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961.
Werner Storek Hendrik Kosslick Vu Anh Tuan Hans-Peter Hennig 《Analytical and bioanalytical chemistry》1994,349(1-3):225-227
Modern solid state NMR techniques [one-dimensional magic angle spinning (MAS) and two-dimensional quadrupole nutation experiments with MAS] are applied for the characterization of mechanochemically activated inorganic powders such as hydrargillite [γ-Al(OH)3] and pseudo-boehmite [synthetic γ-AlO(OH)]. The materials were activated in a vibration mill. 相似文献
962.
Ji?í Barek Pham Tuan Hai Věra Pacáková Karel ?tulík Ivana ?vagrová Ji?í Zima 《Fresenius' Journal of Analytical Chemistry》1994,350(12):678-683
Optimised conditions have been found for the separation of N-nitroso-N-methylaniline derivatives substituted in the position 4 (4-R-NMA, where R =- H,- CH3, - OCH3, - Cl, - CN, - OH and - NO2), using reversed phase HPLC with a C18 chemically bonded stationary phase. Suitable mobile phases are mixtures of aqueous 0.01 mol l–1 KH2PO4 with methanol (4+6) or acetonitrile (7+3), or a mixture of water, methanol, acetonitrile and 80% H3PO4 (200+200+200+3). Four detection techniques have been investigated: Direct UV photometry, polarography on a hanging mercury drop electrode, anodic voltammetry on a glassy carbon fibre array electrode and indirect anodic voltammetric detection after photolytic denitrosation of the analytes. The UV photometry is the most universal and yields limits of detection around 10–6 mol l–1. Polarography exhibits the poorest sensitivity (with a limit of detection of ca. 10–5 mol l–1) but it can be used for selective detection of 4-NO2-NMA. Direct voltammetric detection is selective for the oxidizable derivatives and the limits of detection attained are lower than those obtained by UV photometry (for 4-OH-NMA) or comparable with (for 4-OCH3-NMA). When the analytes are photolytically denitrosated to yield oxidizable derivatives, the voltammetric detection of 4-H-NMA, 4-Cl-NMA, 4-CH3-NMA and 4-NO2-NMA has limits of detection one order of magnitude lower than those obtained UV photometrically. 相似文献
963.
Emission of cluster ions occurs during laser irradiation of substituted pyridines even at threshold laser power densities. The clusters generated include dimers and trimers, and appear in both positive-ion and negative-ion laser mass spectra. Fragments of cluster ions are observed and can be rationlized as losses of neutral molecules from (nM ± H)±. Dissociation of clusters occurs primarily from substituents on the pyridine ring. Laser mass spectrometry of pyridoxine hydrochloride and pyridoxamine-dihydrochloride resulted in the emission of clusters analogous to those observed for nicotinic acid. In contrast to these results, secondary-ion and field-desorption mass spectra of salts contain the ions CnAn?1+ and CnAn+1?, that were not detected in the laser mass spectra. 相似文献
964.
Hung Huynh Aldo Prawira Thi Bich Uyen Le Thanh Chung Vu Huai-Xiang Hao Alan Huang Youzhen Wang Diana Graus Porta 《Experimental & molecular medicine》2020,52(11):1857
Hepatocellular carcinoma (HCC) is a lethal cancer with limited therapeutic options, and standard therapy with sorafenib provides only modest survival benefits. Fibroblast growth factor 19 (FGF19) has been proposed as a driver oncogene, and targeting its receptor, FGFR-4, may provide a better alternative to standard therapy for patients with FGF19-driven tumors. Sixty-three HCC patient-derived xenograft (PDX) models were screened for FGF19 expression. Mice bearing high and low FGF19-expressing tumors were treated with FGF401 and/or vinorelbine, and the antitumor activity of both agents was assessed individually and in combination. Tumor vasculature and intratumoral hypoxia were also examined. High FGF19 expression was detected in 14.3% (9 of 63) of the HCC models tested and may represent a good target for HCC treatment. FGF401 potently inhibited the growth of high FGF19-expressing HCC models regardless of FGF19 gene amplification. Furthermore, FGF401 inhibited the FGF19/FGFR-4 signaling pathway, cell proliferation, and hypoxia, induced apoptosis and blood vessel normalization and prolonged the overall survival (OS) of mice bearing high FGF19 tumors. FGF401 synergistically acted with the microtubule-depolymerizing drug vinorelbine to further suppress tumor growth, promote apoptosis, and prolong the OS of mice bearing high FGF19 tumors, with no evidence of increased toxicity. Our study suggests that a subset of patients with high FGF19-expressing HCC tumors could benefit from FGF401 or FGF401/vinorelbine treatment. A high level of FGF19 in a tumor may serve as a potential biomarker for patient selection.Subject terms: Cancer models, Targeted therapies 相似文献
965.
