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931.
Ruiz J Gonzalo MP Vivanco M Díaz MR García-Granda S 《Chemical communications (Cambridge, England)》2011,47(14):4270-4272
A three-component reaction involving diphosphinoketenimines, isocyanides and water or ethanol leading to the formation of new five-membered azaphosphaheterocycles is described. 相似文献
932.
Aranjuelo I Pintó-Marijuan M Avice JC Fleck I 《Rapid communications in mass spectrometry : RCM》2011,25(11):1527-1535
Stored carbon (C) represents a very important C pool with residence times of years to decades in tree organic matter. With the objective of understanding C assimilation, partitioning and remobilization in 2-year-old Quercus ilex L., those trees were exposed for 7 months to different [CO(2)] (elevated: 700 μmol mol(-1) ; and ambient: 350 μmol mol(-1) CO(2)). The (13)C-isotopic composition of the ambient CO(2) (ca.-12.8‰) was modified (to ca.-19.2‰) under the elevated CO(2) conditions in order to analyze C allocation and partitioning before aerial biomass excision, and during the following regrowth (resprouting). Although after 7 months of growth under elevated [CO(2)], Q. ilex plants increased dry matter production, the absence of significant differences in photosynthetic activity suggests that such an increase was lower than expected. Nitrogen availability was not involved in photosynthetic acclimation. The removal of aboveground organs did not enable the balance between C availability and C requirements to be achieved. The isotopic characterization revealed that before the cutting, C partitioning to the stem (main C sink) prevented leaf C accumulation. During regrowth the roots were the organ with more of the labelled C. Furthermore, developing leaves had more C sink strength than shoots during this period. After the cutting, the amount of C delivered from the root to the development of aboveground organs exceeded the requirements of leaves, with the consequent carbohydrate accumulation. These findings demonstrate that, despite having a new C sink, the responsiveness of those resprouts under elevated [CO(2)] conditions will be strongly conditioned by the plant's capacity to use the extra C present in leaves through its allocation to other organs (roots) and processes (respiration). 相似文献
933.
Agnieszka Kierys Rados?aw Zaleski Marta Grochowicz Jacek Goworek 《Colloid and polymer science》2011,289(7):751-758
The simple and effective approach for preparation of highly porous poly(TRIM)/MCM-41 composite material has been presented. The structural properties of the spherically shaped particles of the composite were investigated by positron annihilation lifetime spectroscopy (PALS) and low temperature adsorption of nitrogen. The parameters characterizing the porosity of investigated materials derived from two different techniques have been compared. PALS provides a convenient tool for characterization of polymer-based composite materials. 相似文献
934.
The capacity to create an increasing variety of bioactive molecules that are designed to assemble in specific configurations has opened up tremendous possibilities in the design of materials with an unprecedented level of control and functionality. A particular challenge involves guiding such self-assembling interactions across scales, thus precisely positioning individual molecules within well-organized, highly-ordered structures. Such hierarchical control is essential if peptides and proteins are to serve as both structural and functional building blocks of biomedical materials. To achieve this goal, top-down techniques are increasingly being used in combination with self-assembling systems to reproducibly manipulate, localize, orient and assemble peptides and proteins to form organized structures. In this tutorial review we provide insight into how both standard and novel top-down techniques are being used in combination with peptide or protein self-assembly to create a new generation of functional materials. 相似文献
935.
