Computational study of conformational preferences of thioamide-containing azaglycine peptides

The effect of thioamide substitution on the conformational stability of an azaglycine-containing peptide, For-AzaGly-NH2 (1), was investigated for the sake of finding possible applications by using ab initio and DFT methods. As model compounds, For-[psiCSNH]-AzaGly-NH2 (2), For-AzaGly-[psiCSNH]-NH2 (3), and For-[psiCSNH]-AzaGly-[psiCSNH]-NH2 (4) were used. Two-dimensional phi-psi potential energy surfaces (PESs) for 2-4 were calculated at the B3LYP/6-31G*//HF/6-31G* level in gas (epsilon = 1.0) and in water (epsilon = 78.4) by applying the isodensity polarizable continuum model (IPCM) method. On the basis of these PESs, the minimum energy conformations for 2-4 were characterized at the B3LYP level with 6-31G*, 6-311G**, and 6-31+G** basis sets. The remarkable structural effect of thioamide substitution for 2-4 is that beta-strand structure is observed as a global or local minimum. The minima of 2-4 are also compared with those for glycine and thioamide-containing glycine peptides. Our theoretical results demonstrate that compounds 2-4 would be used to design controllable secondary structures.     

Syntheses and Crystal Structures of Two Coordination Polymers with Aromatic Dioxide as Bridge Ligands

Two coordination polymers, namely, two-dimensional complex 1 {[Cu(μ- L)1.5(ClO4)2(H2O)].(H2O)0.5}n (L = pyrazine-1,4-dioxide) and one-dimensional complex 2 [Co(μ-L)Br2(H2O)2]n, have been synthesized with pyrazine-1,4-dioxide as bridging ligands, and their crystal structures were determined by X-ray crystallography. Crystal data for complex 1: monoclinic system, space group C2/c, with a = 23.310(3), b = 12.2338(17), c = 10.6075(15) , β = 110.487(2)°, V = 2833.6(7) 3, Z = 8, C6H9Cl2CuN3O12.5, Mr = 457.60, Dc = 2.145 g/cm3, F(000) = 1832 and μ = 1.998 mm-1; and those for 2: monoclinic system, space group C2/c, with a = 11.012(3), b = 7.483(2), c = 11.451(3) , β = 101.654(4)°, V = 924.2(4) 3, Z = 4, C4H8Br2CoN2O4, Mr = 366.87, Dc = 2.637 g/cm3, F(000) = 700 and μ = 10.487 mm-1. 1 shows a two-dimensional sheet structure on the ac plane through the coordination of μ-L bridging ligands with Cu(II) ions, while 2 displays a zigzag one-dimensional chain along the c axis via the coordination of μ-L bridging ligand with Co(II) ions. Hydrogen bonds in 1 and 2 make the sheets (or chains) connect each other to form a three-dimensional structure.     

纳米半导体中多重激子效应研究进展

多重激子效应是指纳米半导体吸收一个高能光子后产生两个甚至多个电子-空穴对的物理过程,不仅具有重要的基础研究意义,而且在新型太阳电池及高性能光电子器件领域具有潜在应用价值.综述了多重激子效应的发展历程;总结了纳米半导体的材料组分、体系结构甚至表面质量对多重激子效应的影响;介绍了多重激子效应的实验测试分析方法以及解释多重激子效应的理论方法;概括了目前多重激子效应在器件中的应用并对其应用前景进行展望.     

钛合金表面铁氧化物膜层类Fenton催化剂制备及降解苯酚性能

采用微弧氧化法在硅酸盐电解液体系中于钛合金表面成功制备了铁氧化物膜层类Fenton催化剂。采用SEM、XRD以及XPS对所得膜层的表面形貌、晶体结构及物相组成进行表征,发现膜层中含有金红石相TiO₂（R-TiO₂）,和非晶态的铁氧化物Fe₃O₄;对膜层的表面形貌分析发现电解液中加入铁氰化钾后表面粗糙度及平均孔尺寸增大。以苯酚作为目标降解物,研究了膜层类Fenton催化活性,同时研究了铁源含量、苯酚浓度、H₂O₂投料量以及pH值对膜层降解苯酚效率的影响,优化了降解条件,研究发现在pH 3.0、温度30℃、H₂O₂ 6.0 mmol·L^-1、苯酚35 mg·L^-1及铁氰化钾含量10 g·L^-1的条件下降解90 min,苯酚降解效率可达90%。通过对不同温度下降解苯酚的反应动力学研究,利用阿伦尼乌斯方程得到了该膜层类Fenton降解苯酚的反应活化能E_a为96.9 kJ·mol^-1。最后,评价了膜层的稳定性并分析了稳定性衰减的原因。     

