响应面法优化辣椒籽油碱异构化制备共轭亚油酸工艺及其氧化稳定性

[目的]研究碱异构化法制备辣椒籽油共轭亚油酸工艺,得到高转化率的辣椒籽油共轭亚油酸,为辣椒副产物综合利用及制备共轭亚油酸的新资源开发提供理论依据.[方法]以共轭亚油酸转化率为指标,以反应时间、反应温度、碱油比和溶油比为主要影响因素,运用响应面中心组合设计(CCD),分析不同因素对辣椒籽油共轭亚油酸转化率的影响,研究辣椒...     

Block copolymer assembly via kinetic control

Block copolymers consist of two or more chemically different polymer segments, or blocks, connected by a covalent linkage. In solution, amphiphilic blocks can self-assemble as a result of energetic repulsion effects between blocks. The degree of repulsion, the lengths of the block segments, and the selectivity of the solvent primarily control the resultant assembled morphology. In an ideal situation, one would like to be able to alter the morphology that forms without having to change the chemistry of the block copolymer. Through the kinetic manipulation of charged, amphiphilic block copolymers in solution, we are able to generate different nanoscale structures with simple block copolymer chemistry. The technique relies on divalent organic counter ions and solvent mixtures to drive the organization of the block copolymers down specific pathways into complex one-dimensional structures. Block copolymers are increasingly used as templating materials; thus, the ability to control the formation of specific patterns and structures is of growing interest and applicability.     

A generalized approach to the modification of solid surfaces

Interfacial interactions underpin phenomena ranging from adhesion to surface wetting. Here, we describe a simple, rapid, and robust approach to modifying solid surfaces, based on an ultrathin cross-linkable film of a random copolymer, which does not rely on specific surface chemistries. Specifically, thin films of benzocyclobutene-functionalized random copolymers of styrene and methyl methacrylate were spin coated or transferred, then thermally cross-linked on a wide variety of metal, metal oxide, semiconductor, and polymeric surfaces, producing a coating with a controlled thickness and well-defined surface energy. The process described can be easily implemented and adapted to other systems.     

Cylindrical block copolymer micelles and co-micelles of controlled length and architecture

Block copolymers consist of two or more chemically different polymers connected by covalent linkages. In solution, repulsion between the blocks leads to a variety of morphologies, which are thermodynamically driven. Polyferrocenyldimethylsilane block copolymers show an unusual propensity to forming cylindrical micelles in solution. We found that the micelle structure grows epitaxially through the addition of more polymer, producing micelles with a narrow size dispersity, in a process analogous to the growth of living polymer. By adding a different block copolymer, we could form co-micelles. We were also able to selectively functionalize different parts of the micelle. Potential applications for these materials include their use in lithographic etch resists, in redox-active templates, and as catalytically active metal nanoparticle precursors.     

豆梨和杜梨砧木根系中多胺代谢与高温胁迫的关系研究

[目的]探讨豆梨(Pyrus calleryana Dcne)和杜梨(P.betulaefolia Bunge)砧木根系中多胺代谢与其耐高温胁迫的关系,对维持根系正常代谢具有重要意义。[方法]以豆梨和杜梨实生苗为试材,比较了45℃处理下2种砧木叶片落叶率的变化,以及在30和45℃下供试材料根系内源多胺种类、形态和含量变化。[结果]豆梨达到65%落叶率的时间比杜梨早8 d;2种砧木根系中均存在游离态和结合态腐胺、己二胺、亚精胺和精胺4种内源多胺;高温胁迫导致2种供试材料的游离态和结合态腐胺、亚精胺及精胺的含量均升高,其中杜梨根系中游离态腐胺、亚精胺和精胺含量,以及结合态精胺含量显著高于豆梨。[结论]多胺代谢变化与供试材料的耐高温胁迫能力有密切关系。     

Eumelanins and pheomelanins: characterization by electron spin resonance spectroscopy

Synthetic dopa melanin and cysteinyldopa melanin have different electron spin resonance spectra. Data are reported for mixtures of these melanins and for dopa-cysteinyldopa copolymers, which are spectroscopically similar. A simple parameterization of the spectra allows estimation of the relative amounts of (i) dopa melanin and cysteinyldopa melanin in mixtures and of (ii) dopa and cysteinyldopa incorporated into copolymers. Several natural eumelanins and pheomelanins have been characterized and shown to be copolymers.     

