排序方式: 共有40条查询结果,搜索用时 31 毫秒
11.
Ariadna Fuente‐Hernàndez Philippe Costes Philippe Kalck Ulises Jáuregui‐Haza Odile Dechy‐Cabaret Martine Urrutigoïty 《应用有机金属化学》2011,25(11):815-819
The CO‐bubbling effect in cycloisomerization reactions of enynes derived from monoterpenes has been studied using PtCl2, [Rh2Cl2(CO)4] and AuCl3 as catalytic systems. All the precursors are efficient catalysts for the cycloisomerization of O‐tethered enynes. The reaction proceeds through exo‐dig and endo‐dig pathways, which are consistent with the exclusive coordination of the alkyne triple bond to the metal center. The CO ligand not only increases the reaction rates but also induces significant variations in the two reaction pathways. Notably, this effect is also strongly dependent on the nature of the starting enyne. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
12.
13.
14.
A Facile and Cost‐effective Electroanalytical Strategy for the Quantification of Deoxyguanosine and Deoxyadenosine in Oligonucleotides Using Screen‐printed Graphite Electrodes
下载免费PDF全文
![点击此处可从《Electroanalysis》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Ariadna Brotons Ignacio Sanjuán Christopher W. Foster Craig E. Banks Francisco José Vidal‐Iglesias José Solla‐Gullón Jesús Iniesta 《Electroanalysis》2016,28(12):3066-3074
The development of electroanalytical methods for the detection and quantification of nucleotides in DNA offers vital implications in assessing the degree of oxidation or epigenetic modification in DNA. Unfortunately, the electrochemical response of oligonucleotides is strongly influenced by the size, composition and nucleic base sequence. In this article, an optimized analytical procedure for the enzymatically breakdown of the oligonucleotides to their corresponding nucleotides for the evaluation of the electrochemical response through the use of square wave voltammetry (SWV) is presented. Enzymatic digestion of oligonucleotides has been optimized in terms of buffer composition, digestion time, strategy for stopping the enzymatic reaction and filtration requirement for enzyme removal, and then compared to an established protocol. Under the optimized protocol SWV response of a number of untreated and enzymatically digested six‐mer oligonucleotides, namely 5′‐GGGGGG‐3′, 5′‐AAAAAA‐3′, 5′‐CGCGCG‐3′ and 5′‐AAACGC‐3′ have been analysed, providing a higher sensitivity for the determination of guanosine and adenosine monophosphate species under digestion conditions with a more facile and cost effective procedure. The novel strategy for the enzymatically treated oligonucleotides in combination with the SWV response provides a proof of principle for feasible applications in the diagnosis of methylated guanosine in DNA as a potential biomarker due to its relation with cancer. 相似文献
15.
Pepiol A Teixidor F Sillanpää R Lupu M Viñas C 《Angewandte Chemie (International ed. in English)》2011,50(52):12491-12495
Step by step: The cluster [3,3'-Co(1,2-C(2)B(9)H(11))(2)](-) is an excellent platform for making a stepwise tunable redox potential system by dehydroiodination. With the addition of up to eight iodine substituents (purple; see picture), there is a fall in the E(1/2)(Co(III)/Co(II)) value from -1.80?V to -0.68?V (vs. Fc(+)/Fc; Fc = ferrocene). A practical application of this tunability has been observed in the growth of polypyrrole. 相似文献
16.
Fuente A Reyes M Alvarez YM Ruiz JA Vélez H Viñas-Bravo O Montiel-Smith S Meza-Reyes S Sandoval-Ramírez J 《Magnetic resonance in chemistry : MRC》2005,43(8):676-678
(1)H and (13)C NMR spectroscopic data for 5alpha-androstanes and halo-5alpha-androstanes with different substituents at positions C-3, C-9, C-11 and C-17 were examined and assigned by a combination of 1D and 2D NMR experiments. The substituent effects on the (13)C chemical shifts were compared with those of epi-androsterone, used as a reference compound. The coupling constants (n)J((19)F,(13)C) were measured for compounds 6, 8, 11 and 14. 相似文献
17.
18.
