Copper-catalyzed arylation of amines using diphenyl pyrrolidine-2-phosphonate as the new ligand

[Chemical reaction: See text] We have developed a general, efficient, and inexpensive catalyst system for arylation of amines by using 10 mol % of CuI as the copper source, 20 mol % of diphenyl pyrrolidine-2-phosphonate (DPP) as the ligand, K3PO4 as the base, and DMF containing 2% water (v/v) as the solvent.     

新显色剂4,4′-二偶氮苯重氮氨基偶氮苯测定水中微量锌的研究

本文报告在四硼酸钠体系中和Triton X-100存在下,锌与新显色剂4,4′-二偶氮苯重氮氨基偶氮苯有灵敏的显色反应。红色络合物在525nm处摩尔吸光系数为1.63×10~5L·mol~(-1)·cm~(-1),并研究了测定锌的各种条件和40余种共存离子对测定的影响。     

Positioning isolation and biochemical analysis of single DNA molecules based on nanomanipulation and single-molecule PCR

Recently, the isolation and biochemical analysis of DNA at the single-molecule level has been recognized as very important for genetic research and clinical analysis. A unique technique for the positioning, dissection, and isolation of single DNA molecules using atomic force microscopy (AFM) has been demonstrated. Full-length genome DNA molecules were first deposited and stretched by a modified "molecular combing" technique onto a 3-aminopropyl triethoxysilane-coated mica substrate. A single DNA fragment was dissected from one of those genome DNA strands with the AFM tip at the desired position, and then isolated (or picked up) after a special operation called "kneading". All the operations including imaging, dissection, and isolation could be carried out with one tip. The isolated DNA fragment on the AFM tip could be successfully amplified by single-molecule PCR.     

Semiempirical Molecular Orbital Studies of the Acylation Step in the Lipase‐Catalyzed Ester Hydrolysis

In this study, we present the results from the semiempirical molecular orbital calculations for the acylation step in the lipase‐catalyzed ester hydrolysis. The results reveal that the lowest energy path for the formation of the tetrahedral intermediate is for the serine residue of the catalytic triad to attack the substrate, followed by coupling heavy atom movement and proton transfer. The calculations of four active site models show that the cooperation of the aspartate group and the oxyanion hole is capable of lowering the activation energy by about 16 kcalmol^?1. Our results further suggest that the lipase‐catalyzed ester hydrolysis adopts the single proton transfer mechanism.     

Direct determination of rare earth impurities in high purity erbium oxide dissolved in nitric acid by inductively coupled plasma mass spectrometry

A novel method was developed for the direct determination of trace quantities of rare earth elements (REEs) in high purity erbium oxide dissolved in nitric acid by inductively coupled plasma mass spectrometry (ICP-MS) in this work. The mass spectra overlap interferences arose from Er matrix on the neighbouring and monoisotopic analytes of ¹⁶⁵Ho(100) and ¹⁶⁹Tm(100) were eliminated by adjusting instrumental peak resolution value from 0.7 to 0.3 amu. The matrix suppression effect of Er on the ion peak signals of REEs impurities was effectively compensated with spiking In as internal standard element. The limit of quantitation (LOQ) of REEs impurities was from 0.0090 to 0.025 μg g⁻¹, the recoveries of spiked sample for REEs were found to be in the range of 90.3-107% through using the proposed method and relative standard deviation (R.S.D.) varied between 2.5% and 6.7%. The novel methodology had been found to be suitable for the direct determination of trace REEs impurities in 99.999-99.9999% high purity Er₂O₃ and the results obtained from this method keep in good agreement with that acquired from high resolution ICP-MS.     

