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991.
Tania Jiménez Sara P. Morcillo Ana Martín‐Lasanta Daniel Collado‐Sanz Prof. Dr. Diego J. Cárdenas Prof. Dr. Andreas Gansäuer Prof. Dr. José Justicia Prof. Dr. Juan M. Cuerva 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(40):12825-12833
A straightforward access to polyhydroxylated terpenoids based on two key titanocene(III)‐mediated reactions is presented: the “head‐to‐tail” Barbier‐type addition of prenyl chlorides to α,β‐unsaturated aldehydes, which allows the introduction of hydroxy groups at desirable positions of the acyclic precursor, and the subsequent bioinspired radical cyclisation. This methodology has been also used in the first total synthesis of pentacyclic sesterstatin 1 and a model compound of the C–D rings of aspergilloxide. 相似文献
992.
Dr. Filip S. Ekholm Dr. Ana Ardá Dr. Patrik Eklund Priv.‐Doz. Dr. Sabine André Prof. Dr. Hans‐Joachim Gabius Prof. Dr. Jesús Jiménez‐Barbero Prof. Dr. Reko Leino 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(45):14392-14405
Galactoglucomannan (GGM) is a polysaccharide mainly consisting of mannose, glucose, and galactose. GGM is the most abundant hemicellulose in the Norway spruce (Picea abies), but is also found in the cell wall of flax seeds, tobacco plants, and kiwifruit. Although several applications for GGM polysaccharides have been developed in pulp and paper manufacturing and the food and medical industries, attempts to synthesize and study distinct fragments of this polysaccharide have not been reported previously. Herein, the synthesis of one of the core trisaccharide units of GGM together with a less‐abundant tetrasaccharide fragment is described. In addition, detailed NMR spectroscopic characterization of the model compounds, comparison of the spectral data with natural GGM, investigation of the acetyl‐group migration phenomena that takes place in the polysaccharide by using small model compounds, and a binding study between the tetrasaccharide model fragment and a galactose‐binding protein (the toxin viscumin) are reported. 相似文献
993.
Hung J Castillo J Jiménez G Hasegawa M Rodriguez M 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2003,59(13):3177-3183
In this work we present spectroscopic study of Boldine (aporphine alkaloid) that possesses important biological activities, in particular, in interaction with the promastigotes of Leishmania mexicana. The results show the applicability of autofluorescence of this drug to determinate the possible mechanism of its biological action. The blue shift and hyperchromic effect in the emission spectrum of the drug in interaction with the parasite cells indicate an energy transference process between them. The morphological change of cell shape of the promastigotes treated with the drug is observed using confocal microscopy. This morphological cell-shape transformation evidences an important interaction between the drug studied and some protein of the parasite cell. Here we describe for the first time the fluorescence properties of the Boldine in the promastigotes of L. mexicana. 相似文献
994.
Yann Ferrand Dr. Emmanuel Klein Dr. Nicholas P. Barwell Matthew P. Crump Dr. Jesus Jiménez‐Barbero Prof. Cristina Vicent Dr. Geert‐Jan Boons Prof. Sampat Ingale Anthony P. Davis Prof. 《Angewandte Chemie (International ed. in English)》2009,48(10):1775-1779
Changing employment : Receptor 1 binds β‐N‐acetylglucosaminyl (β‐GlcNAc) up to 100 times more strongly than it does glucose. This synthetic lectin shows affinities similar to wheat germ agglutinin (WGA), a natural lectin used to bind GlcNAc. Remarkably, 1 is more selective than WGA. It favors especially the glycoside unit in glycopeptide 2 , a model of the serine‐O‐GlcNAc posttranslational protein modification.
995.
Haunschild R Henderson TM Jiménez-Hoyos CA Scuseria GE 《The Journal of chemical physics》2010,133(13):134116
Errors for systems with noninteger occupation have been connected to common failures of density functionals. Previously, global hybrids and pure density functionals have been investigated for systems with noninteger charge and noninteger spin state. Local hybrids have not been investigated for either of those systems to the best of our knowledge. This study intends to close this gap. We investigate systems with noninteger charge to assess the many-electron self-interaction error and systems with noninteger spin state to assess the spin polarization error of recently proposed local hybrids and their range-separated variants. We find that long-range correction is very important to correct for many-electron self-interaction error in cations, whereas most full-range local hybrids seem to be sufficient for anions, where long-range-corrected density functionals tend to overcorrect. On the other hand, while all hitherto proposed long-range-corrected density functionals show large spin polarization errors, the Perdew-Staroverov-Tao-Scuseria (PSTS) functional performs best of all local hybrids in this case and shows an outstanding behavior for the dependence of the energy on the spin polarization. 相似文献
996.
