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51.
Manuel Alberto Flores‐Hidalgo Daniel Glossman‐Mitnik D. H. Galvan Diana Barraza‐Jimenez 《中国化学会会志》2013,60(8):1082-1091
Density Functional Theory employing hybrid and M06 functionals in combination with three different basis sets is used to calculate the ground state of a cage like (ZnO)12 nanocluster which has been consistently reported as the more stable cluster for its particular size. B3LYP and B3PW91 hybrid functionals combined with 6‐31+G*, Lanl2dz and SDD basis sets are employed to treat the ZnO molecular system. Alternatively, three M06 functionals in combination with three basis sets are employed in the nanostructure calculations. Results obtained by treating ZnO sodalite cage nanocluster with M06 functionals demonstrated comparable quality to results obtained with hybrid functionals. Within this study, efficient theoretical DFT methods with the widely known hybrid and the recently created M06 meta‐hybrid functionals are employed to study nanostructured ZnO. Our resulting parameters provide a fresh approach performance wise on the different theoretical methods to treat transition metal nanostructures, particularly, ZnO nanoclusters geometry and electronic structure. 相似文献
52.
Ricardo A. W. Neves Filho Diana C. B. da Silva-Alves Janaína V. dos Anjos 《合成通讯》2013,43(19):2596-2602
A simple and straightforward synthesis of 3-aryl-5-hydroxyalkyl-1,2,4-oxadiazoles is described. The reaction among arylamidoximes, ethyl glycolate or ethyl lactate, and potassium carbonate in refluxing toluene afforded the desired 1,2,4-oxadiazoles in moderate to good yields. The synthesis has been accomplished in a single step, avoiding protection–deprotection protocols. Supplemental materials are available for this article. Go to the publisher's online edition of Synthetic Communications® to view the free supplemental file. 相似文献
53.
54.
Poul Erik Hansen Fadhil S. Kamounah Diana Zhiryakova Yana Manolova Liudmil Antonov 《Tetrahedron letters》2014
It has recently been suggested that 1,1′,1′′-(2,4,6-trihydroxybenzene-1,3,5-triyl)triethanone may be tautomeric. Using 13C NMR chemical shifts and deuterium isotope effects on 13C chemical shifts, it is demonstrated that this is not the case. This compound occurs as a strongly hydrogen bonded benzene structure with hydrogen bonds between OH groups and the acetyl groups in both non-polar and hydrogen donating solvents. Quantum-chemical calculations using MP2 and M06-2X methods show substantial preference for the phenol structure in both the gas phase, and in cyclohexane and methanol. In addition, conventional UV–vis spectroscopy data suggest not tautomeric, but aggregation behaviour of the molecule in methanol and acetonitrile. 相似文献
55.
The ionic liquid 1-ethyl-3-methylimidazolium acetate ([C2mim][OAc]) was successfully used as alternative solvent for native chemical ligation of peptide fragments to produce model peptide LYRAXCRANK (X = G, A, L, N, Q, K, and F). The commonly used buffer system including thiol additives such as thiophenol and benzyl mercaptan can be replaced by the nontoxic ionic liquid [C2mim][OAc]. In addition to improving the solubility of the peptides in [C2mim][OAc], yields and rates of the ligation reactions were found to be efficiently enhanced. 相似文献
56.
Samuel Piña Jr. Diana M. Cedillo Carlos Tamez Nezhueyotl Izquierdo Jason G. Parsons Jose J. Gutierrez 《Tetrahedron letters》2014
Reported here is the reduction of aromatic nitro compounds using sodium borohydride and transition metal sulfides as catalysts. The reaction conditions were optimized using the reduction of nitrobenzene as a model reaction. The catalysts studied were iron sulfide (Fe3S4), copper sulfide (CuS), zinc sulfide (ZnS), cobalt sulfide (Co3S4), and nickel sulfide (NiS). The reduction was monitored using gas chromatography. Quantitative conversions were achieved using Co3S4 and NiS, representing a ten-fold increase in reactivity compared to the non-catalyzed reaction. Fe3S4 and ZnS had no apparent effect on the reduction of nitrobenzene while the reduction using CuS showed a marginal increase. The reduction method was applied to several aryl-nitro derivatives containing either electron-withdrawing or electron-donating groups. Halogen containing aryl-nitro compounds were reduced without dehalogenation. The reduction had no effect on other functional groups such as carboxylic acids, esters, amides, or alkenes, indicating that the reduction is highly chemoselective. 相似文献
57.
