Molecular dynamics simulations of a nucleoside analogue of 1,4-dihydro-4-oxoquinoline-3-carboxylic acid synthesized as a potential antiviral agent: Conformational studies in vacuum and in water

Conformational analysis of nucleosides may have direct applications to the structure–activity relationship (SAR) studies and in the design of new drug candidates. Although conformational analysis may be accessed in many different ways, in this work it was performed using molecular dynamics (MD) simulation in order to study the dynamic behavior of a nucleoside derivative of 1,4-dihydro-4-oxoquinoline-3-carboxylic acid, synthesized by our group as a potential antiviral agent. The MD simulation was carried out during 10 ns in vacuum and in a box of water at two different temperatures (i.e., 300 and 600 K) using the AMBER force field. The in vacuum MD simulation results are in agreement with the crystallographic structure and with the DFT calculations of the nucleoside, revealing the anti conformer as the more stable one. The simulation in water, however, shows that both conformers may exist at 300 K, the temperature of the in vivo and in vitro assays, revealing that both the syn and anti conformers should be considered in a MD simulation study of the inhibitor–enzyme complex. Simulations are also in agreement with the NOE experiment, which shows that the anti conformer is the preferential one in DMSO-d6 solution at 298 K.     

New efficient organocatalytic oxidation of benzylic compounds by molecular oxygen under mild conditions

Efficient aerobic oxidation of benzylic compounds has been achieved under no irradiation using a new organocatalytic system in the presence of acridine yellow and N-hydroxyphthalimide with assistance of a catalytic amount of molecular bromine. Various substrates, especially alkylaromatics, were effectively oxygenated to the corresponding carbonyl compounds with molecular oxygen as oxidant under mild conditions. For instance, indan was oxidized with 92% conversion and 79% selectivity for 1-indanone under 0.3 MPa of O₂ at 75 °C.     

Tweezer分子的合成和对有机阴离子的配位效应

本文报道新的Ｔｗｅｅｚｅｒ（１）的合成，用＾１ＨＮＭＲ研究了新的Ｔｗｅｅｚｅｒ分子和对硝基苯甲酸盐的配位效应，结果表明它兴通过氢键，静电引力和芳环夹心堆叠作用而自动缔合。     

N－（N＇，N＇－二甲氨基甲基）丙烯酰胺－过硫酸钾引发丙烯酰胺聚合的研究

Ｎ－（Ｎ＇，Ｎ＇－二甲氨基甲基）丙烯酰胺－过硫酸钾引发丙烯酰胺聚合的研究潘松汉，唐康泰，王贞，王真智中国科学院广州化学研究所，广州，５１０６５０关键词Ｎ－（Ｎ＇，Ｎ＇－二甲氨基甲基）丙烯酰胺、反应动力学、氧化还原体系、相对分子质量及分布为了制备高质量...     

Solubility of carbazole in binary chloroalkane + dibutyl ether solvent mixtures

Solubilities are reported for carbazole in three binary chloroalkane + dibutyl ether solvent mixtures at 25°C. Results of these measurements are compared with solution models developed for solubility in systems containing specific solute-solvent interactions. A simple model based on a single 1:1 carbazole:dibutyl ether complex described the solubility data, though the calculated equilibrium constant was about one-half of values published previously. A more sophisticated solution model, which assumes both carbazole:dibutyl ether and carbazole:chloroalkane complexes, was needed to thermodynamically describe the systems studied. Equilibrium constants for three presumed carbazole:chloroalkane complexes are calculated from measured carbazole solubilities.     

Evolution of antibodies for environmental monitoring: from mice to plants

Immunoassays are one of the most convenient methods for environmental monitoring, but have been limited so far by low yield and low affinity antibodies (Abs). With the advent of recombinant Ab (rAb) technology and the expression of these Abs in organisms such as yeast, bacteria, insects and plants, widespread monitoring of our food and environment for organic contaminants using immunoassays has become feasible. A multitude of immunoassays have been developed to detect pesticides in soils, ground and river water, foods and biological samples, such as urine and semen. In this paper, we describe advances in Ab production, the move away from using animals, phage-display technologies and the advent of plant-derived Ab expression systems. Finally, we describe future possibilities in Ab technology for environmental monitoring.     

Selective formation of heterodimeric resorcinarene capsules

C_2V-symmetrical resorcinarene tetraesters 1 form in CDCl₃ dimeric capsules encapsulating one Me₄N⁺ cation. The homodimeric capsules of the tetra(3,4,5-trimethoxybenzoate) 1d and tetrabenzoate 1b or tetrafuroylate 1c disproportionate in solution to give quantitatively the heterodimers. The higher stability of the heterodimer is, most probably, caused by π-π attractions between the π-basic trimethoxyphenyl rings of 1d and relatively more π-accepting phenyl or furyl fragments of 1b or 1c.     

Dielectric studies of binary mixtures of n -propyl alcohol and ethylenediamine

Dielectric constant (ε’) and dielectric loss (ε") of n-propyl alcohol (PA), ethylenediamine (EDA) and their binary mixtures, for different mole fractions of ethylenediamine have been experimentally measured at 11.15 GHz microwave frequency. Values of density (ρ), viscosity (η) and square refractive index (n _D ² ) of binary mixtures as well as those of pure liquids are reported. Excess square refractive index, viscosity and activation energy of viscous flow have also been estimated. These parameters have been used to explain the formation of complexes in the system.     

Tailoring approach for exploring electron densities and electrostatic potentials of molecular crystals

Experimental and theoretical studies of electron densities and the corresponding derived entities such as electrostatic potentials have been the primary means of understanding the chemical nature and electronic properties of crystalline substances. Conventional crystal calculation methods such as the embedded cluster models are capable of performing calculations on small and medium-sized molecules, while periodic ab initio methods can treat crystals with up to 200 atoms per unit cell. A linear scaling method, viz. the molecular tailoring approach, has recently been developed for obtaining ab initio quality one-electron properties. In the present study, the molecular tailoring approach is employed to generate electron density, electrostatic potential and interaction density maps with the ibuprofen crystal as a test case. The interaction density and electrostatic potential maps produced in the present work succinctly bring out the actual crystalline environment around a given reference molecule by including the interactions with atoms in its neighborhood. The results obtained from the molecular tailoring approach may thus be expected to enhance our understanding of the environment in the crystalline material with reasonably small computational effort.Contribution to the Jacopo Tomasi Honorary Issue     

Aerobic alcohol oxidation catalyzed by a new, oxygen-bridged heterometallic compound [PPh4][Ru(N)Me2(μ2-O)2Pd((−)-sparteine)]

The reaction between the new hydroxy compound [PPh₄][Ru(N)(OH)₂Me₂] and Pd(OSiMe₃)₂((−)-sparteine) produces (Me₃Si)₂O, H₂O and a new heterobimetallic compound [PPh₄][Ru(N)Me₂(μ₂-O)₂Pd((−)-sparteine)] in good yield. The Ru/Pd bimetallic compound catalyzes the oxidation of aryl and allyl alcohols to the corresponding carbonyl compound in air and the rearrangement of allylic alcohols unsaturated aldehydes. It also oxidizes PPh₃ to O-PPh₃ under O₂.