2-呋喃甲硫醇修饰环糊精形成互锁式螺旋柱状超分子的自组装行为

利用单-(6-氧-对甲基苯磺酰基)-β-环糊精和2-呋喃甲硫醇反应得到单修饰环糊精, 单[6-硫-6-(2-甲基呋喃)]-β-环糊精. 通过X-ray衍射分析及核磁光谱等方法研究了其在溶液和固态中形成线状超分子的分子自组装行为. 结果表明, 化合物在固态中通过呋喃基团从第二面羟基连续插入到另一个环糊精的空腔, 形成了互锁式螺旋柱状超分子, 而且在溶液中也显示了相似的自组装行为, 其键合常数K及聚合度n分别为450 mol^-1·L和1.9.     

共沸蒸馏法制备表面化学改性氢氧化镁纳米颗粒

首次将表面改性剂如硬脂酸、硬脂酸锌或稀土偶联剂加入到传统的共沸蒸馏体系中,使Mg(OH)2纳米颗粒的表面改性和干燥过程同时完成。 通过 XRD、TEM、FT-IR、TG和CAM（接触角测试）等技术手段对样品的结构、形貌和性质进行了表征。 结果表明,表面改性剂不但能够和Mg(OH)2纳米颗粒的表面的OH-离子发生化学反应形成表面修饰层, 减少硬团聚现象,而且还使纳米颗粒表面由亲水性变为疏水性。 另外,对共沸蒸馏法制备表面改性纳米颗粒的机理进行了讨论,为纳米颗粒表面改性提供了一种新思路。     

柠檬酸修饰(CA/GC)电极对多巴胺(DA)和肾上腺素(EP)同时检测

应用电沉积方法制备柠檬酸修饰电极(CA/GC), 差分脉冲法研究多巴胺(DA)和肾上腺素(EP)在该修饰电极上的电化学行为．结果表明, 两样品DA、EP在该电极的还原峰电位差380 mV, 而抗坏血酸(AA)在此电位区无还原峰, 因此可实现该修饰电极对DA和EP的同时检测, 而且高浓度AA不发生干扰．在pH 6.0的磷酸盐缓冲液中, DA和EP还原峰电流与其浓度分别在1.0×10-6 ~ 6.0×10-5 mol•L-1和2.0×10-6 ~ 6.0×10-5 mol•L-1 范围内呈线性关系．CA/GC电极制备简单, 重现性好, 可望用于多巴胺针剂(DA)和肾上腺素针剂(EP)的同时检测     

纳米材料电化学与生物传感器——有机微污染物检测新途径

本文介绍了近年来纳米材料电化学与生物传感器在有机微污染物检测中的研究现状,分析了这些传感器中纳米材料修饰电极的特点,重点阐述了纳米材料在有机微污染物检测中的重要作用,列举了一些纳米材料电化学与生物传感器在有机微污染物检测中的应用。最后对纳米材料电化学与生物传感器用于有机微污染物的检测研究进行了简要评述和展望。     

Molecular Cloning and Characterization of a New Cold-active Extradiol Dioxygenase from a Metagenomic Library Derived from Polychlorinated Biphenyl-contaminated Soil

To find new extradiol dioxygenases(EDOs, EC 1.13.11.2), a metagenomics library was constructed from polychlorinated biphenyl-contaminated soil and was screened for some dioxygenase with aromatic ring cleavage activity. A novel EDO, designated as Bph­C_A, was identified and heterologously expressed in Escherichia coli. The deduced amino acid sequence of BphC­_A exhibited a homology of less than 60% with other known EDOs. Phylogenetic analysis of BphC­_A suggests that the protein is a novel member of the EDO family. The enzyme exhibits higher substrate affinity and catalytic efficiency toward 3-methylcatechol than toward 2,3-dihydroxybiphenyl or catechol, the preferred substrate of other known EDOs. The optimum activity of purified Bph­C_A occurred at pH=8.5 and 35℃, and Bph­C_A showed more than 40% of its initial activity at 5℃. The activity of purified Bph­C_A was significantly induced by Mn²⁺ and slightly reduced by Al³⁺, Cu²⁺ and Zn²⁺.     

