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981.
Pastor-Belda Marta Arroyo-Manzanares Natalia Campillo Natalia Vias Pilar Guluarte Crystal Angulo Carlos Esteban Mara ngeles 《Chromatographia》2022,85(4):353-363
Chromatographia - Nucleobases, nucleosides and nucleotides can act as chemical markers and immunnostimulants. Ultra-high-performance liquid chromatography with electrospray ionization and... 相似文献
982.
983.
CáRDENAS Carlos MU?OZ Macarena CONTRERAS Julia AYERS Paul W. GóMEZ Tatiana FUENTEALBA Patricio 《物理化学学报》2018,34(6):631-638
Chemical reactivity towards electron transfer is captured by the Fukui function.However,this is not well defined when the system or its ions have degenerate or pseudo-degenerate ground states.In such a case,the first-order chemical response is not independent of the perturbation and the correct response has to be computed using the mathematical formalism of perturbation theory for degenerate states.Spatialpseudo-degeneracy is ubiquitous in nanostructures with high symmetry and totally extended systems.Given the size of these systems,using degenerate-state perturbation theory is impractical because it requires the calculation of many excited states.Here we present an alternative to compute the chemical response of extended systems using models of local softness in terms of the local density of states.The local softness is approximately equal to the density of states at the Fermi level.However,such approximation leaves out the contribution of inner states.In order to include and weight the contribution of the states around the Fermi level,a model inspired by the long-range behavior of the local softness is presented.Single wall capped carbon nanotubes(SWCCNT) illustrate the limitation of the frontier orbital theory in extended systems.Thus,we have used a C360 SWCCNT to test the proposed model and how it compares with available models based on the local density of states.Interestingly,a simple Hü ckel approximation captures the main features of chemical response of these systems.Our results suggest that density-of-states models of the softness along simple tight binding Hamiltonians could be used to explore the chemical reactivity of more complex system,such a surfaces and nanoparticles. 相似文献
984.
Hiren Solanki Carlos Angulo-Preckler Kevin Calabro Navdeep Kaur Perrine Lasserre Bastien Cautain Mercedes de la Cruz Fernando Reyes Conxita Avila Olivier P. Thomas 《Tetrahedron letters》2018,59(36):3353-3356
Following ecological and chemical screenings, the Antarctic sponge Phorbas areolatus was chemically investigated for the first time. Three new suberitane derivatives named isosuberitenone B, 19-episuberitenone B, and isoxaspirosuberitenone were identified together with the known compounds suberitenones A and B, and oxaspirosuberitenone after a thorough inspection of their NMR data. These compounds were found to exhibit moderate cytotoxic activity and their presence in this sponge rules out their use as a chemotaxonomic marker for Suberites sponges. 相似文献
985.
The reactivity of 2,3-dehydroproline and 2,3-dehydropipecolic acid methyl ester derivatives with S-nucleophiles in the thio-Michael addition reaction has been explored. The addition of triphenylmethanethiol and subsequent trityl cleavage led to the corresponding cis- and trans-(±)-3-mercaptoproline and pipecolic acid derivatives in good yields. 相似文献
986.
Carlos Urda Marta Pérez Jaime Rodríguez Rogelio Fernández Carlos Jiménez Carmen Cuevas 《Tetrahedron letters》2018,59(26):2577-2580
A new cytotoxic polycyclic alkaloid containing a quinoline moiety, njaoamine I (1) has been isolated from the methanol extract of the sponge Haliclona (Reniera) sp. collected at Okuza Island, Tanzania. The structure of compound 1 was determined by 1D and 2D NMR and HRMS data analysis. Its relative configuration was elucidated by a NOESY experiment and confirmed by comparison of its NMR spectral data to those of njaoamines A–H. Moreover, njaoamine G (2) was also detected by LC/MS analysis of the methanol extract. Njaoamine I (1) displays cytotoxic activity against a panel of three human tumor cell lines in the micromolar range. 相似文献
987.
Enzyme‐Compatible Dynamic Nanoreactors from Electrostatically Bridged Like‐Charged Surfactants and Polyelectrolytes 下载免费PDF全文
Isabell Hofmann Melanie König Dr. Carlos G. Lopez Dr. Ljubica Vojcic Prof. Dr. Walter Richtering Prof. Dr. Ulrich Schwaneberg Dr. Larisa A. Tsarkova 《Angewandte Chemie (International ed. in English)》2018,57(30):9402-9407
Reported is an unanticipated mechanism of attractive electrostatic interactions of fully neutralized polyacrylic acid (PAA) with like‐charged surfactants. Amphiphilic polymer‐surfactant complexes with high interfacial activity and a solubilization capacity exceeding that of conventional micelles are formed by bridging with Ca2+ ions. Incorporation of a protease into such dynamic nanoreactors results in a synergistically enhanced cleaning performance because of the improved solubilization of poorly water‐soluble immobilized proteins. Competitive interfacial and intermolecular interactions on different time‐ and length‐scales have been resolved using colorimetric analysis, dynamic tensiometry, light scattering, and molecular dynamic simulations. The discovered bridging association mechanism suggests reengineering of surfactant/polymer/enzyme formulations of modern detergents and opens new opportunities in advancing labile delivery systems. 相似文献
988.
