal oxide hybrid materials. 相似文献
994.
A remarkably efficient photosensitizer, N719 dye, was used in asymmetric tandem Michael addition/oxyamination of aldehydes, rendering α,β-substituted aldehydes in good yields with excellent levels of enantioselectivity and diastereoselectivity. This is the first report of a multiorganocatalytic reaction involving iminium catalysis and photoinduced singly occupied molecular orbital (SOMO) catalysis. This reaction is expected to expand the scope of tandem organocatalytic reactions. 相似文献
995.
Yul Koh Bo-Rahm Lee Hyo-Jin Yoon Yun-Ho Jang Yoon-Sik Lee Yong-Kweon Kim Byung-Gee Kim 《Analytical and bioanalytical chemistry》2012,404(8):2267-2275
This paper describes a temperature-controllable bead affinity chromatography (BAC) in a microsystem for biomarker detection, and preparing samples for matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF MS) analysis. Cancer marker proteins were captured in the microsystem by BAC with RNA aptamer-immobilized microbeads. The captured proteins were then denatured and released from the microbeads by controlling temperature. The microsystem consists of a microreactor for trapping microbeads and a temperature control unit for thermal treatment of the trapped beads. We used polymethylsilxoane or single crystalline silicon in fabricating two different types of reaction chamber to compare the differences in performance originated from the materials. Carcinoembryonic antigen was concentrated and purified from human serum using the microsystem and detected by MALDI-TOF MS to demonstrate the usefulness of the microsystem. The microsystem simplifies a sample preparation process required for protein analysis and cancer biomarker detection, which will accelerate the process of cancer research. 相似文献
996.
Dae-Woo Jeon Seung-Jae Lee Tak Jeong Jong Hyeob Baek Jae-Woo Park Lee-Woon Jang Myoung Kim In-Hwan Lee Jin-Woo Ju 《Journal of Crystal Growth》2012,338(1):134-138
Chemical lift-off of (11–22) semipolar GaN using triangular cavities was investigated. The (11–22) semipolar GaN was grown using epitaxial lateral overgrowth by metal-organic chemical vapor deposition on m-plane sapphire, in such a way as to keep N terminated surface of c-plane GaN exposed in the cavities. After regrowing 300 μm thick (11–22) semipolar GaN by hydride vapor phase epitaxy for a free-standing (11–22) semipolar GaN substrate, the triangular cavities of the templates were chemically etched in molten KOH. The (000-2) plane in the triangular cavities can be etched in the [0002] direction with the high lateral etching rate of 196 μm/min. The resulting free-standing (11–22) semipolar GaN substrate was confirmed to be strain-free by the Raman analysis. 相似文献
997.
Diabetic nephropathy (DN) is a progressive kidney disease that is caused by injury to kidney glomeruli. Podocytes are glomerular epithelial cells and play critical roles in the glomerular filtration barrier. Recent studies have shown the importance of regulating the podocyte actin cytoskeleton in early DN. The phosphoinositide 3-kinase (PI3K) inhibitor, wortmannin, simultaneously regulates Rac1 and Cdc42, which destabilize the podocyte actin cytoskeleton during early DN. In this study, in order to evaluate the reno-protective effects of wortmannin in early DN by regulating Rac1 and Cdc42, streptozotocin (STZ)-induced proteinuric renal disease (SPRD) rats were treated with wortmannin. The albuminuria value of the SPRD group was 3.55 ± 0.56 mg/day, whereas wortmannin group was 1.77 ± 0.48 mg/day. Also, the albumin to creatinine ratio (ACR) value of the SPRD group was 53.08 ± 10.82 mg/g, whereas wortmannin group was 20.27 ± 6.41 mg/g. Changes in the expression level of nephrin, podocin and Rac1/Cdc42, which is related to actin cytoskeleton in podocytes, by wortmannin administration were confirmed by Western blotting. The expression levels of nephrin (79.66 ± 0.02), podocin (87.81 ± 0.03) and Rac1/Cdc42 (86.12 ± 0.02) in the wortmannin group were higher than the expression levels of nephrin (55.32 ± 0.03), podocin (53.40 ± 0.06) and Rac1/Cdc42 (54.05 ± 0.04) in the SPRD group. In addition, expression and localization of nephrin, podocin and desmin were confirmed by immunofluorescence. In summary, we found for the first time that wortmannin has a reno-protective effect on SPRD rats during the early DN. The beneficial effects of wortmannin in SPRD rats indicate that this compound could be used to delay the progression of the disease during the early DN stage. 相似文献
998.
Xu J Jang K Choi J Jin J Park JH Kim HJ Oh DH Ahn JR Son SU 《Chemical communications (Cambridge, England)》2012,48(50):6244-6246
Through an organometallic approach, ultrathin SnO(x)Fe(y)S(z) plates with ~2 nm single layer-thicknesses were obtained and their graphene composites showed very promising discharge capacities of up to 736 mA h g(-1) and excellent stabilities as anode materials in lithium ion batteries. 相似文献
999.
Kim JH Lee E Park JS Kataoka K Jang WD 《Chemical communications (Cambridge, England)》2012,48(30):3662-3664
Dendritic-linear block copolymers that have pH responsive poly(benzyl ether) dendrons and temperature responsive PiPrOx chains have been designed by copper-mediated click reactions. These copolymers exhibit sharp thermal transitions with a wide range of pH-dependent thermal transition temperatures. 相似文献
1000.
Pang SC Hyun H Lee S Jang D Lee MJ Kang SH Ahn KH 《Chemical communications (Cambridge, England)》2012,48(31):3745-3747
A new diarylethene-derived photochromic compound, with little cytotoxicity, plasma membrane-permeability, and efficient photoswitchability in cells upon alternative UV and visible light irradiation, was synthesized and applied to live cell imaging. 相似文献