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881.
Dasari R Ibañez FJ Zamborini FP 《Langmuir : the ACS journal of surfaces and colloids》2011,27(11):7285-7293
A simple electrochemical approach was used for fabricating electrode/metal nanowire/(molecule or polymer)/electrode junctions for sensing or molecular electronics applications. The procedure for fabricating these molecule-based devices involves electropolymerization of phenol or chemisorption of alkanethiols on one set of electrodes (E1) and electrodeposition of Ag metal nano/microwires on a second electrode (E2) which is ~5 μm away from E1. Under appropriate deposition conditions, Ag nanowires grow from E2 and cross over to E1, forming a E1/(molecule or polymer)/Ag nanowire (NW)/E2 junction. The junction resistance was controlled by (1) electrodepositing polyphenol of varied densities on E1 and (2) assembling alkanethiols of different chain lengths on E1. Ag NWs at high resistance E1/polyphenol/Ag NW/E2 junctions functionalized with Pd monolayer protected clusters (MPCs) responded fast and reversibly to H(2) concentrations as low as 0.11% in a nitrogen carrier gas by a resistance decrease, likely due to volume expansion of the Pd nanoparticles, demonstrating the use of these electrochemically fabricated junctions for gas sensing applications. 相似文献
882.
Lu CT Chen SA Bretaña NA Cheng TH Lee TY 《Journal of computer-aided molecular design》2011,25(10):987-995
In proteins, glutamate (Glu) residues are transformed into γ-carboxyglutamate (Gla) residues in a process called carboxylation.
The process of protein carboxylation catalyzed by γ-glutamyl carboxylase is deemed to be important due to its involvement
in biological processes such as blood clotting cascade and bone growth. There is an increasing interest within the scientific
community to identify protein carboxylation sites. However, experimental identification of carboxylation sites via mass spectrometry-based
methods is observed to be expensive, time-consuming, and labor-intensive. Thus, we were motivated to design a computational
method for identifying protein carboxylation sites. This work aims to investigate the protein carboxylation by considering
the composition of amino acids that surround modification sites. With the implication of a modified residue prefers to be
accessible on the surface of a protein, the solvent-accessible surface area (ASA) around carboxylation sites is also investigated.
Radial basis function network is then employed to build a predictive model using various features for identifying carboxylation
sites. Based on a five-fold cross-validation evaluation, a predictive model trained using the combined features of amino acid
sequence (AA20D), amino acid composition, and ASA, yields the highest accuracy at 0.874. Furthermore, an independent test
done involving data not included in the cross-validation process indicates that in silico identification is a feasible means of preliminary analysis. Additionally, the predictive method presented in this work is
implemented as Carboxylator (), a web-based tool for identifying carboxylated proteins with modification sites in order to help users in investigating
γ-glutamyl carboxylation. 相似文献
883.
Abel Zúñiga-Moreno Carmen M. Reza-San Germán Oscar G. Rojas-Valencia Elizabeth P. Juárez-Camacho 《Journal of solution chemistry》2011,40(4):621-631
Densities of the binary mixture of nonane with decane were measured at temperatures from 283.15 to 353.15 K at atmospheric
pressure (0.7 atm). Measurements have been made over the full range of compositions and for the pure compounds by using a
vibrating-tube densimeter (VTD). Excess molar volumes have been obtained from these experimental results and were fitted to
a Redlich–Kister type expansion. The excess molar volumes exhibit small positive and small negative deviations from ideal
behavior in the temperature interval studied. Partial molar volumes and partial molar volumes at infinite dilution have been
determined for each component. 相似文献
884.
Two open substituted benzodipyrroles were tested as hydrogen-bond-forming anion ionophores for the development of anion-selective electrodes. These compounds were incorporated in plasticized polymeric membranes with different plasticizers, using different membrane compositions to explore their response towards several anions. The electrodes constructed with membranes containing 2-nitrophenyl octyl ether and a 0.5 molar ratio ionic additive/ionophore showed pronounced anti-Hofmeister behaviour, providing a significantly enhanced response towards the divalent anions sulfate, sulfite, thiosulfate and oxalate. The selected electrodes were also evaluated in terms of detection limits and selectivity. 1H NMR experiments were carried out in an attempt to explain some aspects of the behaviour observed. 相似文献
885.
