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891.
We apply first-principles calculations to investigate the interplay between electronic and magnetic properties of carbon nanotubes with line defects. We consider three types of defects: lines of C--O--C epoxy groups, and defects resulting from the substitution of the oxygen atoms by CH2 or C2H4 divalent radicals. We find that the line defects behave as pairs of coupled graphene edge states, and a variety of electronic and magnetic ground states is predicted as a function of defect type, nanotube diameter, and a possibly applied transverse electric field. 相似文献
892.
Bianca Schweitzer Arlindo C. Felippe Alexandre Dal Bó Edson Minatti Dino Zanette 《Macromolecular Symposia》2005,229(1):208-216
Summary: In this study sodium cholate (NaC) was used as a representative bile salt for the competitive binding between NaC and sodium dodecyl sulfate (SDS) in bovine serum albumin (BSA), in 0.02 M tris-HCl buffer solution at pH 7.50 and 25 °C. The NaC and SDS associations with BSA were monitored at low surfactant concentrations where only this specific binding process can develop. The applied method to monitor the binding was based on the analysis of the effect of SDS and NaC concentrations and their mixtures upon the fluorescence intensity of the BSA tryptophan residues. This consists of the measurement of the surfactant monomer partitioning between the dispersion medium and the microaggregates on the protein molecule where the binding is indicated by the quenching of the fluorescence chromophores. Experimentally, varying the protein concentration, the surfactant concentration needed to reach a given Io/I ratio (Io and I are the intensities with and without protein, respectively) was measured. The analyses, based on the average number of surfactant molecules bound on the protein, indicated that the SDS is a more efficient quencher than the bile salt. The need for 4–6 NaC bound molecules to give the same protein quenching efficiency by a single molecule of SDS was estimated. We concluded that the differences in the competitive binding on the protein are exclusively related to the quenching efficiency in the formation of the nonfluorescent fluorophore-quencher complex via a physical contact and static quenching process. 相似文献
893.
S. Peeterbroeck M. Alexandre J.B. Nagy N. Moreau A. Destrée F. Monteverde A. Rulmont R. Jérôme Ph. Dubois 《Macromolecular Symposia》2005,221(1):115-126
Morphological and rheological properties of new ternary nanocomposites based on ethylene vinyl acetate copolymers (EVA), commercial organo-modified clays (organoclays) and purified multi-walled carbon nanotubes (MWNTs), prepared via direct melt blending, have been evaluated. For sake of comparison, the corresponding binary compositions, i.e., EVA filled with either organoclays or MWNTs, have been investigated as well. While extensive exfoliation can be observed for binary EVA/clay nanocomposites, the addition of MWNTs appears to limit clay exfoliation. Rheological properties show that both clay and MWNTs increase the elastic modulus of the nanocomposites, reflecting the high degree of nanoparticle interconnectivity that can be found in these materials. 相似文献
894.
Andrii Tarasov Federico Garzelli Christoph Schuessler Stefanie Fritsch Christophe Loisel Alexandre Pons Claus-Dieter Patz Doris Rauhut Rainer Jung 《Molecules (Basel, Switzerland)》2021,26(20)
Storage temperature is one of the most important factors affecting wine aging. Along with bottling parameters (type of stopper, SO2 level and dissolved O2 in wine), they determine how fast wine will evolve, reach its optimum and decline in sensory quality. At the same time, lowering of the SO2 level in wine has been a hot topic in recent years. In the current work, we investigated how Riesling wine evolved on the molecular level in warm (~25 °C) and cool (~15 °C) conditions depending on the SO2 level in the wine (low, medium and high), flushing of the bottle’s headspace with CO2 and three types of stoppers (Diam 30, Diam 30 origin and Diam 5) with different OIR levels (0.8–1.3 mg) and OTR levels (0.3–0.4 mg/year). It was demonstrated that the evolution of primary and secondary aromas, wine color and low molecular weight sulfur compounds (LMWSCs) during the two years of aging mainly depended on the storage temperature. Variation in the SO2 level and CO2 in the headspace affected mostly certain LMWSCs (H2S, MeSH) and β-damascenone. New aspects of C13-norisprenoids and monoterpenoids behavior in Riesling wine with different levels of SO2 and O2 were discussed. All three types of stoppers showed very close wine preservation properties during the two years of storage. The sensory analysis revealed that, after only six months, the warm stored wines with a low SO2 level were more oxidized and different from the samples with medium and high SO2 levels. A similar tendency was also observed for the cool stored samples. 相似文献
895.
