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排序方式: 共有969条查询结果,搜索用时 93 毫秒
961.
962.
Abel Carreras Andreas Lorbach Guillermo C. Bazan Pere Alemany Guang Wu Miguel A. Garcia-Garibay Emily F. Maverick 《Helvetica chimica acta》2023,106(2):e202200142
A single-crystal X-ray study of a fullerene-imidazole adduct at nine temperatures (80 K≤T≤480 K), accompanied by energy calculations, strongly suggested thermal motion of the C60 moiety with respect to the imidazolium heterocycle. Analysis of the anisotropic displacement parameters, calculations of frequencies, and the refinement of disorder models for the crystal at four temperatures (230 K≤T≤380 K) lead to the conclusion that the rotator is moving at all temperatures. The rotation barrier is low, with one preferred crystallographic site and several other energy minima. 相似文献
963.
Rubn Toscano Mnica Moya Carlos Amabile Guillermo Penieres Cecilio Alvarez 《Heteroatom Chemistry》2000,11(4):308-312
The synthesis, characterization and biological activity of N′‐trifluoromethanesulfonyl‐2‐aminopyridine in connection with our studies of trifluoromethanesulfonyl derivatives of the pyridine ring have been achieved. In solution an equilibrium (∼ 50:50%) of the amide and imide tautomeric forms was observed, while in the solid state only the imide form was present. Biological tests on the compound showed no effect either upon the growth of Escherichia coli or on Staphylococcus aureus in the agar diffusion tests; however, the growth of Enterococcus faecalis was effectively inhibited. © 2000 John Wiley & Sons, Inc. Heteroatom Chem 11:308–312, 2000 相似文献
964.
Ivana Marić Liangliang Yang Xiufeng Li Guillermo Monreal Santiago Charalampos G. Pappas Xinkai Qiu Joshua A. Dijksman Kirill Mikhailov Patrick van Rijn Sijbren Otto 《Angewandte Chemie (International ed. in English)》2023,62(14):e202216475
Dynamic covalent chemistry (DCC) has proven to be a valuable tool in creating fascinating molecules, structures, and emergent properties in fully synthetic systems. Here we report a system that uses two dynamic covalent bonds in tandem, namely disulfides and hydrazones, for the formation of hydrogels containing biologically relevant ligands. The reversibility of disulfide bonds allows fiber formation upon oxidation of dithiol-peptide building block, while the reaction between NH−NH2 functionalized C-terminus and aldehyde cross-linkers results in a gel. The same bond-forming reaction was exploited for the “decoration” of the supramolecular assemblies by cell-adhesion-promoting sequences (RGD and LDV). Fast triggered gelation, cytocompatibility and ability to “on-demand” chemically customize fibrillar scaffold offer potential for applying these systems as a bioactive platform for cell culture and tissue engineering. 相似文献
965.
Dr. Yue Zeng Prof. Haotian Bai Wen Yu Shengpeng Xia Dr. Qi Shen Prof. Yiming Huang Prof. Fengting Lv Prof. Guillermo C. Bazan Prof. Shu Wang 《Angewandte Chemie (International ed. in English)》2023,62(30):e202303877
A conductive polymer-based photosynthetic biohybrid is constructed to enhance biological nitrogen fixation by increasing nitrogenase activity in the non-photosynthetic bacterium Azotobacter Chroococcum (A. Chroococcum). The light-harvesting cationic poly(fluorene-alt-phenylene) (PFP) electrostatically binds to the surface of the bacteria and possesses satisfactory conductivity to facilitate electron transfer to the bacterium, promoting the nitrogen fixation pathway through redox proteins on the surface of the bacteria when under illumination. Therefore, the nitrogenase activity, hydrogen, NH4+-N and L-amino acids production are increased by 260 %, 37 %, 44 %, and 47 %, respectively. The expression levels of nifD and nifK encoding molybdenum-iron (MoFe) protein and relevant nitrogen-fixing proteins are up-regulated. These photoactive conductive polymer-bacteria biohybrids provide a new method for improving the biological nitrogen fixation capability of non-photosynthetic nitrogen-fixing bacteria. 相似文献
966.
We show an approximation theorem of Runge type for solutions of the generalized Vekua equation , where L belongs to a class of degenerate elliptic planar vector fields and . To prove the theorem, we make use of an integral representation for the solutions of the generalized Vekua equation valid on relatively compact sets. As an application, we study the global solvability of the equation with and some of its consequences. 相似文献
967.
Shivender Singh Saini Guillermo J. Copello Solange Binotto Fagan Mariana Zancan Tonel 《Journal of separation science》2023,46(8):2300012
Computationally and spectroscopically assisted analytical comparative investigation into the extraction of bisphenol A using three cyclodextrins, that is, α, β, and γ respectively, were performed. A simple, self-tailored μ-solid-phase extraction podium was used to extract bisphenol A from water samples, and high-performance liquid chromatography-ultraviolet was used for the qualitative and quantitative analysis of bisphenol A. Density functional theory first principle calculations, attenuated total reflectance Fourier-transform infrared spectroscopy and Fourier-transform Raman spectroscopy data supports the analytical selection of β-cyclodextrin as the adsorbent for bisphenol A extraction. Analytical optimization of various parameters including sample volume, sample pH, eluting solvent and its volume was performed to discover the most proper conditions for maximum extraction. Under the optimized conditions, a limit of detection value of 0.70 ng/ml and a limit of quantification value of 2.31 ng/ml was achieved with β-cyclodextrin, with recovery (%) values over 98.40–102.50 in real source water samples. Overall, well assisted by comprehensive computational and spectroscopic studies, a novel, simple, sensitive and economic analytical method was developed for the extraction of bisphenol A from source water using cyclodextrin. 相似文献
968.
Erik Geissler Anne-Marie Hecht Armel Guillermo Ferenc Horkay Jean Franois Legrand Simon Mallam 《Macromolecular Symposia》1993,76(1):163-174
Measurements of swelling pressure, neutron spin-echo scattering, and dynamic light scattering were made in an end-linked poly(dimethylsiloxane) (PDMS) gel swollen to equilibrium in a good solvent (toluene) and also in the equivalent solution. The macroscopic osmotic modulus is depressed in the gel. Neutron spin echo observations at intermediate and high values of the scattering vector Q reveal that the mobility of the monomers is unaffected by cross-linking. Elastic neutron scattering at small Q detects non-uniformities in the polymer concentration distribution, which are absent from the solution. These non-uniformities play a major role in the dynamic response of the system at lower Q, and and appear to be the cause of the observed reduction in osmotic pressure. 相似文献
969.
Francesco Ciardelli Angelina Altomare Giuseppe Conti Guillermo Arribas Bernardo Mendez Alida Ismayel 《Macromolecular Symposia》1994,80(1):29-44
Macromolecular ligands have been widely used in the past two decades with the objective of preparing structurally defined heterogeneous catalysts from soluble organometallic complexes. This activity has been largely reconsidered and focused on few specific systems. In this connection the present paper reviews recent data concerning the preparation of macromolecular metal complexes derived from transition metals which can produce active catalytic complexes for olefin polymerization and oligomerization and comparison is made about the suitability of both organic resins (crosslinked polystyrene) and inorganic materials (silica, alumina and zeolites). 相似文献