渗透胁迫对玉米幼苗根尖线粒体ATPase活性与结合态多胺含量的影响

[目的]探讨线粒体膜上结合态多胺与渗透胁迫的关系。[方法]以抗旱性不同的玉米(Zea maysL.)品种农大108(抗旱性较强)和掖单13(抗旱性较弱)幼苗为材料,研究在聚乙二醇(PEG)-6000渗透胁迫下,幼苗根线粒体ATPase水解活性与膜上非共价结合态亚精胺(Spd)含量的关系。[结果]渗透胁迫条件下,抗性强的农大108的ATPase活性下降的幅度明显小于抗性弱的品种掖单13,而农大108的线粒体膜上非共价结合亚精胺的上升幅度明显大于掖单13。外源Spd处理,明显促进了掖单13在胁迫条件下非共价结合Spd含量的增加,同时抑制其在胁迫条件下ATPase活性的降低,从而提高了掖单13幼苗的抗性;Spd生物合成的专一性抑制剂——甲基乙二醛-双(鸟嘌呤腙)(MGBG)处理,显著抑制了农大108在胁迫条件下膜上非共价结合Spd的增加,同时促进其在胁迫条件下ATPase活性的降低,从而明显降低了农大108幼苗的抗性。[结论]线粒体膜上的非共价结合的Spd可能通过维持ATPase活性的稳定来提高玉米幼苗的抗渗透胁迫能力。     

Selective destruction of target cells by diphtheria toxin conjugated to antibody directed against antigens on the cells

Monkey-kidney cells bearing new surface antigens induced by infection with mumps virus were lysed selectively by diphtheria toxin conjugated to antibody against mumps antigens.     

Ordered mesoporous materials from metal nanoparticle-block copolymer self-assembly

The synthesis of ordered mesoporous metal composites and ordered mesoporous metals is a challenge because metals have high surface energies that favor low surface areas. We present results from the self-assembly of block copolymers with ligand-stabilized platinum nanoparticles, leading to lamellar CCM-Pt-4 and inverse hexagonal (CCM-Pt-6) hybrid mesostructures with high nanoparticle loadings. Pyrolysis of the CCM-Pt-6 hybrid produces an ordered mesoporous platinum-carbon nanocomposite with open and large pores (>/=10 nanometers). Removal of the carbon leads to ordered porous platinum mesostructures. The platinum-carbon nanocomposite has very high electrical conductivity (400 siemens per centimeter) for an ordered mesoporous material fabricated from block copolymer self-assembly.     

Helical superstructures from charged Poly(styrene)-Poly(isocyanodipeptide) block copolymers

Amphiphilic block copolymers containing a poly(styrene) tail and a charged helical poly(isocyanide) headgroup derived from isocyano-L-alanine-L-alanine and isocyano-L-alanine-L-histidine were prepared. Analogous to low-molecular mass surfactants, these block copolymers self-assembled in aqueous systems to form micelles, vesicles, and bilayer aggregates. The morphology of these aggregates can be controlled by variation of the length of the poly(isocyanide) block, the pH, and the anion-headgroup interactions. The chirality of the macromolecules results in the formation of helical superstructures that have a helical sense opposite to that of the constituent block copolymers. The great variety of morphologies displayed by these block copolymers and the fact that they are easily accessible from poly(styrene) and different types of peptides open new opportunities for applications in the fields of life and materials sciences.     

Chain length recognition: core-shell supramolecular assembly from oppositely charged block copolymers

Molecular recognition based on length was found to occur between oppositely charged pairs of flexible and randomly coiled block copolymers in an aqueous milieu. Matched pairs with the same block lengths of polyanions and polycations exclusively formed even in mixtures with different block lengths. These assemblies of the charged segments with matched chain lengths then formed larger core-shell-type supramolecular assemblies with an extremely narrow size distribution due to the strict phase separation between core- and shell-forming segments.     

Catalytic production of olefin block copolymers via chain shuttling polymerization

We report a catalytic system that produces olefin block copolymers with alternating semicrystalline and amorphous segments, achieved by varying the ratio of alpha-olefin to ethylene in the two types of blocks. The system uses a chain shuttling agent to transfer growing chains between two distinct catalysts with different monomer selectivities in a single polymerization reactor. The block copolymers simultaneously have high melting temperatures and low glass transition temperatures, and therefore they maintain excellent elastomeric properties at high temperatures. Furthermore, the materials are effectively produced in economically favorable, continuous polymerization processes.     

淀粉与偶氮化合物接枝共聚物对金属离子吸附效果的研究

合成了4种偶氮化合物与淀粉的接枝共聚物的不溶性树脂,首次用以吸附二价金属离子,研究了其静态吸附量以及各种相关因素对吸附的影响。     

羧甲基纤维素接枝甲基丙烯酸甲酯对稻壳水泥复合材料的增强作用

利用羧甲基纤维素和甲基丙烯酸甲酯在水介质中用过硫酸钾为引发剂,合成稻壳-水泥复合材料的偶联剂--羧甲基纤维素接枝甲基丙烯酸甲酯(CMC-g-PMMA).共聚物采用傅立叶红外光谱(FTIR)、扫描电镜(SEM)进行表征.并采用X射线能量散射分析(EDXA)测量共聚物中葡萄糖环上甲基丙烯酸甲酯的个数.采用CMC-g-PMMA作为植物纤维表面处理剂,与水泥一并制成复合材料.对材料密度、24 h吸水厚度膨胀率、抗弯强度进行了测试(万能力学实验机),对表面形貌进行观察(体视显微镜).结果表明:添加CMC-g-PMMA可大幅度提高稻壳-水泥复合材料的抗弯强度和弹性模量,当稻壳比例为20%,CMC-g-PMMA比例为1%时,抗弯强度和弹性模量分别为未添加助剂试样的2.27倍和2.71倍.同时讨论了CMC-g-PMMA的增强机理.     

