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排序方式: 共有48条查询结果,搜索用时 15 毫秒
1.
Maria Teresa Cocco Cenzo Congiu Valentina Onnis Angela Maria Bernard Pier Paolo Piras 《Journal of heterocyclic chemistry》1997,34(4):1347-1350
A simple approach to the fluorinated 1,5-benzoxazepine ring system is described. By reacting commercially accessible aminophenols 1 and the trifluoroacetylvinyl ether 2, high yields of enaminones 3 were obtained. Functionalization of methyl group of compounds 3 gave rise to dieneamines 4 that were cyclized in acidic environment to benzoxazepine derivatives 5. 相似文献
2.
Vidali G Pirronello V Li L Roser J Manicó G Congiu E Mehl H Lederhendler A Perets HB Brucato JR Biham O 《The journal of physical chemistry. A》2007,111(49):12611-12619
The study of the formation of molecular hydrogen on low-temperature surfaces is of interest both because it enables the exploration of elementary steps in the heterogeneous catalysis of a simple molecule and because of its applications in astrochemistry. Here, we report results of experiments of molecular hydrogen formation on amorphous silicate surfaces using temperature-programmed desorption (TPD). In these experiments, beams of H and D atoms are irradiated on the surface of an amorphous silicate sample. The desorption rate of HD molecules is monitored using a mass spectrometer during a subsequent TPD run. The results are analyzed using rate equations, and the energy barriers of the processes leading to molecular hydrogen formation are obtained from the TPD data. We show that a model based on a single isotope provides the correct results for the activation energies for diffusion and desorption of H atoms. These results are used in order to evaluate the formation rate of H2 on dust grains under the actual conditions present in interstellar clouds. It is found that, under typical conditions in diffuse interstellar clouds, amorphous silicate grains are efficient catalysts of H2 formation when the grain temperatures are between 9 and 14 K. This temperature window is within the typical range of grain temperatures in diffuse clouds. It is thus concluded that amorphous silicates are good candidates to be efficient catalysts of H2 formation in diffuse clouds. 相似文献
3.
Structural characterization of a new lipid/DNA complex showing a selective transfection efficiency in ovarian cancer cells 总被引:5,自引:0,他引:5
Caracciolo G Pozzi D Caminiti R Congiu Castellano A 《The European physical journal. E, Soft matter》2003,10(4):331-336
We investigated, for the first time, by using Energy Dispersive X-ray Diffraction, the structure of a new ternary cationic
liposome formulated with dioleoyl trimethylammonium propane (DOTAP), 1,2-dioleoyl-3-phosphatidylethanolamine (DOPE) and cholesterol
(Chol) (DDC) which has been recently found to have a selective high gene transfer ability in ovarian cancer cells. Our structural
results provide a further experimental support to the widely accepted statement that there is not a simple and direct correlation
between structure and transfection efficiency and that the factors controlling cationic lipid/DNA (CL-DNA) complexes-mediated
gene transfer depend not only on the formulations of the cationic liposomes and their thermodynamic phase, but also significantly
on the cell properties.
Received: 28 October 2002 / Accepted: 21 March 2003 / Published online: 15 April 2003
RID="a"
ID="a"e-mail: a.congiu@caspur.it 相似文献
4.
Accolla M Congiu E Dulieu F Manicò G Chaabouni H Matar E Mokrane H Lemaire JL Pirronello V 《Physical chemistry chemical physics : PCCP》2011,13(17):8037-8045
The morphology of water ice in the interstellar medium is still an open question. Although accretion of gaseous water could not be the only possible origin of the observed icy mantles covering dust grains in cold molecular clouds, it is well known that water accreted from the gas phase on surfaces kept at 10 K forms ice films that exhibit a very high porosity. It is also known that in the dark clouds H(2) formation occurs on the icy surface of dust grains and that part of the energy (4.48 eV) released when adsorbed atoms react to form H(2) is deposited in the ice. The experimental study described in the present work focuses on how relevant changes of the ice morphology result from atomic hydrogen exposure and subsequent recombination. Using the temperature-programmed desorption (TPD) technique and a method of inversion analysis of TPD spectra, we show that there is an exponential decrease in the porosity of the amorphous water ice sample following D-atom irradiation. This decrease is inversely proportional to the thickness of the ice and has a value of ?(0) = 2 × 10(16) D-atoms cm(-2) per layer of H(2)O. We also use a model which confirms that the binding sites on the porous ice are destroyed regardless of their energy depth, and that the reduction of the porosity corresponds in fact to a reduction of the effective area. This reduction appears to be compatible with the fraction of D(2) formation energy transferred to the porous ice network. Under interstellar conditions, this effect is likely to be efficient and, together with other compaction processes, provides a good argument to believe that interstellar ice is amorphous and non-porous. 相似文献
5.