Gutiérrez-Sánchez C Olea D Marques M Fernández VM Pereira IA Vélez M De Lacey AL 《Langmuir : the ACS journal of surfaces and colloids》2011,27(10):6449-6457
The interaction of redox enzymes with electrodes is of great interest for studying the catalytic mechanisms of redox enzymes and for bioelectronic applications. Efficient electron transport between the biocatalysts and the electrodes has achieved more success with soluble enzymes than with membrane enzymes because of the higher structural complexity and instability of the latter proteins. In this work, we report a strategy for immobilizing a membrane-bound enzyme onto gold electrodes with a controlled orientation in its fully active conformation. The immobilized redox enzyme is the Ni-Fe-Se hydrogenase from Desulfovibrio vulgaris Hildenborough, which catalyzes H(2)-oxidation reversibly and is associated with the cytoplasmic membrane by a lipidic tail. Gold surfaces modified with this enzyme and phospholipids have been studied by atomic force microscopy (AFM) and electrochemical methods. The combined study indicates that by a two-step immobilization procedure the hydrogenase can be inserted via its lipidic tail onto a phospholipidic bilayer formed over the gold surface, allowing only mediated electron transfer between the enzyme and electrode. However, a one-step immobilization procedure favors the formation of a hydrogenase monolayer over the gold surface with its lipidic tail inserted into a phospholipid bilayer formed on top of the hydrogenase molecules. This latter method has allowed for the first time efficient electron transfer between a membrane-bound enzyme in its native conformation and an electrode. 相似文献
936.
Suárez-Herrera MF Costa-Figueiredo M Feliu JM 《Langmuir : the ACS journal of surfaces and colloids》2012,28(11):5286-5294
The first part of this report studies the electrochemical properties of single-crystal platinum electrodes in acetonitrile electrolytes by means of cyclic voltammetry. Potential difference infrared spectroscopy in conjunction with linear voltammetry was used to obtain a molecular-level picture of this interface. The second part of this report studies the hydrogen evolution and the hydrogen oxidation reactions on the three low-index faces of Pt electrodes in acetonitrile electrolytes. The data (CVs and IR spectra) strongly suggest that acetonitrile and CN(-) molecules are adsorbed on single-crystal platinum electrodes in the range of -1.5 to 0.3 V versus Ag/AgCl. Those species block part of the adsorption sites for hydrogen adatoms, and they decompose on the surface in the presence of water. The nature of the cation and the presence of water strongly affect the onset of acetonitrile electrolysis and the kinetics and stability of the adsorbed species on the electrode. Finally, the hydrogen evolution and the hydrogen oxidation reactions on platinum single-crystal surfaces in acetonitrile electrolytes are strongly affected by the surface-energy state of Pt electrodes. 相似文献
937.
Ana Negri Jihong Li Sarasija Naini Barry S. Coller Marta Filizola 《Journal of computer-aided molecular design》2012,26(9):1005-1015
Integrin αIIbβ3 has emerged as an important therapeutic target for thrombotic vascular diseases owing to its pivotal role in mediating platelet aggregation through interaction with adhesive ligands. In the search for effective anti-thrombotic agents that can be administered orally without inducing the high-affinity ligand binding state, we recently discovered via high-throughput screening of 33,264 compounds a novel, αIIbβ3-selective inhibitor (RUC-1) of adenosine-5′-diphosphate (ADP) -induced platelet aggregation that exhibits a different chemical scaffold and mode of binding with respect to classical Arg-Gly-Asp (RGD)-mimicking αIIbβ3 antagonists. Most importantly, RUC-1 and its higher-affinity derivative, RUC-2, do not induce major conformational changes in the protein β3 subunit or prime the receptor to bind ligand. To identify additional αIIbβ3-selective chemotypes that inhibit platelet aggregation through similar mechanisms, we screened in silico over 2.5 million commercially available, ‘lead-like’ small molecules based on complementarity to the predicted binding mode of RUC-2 into the RUC-1-αIIbβ3 crystal structure. This first reported structure-based virtual screening application to the αIIbβ3 integrin led to the identification of 2 αIIbβ3-selective antagonists out of 4 tested, which compares favorably with the 0.003?% “hit rate” of our previous high-throughput chemical screening study. The newly identified compounds, like RUC-1 and RUC-2, showed specificity for αIIbβ3 compared to αVβ3 and did not prime the receptor to bind ligand. They thus may hold promise as αIIbβ3 antagonist therapeutic scaffolds. 相似文献
938.