共轭双键对脂肪酸紫外吸收的影响

[目的]测定共轭亚油酸及部分非共轭脂肪酸的紫外吸收,研究共轭双键对脂肪酸紫外吸收的影响。[方法]测定多种脂肪酸及其混合物的吸光度,并利用气相色谱法测定脂肪酸组分含量。[结果]当加入少量的共轭亚油酸时,混合脂肪酸的紫外吸收曲线表现出明显变化。[结论]共轭双键对脂肪酸在230～240nm范围内的紫外吸收有显著影响,从而为共轭成分的存在提供了检测依据。     

木质素的化学改性方法及其应用

根据有关文献资料,综述了由制浆造纸黑液回收的木质素的化学改性方法及其应用的研究进展,内容主要包括木质素的磺化、磺甲基化,木质素与丙烯酰胺、丙烯酸和多元单体接枝共聚、缩合、交联,木质素的氧化氨解、稀硝酸氧化,木质素脱甲基化、硫化以及常温常压、高温加压等反应改性。综合分析表明,改性后木质素分子量提高,水溶性、表面活性增强,其改性产物分别在混凝土外加剂、石油开采、染料分散、肥料增效缓释、合成木材、削减地表径流、固沙保水等方面有良好的应用前景。木质素的化学改性既拓宽了木质素的应用范围,也提高了其实用价值。加强木质素的改性与应用研究对保护生态环境,推动工业木质素应用的发展,促进制浆造纸废液污染治理,开发可自然再生资源的有效利用具有重要意义。     

Discovery of a Frank-Kasper sigma phase in sphere-forming block copolymer melts

Sphere-forming block copolymers are known to self-assemble into body-centered cubic crystals near the order-disorder transition temperature. Small-angle x-ray scattering and transmission electron microscopy experiments on diblock and tetrablock copolymer melts have revealed an equilibrium phase characterized by a large tetragonal unit cell containing 30 microphase-separated spheres. This structure, referred to as the sigma (σ) phase by Frank and Kasper more than 50 years ago, nucleates and grows from the body-centered cubic phase similar to its occurrence in metal alloys and is a crystal approximant to dodecagonal quasicrystals. Formation of the σ phase in undiluted linear block copolymers (and certain branched dendrimers) appears to be mediated by macromolecular packing frustration, an entropic contribution to the interparticle interactions that control the sphere-packing geometry.     

Hierarchically ordered oxides

Porous silica, niobia, and titania with three-dimensional structures patterned over multiple length scales were prepared by combining micromolding, polystyrene sphere templating, and cooperative assembly of inorganic sol-gel species with amphiphilic triblock copolymers. The resulting materials show hierarchical ordering over several discrete and tunable length scales ranging from 10 nanometers to several micrometers. The respective ordered structures can be independently modified by choosing different mold patterns, latex spheres, and block copolymers. The examples presented demonstrate the compositional and structural diversities that are possible with this simple approach.     

木质素磺酸盐与丙烯酰胺接枝改性研究

[目的]提高木质素磺酸盐的水处理能力。[方法]以粘度和产率为表征量,研究不同引发剂对木质素磺酸钠与丙烯酰胺接枝共聚反应的影响;通过正交试验研究引发剂用量、温度、单体丙烯酰胺用量对接枝共聚物粘度的影响,并对反应条件进行优化;同时对原料及改性物的结构进行分析。[结果]K2S2O8/Na2S2O3引发的接枝反应效果较好,反应产物具有最大的粘度和较大的反应产率及较小的表面张力;（NH4）2Ce（NO3）6、（NH4）2S2O8、（NH4）2Fe（SO4）2.6H2O/H2O2引发的反应产物粘度较小,产率较低。接枝共聚反应的优化条件为：K2S2O8/Na2S2O3用量6×10^-3mol/L,反应温度40℃,丙烯酰胺用量8 g,此条件下的改性产物可作为优良絮凝剂。[结论]该研究优化了木质素磺酸盐与丙烯酰胺接枝共聚反应的条件。     

HIV-infected cells are killed by rCD4-ricin A chain

The gp120 envelope glycoprotein of the human immunodeficiency virus (HIV), which is expressed on the surface of many HIV-infected cells, binds to the cell surface molecule CD4. Soluble derivatives of recombinant CD4 (rCD4) that bind gp120 with high affinity are attractive vehicles for targeting a cytotoxic reagent to HIV-infected cells. Soluble rCD4 was conjugated to the active subunit of the toxin ricin. This conjugate killed HIV-infected H9 cells but was 1/1000 as toxic to uninfected H9 cells (which do not express gp120) and was not toxic to Daudi cells (which express major histocompatibility class II antigens, the putative natural ligand for cell surface CD4). Specific killing of infected cells can be blocked by rgp120, rCD4, or a monoclonal antibody to the gp120 binding site on CD4.