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81.
Shiv Poojan Seung-Hyun Bae Jae-Woong Min Eun Young Lee Yura Song Hee Yeon Kim Hye Won Sim Eun-Kyung Kang Young-Ho Kim Hae-Ock Lee Yourae Hong Woong-Yang Park Hyonchol Jang Kyeong-Man Hong 《Experimental & molecular medicine》2020,52(7):1102
To elucidate the epigenetic mechanisms of drug resistance, epigenetically reprogrammed H460 cancer cells (R-H460) were established by the transient introduction of reprogramming factors. Then, the R-H460 cells were induced to differentiate by the withdrawal of stem cell media for various durations, which resulted in differentiated R-H460 cells (dR-H460). Notably, dR-H460 cells differentiated for 13 days (13dR-H460 cells) formed a significantly greater number of colonies showing drug resistance to both cisplatin and paclitaxel, whereas the dR-H460 cells differentiated for 40 days (40dR-H460 cells) lost drug resistance; this suggests that 13dR-cancer cells present short-term resistance (less than a month). Similarly, increased drug resistance to both cisplatin and paclitaxel was observed in another R-cancer cell model prepared from N87 cells. The resistant phenotype of the cisplatin-resistant (CR) colonies obtained through cisplatin treatment was maintained for 2–3 months after drug treatment, suggesting that drug treatment transforms cells with short-term resistance into cells with medium-term resistance. In single-cell analyses, heterogeneity was not found to increase in 13dR-H460 cells, suggesting that cancer cells with short-term resistance, rather than heterogeneous cells, may confer epigenetically driven drug resistance in our reprogrammed cancer model. The epigenetically driven short-term and medium-term drug resistance mechanisms could provide new cancer-fighting strategies involving the control of cancer cells during epigenetic transition.Subject terms: Tumour heterogeneity, Epigenetics 相似文献
82.
Photocatalytic synthesis of copper colloids from CuII by the ferrihydrite core of ferritin 总被引:1,自引:0,他引:1
The iron-storage protein ferritin encapsulates a nanoparticle of iron oxide. The size and properties of these nanoparticles can be adjusted by controlled oxidative hydrolysis reactions of Fe(II). This mineralized ferritin protein cage has previously been shown to act as an effective photocatalyst for reduction of Cr(VI). In the present work, we demonstrate that Fe(O)OH-mineralized ferritin catalyzes the photoreduction of Cu(II) to form a stable, air-sensitive, colloidal dispersion of Cu(0). In addition, the particle sizes of the Cu colloids can be controlled by varying the ratio of Cu(II) to ferritin. This illustrates an important principle, namely that the properties of one preformed material can be utilized for the specific synthesis of a second material, thus tailoring the desired physical properties of the final products. This procedure represents a multistep materials synthesis: the formation of a new nanomaterial from a catalytic precursor. 相似文献
83.
Ryu I 《Chemical record (New York, N.Y.)》2002,2(4):249-258
New approaches in radical carbonylation chemistry are described. We have successfully integrated tin mediated radical carbonylation chemistry into modern fluorous applications and separation techniques. We revealed that radical carbonylation reactions can be performed using fluorous tin mediators, such as fluorous tin hydride and fluorous allyltin reagents. Fine tuning of the reaction conditions resulted in a good efficiency equivalent to conventional tin mediators. The tedious procedure of removing organotin byproducts can be circumvented through the use of fluorous/organic liquid-liquid extraction or fluorous liquid-solid phase extraction with fluorous reverse phase silica (FRPS). Also described are newly developed tandem carbonylation reactions that are based on species hybridization approaches. Using a radical/anionic hybrid system based on zinc-induced one-electron reduction, we achieved a three-component coupling reaction consisting of 4-alkenyl iodides, carbon monoxide, and electron-deficient alkenes. We observed two types of annulations processes, namely [4 + 1](radical)/[3 + 2](anionic) and [5 + 1](radical)/[3 + 2](anionic), which lead to the production of bicyclo[3.3.0]octanols and bicyclo[3.2.1]octanols, respectively. We found a radical/palladium hybrid system to be useful in the construction of new cyclic systems that incorporate two or three molecules of carbon monoxide. 相似文献
84.
Yoshitaka Uenoyama Takahide Fukuyama Keisuke Morimoto Osamu Nobuta Hidefumi Nagai Ilhyong Ryu 《Helvetica chimica acta》2006,89(10):2483-2494
The carbonylation of alkanes 1 under radical‐reaction conditions was examined by using ethynyl triflone A as the unimolecular chain‐transfer (UMCT) reagent. Good to moderate yields of ethynyl ketones 2 were prepared by means of this three‐component coupling reaction. Higher CO pressures as well as lower concentrations of triflone A improved the efficiency of the reaction over the direct addition, the latter leading to alkylated ethynes 3 . In contrast to the reaction with A , the reaction of cyclohexane ( 1a ) with allyl triflone B (= ethyl 2‐methylene‐3‐[(trifluoromethyl)sulfonyl]propanoate) in the presence of CO gave a mixture of carbonylation products, including 8a formed from two molecules each of cyclohexane, CO, and allyl triflone B . 相似文献
85.
