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61.
John Snyder Koji Nakanishi Gloria Chaverria Yolanda Leal Celso C. Ochoa Xorge A. Dominguez 《Tetrahedron letters》1981,22(50):5015-5018
The fruit extract of the Mexican shrub Sarg. has afforded castanaguyone ; it is the first biisocoumarin encountered in nature. 相似文献
62.
Daniel Butruille Xorge A. Dominguez Grard Teller 《Journal of mass spectrometry : JMS》1973,7(1):119-121
Mass spectra of three natural aromatic compounds are reported: 1,4-dimethoxy-2,3,5,6-tetrachlorobenzene (I), 4-methoxy-2,3,5,6-tetrachlorophenol (II) and 1,4-dimethoxy-2-nitro-3,5,6-trichlorobenzene (III). Main fragmentations are explained according to the formation of a quinoid structure (a), which leads under electron-impact to the formation of a chlorocyclopropenone ion (c). Secondary routes giving [CxCl]+ ions are also proposed. Emphasis is given to the variations introduced into the fragmentation by the presence of a nitro group. 相似文献
63.
Dominguez Z Dang H Strouse MJ Garcia-Garibay MA 《Journal of the American Chemical Society》2002,124(11):2398-2399
We describe our efforts toward the preparation of materials built with molecules possessing topologies analogous to those of macroscopic compasses and gyroscopes. Samples of 1,4-bis(3,3,3-triphenylpropynyl)benzene (3) were prepared by a simple two-step procedure from triphenylmethyl chloride (1) and 1,4-diiodobenzene. The structure of compound 3 is such that the central phenylene can play the role of a gyroscope wheel while the two tritylpropynyl groups can act as an axle and shielding framework. Crystals of a benzene clathrate were characterized by single crystal X-ray diffraction and variable-temperature solid state NMR while their thermal stability was determined by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The rotational dynamics of the phenylene group in the benzene clathrate and in desolvated samples were characterized in terms of a two-fold flipping process. Solid state rotational barriers of ca. 12.8 and 14.6 kcal/mol were estimated for the benzene clathrate and desolvated samples, respectively. 相似文献
64.
Peter Agback Andrey Shernyukov Francisco Dominguez Tatiana Agback Elena I. Frolova 《Molecules (Basel, Switzerland)》2020,25(24)
In recent years, intrinsically disordered proteins (IDPs) and disordered domains have attracted great attention. Many of them contain linear motifs that mediate interactions with other factors during formation of multicomponent protein complexes. NMR spectrometry is a valuable tool for characterizing this type of interactions on both amino acid (aa) and atomic levels. Alphaviruses encode a nonstructural protein nsP3, which drives viral replication complex assembly. nsP3 proteins contain over 200-aa-long hypervariable domains (HVDs), which exhibits no homology between different alphavirus species, are predicted to be intrinsically disordered and appear to be critical for alphavirus adaptation to different cells. Previously, we have shown that nsP3 HVD of chikungunya virus (CHIKV) is completely disordered with low tendency to form secondary structures in free form. In this new study, we used novel NMR approaches to assign the spectra for the nsP3 HVD of Venezuelan equine encephalitis virus (VEEV). The HVDs of CHIKV and VEEV have no homology but are both involved in replication complex assembly and function. We have found that VEEV nsP3 HVD is also mostly disordered but contains a short stable α-helix in its C-terminal fragment, which mediates interaction with the members of cellular Fragile X syndrome protein family. Our NMR data also suggest that VEEV HVD has several regions with tendency to form secondary structures. 相似文献
65.
Efstratios N. Pistikopoulos Luis Dominguez Christos Panos Konstantinos Kouramas Altannar Chinchuluun 《Computational Management Science》2012,9(2):183-203
This paper presents an overview of recent theoretical and algorithmic advances, and applications in the areas of multi-parametric
programming and explicit/multi-parametric model predictive control (mp-MPC). In multi-parametric programming, advances include
areas such as nonlinear multi-parametric programming (mp-NLP), bi-level programming, dynamic programming and global optimization
for multi-parametric mixed-integer linear programming problems (mp-MILPs). In multi-parametric/explicit MPC (mp-MPC), advances
include areas such as robust multi-parametric control, multi-parametric nonlinear MPC (mp-NMPC) and model reduction in mp-MPC.
A comprehensive framework for multi-parametric programming and control is also presented. Recent applications include a hydrogen
storage device, a fuel cell power generation system, an unmanned autonomous vehicle (UAV) and a hybrid pressure swing adsorption
(PSA) system. 相似文献
66.