Sergey V. Prikhodko Diana C. Rambaldi Andrew King Elizabeth Burr Vanessa Muros Ioanna Kakoulli 《Journal of Raman spectroscopy : JRS》2015,46(7):632-635
In the past decade Surface Enhanced Raman Scattering (SERS) has emerged as a powerful technique for the analysis of artistic, historical and archaeological material culture. However, the identification of organic compounds in complex samples using SERS can be challenging owing to the complexity in optimizing the adsorption of target analytes onto the plasmonic substrate and the difficulty to identify proper areas on the sample for robust SERS analysis using optical systems. Scanning electron microscopy (SEM) interfaced with Raman spectromicroscopy (μRS) provides an ideal hyphenated system to overcome the last challenge by: (1) evaluating the nanoparticles coverage/distribution on the sample and (2) locating suitable areas for successful and reproducible SERS analysis. In this paper we demonstrate the potential of a system interfacing SEM and μRS for single fiber, extractionless analysis in the characterization of dyes from reference collections and archaeological textiles. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
58.
Agnieszka Nowacka-Perrin Thomas Steglich Daniel Topgaard Diana Bernin 《Magnetic resonance in chemistry : MRC》2022,60(7):671-677
Convenience food products tend to alter their quality and texture while stored. Texture-giving food components are often starch-rich ingredients, such as pasta or rice. Starch transforms depending on time, temperature and water content, which alters the properties of products. Monitoring these transformations, which are associated with a change in mobility of the starch chain segments, could optimize the quality of food products containing multiple ingredients. In order to do so, we applied a simple and efficient in situ 13C solid-state magic angle spinning (MAS) NMR approach, based on two different polarization transfer schemes, cross polarization (CP) and insensitive nuclei enhanced by polarization transfer (INEPT). The efficiency of the CP and INEPT transfer depends strongly on the mobility of chain segments—the time scale of reorientation of the CH-bond and the order parameter. Rigid crystalline or amorphous starch chains give rise to CP peaks, whereas mobile gelatinized starch chains appear as INEPT peaks. Comparing 13C solid-state MAS NMR experiments based on CP and INEPT allows insight into the progress of gelatinization, and other starch transformations, by reporting on both rigid and mobile starch chains simultaneously with atomic resolution by the 13C chemical shift. In conjunction with 1H solid-state MAS NMR, complementary information about other food components present at low concentration, such as lipids and protein, can be obtained. We demonstrate our approach on starch-based products and commercial pasta as a function of temperature and storage. 相似文献
59.
Arajo Joana C. Teixeira Pilar Fangueiro Raul Ferreira Diana P. 《Cellulose (London, England)》2022,29(10):5659-5676
Cellulose - Core–shell nanoparticles (NPs) based on metal oxides, namely magnesium oxide (MgO) and silica (SiO2), are a fantastic alternative for natural fibers’ functionalization. In... 相似文献
60.
Ana Margarida Silva Diana Pinto Iva Fernandes Victor de Freitas María de la Luz Cdiz-Gurrea Paulo Costa Cristina Delerue-Matos Francisca Rodrigues 《Molecules (Basel, Switzerland)》2021,26(8)
During kiwiberry production, different by-products are generated, including leaves that are removed to increase the fruit’s solar exposure. The aim of this work was to extract bioactive compounds from kiwiberry leaf by employing microwave-assisted extraction (MAE). Compatible food solvents (water and ethanol) were employed. The alcoholic extract contained the highest phenolic and flavonoid contents (629.48 mg of gallic acid equivalents (GAE) per gram of plant material on dry weight (dw) (GAE/g dw) and 136.81 mg of catechin equivalents per gram of plant material on dw (CAE/g dw), respectively). Oppositely, the hydroalcoholic extract achieved the highest antioxidant activity and scavenging activity against reactive oxygen and nitrogen species (IC50 = 29.10 μg/mL for O2•−, IC50 = 1.87 μg/mL for HOCl and IC50 = 1.18 μg/mL for •NO). The phenolic profile showed the presence of caffeoylquinic acids, proanthocyanidin, and quercetin in all samples. However, caffeoylquinic acids and quercetin were detected in higher amounts in the alcoholic extract, while proanthocyanidins were prevalent in the hydroalcoholic extract. No adverse effects were observed on Caco-2 viability, while the highest concentration (1000 µg/mL) of hydroalcoholic and alcoholic extracts conducted to a decrease of HT29-MTX viability. These results highlight the MAE potentialities to extract bioactive compounds from kiwiberry leaf. 相似文献