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61.
Both preferential sorption and second virial coefficients for PMMA-CCl4-chloroalkane (butyl chloride, sec. butyl chloride and tert. butyl chloride) have been studied by laser light scattering and differential refractometry of equilibrium dialysis at 298 K. The results indicate that the chloroalkane is always preferentially adsorbed on PMMA. In order to predict the experimental values of the preferential sorption coefficient, Read's equation has been used. 相似文献
62.
We have studied the variation of the cosolvent power for PMMACCl4—chloroalkane (butyl chloride, sec.butyl chloride and tert.butyl chloride) systems. The results indicate that, when the polarity and branching of the chloroalkane increase, the cosolvent power of the binary solvent mixture decreases. 相似文献
63.
Palacios F Ochoa de Retana AM Oyarzabal J Pascual S Fernández de Trocóniz G 《The Journal of organic chemistry》2008,73(12):4568-4574
A simple and efficient stereoselective synthesis of fluorine containing beta-aminophosphonates by reduction of beta-enaminophosphonates is described. Reduction with sodium cyanborohydride in the presence of zinc chloride and the catalytic hydrogenation of beta-enaminophosphonates gives beta-aminophosphonates. beta-Enaminophosphonates are also used as intermediates for the regioselective synthesis of fluoroalkyl-substituted pyridines. 相似文献
64.
Rodrigo Ochoa Stanley J. Watowich Andrés Flórez Carol V. Mesa Sara M. Robledo Carlos Muskus 《Journal of computer-aided molecular design》2016,30(7):541-552
The trypanosomatid protozoa Leishmania is endemic in ~100 countries, with infections causing ~2 million new cases of leishmaniasis annually. Disease symptoms can include severe skin and mucosal ulcers, fever, anemia, splenomegaly, and death. Unfortunately, therapeutics approved to treat leishmaniasis are associated with potentially severe side effects, including death. Furthermore, drug-resistant Leishmania parasites have developed in most endemic countries. To address an urgent need for new, safe and inexpensive anti-leishmanial drugs, we utilized the IBM World Community Grid to complete computer-based drug discovery screens (Drug Search for Leishmaniasis) using unique leishmanial proteins and a database of 600,000 drug-like small molecules. Protein structures from different Leishmania species were selected for molecular dynamics (MD) simulations, and a series of conformational “snapshots” were chosen from each MD trajectory to simulate the protein’s flexibility. A Relaxed Complex Scheme methodology was used to screen ~2000 MD conformations against the small molecule database, producing >1 billion protein-ligand structures. For each protein target, a binding spectrum was calculated to identify compounds predicted to bind with highest average affinity to all protein conformations. Significantly, four different Leishmania protein targets were predicted to strongly bind small molecules, with the strongest binding interactions predicted to occur for dihydroorotate dehydrogenase (LmDHODH; PDB:3MJY). A number of predicted tight-binding LmDHODH inhibitors were tested in vitro and potent selective inhibitors of Leishmania panamensis were identified. These promising small molecules are suitable for further development using iterative structure-based optimization and in vitro/in vivo validation assays. 相似文献
65.
Gerardo Ochoa Corey D. Pilgrim Michele N. Martin Christopher A. Colla Peter Klavins Prof. Matthew P. Augustine Prof. William H. Casey 《Angewandte Chemie (International ed. in English)》2015,54(51):15444-15447
Nuclear spin relaxation rates of 2H and 139La in LaCl3+2H2O and La(ClO4)3+2H2O solutions were determined as a function of pressure in order to demonstrate a new NMR probe designed for solution spectroscopy at geochemical pressures. The 2H longitudinal relaxation rates (T1) vary linearly to 1.6 GPa, consistent with previous work at lower pressures. The 139La T1 values vary both with solution chemistry and pressure, but converge with pressure, suggesting that the combined effects of increased viscosity and enhanced rates of ligand exchange control relaxation. This simple NMR probe design allows experiments on aqueous solutions to pressures corresponding roughly to those at the base of the Earth’s continental crust. 相似文献
66.
Adrian Tlahuext‐Aca Prof. Dr. Herbert Höpfl Felipe Medrano‐Valenzuela Jorge Guerrero‐Alvarez Hugo Tlahuext Karen Ochoa Lara Viviana Reyes‐Márquez Margarita Tlahuextl 《无机化学与普通化学杂志》2012,638(11):1731-1738
Nine mononuclear diorganotin(IV) dithiocarbamate complexes 1 – 9 with 19‐, 20‐ and 21‐membered macrocyclic structures were synthesized from dimethyl, di‐n‐butyl, and diphenyltin(IV) dichloride and three bis‐dithiocarbamate ligands derived from secondary bis‐amines having aromatic spacer groups. All compounds were characterized by elemental analysis, mass spectrometry, and spectroscopic methods (IR and 1H, 13C, and 119Sn NMR). Additionally, quantum chemical DFT calculations were performed for the dimethyltin(IV) derivatives in order to model the molecular structures. For one compound series the NMR spectra showed a concentration‐dependent behavior in solution, which was analyzed in detail and permitted to postulate the existence of an equilibrium with the corresponding [2+2] macrocycles. 相似文献
67.
G. Martin N. Ochoa K. Saï E. Hervé-Luanco G. Cailletaud 《International Journal of Solids and Structures》2014
A mean field mechanical model describing the inelastic behavior and strong anisotropy of Directionally Solidified (DS) materials is developed. Its material parameters are calibrated by comparison with the Finite Element (FE) computation of a Representative Volume Element (RVE). In the case of a large grain alloy where microstructure size cannot be neglected with respect to geometrical variations, this approach is a good candidate to evaluate the local scatter coming from the material heterogeneity. 相似文献
68.
A 3-3-1 model is constructed for three families that can be embedded into a single SU(8) unified model. Assuming appropriate branching rules and symmetry-breaking pattern, a complete fermion content is found within irreducible representations of SU(8), where light Standard Model fermions, heavy 3-3-1 fermions and superheavy fermions may be distinguished. 相似文献
69.
Laura Rivard Jagan Srinivasan Allison Stone Stacy Ochoa Paul W Sternberg Curtis M Loer 《BMC neuroscience》2010,11(1):22
Background
Survival of an animal depends on its ability to match its responses to environmental conditions. To generate an optimal behavioral output, the nervous system must process sensory information and generate a directed motor output in response to stimuli. The nervous system should also store information about experiences to use in the future. The diverse group of free-living nematodes provides an excellent system to study macro- and microevolution of molecular, morphological and behavioral character states associated with such nervous system function. We asked whether an adaptive behavior would vary among bacterivorous nematodes and whether differences in the neurotransmitter systems known to regulate the behavior in one species would reflect differences seen in the adaptive behavior among those species. Caenorhabditis elegans worms slow in the presence of food; this 'basal' slowing is triggered by dopaminergic mechanosensory neurons that detect bacteria. Starved worms slow more dramatically; this 'enhanced' slowing is regulated by serotonin. 相似文献70.
We generalize the Poland-Scheraga model to consider DNA denaturation in the presence of an external stretching force. We demonstrate the existence of a force-induced DNA denaturation transition and obtain the temperature-force phase diagram. The transition is determined by the loop exponent c, for which we find the new value c = 4 nu-1/2 such that the transition is second order with c = 1.85 < 2 in d = 3. We show that a finite stretching force F destabilizes DNA, corresponding to a lower melting temperature T(F), in agreement with single-molecule DNA stretching experiments. 相似文献