Maxime Charman Frédéric Léonardi Sébastien Dominguez Cédric Bissuel Christophe Derail 《Journal of Polymer Science.Polymer Physics》2011,49(22):1597-1604
The dispersion of multiwalled carbon nanotubes (CNTs) in an ethylene propylene rubber matrix was investigated using an internal mixer. Poly(ethylene‐co‐polyvinyl acetate) (EVA) statistic copolymer was used as a dispersing agent. The effects of the concentration of the dispersing agent and the matrix viscosity on the quality of the dispersion of 1 wt % of CNTs were studied by using microscopy and rheology in the melt state. It was demonstrated that the dispersion is governed principally by the viscosity of the matrix. As expected, better dispersion was observed when the matrix exhibited a lower viscosity. The influence of the filler content on the rheological and electrical properties is presented. A Cross model with a yield stress is proposed to describe the rheological behavior of these materials, which exhibit a viscoelastic solid behavior from 1 wt % CNT content. Electrical measurement data indicate that the electrical percolation threshold was 2.9 wt %. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 49: 1597–1604, 2011 相似文献
67.
D. Dominguez J. M. Romo-Herrera F. Solorio H. A. Borbón-Núñez M. Landeros J. N. Díaz de León E. Contreras O. E. Contreras A. Olivas E. A. Reynoso-Soto H. Tiznado G. Soto 《Journal of nanoparticle research》2018,20(9):246
This work addresses the production of stand-alone ceramic nanotubes by the template-based ALD method at low temperature. Nitrogen-doped multiwalled carbon nanotubes (CNTs) were coated with ZnO. Afterward, the template removal was evaluated by two different approaches: using oxidation in dry air or in an ozone-rich atmosphere. The samples treated by the two different methods were analyzed by XRD, TEM, SAED, and Raman spectroscopy. The dry air atmosphere requires high temperatures (~?700 °C) for a complete CNT removal; at that temperature, the ZnO tubular shape is completely collapsed due to recrystallization. Under ozone atmosphere, the template can be removed at temperatures as low as 85 °C; this temperature is lower than the ALD preparation temperature (120 °C). The ozone treatment maintains the tubular shape of the ZnO nanostructures. Photocatalytic activity of the ZnO samples was evaluated using the photo-oxidation of Amaranth as probe reaction, showing a higher activity the ZnO nanotubes obtained from the low-temperature ozone treatment than the high-temperature processed materials. The use of ozone for the template removal reinforces the template-based ALD method to produce inorganic nanotubes. 相似文献
68.
Martinez AV DeSensi SC Dominguez L Rivera E Straub JE 《The Journal of chemical physics》2011,134(5):055107
Characterization of the molecular interactions that stabilize the folded state of proteins including hydrogen bond formation, solvation, molecular crowding, and interaction with membrane environments is a fundamental goal of theoretical biophysics. Inspired by recent experimental studies by Gai and co-workers, we have used molecular dynamics simulations to explore the structure and dynamics of the alanine-rich AKA(2) peptide in bulk solution and in a reverse micelle environment. The simulated structure of the reverse micelle shows substantial deviations from a spherical geometry. The AKA(2) peptide is observed to (1) remain in a helical conformation within a spherically constrained reverse micelle and (2) partially unfold when simulated in an unconstrained reverse micelle environment, in agreement with experiment. While aqueous solvation is found to stabilize the N- and C-termini random coil portions of the peptide, the helical core region is stabilized by significant interaction between the nonpolar surface of the helix and the aliphatic chains of the AOT surfactant. The results suggest an important role for nonpolar peptide-surfactant and peptide-lipid interactions in stabilizing helical geometries of peptides in reverse micelle environments. 相似文献
69.
70.
We demonstrate that a commercial instrument that provides measurements of 18O/16O and D/H ratios in water samples can be modified to also provide measurements of 17O/16O. This additional capability and associated precision allows for the discernment between conventional mass-dependent processes, such as isotope exchange and evaporation and mass-independent processes that arise from non-equilibrium chemical and photochemical processes. We demonstrate this resolution by performing a series of experiments including evaporation and reservoir-mixing with 17O enriched water samples followed by evaporation. The ability to simultaneously measure 16O, 17O, and 18O abundances in water samples using the procedures described here should help to facilitate multi-isotopic studies of water (and other compounds) in astrochemical, geochemical, and biological studies. 相似文献