Synthesis and Crystal Structure of a Three-dimensional Cd(Ⅱ) Coordination Polymer [Cd(μ1,3-SCN)(μ3-pco)]n (pco = Pyrazine-2-carboxylate 4-oxide Anion)

The three-dimensional complex [Cd(μ1,3-SCN)(μ3-pco)]n has been synthesized with μ1,3-SCN- and pco as mixed bridged ligands. The crystal belongs to monoclinic, space group P21/n with a = 10.3777(16), b = 6.2592(9), c = 13.150(2) (A), β= 97.317(2)°, V=847.2(2) (A)3, Z= 4,C6H3CdN3O3S, Mr = 309.575, Dc = 2.427 g/cm3, F(000) = 592 and μ = 2.804 mm-1. The structure was refined to R = 0.0255 and wR = 0.0550 for 1712 observed reflections (I＞2σ(I)). In the crystal the Cd(Ⅱ) ions are coordinated by μ1,3-SCN- and μ3-pco bridge ligands to form a three-dimensional structure.     

Studies on Middle-Phase Microemulsions of Green Surfactant n-Dodecyl Polyglucoside C12G1.46

The three-phases behavior in the quaternary stsem of n-dodecyl polyglucoside C12G1.46/1-butanol/cyclohexane/water has been studied at 40℃ in terms of the variables γ and δ.Increasing δ at constant γcauses a phase inversion from an oil-in-water microemulsion in contact with excess oil(winsor I or 2) to a water-in-oil microemulsion in contact with excess water (winsor Ⅱor 2)via a middle-phase microemulsion in contact with excess oil and water(winsor Ⅲor 3).By taking into account the different solubilities of alkyl polyglucoside and 1-butanol in the oil phase,the composition of the hydrophile-lipophile balanced interfacial film in the middle of the three-phase body can be calculated.The effects of different oils and aqueous media on the phase behavior and on the composition of the interfacial film and the efficiency for alkyl polyglucoside to make equal weights of water and oil to a single phase were investigated.It was found that the oil molecules with small molecular volumes can improve the solubilizing efficiency of the surfactant to form single-phase microemulsion.In inorganic salt(NaCl) and acid(HCl) solutions,less 1-butanol is needed than that in alkali(NaOH) solution to form middle-phase microemulsion.     

质子辐射下互补金属氧化物半导体有源像素传感器暗信号退化机理研究

对某国产0.5 μm工艺制造的互补金属氧化物半导体有源像素传感器进行了10 MeV质子辐射试验, 当辐射注量达到预定注量点时, 采用离线的测试方法, 定量测试了器件暗信号的变化情况. 试验结果表明, 随着辐射注量的增加暗信号迅速增大. 采用MULASSIS (multi-layered shielding simulation software)软件计算了电离损伤剂量和位移损伤剂量, 在与γ辐射试验数据对比的基础上, 结合器件结构和工艺参数, 建立了分离质子辐射引起的电离效应和位移效应理论模型, 深入分析了器件暗信号的退化机理. 研究结果表明, 对该国产器件而言, 电离效应导致的表面暗信号和位移效应导致的体暗信号对整个器件暗信号退化的贡献大致相当.     

Landau系统四类规范不变的升降算符

借助圆心坐标算符和初机械动量算符,给出Landau系统(带电粒子在垂直于均匀磁场平面内的运动)的四类升降算符,并讨论相应的选择定则和守恒量子数 关键词： Landau系统 升降算符     

Evaluation of a Apo-1/Fas promoter polymorphism in Korean stroke patients

Apoptosis has been implicated in the pathogenesis of neurodegenerative diseases such as stroke and Alzheimer's disease. Apo-1/Fas gene is one of the mediators of apoptosis in stroke. Mval polymorphism is the first polymorphic marker identified in the Apo-1/Fas gene promoter, which was typed by PCR and followed by Mval digestion and gel electrophoresis. DNA isolated from peripheral blood collected from 91 stroke patients and 103 healthy blood donors was used for genotypes of GG, GA and AA by sequence specific primer PCR. Mval polymorphism was examined based on Fas gene promotor region by restriction fragment length polymorphism (RFLP). The Fas-GG genotype was the least frequent in patients with stroke and healthy controls (P = 0.57). In normal Korean controls the Mval polymorphism GA, AA and GG were 48.6%, 34.9% and 16.5%. In stroke patients were 56.2%, 29.6% and 14.2% respectively. And the allelic frequencies of Mval*2 (G) allele were less frequent than Mval*1 (A) allele in patients with stroke and healthy controls (P = 0.76). In normal Korean controls Mval*1 (A) and Mval*2 (G) alleles were 59.2% and 40.8%. In stroke patients were 57.6% and 42.4%, respectively. Our results, pending confirmation in a larger study, indicate that the Fas genotype may not appear to be a risk factor for stroke in Korean stroke patients.