Highly Efficient Synthesis of Optically Pure (S)-1-phenyl-1,2-ethanediol by a Self-Sufficient Whole Cell Biocatalyst

Terminal vicinal diols are important chiral building blocks and intermediates in organic synthesis. Reduction of α-hydroxy ketones provides a straightforward approach to access these important compounds. In this study, it has been found that asymmetric reduction of a series of α-hydroxy aromatic ketones and 1-hydroxy-2-pentanone, catalyzed by Candida magnolia carbonyl reductase (CMCR) with glucose dehydrogenase (GDH) from Bacillus subtilis for cofactor regeneration, afforded 1-aryl-1,2-ethanediols and pentane-1,2-diol, respectively, in up to 99 % ee. In order to evaluate the efficiency of the bioreduction, lyophilized recombinant Escherichia coli whole cells coexpressing CMCR and GDH genes were used as the biocatalyst and α-hydroxy acetophenone as the model substrate, and the reaction conditions, such as pH, cosolvent, the amount of biocatalyst and the presences of a cofactor (i.e., NADP⁺), were optimized. Under the optimized conditions (pH 6, 16 h), the bioreduction proceeded smoothly at 1.0 m substrate concentration without the external addition of cofactor, and the product (S)-1-phenyl-1,2-ethanediol was isolated with 90 % yield and 99 % ee. This offers a practical biocatalytic method for the preparation of these important vicinal diols.     

Enantioselective Total Syntheses of (−)-20-epi-Vincamine and (−)-20-epi-Eburnamonine by Ir-Catalyzed Asymmetric Imine Hydrogenation/Lactamization Cascade

The Eburnamine-Vincamine alkaloids have been studied intensively over the past six decades for their outstandingly potent vasorelaxation activity. Stereocontrolled assembly of the C20/C21 adjacent chiral centers has been a formidable challenge in the synthesis of this family. Herein, we report a concise stereoselective total synthesis of two trans-ring-fused non-natural analogues, (−)-20-epi-Vincamine and (−)-20-epi-Eburnamonine, that features the following key steps: a) a continuous-flow oxidation/lactam alcoholysis cascade producing the symmetrical dihydro-β-carboline diester precursors, and b) a highly stereoselective Ir/f-Binaphane-catalyzed hydrogenation/lactamization cascade leading to the privileged trans-(20R, 21S) lactam ester scaffold with high-level enantio- and diastereocontrol.     

宇宙中最神秘的一种天体--类星体

为纪念相对论发表100周年，联合国大会通过决议，将今年命名为“国际物理年”．在国际物理年中，天文学也是不可缺少的内容．当年，爱因斯坦的广义相对论只能用天文学来检验；物理学发展到今天，更是和天文学息息相关．李政道先生把宇宙中的暗物质作为21世纪物理学前沿的主要课题之一．近代天体物理学提出的问题一个个都向物理学提出了挑战．其中，有一种神秘的天体，从20世纪60年代跨越到21世纪，观测、观测、再观测，却始终没有得到满意的答案，它就是类星体．     

Quantification of pegylated liposomal doxorubicin and doxorubicinol in rat plasma by liquid chromatography/electrospray tandem mass spectroscopy: Application to preclinical pharmacokinetic studies

A high-performance liquid chromatography-tandem mass spectrometric method (LC/MS/MS) has been developed and validated for the determination of pegylated liposomal doxorubicin and its metabolite doxorubicinol in rat plasma. One hundred microliters plasma samples were treated with Triton X-100 to immediately disperse the liposome. Then the samples were extracted by a single methanol:acetone protein precipitation step in the presence of additional 50microL of 70% (w/v) zinc sulfate, and subsequently analyzed by LC/MS/MS using positive turbo-ion spray ionization mode operating the instrument in the multiple-reaction-monitoring (MRM) mode. The related compound daunorubicin was used as internal standard. The validated concentration ranges were from 20 to 8000ng/mL for doxorubicin and from 0.05 to 20.0ng/mL for doxorubicinol. An effective LC-MS/MS method was developed to quantify trace amount of doxorubicinol with little interference from doxorubicin. The autosampler carryover was minimized from 285 to 10.5% by increasing the washing times of the valves when the used pentafluorophenylpropyl HPLC column had no contribution to the carryover. The relative matrix effect from six unique lots was absent for both compounds. Results obtained from the GLP validation study demonstrated good accuracy (85-110%) and precision (CV less than 14%) across the calibration ranges for both compounds. This method was applied to study the pharmacokinetic profiles of doxorubicin and doxorubicinol in rats after a single dose administration of Stealth-49 liposomal doxorubicin HCl. The mean AUC value for doxorubicinol was found to be only 0.011% of that of doxorubicin.     