Giant Volume Change and Topological Gaps in Temperature‐ and Pressure‐Induced Phase Transitions: Experimental and Computational Study of ThMo2O8
下载免费PDF全文
![点击此处可从《Chemistry (Weinheim an der Bergstrasse, Germany)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Bin Xiao Dr. Philip Kegler Prof. Dr. Thorsten M. Gesing Dr. Lars Robben Dr. Ariadna Blanca‐Romero Dr. Piotr M. Kowalski Dr. Yan Li Dr. Vladislav Klepov Prof. Dr. Dirk Bosbach Prof. Dr. Evgeny V. Alekseev 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(3):946-958
By applying high temperature (1270 K) and high pressure (3.5 GPa), significant changes occur in the structural volume and crystal topology of ThMo2O8, allowing the formation of an unexpected new ThMo2O8 polymorph (high‐temperature/high‐pressure (HT/HP) orthorhombic ThMo2O8). Compared with the other three ThMo2O8 polymorphs prepared at the ambient pressure (monoclinic, orthorhombic, and hexagonal phases), the molar volume for the quenched HT/HP–orthorhombic ThMo2O8 is decreased by almost 20 %. As a result of such a dramatic structural transformation, a permanent high‐pressure quenchable state is able to be sustained when the pressure is released. The crystal structures of the three ambient ThMo2O8 phases are based on three‐dimensional (3D) frameworks constructed from corner‐sharing ThOx (x=6, 8, or 9) polyhedra and MoO4 tetrahedra. The HT/HP–orthorhombic ThMo2O8, however, crystallizes in a novel structural topology, exhibiting very dense arrangements of ThO11 and MoO4+1 polyhedra connecting along the crystallographic c axis. The phase transitions among all four of these ThMo2O8 polymorphs are unveiled and fully characterized with regard to the structural transformation, thermal stability, and vibrational properties. The complementary first principles calculations of Gibbs free energies reveal the underlying energetics of the phase transition, which support the experimental findings. 相似文献
19.
The cosmological model consisting of a nonlinear magnetic field obeying the Lagrangian \(\mathcal {L}= \gamma F^{\alpha },\, F\) being the electromagnetic invariant, coupled to a Robertson-Walker geometry is tested with observational data of Type Ia Supernovae, Long Gamma-Ray Bursts and Hubble parameter measurements. The statistical analysis show that the inclusion of nonlinear electromagnetic matter is enough to produce the observed accelerated expansion, with not need of including a dark energy component. The electromagnetic matter with abundance \(\varOmega _B\) , gives as best fit from the combination of all observational data sets \(\varOmega _B=0.562^{+0.037}_{-0.038}\) for the scenario in which \(\alpha =-1, \varOmega _B=0.654^{+0.040}_{-0.040}\) for the scenario with \(\alpha =-1/4\) and \(\varOmega _B=0.683^{+0.039}_{-0.043}\) for the one with \(\alpha =-1/8\) . These results indicate that nonlinear electromagnetic matter could play the role of dark energy, with the theoretical advantage of being a mensurable field. 相似文献
20.
Muñoz MA Pacheco A Becker MI Silva E Ebensperger R Garcia AM De Ioannes AE Edwards AM 《Journal of photochemistry and photobiology. B, Biology》2011,103(1):57-67
Riboflavin (RF) is an endogenous cell component and an efficient photosensitizer that can act by both types I and II photochemical mechanisms. Human tumor cells lines cultured in vitro, were used as model to study the effect of a photosensitizer synthesized from riboflavin, the 2',3',4',5'-riboflavin-tetrabutyrate (RTB), to increase the flavin concentration in the human promyelocytic leukemia cell line HL-60 and the human epithelial cervical cancer cell line HeLa. We demonstrate that this compound, alone or with Trp, has a toxic dose-response effect evidenced by abnormal cell morphology and a decrease in the cell proliferation rate. The mechanism of cell death was investigated and the experimental evidence indicates that it proceeds primarily via apoptosis; however, autophagy cannot be discarded. Nuclear fluorescent staining with Hoechst 33258 and transmission electron microscopy of the cells showed condensed chromatin margination at the nuclear periphery and the formation of apoptotic bodies. Furthermore, Caspase-3 activity was demonstrated in both cell lines. In addition, the characteristic apoptotic DNA ladder was observed in HL-60 cells. On the other hand, a high cytoplasmic vacuolization was observed by electron transmission and confocal microscopy. LysoTraker-red localization in the vacuoles was observed by fluorescence microscopy, and a significant decrease in the number of vacuoles and in the cell proliferation rate diminution was observed when irradiation was performed in the presence of the autophagy inhibitor 3-methyladenine. Considering that both cell death mechanisms have a dual role in the killing of tumor cells in vivo, a harmful effect that does not cause inflammation leading to tumor prophylaxis, we conclude that RTB could have potential clinical applications. 相似文献