Quantitative analysis of bilobalide and ginkgolides from Ginkgo biloba leaves and Ginkgo products using (1)H-NMR 总被引:2,自引:0,他引:2
Choi YH Choi HK Hazekamp A Bermejo P Schilder Y Erkelens C Verpoorte R 《Chemical & pharmaceutical bulletin》2003,51(2):158-161
1H-NMR spectrometry was applied to the quantitative analysis of the bilobalide, ginkgolides A, B, and C in Ginkgo biloba leaves and six kinds of commercial Ginkgo products without any chromatographic purification. The experiment was performed by the analysis of each singlet H-12, which were well separated in the range of delta 6.0-7.0 in the (1)H-NMR spectrum. However, the H-12 protons of bilobalide and ginkgolides may have overlapped with H-6 or H-8 protons of the Ginkgo flavonoids. Therefore, the optimum (1)H-NMR solvent for the analysis of the compound was selected through the evaluation of solvent effects on the resolution of these signals from the compounds. Acetone-d(6)-benzene-d(6) (50 : 50) was found to be the best one among the solvents evaluated. The quantity of the compounds was calculated by the relative ratio of the intensity of each compound to the known amount of internal standard (25 microgram), phloroglucinol. This method allows rapid and simple quantitation of underivatized bilobalide and ginkgolides in 5 min without any pre-purification steps. 相似文献
86.
The photoinduced charge transfer that had been suggested to result in the dissociation of phenol on Ag(111) was investigated by two-photon photoemission spectroscopy. An unoccupied intermediate state was positively identified, which was found to be located 3.22 eV above the Fermi level. From the photoelectron energy dispersion, the effective mass of the intermediate state was determined to be (15 +/- 10)m(e) for a 1 ML coverage of phenol. This implies that the excited electron is localized mainly on the adsorbed phenol, forming a molecular resonance state. Polarization dependence of the photoelectron intensity suggested that the initial photoexcitation of the substrate produces hot electrons that scatter into the molecular resonance state, leading ultimately to the dissociation of the adsorbate. These results are the first two-photon photoemission study to characterize the transient anionic state involved in photodissociation of a molecule adsorbed on a metal surface. 相似文献
87.
Witzmann FA Bauer MD Fieno AM Grant RA Keough TW Kornguth SE Lacey MP Siegel FL Sun Y Wright LS Young RS Witten ML 《Electrophoresis》1999,20(18):3659-3669
We analyzed protein expression in the cytosolic fraction prepared from whole lung tissue in male Swiss-Webster mice exposed 1 h/day for seven days to aerosolized JP-8 jet fuel at concentrations of 1000 and 2500 mg/m3, simulating military occupational exposure. Lung cytosol samples were solubilized and separated via large scale, high resolution two-dimensional electrophoresis (2-DE) and gel patterns scanned, digitized and processed for statistical analysis. Significant quantitative and qualitative changes in tissue cytosol proteins resulted from jet fuel exposure. Several of the altered proteins were identified by peptide mass fingerprinting, confirmed by sequence tag analysis, and related to impaired protein synthetic machinery, toxic/metabolic stress and detoxification systems, ultrastructural damage, and functional responses to CO2 handling, acid-base homeostasis and fluid secretion. These results demonstrate a significant but comparatively moderate JP-8 effect on protein expression and corroborate previous morphological and biochemical evidence. Further molecular marker development and mechanistic inferences from these observations await proteomic analysis of whole tissue homogenates and other cell compartment, i.e., mitochondria, microsomes, and nuclei of lung and other targets. 相似文献
88.
Chan Sik Cho Tae Kyung Kim Bok Tae Kim Tae-Jeong Kim Sang Chul Shim 《Journal of organometallic chemistry》2002,650(1-2):65-68
Nitroarenes react with trialkylamines in the presence of a catalytic amount of a ruthenium catalyst together with tin(II) chloride dihydrate at 180 °C in an aqueous medium (toluene–H2O) to afford the corresponding quinolines in moderate to good yields. The catalytic pathway seems to be proceeded via a sequence involving initial reduction of nitroarenes to anilines, alkyl group transfer from alkylamines to anilines to form an imine, dimerization of imine, and heterocyclization. 相似文献
89.
Young PM Price R Lewis D Edge S Traini D 《Journal of colloid and interface science》2003,262(1):298-302
Drug particulate interactions in pressurized metered dose inhalers (pMDI) may lead to a decrease in aerosolization efficiency and subsequent efficacy in patient treatment. The interactions between salbutamol sulfate (commonly used in Ventolin pMDIs) and a series of pMDI canister materials were investigated using the atomic force microscope (AFM) colloid probe technique. Approximately 4000 individual force-distance curves were determined for a drug probe and three surfaces (10 x 10 mum areas) in situ, in a model propellant. The area under each force-distance curve was integrated to obtain separation energy values. Median separation energy values followed the rank order borosilicate glass > aluminum > PTFE, suggesting PTFE to be the most suitable canister coating. 相似文献
90.
W.John Albery David Clark Humphrey J.J. Drummond Anthony J.M. Coombs William K. Young Clive E.W. Hahn 《Journal of Electroanalytical Chemistry》1992,340(1-2)
A novel electrochemical sensor for the determination of CO2 in expired breath is described. The sensor works by generating
from the reduction of O2 in dimethyl sulphoxide (DMSO) in a generating pulse. There is a rapid titration reaction between the
and any CO2 present. In the recovery pulse the amount of unreacted
is determined. The larger the concentration of CO2 the less
is found in the recovery pulse. The solubilities and diffusion coefficients of O2 and CO2 in DMSO have been determined using rotating disc voltammetry and rotation speed step experiments. The stoichiometry, the product, and the rate constant of the titration reaction have been determined using ring—disc voltammetry and laser Raman spectroscopy. The operation and the effect of adventitious water on the sensor are described. Results are presented which show that the sensor can indeed measure the breath-by-breath rhythm of expired CO2 from a human subject. 相似文献