Expression and Characterization of a Thermostable Acyl-peptide Releasing Enzyme ST0779 from Sulfolobus tokodaii

Acyl-peptide releasing enzyme(AARE) belongs to a serine peptidase family and catalyzes the NH₂-terminal hydrolysis of N^α-acylpeptides to release N^α-acylated amino acids. ORF0779(ORF=open reading frame) from thermophilic archaea Sulfolobus tokodaii(ST0779) was cloned and expressed in E. coli BL21 and the expressed protein was identified as a thermostable AARE. The target protein could be optimally overexpressed in E. coli at 30 ℃ for 8 h with 0.1 mmol/L isopropyl β-dthiogalactoside(IPTG). The crude enzyme was heated at 70 ℃ for 30 min, and then the target protein could account for above 40% of the total protein. The purification fold was 27 and the enzyme showed both esterase activity and peptidase activity. The optimal temperature and pH for ST0779 were 70 ℃ and 8.0 when Ac-Ala₃ was used as substrate. The half-life of the enzyme(0.2 mg/mL) at 90 ℃ was about 16 h, indicating that the enzyme exhibits a favorable thermostability. The activity of ST0779 could still remain over 85% after being treated at 25 ℃ in different buffers with pH range from 6.0 to10.0 for 24 h, which indicates ST0779 is stable in neutral or slight alkali environment. Under neutral or slightly alkali conditions, the enzyme exhibits really high catalytic efficiency against acyl-peptide, and the optimal substrate is Ac-Ala₃. Most metal ions have no inhibition effect on the activity of ST0779, while 4% activity of ST0779 is inhibited in the presence of K⁺. This enzyme was supposed to be applied in the analysis of protein sequencing and the synthesis of small peptides.     

基于葫芦[8]脲主-客体作用的温度及pH敏感壳聚糖超分子凝胶制备与性能

壳聚糖侧链改性合成N-(4-二甲氨基苯甲基)壳聚糖(MBCS), 通过葫芦[8]脲(Q[8])与MBCS侧链之间的主客体作用制得Q[8]/MBCS超分子凝胶. 利用红外光谱、紫外光谱、¹H NMR、X-射线粉末衍射(XRD)、热重分析(TG)和差示扫描量热(DSC)等技术对改性壳聚糖及凝胶进行表征. 以5-氟尿嘧啶(5-Fu)为模型药物, 研究载药凝胶在不同pH环境下的释药行为. 结果表明Q[8]/MBCS体系在酸性条件下, 可组装形成超分子凝胶, 该凝胶体系具有温敏性和pH敏感性. 扫描电镜(SEM)图显示凝胶具有网状交联结构, ¹H NMR谱显示, 在酸性条件下, Q[8]与MBCS含氮侧链基团间发生主客体包合作用是超分子凝胶形成的主要原因. Q[8]/MBCS载药凝胶在酸性介质中对药物具有明显的缓释作用.     

Multi-Soliton Solutions and Integrable Discretization for a Coupled Modified Volterra Lattice Equation

In this paper, we study a coupled modified Volterra lattice equation which is an integrable semidiscrete version of the coupled KdV and the coupled mKdV equation. By using the Darboux transformation, we obtain its new explicit solutions including multi-soliton and multi-positon. Furthermore, an integrable discretization of the coupled modified Volterra lattice equation is constructed.     

Density-Dependent Conformable Space-time Fractional Diffusion-Reaction Equation and Its Exact Solutions

In this article, a special type of fractional differential equations(FDEs) named the density-dependent conformable fractional diffusion-reaction(DDCFDR) equation is studied. Aforementioned equation has a significant role in the modelling of some phenomena arising in the applied science. The well-organized methods, including the exp(-φ(ε))-expansion and modified Kudryashov methods are exerted to generate the exact solutions of this equation such that some of the solutions are new and have been reported for the first time. Results illustrate that both methods have a great performance in handling the DDCFDR equation.     

Modified Vonk's Method to Determine Crystallinity and Crystal Distortion in Polymers

Using a modified method developed from Vonk's method, detailed values of crystallinity and crystal disorder were obtained by wide angle X-ray diffraction (WAXD). In Vonk's method, the crystallinity (w) is determined by extrapolation of the WAXD experimental curve back to zero scattering angle, while the distortion factor (k) is determined by the inclination of the experimental curve at zero scattering angle. In our new method, both w and k are determined at the same time by using the least squares method. In order to show the efficiency of our method, the new fitting procedure was applied to the experimental values of polyethylene and polyethylene terephthalate as measured by Vonk, and the values of w and k determined by our new method were compared with those found by Vonk's method. The new fitting method has the advantage that it uses the whole experimental curve. Moreover, our modified Vonk's method enables us to discuss crystal distortions as arising from first-kind (thermal) disorder and second-kind (paracrystalline) disorder.