Manuel Algarra Iulius Bobos José Jiménez-Jiménez Ramón Moreno-Tost Enrique Rodríguez-Castellón Joaquim C. G. Esteves da Silva 《Journal of inclusion phenomena and macrocyclic chemistry》2010,67(1-2):225-232
The synthesis and characterization of cadmium sulphide (CdS) quantum dots, conjugated in a porous phosphate heterostructure functionalized with aminopropyl groups is described. The resulting material has fluorescence properties with maximum emission intensity at 575 nm. The fluorescent materials are not soluble in water and exhibit high stability in aqueous solution in the pH ranges from 2 to 9. Energy dispersive X-ray spectroscopy confirmed the qualitative elemental composition of the synthesized materials and X-ray photoelectron spectra showed a surface S/Cd atomic ratio of 1.09. SEM images show that the materials are amorphous, possessing porous with sizes of several tens nanometres, homogeneous and exhibit a layered morphology. The adsorption–desorption analysis by N2 at 77 K showed the accessibility of the CdS quantum dots onto the pores of the structure. The CdS quantum dots were stabilized by mercaptopropionic acid and bounded to the host materials by amine groups. 相似文献
997.
Marta León José Jiménez-Jiménez Antonio Jiménez-López Enrique Rodríguez-Castellón Dolores Soriano José M. López Nieto 《Solid State Sciences》2010,12(6):996-1001
Vanadium oxide–containing mesoporous materials, based on a surfactant expanded zirconium phosphate with silica galleries into the interlayer space, named porous phosphate heterostructure (PPH), were prepared by using TEOS and vanadium oxytripropoxide in n-propanol as sources of Si and V, respectively; with different Si/V molar ratios of 1, 2, 5 and 25; and calcining at 550 °C for 6 h. Using this method, vanadium can be partially incorporated to the structure of the gallery, but the surface area strongly decreases and the appearance of V2O5 crystallites increases when increasing the vanadium content. The catalysts were characterized by XRD, XPS, TEM, and Raman, and tested in the selective catalytic oxidation of H2S using a fixed bed reactor, at atmospheric pressure, at 180–260 °C. The catalysts with high contents of vanadium are very active at 200 °C, showing H2S conversions of 85–99%, with a high selectivity to elemental sulphur and with a low formation of SO2. Accordingly V2O5 crystallites can be proposed as active and selective although the catalytic behavior is related to the number of accessible V-sites in the surface of the catalyst. 相似文献
998.
Jim N Burnell 《BMC biochemistry》2010,11(1):1
Background
Phosphoenolpyruvate synthetase (PEPS; EC 2.7.9.2) catalyzes the synthesis of phosphoenolpyruvate from pyruvate in Escherichia coli when cells are grown on a three carbon source. It also catalyses the anabolic conversion of pyruvate to phosphoenolpyruvate in gluconeogenesis. A bioinformatics search conducted following the successful cloning and expression of maize leaf pyruvate, orthophosphate dikinase regulatory protein (PDRP) revealed the presence of PDRP homologs in more than 300 bacterial species; the PDRP homolog was identified as DUF299. 相似文献999.
Jiménez VA 《Journal of chemical information and modeling》2010,50(12):2176-2190
Herein, I report a DFT study on the bioactive conformation of epothilone A based on the analysis of 92 stable conformations of free and bound epothilone to a reduced model of tubulin receptor. The equilibrium structures and relative energies were studied using B3LYP and X3LYP functionals and the 6-31G(d) standard basis set, which was considered appropriate for the size of the systems under study. Calculated relative energies of free and bound epothilones led me to propose a new model for the bioactive conformation of epothilone A, which accounts for several structure-activity data. 相似文献
1000.
Fernanda Botelho James Jamison Antonio Jiménez-Vargas 《Journal of Mathematical Analysis and Applications》2012,386(2):910-920
We characterize projections on spaces of Lipschitz functions expressed as the average of two and three linear surjective isometries. Generalized bi-circular projections are the only projections on these spaces given as the convex combination of two surjective isometries. 相似文献