Parameter estimation for chaotic systems by hybrid differential evolution algorithm and artificial bee colony algorithm

This paper is concerned with the parameter estimation of nonlinear chaotic system, which could be essentially formulated as a multi-dimensional optimization problem. In this paper, a hybrid algorithm by combining differential evolution with artificial bee colony is implemented to solve parameter estimation for chaotic systems. Hybrid algorithm combines the exploration of differential evolution with the exploitation of the artificial bee colony effectively. Experiments have been conducted on Lorenz system and Chen system. The proposed algorithm is applied to estimate the parameters of two chaotic systems. Simulation results and comparisons demonstrate that the proposed algorithm is better or at least comparable to differential evolution, artificial bee colony, particle swarm optimization, and genetic algorithm from literature when considering the quality of the solutions obtained.     

Anti-Symmetric Electromagnetic Interactions’ Response in Electron Circular Dichroism and Chiral Origin of Periodic,Complementary Twisted Angle in Twisted Bilayer Graphene

Many novel physical properties of twisted bilayer graphene have been discovered and studied successively, but the physical mechanism of the chiral modulation of BLG by a twisted angle lacks theoretical research. In this work, the density functional theory, the wavefunction analysis of the excited state, and the quantum theory of atoms in molecules are used to calculate and analyze the anti-symmetric chiral characteristics of zigzag-edge twisted bilayer graphene quantum dots based on periodic complementary twisted angles. The analysis of the partial density of states shows that Moiré superlattices can effectively adjust the contribution of the atomic basis function of the fragment to the transition dipole moment. The topological analysis of electron density indicates that the Moiré superlattices structure can enhance the localization of the system, increasing the electron density of the Moiré central ring, reducing the electron surge capacity in general and inducing the reversed helical properties of the top and underlying graphene, which can be used as the origin of the chiral discrimination; it also reveals the mole in the superlattice chiral physical mechanism. On this basis, we will also study the nonlinear optical properties of twisted bilayer graphene based on a twisted angle.     

Improvement of electrochemical properties of MgO-coated LiNi0.4Co0.2Mn0.4O2 cathode materials for lithium ion batteries

The surface of LiNi_0.4Co_0.2Mn_0.4O₂ cathode is coated using MgO coating materials. The electrochemical properties of the coated materials are investigated as a function of the pH value of the coating solution and the composition of coating materials. Their microscopic structural features have been investigated using scanning electron microscopy and X-ray diffraction. The electrochemical properties of the samples were monitored using coin-cell by galvanostatic charge–discharge cycling test, EDS test, EIS test, and cyclic voltammetry. The coating solution with pH?=?10.5 is found to be favorable for the formation of stable coating layers, which enhances the electrochemical properties. In contrast, 2 % MgO-coated LiNi_0.4Co_0.2Mn_0.4O₂ shows better cycle performance and rate capability than the bare sample. Such enhancements are attributed to the presence of a stable MgO layer which acts as the interfacial stabilizer on the surface of LiNi_0.4Co_0.2Mn_0.4O₂.     

