Structure and dynamics of self-assembled poly(ethylene glycol) based coiled-coil nano-objects.

Herein we describe the structure and dynamics of self-assembled nano-objects generated from poly(ethylene glycol) based (PEG-ylated) coiled-coil hybrid block copolymers. Electron paramagnetic resonance (EPR) experiments on spin-labeled samples provided a strong indication for a parallel alignment of the peptide helices in at least the dimeric coiled-coil nano-object and indicated that the PEG chains are folded rather closely around the peptide core of the nano-objects. The EPR results were supported by AFM studies, which revealed the presence of discrete nanosized objects in thin, spin cast films of the block copolymers on mica substrates. Since their size and structure may be engineered via directed mutations in the amino acid sequence, these nano-objects may be interesting building blocks for the development of supramolecular materials with various potential applications.     

On the Rigidity of Polynorbornenes with Dipolar Pendant Groups

A range of polynorbornenes (PNBs) with fused dipolar pendant groups at C‐5,6 positions was synthesized by ring‐opening metathesis polymerization catalyzed by a ruthenium carbene complex (Grubbs I). Photophysical studies, EFISH measurements, and atomic force microscopy images have been used to investigate the structures and morphology of these polymers. These results suggest that the polymers may adopt rigid rod‐like structures. The presence of the double bonds in PNBs appeared to be indispensable for the rigidity of the polymers. Interaction between unsaturated pendant groups may result in coherent alignment leading to a rod‐like structure.     

Nonisothermal Kinetics of Sub‐Solidus Phase Transitions in C10Zn,C16Zn and Their Binary System

Nonisothermal kinetics of the solid‐solid phase transition in (n‐C₁₀H₂₁NH₃)₂ZnCl₄(C₁₀Zn), (n‐C₁₆H₃₃NH₃)₂ZnCl₄(C₁₆Zn) and their binary system were determined by Kissinger and Ozawa methods from DSC measurements. The activation energy E_a of the binary system shows a waving dependence on W_C10Zn%, which is caused by not only an intermediate (C₁₀H₂₁NH₃)(n‐C₁₆H₃₃NH₃)ZnCl₄ but also three solid solution ranges (α, β, γ) in the phase diagram of C₁₀Zn‐C₁₆Zn. The variations of the layer d‐spacing are also convenient for the above result.     

Photocycloaddition of Cyclohex‐2‐enones to Penta‐1,2,4‐triene

Dihydrothiinone 9a undergoes photocycloaddition regioselectively to all three C?C bonds of penta‐1,2,4‐triene ( 10 ), the relative stabilities of the biradical intermediates determining the product distribution. In contrast, cyclohexenone 9b and dihydropyranone 9c afford more complex mixtures of bicyclo[4.2.0]octanones, which also turn out to be less stable on chromatographic workup, reflecting the higher strain due to the shorter bond lengths (C? O and C? C vs. C? S) in the six‐membered rings, respectively.     

Electronic structure of BeH2

Nonorthogonal single‐configuration and multiconfiguration ab initio calculations are carried out on the BeH₂ molecule in its equilibrium (D_∞h) geometry, using a highly optimized even‐tempered Slater‐type orbital (STO) basis set. The results are used as a basis for a discussion of the electronic structure of the molecule in modern‐VB terms. A value of R_e = 1.329 Å is obtained. Values are also obtained for the symmetric‐stretch harmonic frequency (2053 cm^?1), electric quadrupole moment (?5.60 Buckingham), and nuclear quadrupole coupling constants (?3.59 MHz for ⁹Be and 0.0915 MHz for ²H). © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2006     