Maria Teresa Cocco Cenzo Congiu Valentina Onnis 《Journal of heterocyclic chemistry》1995,32(2):463-466
The heterocyclization of 3-aminopropenethioamides 1 and 2 with 2-bromoacetophenone is reported. The p-toluenesulphonic acid catalyzed reaction gives a direct route to 1,4-thiazepines 3 and 5 , while in the presence of triethylamine thiophene 4 and 1,4-thiazepin-5-one 6 are obtained. 相似文献
6.
Maria Teresa Cocco Cenzo Congiu Valentina Onnis Angela Maria Bernard Pier Paolo Piras 《Journal of heterocyclic chemistry》1997,34(4):1283-1290
The reaction between N1-acylacetamidrazones 1 and enol ether 2 is described. Depending on the reaction conditions and on the substitution pattern of amidrazones 2-acylhydrazino-4-methyl-6-trifluoro-methylpyridines 3 and/or 2-acylhydrazino-6-methyl-4-trifluoromethylpyridines 4 were obtained. 相似文献
7.
In this study we report the results of cytogenetic tests, namely a search for chromosome aberrations (CA) and sister chromatid exchanges (SCEs), performed on human amniotic fluid cells cultured and treated with Cadmium chloride. The cells from primary cultures were exposed to CdCl2 at 1 microM and 10 microM for 24 h. At the higher dose, no metaphases were scored and at the lower dose (1 microM) no effects were evident on cell proliferation, and no chromosome aberrations were found. In the subsequent experiments we used cells from subcultures exposed to 1 microM and 5 microM CdCl2. At the 5 microM dose was evident the induction of chromatid breaks, while the frequency of sister chromatid exchanges shows a small increase, not statistically significant at the dose of 1 microM. In this study we positively demonstrated that amniotic fluid cells grown in vitro are reliable for testing various mutagenic or teratogenic substances. With regard to cadmium treatment results, it is evident a clastogenic effect of cadmium chloride but not a significant induction of SCEs. 相似文献
8.
Esposito C Generosi J Mossa G Masotti A Castellano AC 《Colloids and surfaces. B, Biointerfaces》2006,53(2):187-192
The effect of serum on structural properties of dimethyl-dioctadecyl-ammonium bromide (DDAB)–1,2-dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE) liposomes and DDAB–DOPE/DNA lipoplexes has been investigated by energy dispersive X-ray diffraction (EDXD) technique, at different cationic lipid/DNA weight ratios (ρ). The role of serum on the size of lipoplexes has also been studied by dynamic light scattering. Lipoplex transfection efficiency (TE) as a function of ρ, and lipoplex toxicity to C6 rat glioma cells have been evaluated in Dulbecco's Modified Eagle Medium (DMEM) with and without serum. A multi-parametric analysis concerning the role of size, structure and cytotoxicity on transfection efficiency contributes to explain the experimental observation that 3β-[N-(N′,N′-dimethylaminoethane)carbamoyl]-cholesterol (DC-Chol)–DOPE/DNA transfect C6 cells better than DDAB–DOPE/DNA lipoplexes. 相似文献
9.
Giovanni Cerioni Maria Teresa Cocco Cenzo Congiu Antonio Maccioni 《Journal of heterocyclic chemistry》1981,18(7):1379-1382
A synthesis of 1-aminoimidazoles by reaction between α-halogenoketones and N-acetylamidrazones is described. Structure and position of substituent groups in the synthesized aminoimidazoles were established by spectroscopical methods. 相似文献
10.
Maria Teresa Cocco Cenzo Congiu Valentina Onnis Antonio Maccioni 《Journal of heterocyclic chemistry》1991,28(3):797-800
The reaction of N1-acyl-2-ethoxycarbonylacetamidrazones with ethyl ethoxymethylenecyanoacetate (EMCA) has been examined. The acetamidrazone 1a reacts with EMCA in boiling dimethyl sulphoxide to give the 1,2,4-triazolo[4,3-a]pyridin-3(2H)-one 2 in excellent yield. Similarly from the amidrazones 1b-h the 1,2,4-triazolo[4,3-a]pyridines 3b-h were obtained. When the reaction between the amidrazones and EMCA was performed in ethanolic solution, the 6-(2-acylhydrazino)-pyridines 4 were isolated. Ring closure of 4 afforded the 1,2,4-triazolo[4,3-a]pyridines. 相似文献