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81.
A series of iridium tetrahydride complexes [Ir(H)4(PSiP‐R)] bearing a tridentate pincer‐type bis(phosphino)silyl ligand ([{2‐(R2P)C6H4}2MeSi]−, PSiP‐R, R=Cy, iPr, or tBu) were synthesized by the reduction of [IrCl(H)(PSiP‐R)] with Me4N ⋅ BH4 under argon. The same reaction under a nitrogen atmosphere afforded a rare example of thermally stable iridium(III)–dinitrogen complexes, [Ir(H)2(N2)(PSiP‐R)]. Two isomeric dinitrogen complexes were produced, in which the PSiP ligand coordinated to the iridium center in meridional and facial orientations, respectively. Attempted substitution of the dinitrogen ligand in [Ir(H)2(N2)(PSiP‐Cy)] with PMe3 required heating at 150 °C to give the expected [Ir(H)2(PMe3)(PSiP‐Cy)] and a trigonal bipyramidal iridium(I)–dinitrogen complex, [Ir(N2)(PMe3)(PSiP‐Cy)]. The reaction of [Ir(H)4(PSiP‐Cy)] with three equivalents of 2‐norbornene (nbe) in benzene afforded [IrI(nbe)(PSiP‐Cy)] in a high yield, while a similar reaction of [Ir(H)4(PSiP‐R)] with an excess of 3,3‐dimethylbutene (tbe) in benzene gave the C H bond activation product, [IrIII(H)(Ph)(PSiP‐R)], in high yield. The oxidative addition of benzene is reversible; heating [IrIII(H)(Ph)(PSiP‐Cy)] in the presence of PPh3 in benzene resulted in reductive elimination of benzene, coordination of PPh3, and activation of the C H bond of one aromatic ring in PPh3. [IrIII(H)(Ph)(PSiP‐R)] catalyzed a direct borylation reaction of the benzene C H bond with bis(pinacolato)diboron. Molecular structures of most of the new complexes in this study were determined by a single‐crystal X‐ray analysis. 相似文献
82.
J. Choi S.‐Y. Kwak S. Kang S.‐S. Lee M. Park S. Lim J. Kim C. R. Choe S. I. Hong 《Journal of polymer science. Part A, Polymer chemistry》2002,40(23):4368-4377
Monodisperse polystyrene particles crosslinked with different concentrations of divinylbenzene were synthesized in the 3.2–9.1 μm size range by dispersion polymerization in an isopropyl alcohol/toluene mixed‐dispersion medium with poly(N‐vinylpyrrolidone) as a steric stabilizer and 2,2′‐azobisisobutyronitrile as a radical initiator. The effects of the reaction parameters such as the crosslinking agent concentration, media solvency (controlled by varying the amount of toluene addition), the initiator concentration, and the stabilizer concentration on the particle size and size distribution were investigated with reference particles with a monodisperse size distribution and crosslinked by 1.5 wt % divinylbenzene. The appropriate increase in media solvency was a prerequisite for preparing crosslinked particles without coagulated and/or odd‐shaped particles. The investigation of the effects of the polymerization parameters also shows that only specific sets of conditions produce particles with a monodisperse size distribution. The glass‐transition temperatures of the particles increased with increasing divinylbenzene concentration. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4368–4377, 2002 相似文献
83.
Se-Jin Kim Joon Ho Hur Channy Park Hyung-Jin Kim Gi-Su Oh Joon No Lee Su-Jin Yoo Seong-Kyu Choe Hong-Seob So David J Lim Sung K Moon Raekil Park 《Experimental & molecular medicine》2015,47(2):e142
Bucillamine is used for the treatment of rheumatoid arthritis. This study investigated the protective effects of bucillamine against cisplatin-induced damage in auditory cells, the organ of Corti from postnatal rats (P2) and adult Balb/C mice. Cisplatin increases the catalytic activity of caspase-3 and caspase-8 proteases and the production of free radicals, which were significantly suppressed by pretreatment with bucillamine. Bucillamine induces the intranuclear translocation of Nrf2 and thereby increases the expression of γ-glutamylcysteine synthetase (γ-GCS) and glutathione synthetase (GSS), which further induces intracellular antioxidant glutathione (GSH), heme oxygenase 1 (HO-1) and superoxide dismutase 2 (SOD2). However, knockdown studies of HO-1 and SOD2 suggest that the protective effect of bucillamine against cisplatin is independent of the enzymatic activity of HO-1 and SOD. Furthermore, pretreatment with bucillamine protects sensory hair cells on organ of Corti explants from cisplatin-induced cytotoxicity concomitantly with inhibition of caspase-3 activation. The auditory-brainstem-evoked response of cisplatin-injected mice shows marked increases in hearing threshold shifts, which was markedly suppressed by pretreatment with bucillamine in vivo. Taken together, bucillamine protects sensory hair cells from cisplatin through a scavenging effect on itself, as well as the induction of intracellular GSH. 相似文献
84.
Sang-Young Kim Hyeon-Man Baek Jung-Hoon Lee Dae-Hyun Kim Jin-Young Jung Do-Wan Lee Jung-Whan Min Ji-Yeon Park Seu-Ran Lee Bo-Young Choe 《Journal of Radioanalytical and Nuclear Chemistry》2014,302(1):533-541
In this work, we present the feasibility of using a parallel RF transmit with multiple RF sources imaging method (MultiTransmit imaging) in polymer gel dosimetry. Image quality and B1 field homogeneity was statistically better in the MultiTransmit imaging method than in conventional single source RF transmission imaging method. In particular, the standard uncertainty of R 2 was lower on the MultiTransmit images than on the conventional images. Furthermore, the MultiTransmit measurement showed improved dose resolution. Improved image quality and B1 homogeneity results in reduced dose uncertainty, thereby suggesting the feasibility of MultiTransmit MR imaging in gel dosimetry. 相似文献
85.