Douglas Iafrate Castelhano Juliana de Almeida Carlos Henrique de Paiva Pinheiro Rodnei Bertazzoli Christiane de Arruda Rodrigues 《Journal of Solid State Electrochemistry》2018,22(8):2445-2455
Although TiO2 anatase phase has been widely chosen as the main photocatalyst, it presents high electron/hole recombination rate. However, today, what is sought is a semiconductor material with enhanced photocatalytic activity with higher photon to electron conversion efficiency by introduction of electrons trap dopants. In this paper, TiO2 nanotubes arrays obtained by anodization of Ti substrates were decorated with Ru via electrodeposition, and their photo-response was investigated. First, voltammetric experiments were performed to elucidate the route of Ru reduction on the TiO2 surface and to select the range of potentials for Ru deposition. The reduction potentials were used for controlling the amount of Ru distributed all over the surface. Although Ru was electrodeposited at potentials over the range from ??0.025 to ??0.188 V vs. Ag/AgCl, the deposition of 3.7 mC cm?2 at ??0.100 V for 30 min resulted in a tenfold greater photocurrent when compared to the recorded photocurrent for the undecorated TiO2 nanotubes array. Next, Ru-decorated TiO2 nanotubes with a length of 323?±?18 nm and inner and outer diameters of 91 and 104 nm, respectively, were characterized using SEM-WDS, SEM-FEG, XRD, and XPS. UV-Vis-NIR diffuse reflectance spectroscopy and photoluminescence (PL) measurements, which revealed a maximum PL emission at 445 nm, showed that for the array of Ru-decorated TiO2 nanotubes, the electron-hole recombination may be effectively inhibited by the presence of ruthenium electrodeposited, which can make this photocatalyst even more attractive for environmental applications. The performances of the TiO2 and Ru-decorated TiO2 catalysts were compared in heterogeneous photocatalysis experiments for color removal of an azo-dye, which presented a pseudo-first-order rate constant more than twofold greater for the Ru-decorated TiO2 catalysts. 相似文献
989.
Natarajan Arumugam Abdulrahman I. Almansour Raju Suresh Kumar Vaiyapuri Subbarayan Periasamy Jegan Athinarayanan Ali A. Alshatwi Periyasami Govindasami Mohammad Altaf J. Carlos Menéndez 《Tetrahedron》2018,74(38):5358-5366
A small library of novel hybrid spiroheterocycles containing spirooxindole, pyrrolidine and indole/imidazole moieties were synthesized with complete regio- and diastereoselectively in good to excellent yields from a three-component process starting from a series of variously substituted (E)-(2-nitrovinyl)benzenes, indoline-2,3-dione derivatives and l-tryptophan or l-histidine in an ionic liquid. The key step of this transformation is a 1,3-dipolar cycloaddition reaction involving a rare class of in situ-generated azomethine ylides derived from aromatic amino acids. The compounds thus synthesized were evaluated for their anticancer activity and were shown to inhibit the proliferation of FaDu cells, a human epithelial cell line isolated from a squamous cell carcinoma of the hypopharynx, via apoptotic cell death. 相似文献
990.
John T. Gupton Alex Shimozono Evan Crawford Joe Ortolani Evan Clark Matt Mahoney Campbell Heese Jeffrey Noble Carlos Perez Mandry Rene Kanters Raymond N. Dominey Emma W. Goldman James A. Sikorski Daniel C. Fisher 《Tetrahedron》2018,74(21):2650-2663
Highly functionalized pyrroles with appropriate regiochemical functionality represent an important class of marine natural products and potential drug candidates. We describe herein a detailed study of the reaction of α-aminoacid esters with vinylogous amides and also β-halovinylaldehydes for the regiospecific synthesis of 2,3,4-trisubstituted and 1,2,3,4-tetrasubstituted pyrroles. Since the vinylogous amides and β-halovinylaldehydes are readily available precursors, rapid access to a wide variety of unsymmetrically substituted pyrroles is accomplished via this methodology. 相似文献