Anna Baranowska-Korczyc Anna Reszka Kamil Sobczak Bo?ena Sikora Piotr Dziawa Marta Aleszkiewicz ?ukasz K?opotowski Wojciech Paszkowicz Piotr D?u?ewski Bogdan J. Kowalski Tomasz A. Kowalewski Maciej Sawicki Danek Elbaum Krzysztof Fronc 《Journal of Sol-Gel Science and Technology》2012,61(3):494-500
We demonstrate structural and room temperature magnetic properties of Fe doped ZnO nanofibers (NFs) obtained by electrospinning followed by calcination. The observed NFs, formed from crystalographically oriented, approximately 4.5?nm particles conglomerates, were approximately 200?nm in diameter. The reported synthesis of room temperature ferromagnetic Fe doped ZnO NFs is both facile and economical, and is therefore suggested as a generic method of fabricating biocompatible magnetic materials. The major substrates selected for the NFs synthesis (Zn, Fe) comprised of relatively low toxicity materials. Incorporating 10% Fe into ZnO does not modify the wurtzite crystal structure of the host material. No evidence of impurity phase was detected by either X-ray or electron diffraction. Magnetometry studies and Magnetic Force Microscopy imaging reveal a local ferromagnetic order that persists up to room temperature. We suggest that the observed phenomenon is either due to a mechanism mediated by presence of oxygen vacancies and/or is related to iron-rich precipitates. 相似文献
939.
Renata Los Marta Wesoowska‐Trojanowska Anna Malm Monika M. Karpiska Joanna Matysiak Andrzej Niewiadomy Urszula Gaszcz 《Heteroatom Chemistry》2012,23(3):265-275
A new synthesis method of benzimidazoles, dihydroquinazolines, and other related compounds containing a 2,4‐dihydroxyphenyl moiety was elaborated. Their structures were identified from elemental, infrared, 1H NMR, 13C NMR, and mass spectra analyses. The minimal inhibitory concentration values of the compounds toward eight reference bacterial strains were determined by the two‐fold serial microdilution broth method. The compounds exhibited substantial inhibitory effects against the Gram‐positive strains tested contrary to Gram‐negative ones. The compounds of imidazopyridine, N‐methylbenzimidazole, and dihydroquinazoline structures exhibited the largest activity. The magnification of covering a two‐nitrogen atom heterocyclic ring fused to a benzene one decreases the biological effect. © 2012 Wiley Periodicals, Inc. Heteroatom Chem 23:265–275, 2012; View this article online at wileyonlinelibrary.com . DOI 10.1002/hc.21012 相似文献
940.
In this study, in‐line solid‐phase extraction (SPE) was used as an enrichment technique in combination with CE for the preconcentration and separation of 2‐ethylidene‐1,5‐dimethyl‐3,3‐diphenylpyrrolidine (EDDP), cocaine (COC), codeine (COD) and 6‐acetylmorphine (6AM). The separation buffer (BGE) used was 80 mM disodium phosphate anhydrous and 6 mM of HCl (final BGE pH of 3). The SPE extractor consists of a small segment of capillary filled with Oasis HLB sorbent and inserted into the inlet section of the electrophoretic capillary. Different parameters affecting preconcentration were evaluated, such as sample pH, the volume of the elution plug and sample injection time. The detection limits (LODs) reached for standard samples by in‐line SPE‐CE‐UV ranged between 50 and 200 ng/L, with sensitivity enhancement factors ranging from 2300 to 5300. Reproducibility values (expressed in terms of relative standard deviation) were below 7.6% for standard samples. This is a simple and an effective method for the determination of the studied drugs of abuse and their metabolites. The applicability of the developed method was demonstrated in tap and river water samples which were directly analyzed without any off‐line pretreatment. Analytical parameters were evaluated and LODs were between 70 and 270 ng/L with relative recoveries between 85 and 97%. 相似文献