TiO2 sol-gel derived amperometric biosensor for H2O2 on the electropolymerized phenazine methosulfate modified electrode

A novel hydrogen peroxide biosensor was developed based on the immobilization of horseradish peroxidase (HRP) in a TiO(2) sol-gel matrix on an electropolymerized phenazine methosulfate (PMS) modified electrode surface. Such membranes are of interest due to their high surface area, biological compatibility, and ease of fabrication. HRP entrapped in the TiO(2) matix was stable and retained its activity to a large extent. Cyclic voltammetry and amperometric measurements were employed to demonstrate the feasibility of electron transfer between immobilized HRP and the glassy carbon electrode via electropolymerized PMS. The influence of various experimental parameters such as operating potential, pH, temperature, and stability was investigated for optimum analytical performance. The biosensor provided a wide linear calibration range from 4.0x10(-6) M to 1.0x10(-3) M, with a detection limit of 8.0x10(-7) M at a signal-to-noise ratio of 3. The sensor retained 80% of its original activity after two months of operation.     

Chirality transfer from guest chiral metal complexes to inorganic framework: the role of hydrogen bonding

The structure elucidation of a new zinc phosphate [Co(II)(en)(3)][Zn(4)(H(2)PO(4))(3)(HPO(4))(2)(PO(4))(2 H(2)O)(2)] (1) reveals that the racemic cobalt complex templates the zinc phosphate framework in such a way that the local C(2) point symmetry of the structural motif of the inorganic framework conforms with that of the cobalt complex pairing with it, in essence transferring its chirality to the inorganic host. An analysis of hydrogen bonding between the guest molecules and the inorganic host framework reveals that hydrogen bonding is responsible for the stereospecific structural arrangement. Upon examining previously reported chiral metal-complex-templated structures of metal phosphates, it is revealed that such hydrogen bonding is the common origin for inducing chirality transfer in metal-phosphate frameworks templated with chiral metal complexes. Crystal data of 1: orthorhombic, Pbcn (no. 60), a=10.4787(8) A, b=20.0091(14) A, c=14.9594(10) A, and Z=2.     

The effects of alternative stress on the cell membrane deformability of chrysanthemum callus cells

The effects of alternative stress, which was generated through a strong sound field apparatus set up in our lab, on cultured chrysanthemum callus cells were studied. Meanwhile we measured the deformability of chrysanthemum cell membranes and studied the influence of the cytoskeleton after the treatment of colchicine using micropipette aspiration technique. Based on our experimental results, we found that the deformability of cell membrane decreased in stress condition. However, the effect disappeared after the treatment of cytochalasin. Therefore, we thought that the reason on the deformability of cells decreasing was the microfilament rearranging and consequently the cells becoming more rigid under the alternative stress.     

Crossed-beam study of Co+(3F4)+propane: experiment and density functional theory

A pulsed beam of Co+(3F4) crosses a pulsed beam of C3H8 or C3D8 gas under single collision conditions at collision energies of 0.01 eV and 0.21 eV. After a variable time delay t(ext) = 1-8 micros a fast high voltage pulse extracts product ions into a field-free flight tube for mass analysis. Consistent with earlier work, we observe prompt CoC3H6+ +H2 elimination products in 3:1 excess over CoC2H4+ +CH4 products at 0.21 eV on a 2-10 micros time scale. Long-lived CoC3H8+ complexes fragment predominantly back to Co+ +C3H8 reactants and to H2 elimination products on a 6-24 micros time scale. Density functional theory (B3LYP) calculations provide energies, geometries, and harmonic vibrational frequencies at key stationary points for use in a statistical rate model of the reaction. By adjusting two key multicenter transition state (MCTS) energies downward by 4-7 kcal mol(-1), we obtain good agreement with our decay time results and with the cross section versus collision energy of Armentrout and co-workers from 0.1-1.0 eV. B3LYP theory succeeds in finding relative energies of the MCTSs leading to CH4 and H2 in the proper order to explain the different product branching ratio for Co+ (which favors H2 over CH4) compared with its nearest neighbors Fe+ and Ni+ (which favor CH4 over H2).     

Perturbations in thenp 1,3 P Rydberg sequences of neutralYb probed by Zeeman-effect and lifetime measurements

Thenp P Rydberg sequence of neutral Ytterbium is strongly perturbed. These perturbations were monitored by measuring theg _J factors and lifetimes of 19 states, including both singlets and triplets as well as states from the perturbing configurations. A pulsed laser setup was used. Theg _J factors were obtained from a Zeeman quantum-beat experiment and the lifetimes by direct observation of the decay of the fluorescence light.