Silva NL Betancur GJ Vasquez MP Gomes Ede B Pereira N 《Applied biochemistry and biotechnology》2011,163(7):928-936
Current research indicates the ethanol fuel production from lignocellulosic materials, such as residual wood chips from the
cellulose industry, as new emerging technology. This work aimed at evaluating the ethanol production from hemicellulose of
eucalyptus chips by diluted acid pretreatment and the subsequent fermentation of the generated hydrolysate by a flocculating
strain of Pichia stipitis. The remaining solid fraction generated after pretreatment was subjected to enzymatic hydrolysis, which was carried out simultaneously
with glucose fermentation [saccharification and fermentation (SSF) process] using a strain of Saccharomyces cerevisiae. The acid pretreatment was evaluated using a central composite design for sulfuric acid concentration (1.0–4.0 v/v) and solid to liquid ratio (1:2–1:4, grams to milliliter) as independent variables. A maximum xylose concentration of 50 g/L
was obtained in the hemicellulosic hydrolysate. The fermentation of hemicellulosic hydrolysate and the SSF process were performed
in bioreactors and the final ethanol concentrations of 15.3 g/L and 28.7 g/L were obtained, respectively. 相似文献
886.
In this review, we present applications of NMR spectroscopy as a potent tool for the study of molecular interactions. It is clear that a variety of NMR methods may be employed to deduce key features of ligand–receptor molecular recognition processes, looking at the process from the perspective of the receptor or the ligand. We have not provided an exhaustive review, but we have tried to focus on describing the different aspects within this research topic. We have therefore selected examples accordingly, depending on the particular problem under study or the application/development of protocols to circumvent the technical problems that may be found when working in this field. 相似文献
887.
888.
Díaz de Greñu B Iglesias Hernández P Espona M Quiñonero D Light ME Torroba T Pérez-Tomás R Quesada R 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(50):14074-14083
Synthetic prodiginine obatoclax shows promise as a potential anticancer drug. This compound promotes apoptosis of cancer cells, although the mechanism of action is unclear. To date, only the inhibition of BCL-2 proteins has been proposed as a mechanism of action. To gain insight into other possible modes of action, we have studied the anion-binding properties of obatoclax and related analogues in solution, in the solid state, and by means of density functional theory calculations. These compounds are well suited to interact with anions such as chloride and bicarbonate. The anion-transport properties of the compounds synthesized were assayed in model phospholipid liposomes by using a chloride-selective-electrode technique and (13)C NMR spectroscopy. The results demonstrated that these compounds are efficient anion exchangers that promote chloride, bicarbonate, and nitrate transport through lipid bilayers at very low concentrations. In vitro studies on small-cell lung carcinoma cell line GLC4 showed that active ionophores are able to discharge pH gradients in living cells and the cytotoxicity of these compounds correlates well with ionophoric activity. 相似文献
889.
Alcaide B Almendros P Martínez del Campo T Redondo MC Fernández I 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(52):15005-15013
An efficient chemodivergent metal-controlled methodology for the generation of different highly functionalized oxygen heterocycles from common enallenol substrates has been developed. Chemoselectivity control in the O-C functionalization of an enallenol can be achieved through the choice of catalyst: AuCl(3), PdCl(2), and [PtCl(2)(CH(2)=CH(2))](2) exclusively afford dihydrofurans through selective activation of the allenol moiety, whereas FeCl(3) solely gives tetrahydrofurans or tetrahydropyrans through selective activation of the alkenol moiety. We have also shown that a combination of metal-mediated hydroalkoxylation and allenic aminocyclization reactions can lead to a useful preparation of the tetrahydrofuro[3,2-b]piperidine core of the antimalarial alkaloid isofebrifugine. These divergent heterocyclization reactions have been developed experimentally and additionally, their mechanisms have been investigated by a theoretical study. 相似文献
890.
Pérez-Ojeda ME Trastoy B López-Arbeloa Í Bañuelos J Costela Á García-Moreno I Chiara JL 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(47):13258-13268
New hybrid organic–inorganic dyes based on an azide‐functionalized cubic octasilsesquioxane (POSS) as the inorganic part and a 4,4‐difluoro‐4‐bora‐3a,4a‐diaza‐s‐indacene (BDP) chromophore as the organic component have been synthesized by copper(I)‐catalyzed 1,3‐dipolar cycloaddition of azides to alkynes. We have studied the effects of the linkage group of BDP to the POSS unit and the degree of functionalization of this inorganic core on the ensuing optical properties by comparison with model dyes. The high fluorescence of the BDP dye is preserved in spite of the linked chain at its meso position, even after attaching one BDP moiety to the POSS core. The laser action of the new dyes has been analyzed under transversal pumping at 532 nm in both the liquid phase and when incorporated into solid polymeric matrices. The monosubstituted new hybrid dye exhibits high lasing efficiency of up to 56 % with high photostability, with its laser output remaining at the initial value after 4×105 pump pulses in the same position of the sample at a repetition rate of 30 Hz. However, functionalization of the POSS core with eight fluorophores leads to dye aggregation, as quantum mechanical simulation has revealed, worsening the optical properties and extinguishing the laser action. The new hybrid systems based on dye‐linked POSS nanoparticles open up the possibility of using these new photonic materials as alternative sources for optoelectronic devices, competing with dendronized or grafted polymers. 相似文献