Laccase Biosensor on Monolayer‐Modified Gold Electrode

Laccase enzymes from two different sources, namely, tree laccase from Rhus vernicifera and fungal laccase from Coriolus hirsutus were used for the development of biosensor for catechol. Laccase was immobilized onto the amine terminated thiol monolayers on gold surface by glutaraldehyde coupling. From the different thiol monolayers investigated, cystamine was found to be optimal with respect to sensitivity, stability, reproducibility, and other electrochemical properties of the enzyme electrode. Linear calibration in the range between 1 and 400 μM for catechol was obtained for fungal laccase covalently coupled on the electrode surface. The kinetic parameters determined using the Lineweaver‐Burk and Eadie‐Hofstee plots were K_m=0.65 mM and V_max=24.5 μA for fungal laccase compared to K_m=5.4 mM and V_max=6.6 μA for tree laccase on cystamine monolayer. The electrode showed good stability for 1 month without loosing appreciable activity when stored dry in a refrigerator at ?20 °C.     

锂离子电池负极合金CoSn和Cu-Sn的制备与表征

CoSn alloy and Cu-Sn samples were synthesized by H₂-reduction following solid-state reaction between Co(Ⅱ)， Cu(Ⅱ)， Sn(Ⅳ) and NaOH at ambient temperature. The samples were characterized by XRD， SEM. The results showed that CoSn alloy (80～200nm) is globe-shaped， ultrafine hexagonal material， and Cu-Sn alloy powder consists of two phases， i.e. Cu₆Sn₅ and Cu₃Sn. Cu-Sn powder has spherical morphology and the particle size is estimated to be 60～70nm. The electrochemical performances of CoSn alloy and Cu-Sn powder were studied using lithium-ions model cell Li/LiPF₆ (EC+DMC)/CoSn (or Cu-Sn). It was demonstrated the reversible discharge capacities for 10 cycles keep above 280mAh·g^-1 for nanophase Cu-Sn， and 60mAh·g^-1 for CoSn alloy. Differ-ential capacity plots showed that the reaction mechanisms of Cu-Sn with lithium were reversible.     

汞电极表面电荷的快速估算

本文报导了用交流示波极谱快速估算电极表面电荷的方法。该方法使用仪器简单,测量快速,操作简便,在吸附研究中很有用处。     

Polarized basis sets of Slater-type orbitals: H to Ne atoms

We present three Slater-type atomic orbital (STO) valence basis (VB) sets for the first and second row atoms, referred to as the VB1, VB2, and VB3 bases. The smallest VB1 basis has the following structure: [3, 1] for the H and He atoms, [5, 1] for Li and Be, and [5, 3, 1] for the B to Ne series. For the VB2 and VB3 bases, both the number of shells and the number of functions per shell are successively increased by one with respect to VB1. With the exception of the H and Li atoms, the exponents for the VB1 bases were obtained by minimizing the sum of the Hartree-Fock (HF) and frozen-core singles and doubles configuration interaction (CISD FC) energies of the respective atoms in their ground state. For H and Li, we minimized the sum of the HF and CISD FC energies of the corresponding diatoms (i.e., of H(2) or Li(2)) plus the ground-state energy of the atom. In the case of the VB2 basis sets, the sum that was minimized also included the energies of the positive and negative ions, and for the VB3 bases, the energies of a few lowest lying excited states of the atom. To account for the core correlations, the VBx (x = 1, 2, and 3) basis sets for the Li to Ne series were enlarged by one function per shell. The exponents of these extended (core-valence, CV) basis sets, referred to, respectively, as the CVBx (x = 1, 2, and 3) bases, were optimized by relying on the same criteria as in the case of the VBx (x = 1, 2, and 3) bases, except that the full CISD rather than CISD FC energies were employed. We show that these polarized STO basis sets provide good HF and CI energies for the ground and excited states of the atoms considered, as well as for the corresponding ions.     

Evaluation of a PVC‐Based Thionine‐Zeolite and Zeolite Free Membranes as Sensing Elements in Ion Selective Electrode

The construction and performance characteristics of thionine electrodes based on the ion‐pair complex thionine‐tungstophosphate and thionine‐mordenite zeolite embedded in a polyvinyl chloride (PVC) matrix is described. Thionine electrode based on the ion‐pair is used for the indirect determination of ascorbic acid by standard addition method.