Thais Kroetz Pablo Andrei Nogara Fabiano da Silveira Santos Lilian Camargo da Luz Viktor Saraiva Cmara Joo Batista Teixeira da Rocha Alexandre Gonalves Dal-B Fabiano Severo Rodembusch 《Molecules (Basel, Switzerland)》2021,26(21)
In this study, the interactions of ESIPT fluorescent lipophile-based benzazoles with bovine serum albumin (BSA) were studied and their binding affinity was evaluated. In phosphate-buffered saline (PBS) solution these compounds produce absorption maxima in the UV region and a main fluorescence emission with a large Stokes shift in the blue–green regions due to a proton transfer process in the excited state. The interactions of the benzazoles with BSA were studied using UV-Vis absorption and steady-state fluorescence spectroscopy. The observed spectral quenching of BSA indicates that these compounds could bind to BSA through a strong binding affinity afforded by a static quenching mechanism (Kq~1012 L·mol−1·s−1). The docking simulations indicate that compounds 13 and 16 bind closely to Trp134 in domain I, adopting similar binding poses and interactions. On the other hand, compounds 12, 14, 15, and 17 were bound between domains I and III and did not directly interact with Trp134. 相似文献
896.
897.
Alexandre S. Miranda Paula M. Marcos Jos R. Ascenso Mrio N. Berberan-Santos Filipe Menezes 《Molecules (Basel, Switzerland)》2022,27(10)
Fluorescent receptors (4a–4c) based on (thio)ureido-functionalized hexahomotrioxacalix[3]arenes were synthesised and obtained in the partial cone conformation in solution. Naphthyl or pyrenyl fluorogenic units were introduced at the lower rim of the calixarene skeleton via a butyl spacer. The binding of biologically and environmentally relevant anions was studied with NMR, UV–vis absorption, and fluorescence titrations. Fluorescence of the pyrenyl receptor 4c displays both monomer and excimer fluorescence. The thermodynamics of complexation was determined in acetonitrile and was entropy-driven. Computational studies were also performed to bring further insight into the binding process. The data showed that association constants increase with the anion basicity, and AcO−, BzO− and F− were the best bound anions for all receptors. Pyrenylurea 4c is a slightly better receptor than naphthylurea 4a, and both are more efficient than naphthyl thiourea 4b. In addition, ureas 4a and 4c were also tested as ditopic receptors in the recognition of alkylammonium salts. 相似文献
898.
Maira Smaniotto Cucielo Roberta Carvalho Cesrio Henrique Spaulonci Silveira Letícia Barbosa Gaiotte Srgio Alexandre Alcantara dos Santos Debora Aparecida Pires de Campos Zuccari Fbio Rodrigues Ferreira Seiva Russel J. Reiter Luiz Gustavo de Almeida Chuffa 《Molecules (Basel, Switzerland)》2022,27(14)
Ovarian cancer (OC) is the most lethal gynecologic malignancy, and melatonin has shown various antitumor properties. Herein, we investigated the influence of melatonin therapy on energy metabolism and mitochondrial integrity in SKOV-3 cells and tested whether its effects depended on MT1 receptor activation. SKOV-3 cells were exposed to different melatonin concentrations, and experimental groups were divided as to the presence of MT1 receptors (melatonin groups) or receptor absence by RNAi silencing (siRNA MT1+melatonin). Intracellular melatonin levels increased after treatment with melatonin independent of the MT1. The mitochondrial membrane potential of SKOV-3 cells decreased in the group treated with the highest melatonin concentration. Melatonin reduced cellular glucose consumption, while MT1 knockdown increased its consumption. Interconversion of lactate to pyruvate increased after treatment with melatonin and was remarkable in siRNA MT1 groups. Moreover, lactate dehydrogenase activity decreased with melatonin and increased after MT1 silencing at all concentrations. The UCSC XenaBrowser tool showed a positive correlation between the human ASMTL gene and the ATP synthase genes, succinate dehydrogenase gene (SDHD), and pyruvate dehydrogenase genes (PDHA and PDHB). We conclude that melatonin changes the glycolytic phenotype and mitochondrial integrity of SKOV-3 cells independent of the MT1 receptor, thus decreasing the survival advantage of OC cells. 相似文献
899.
900.