Neatly arranged gold nanoparticles (AuNPs) were directly electrodeposited on an electrochemically polymerized self‐assembled monolayer (SAM) of thiol‐functionalized 3,4‐ethylenedioxythiophene (EDOT) derivative, EDTMSHA. A thiolated single‐stranded DNA (ssDNA) aptamer with high specificity to LPS was immobilized on the AuNPs/conducting polymer composite film, serving as sensing platform for LPS detection. Electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), scanning electron microscope (SEM), and atomic force microscopy (AFM) were utilized to characterize the modification and detection processes. The electron transfer resistance was found to have a linear relationship with LPS concentration from 0.1 pg/mL to 1 ng/mL. 相似文献
86.
Hoseok Lee Kyucheol Cho Tae-Kwang Ahn Soonja Choe Il-Joong Kim Inha Park Byung H. Lee 《Journal of Polymer Science.Polymer Physics》1997,35(10):1633-1642
Extensive thermal and relaxational behavior in the blends of linear low-density polyethylene (LLDPE) (1-octene comonomer) with low-density polyethylene (LDPE) and high-density polyethylene (HDPE) have been investigated to elucidate miscibility and molecular relaxations in the crystalline and amorphous phases by using a differential scanning calorimeter (DSC) and a dynamic mechanical thermal analyzer (DMTA). In the LLDPE/LDPE blends, two distinct endotherms during melting and crystallization by DSC were observed supporting the belief that LLDPE and LDPE exclude one another during crystallization. However, the dynamic mechanical β and γ relaxations of the blends indicate that the two constituents are miscible in the amorphous phase, while LLDPE dominates α relaxation. In the LLDPE/HDPE system, there was a single composition-dependent peak during melting and crystallization, and the heat of fusion varied linearly with composition supporting the incorporation of HDPE into the LLDPE crystals. The dynamic mechanical α, β, and γ relaxations of the blends display an intermediate behavior that indicates miscibility in both the crystalline and amorphous phases. In the LDPE/HDPE blend, the melting or crystallization peaks of LDPE were strongly influenced by HDPE. The behavior of the α relaxation was dominated by HDPE, while those of β and γ relaxations were intermediate of the constituents, which were similar to those of the LLDPE/HDPE blends. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35 : 1633–1642, 1997 相似文献
87.
Dae-Won Park Na-Young Mun Eun-Ha Lee Youngson Choe Sang-Wook Park 《Reaction Kinetics and Catalysis Letters》2006,89(1):149-156
Summary Selective ammoxidation of ethylene over Co-ZSM-5 prepared by aqueous and solid-state ion exchange has been studied. The catalyst
prepared using solid-state exchange showed higher activity and selectivity to acetonitrile. Catalysts tested in the ammoxidation
of ethylene were previously characterized by chemical analysis, XRD, N2-BET measurements and FTIR. TPD of ammonia and FTIR of pyridine used as probe molecule showed that solid-state ion exchange
of H-ZSM-5 with cobalt generates new Lewis acid sites which seem to play a role in the ammoxidation reaction. 相似文献
88.
Mingyo Kim Yongho Choe Heewon Lee Min-Gyu Jeon Jin-Ho Park Hae Sook Noh Yun-Hong Cheon Hee Jin Park Jaehun Park Sung Jae Shin Kyunglim Lee Sang-Il Lee 《Experimental & molecular medicine》2021,53(1):67
Histamine releasing factor/translationally controlled tumor protein (HRF/TCTP) stimulates cancer progression and allergic responses, but the role of HRF/TCTP in rheumatoid arthritis (RA) remains undefined. In this study, we explored the pathogenic significance of HRF/TCTP and evaluated the therapeutic effects of HRF/TCTP blockade in RA. HRF/TCTP transgenic (TG) and knockdown (KD) mice with collagen-induced arthritis (CIA) were used to determine the experimental phenotypes of RA. HRF/TCTP levels in the sera of RA patients were measured and compared to those from patients with osteoarthritis (OA), ankylosing spondylitis, Behçet’s disease, and healthy controls. HRF/TCTP expression was also assessed in the synovium and fibroblast-like synoviocytes (FLSs) obtained from RA or OA patients. Finally, we assessed the effects of HRF/TCTP and dimerized HRF/TCTP-binding peptide-2 (dTBP2), an HRF/TCTP inhibitor, in RA-FLSs and CIA mice. Our clinical, radiological, histological, and biochemical analyses indicate that inflammatory responses and joint destruction were increased in HRF/TCTP TG mice and decreased in KD mice compared to wild-type littermates. HRF/TCTP levels in the sera, synovial fluid, synovium, and FLSs were higher in patients with RA than in control groups. Serum levels of HRF/TCTP correlated well with RA disease activity. The tumor-like aggressiveness of RA-FLSs was exacerbated by HRF/TCTP stimulation and ameliorated by dTBP2 treatment. dTBP2 exerted protective and therapeutic effects in CIA mice and had no detrimental effects in a murine tuberculosis model. Our results indicate that HRF/TCTP is a novel biomarker and therapeutic target for the diagnosis and treatment of RA.Subject terms: Translational research, Autoimmunity 相似文献
89.
90.
Hee Joon LeeKyungho Park Goun BaeJaehoon Choe Kwang Ho Song Sunwoo Lee 《Tetrahedron letters》2011,52(39):5064-5067
Unsymmetric diaryl alkynes were synthesized from the palladium-catalyzed decarboxylative coupling of aryl halides and propiolic acid using a continuous flow reaction system. This flow chemistry system continuously gave the desired products in moderate to good yields, and produced less byproduct than was formed in the batch reaction. 相似文献