Nguyen QV Leconte S Brown E Grée D Grée R Dujardin G 《The Journal of organic chemistry》2005,70(7):2641-2650
[reaction: see text] Under standard hydroboration-oxidation conditions, the dihydropyrans 4 underwent a highly stereocontrolled tandem reaction, involving the expected hydration of the double bond together with the reduction of the ketal moiety. This unprecedented transformation gives rise to a short, [4 + 2]-based synthetic route to (+/-)-beta-C-naphthyl-2-deoxyglycosides 5, which allows a significant structural and functional diversity at C-6. We thus described the first synthesis of (+/-)-C-aryl-6-fluoro and -6,6-difluoro olivosides, via the allylic mono- and difluorides produced by regioselective fluorination of, respectively, hydroxyalkyl and oxoalkyl dihydropyran derivatives. 相似文献
966.
Nguyen Thi Hoang Anh Khieu Thi Tam Nguyen Van Tuan Dao Duc Thien Tran Duc Quan Nguyen Thanh Tam 《Natural product research》2019,33(6):796-802
This study describes the chemical constituents of Oldenlandia pinifolia (Wall. Ex G. Don) Kuntze (synonym Hedyotis pinifolia Wall. Ex G. Don) and discusses their anti-proliferative activities. Thirteen compounds were isolated from the n-hexane, ethyl acetate and n-butanol extracts of whole plants O. pinifolia by chromatography method. Their structures were elucidated using MS and NMR analysis and compared with reported data. They are three anthraquinones, a carotenoid, two triterpenes, four iridoid glycosides and three flavonoid glycosides. Among them, 2-methyl-1,4,6-trihydroxy-anthraquinone is a new one, and three compounds were found for the first time in this genus. MTT assay resulted that the n-butanol extract and four isolated compounds inhibited the proliferation of chronic myelogenous leukaemia cells. The results from Hoechst 33343 staining and caspase 3-inducing exhibited that those four tested compounds induced apoptosis and activated caspase 3 (p < 0.05). One of them, isorhamnetin-3-O-β-rutinoside showed the most activity with IC50 value of 394.68 ± 25.12 μM. 相似文献
967.
Din' Khoang Vu G. V. Pshenichnyi V. A. Mashenkov L. S. Stanishevskii 《Chemistry of Heterocyclic Compounds》1993,29(12):1450-1453
By alkylation of stereoisomeric 7a-methyl-2-oxo-5-phenylfuro-[2,3-c]piperidines with phenacyl bromide and subsequent reduction of the keto group by sodium borohydride, amino alcohols were obtained; heating of these products in 70% sulfuric acid affords 3a,4,6,7,11b,12-hexahydro-3a-methyl-7-phenylbenzo[a]furo[2,3-g]quinolizines. It was found that the cis-quinolizidine, upon heating to 150°C in acetic acid, is isomerized to the trans-quinolizidine.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1679–1682, December, 1993. 相似文献
968.
J. L. Vučina D. A. Vuga N. S. Vukićević-Nikolić 《Journal of Radioanalytical and Nuclear Chemistry》1995,199(2):135-142
Some factors which could adversely affect the integrity of eight routine99mTc radiopharmaceuticals have been investigated. The radiochemical purity of the preparations was determined both under standard (reconstitution according to the manufacturer's instructions) and under experimental conditions (higher contents of longlived99Tc and copper). The influence of radiolytically produced hydrogen peroxide as well as the effect of introduction of air during the addition of pertechnetate as an example of poor labeling technique were examined. The radiochemical analyses were performed by paper and TL chromatography and electrophoresis. 相似文献
969.
H. D. Tuan 《Journal of Optimization Theory and Applications》1995,85(2):435-472
LetF:[0, T]×R
n
2
R
n
be a set-valued map with compact values; let :R
n
R
m
be a locally Lipschitzian map,z(t) a given trajectory, andR the reachable set atT of the differential inclusion
. We prove sufficient conditions for (z(T))intR and establish necessary conditions in maximum principle form for (z(T))(R). As a consequence of these results, we show that every boundary trajectory is simultaneously a Pontryagin extremal, Lagrangian extremal, and relaxed Lagrangian extremal.The author is grateful to an anonymous referee for his valuable remarks and comments which have helped to improve the paper.The paper was written while the author was visiting the laboratory of Prof. S. Suzuki, Department of Mechanical Engineering, Sophia University, Tokyo, Japan. 相似文献
970.
A. N. Levov An’ Le Tuan A. T. Soldatenkov Chyong Khong Khieu V. N. Khrustalev 《Russian Journal of Organic Chemistry》2008,44(4):612-616
The result of acylation of dibenzoaza-14-crowns-4 containing a 4-oxopiperidine fragment with acetic anhydride depends on the substituent on the nitrogen atom. The NH-substrates initially undergo acylation at the piperidine nitrogen atom, followed by enolization and O-acylation. The acylation of N-methyl derivatives is accompanied by cleavage of the piperidine ring at the C-N bond with formation of acetylamino-substituted dibenzo-16-crowns-3. The structure of the latter was determined by X-ray analysis. 相似文献