Validated hydrophilic interaction LC-MS/MS method for determination of 2-pyrrolidinone residue: applied to a depletion study of 2-pyrrolidinone in swine liver

A hydrophilic interaction high-performance liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) method for determination of 2-pyrrolidinone in swine liver was developed and validated. After the fortification of 2-pyrrolidinone-d₆ as the internal standard, 2-pyrrolidinone in swine liver was extracted by acetonitrile, and the supernatant was led through a C18 + WAX mixed-mode solid phase extraction (SPE) cartridge. Furthermore, the eluate was adjusted to pH 5.0 and then led through a strong cationic exchange SPE cartridge. 2-Pyrrolidinone and 2-pyrrolidinone-d₆ were concentrated and eluted by acetonitrile containing 2% ammonium hydroxide. The final eluate was acidified and then injected for hydrophilic interaction LC-MS/MS analysis. Mass spectrometry detection was carried using positive turbo-ion spray ionization mode. The multiple reaction monitoring transitions were 86 → 69 for 2-pyrrolidinone and 92 → 75 for 2-pyrrolidinone-d₆. The C18 + WAX mixed-mode SPE cleanup greatly prevented the rapid contamination of mass spectrometer. The further SCX SPE cleanup thoroughly eliminated the absolute matrix effect. Solvent calibration standards could be readily used for quantitative analysis of 2-pyrrolidinone with excellent precision and accuracy. Endogenous levels of 2-pyrrolidinone in some blank matrices was readily determined. Full recoveries were readily achieved by the optimize extraction protocol, and thus the role of 2-pyrrolidinone-d₆ was to just compensate the variation of the injections. The detection limit was 5 ng g⁻¹ swine liver. The validated method was applied to a depletion study of 2-pyrrolidinone in swine liver following intramuscular administration of a drug 2-pyrrolidinone formulation. The matrix effect from tissue samples usually represented a technical challenge for LC-MS/MS analysis, and a very small molecule such as 2-pyrrolidinone also represented a technical barrier for LC-MS/MS analysis. However, the extraction protocol developed in the present study reached the best outcome: zero matrix effect and full recovery.     

The Formation of Surface Lithium–Iron Ternary Hydride and its Function on Catalytic Ammonia Synthesis at Low Temperatures

Lithium hydride (LiH) has a strong effect on iron leading to an approximately 3 orders of magnitude increase in catalytic ammonia synthesis. The existence of lithium–iron ternary hydride species at the surface/interface of the catalyst were identified and characterized for the first time by gas-phase optical spectroscopy coupled with mass spectrometry and quantum chemical calculations. The ternary hydride species may serve as centers that readily activate and hydrogenate dinitrogen, forming Fe-(NH₂)-Li and LiNH₂ moieties—possibly through a redox reaction of dinitrogen and hydridic hydrogen (LiH) that is mediated by iron—showing distinct differences from ammonia formation mediated by conventional iron or ruthenium-based catalysts. Hydrogen-associated activation and conversion of dinitrogen are discussed.     

CO oxidation on the heterodinuclear tantalum-nickel monoxide carbonyl complex anions

The series of heterodinuclear metal oxide carbonyls in the form of TaNiO(CO)_n(n=5-8) are generated in the pulsed-laser vaporization source and characterized by mass-selected photoelectron velocity-map spectroscopy.During the consecutive CO adsorption,the μ~2-O-bent structure initially is the most favorable for TaNiO(CO)_5,and subsequently both μ~2-O-bent and μ~2-O-linear structures are degenerate for TaNiO(CO)_6,then the μ~2-O-linear structure is most preferential for TaNiO(CO)_7,and finally theη_2-CO_2-tagged structure is the most ene rgetically competitive one for TaNiO(CO)_8,i.e., the CO oxidation occurs at n=8.ln contrast to the literature reported CO oxidation on heteronuclear metal oxide complexes generally proceeding via Langmuir-Hinshelwood-like mechanism,complementary theo retical calculations suggest that both Langmuir-Hinshelwood-like and Eley-Rideal-like mechanisms prevail for the CO oxidation reaction on TaNiO(CO)_8 complex.Our findings provide new insight into the composition-selective mechanism of CO oxidation on heteronuclear metal complexes,of which the composition be tailored to fulfill the desired chemical behaviors.