Towards manipulation of post-biosynthetic events in secondary metabolism of plant cell cultures

Plant cell cultures have been suggested as a feasible technology for the production of a myriad of plant-derived metabolites. However, commercial application of plant cell culture has met limited success with only a handful of metabolites produced at the pilot- and commercial-scales. To improve the production of secondary metabolites in plant cell cultures, efforts have been devoted predominantly to the optimization of biosynthetic pathways by both process and genetic engineering approaches. Given that secondary metabolism includes-the synthesis. metabolism and catabolism of endogenous compounds by the specialized proteins, this review intends to draw attention to the manipulation and optimization of post-biosynthetic events that follow the formation of core metabolite structures in biosynthetic pathways. These post-biosynthetic events-the chemical and enzymatic modifications, transport, storage/secretion and catabolism/degradation have been largely unexplored in the past. Potential areas are identified where further research is needed to answer fundamental questions that have implications for advanced bioprocess design. Anthocyanin production by plant cell cultures is used as a case study for this discussion, as it presents a good example of compounds for which there are extensive research publications but still no commercial bioprocess. It is perceived that research on post-biosynthetic processes may lead to future opportunities for significant advances in commercial plant cell cultures. (C) 2002 Elsevier Science Inc. All rights reserved.

Preparation and characterization of multiwalled carbon nanotube-supported platinum for cathode catalysts of direct methanol fuel cells

Multiwalled carbon nanotube-supported Pt (Pt/MWNT) nanocomposites were prepared by both the aqueous solution reduction of a Pt salt (HCHO reduction) and the reduction of a Pt ion salt in ethylene glycol solution. For comparison, a Pt/XC-72 nanocomposite was also prepared by the EG method. The Pt/MWNT catalyst prepared by the EG method has a high and homogeneous dispersion of spherical Pt metal particles with a narrow particle-size distribution. TEM images show that the Pt particle size is in the range of 2-5 nm with a peak at 2.6 nm, which is consistent with 2.5 nm obtained from the XRD broadening calculation. Surface chemical modifications of MWNTs and water content in EG solvent are found to be the key factors in depositing Pt particles on MWNTs. In the case of the direct methanol fuel cell (DMFC) test, the Pt/MWNT catalyst prepared by EG reduction is slightly superior to the catalyst prepared by aqueous reduction and displays significantly higher performance than the Pt/XC-72 catalyst. These differences in catalytic performance between the MWNT-supported or the carbon black XC-72-supported catalysts are attributed to a greater dispersion of the supported Pt particles when the EG method is used, in contrast to aqueous HCHO reduction and to possible unique structural and higher electrical properties when contrasting MWNTs to carbon black XC-72 as a support.

Preparation of uniform calcium alginate gel beads by membrane emulsification coupled with internal gelation

With the objective of making calcium alginate gel beads with small and uniform size, membrane emulsification coupled with internal gelation was proposed. Spherical gel beads with mean size of about 50 mum, and even smaller ones in water, and with narrow size distribution were successfully obtained. Experimental studies focusing mainly on the effect of process parameters on bead properties were performed. The size of the beads was mainly dependent on the diameter of the membrane pores. High transmembrane pressure made for large gel beads with wide size distribution. Low sodium alginate concentration produced nonspherical beads, whereas a high concentration was unsuitable for the production of small beads with narrow distribution. Thus 1.5% w/v was enough. A high surfactant concentration favored the formation of small beads, but the adverse effect on mass transfer should be considered in this novel process. (C) 2002 Wiley Periodicals, Inc.

Preparation and characteristics of nonflammable polyimide materials

The thermal and flame-retardant properties of homo- and copolyimides were evaluated. Those containing sulfone linkages in the backbone were found to be more flame retardant. Both properties were dependent on the composition. A polyimide/silica nanocomposite was obtained through sol-gel processing. The effects of the addition of silica an the dispersion, interfacial adhesion, fire resistance, mechanical properties, and thermal stability of the composites were investigated. SEM analysis showed a good dispersion of silica with a diameter of 50-300 nm in the organic matrices. The addition of silica increased the fire retardancy and mechanical properties of the composites. (C) 2000 John Wiley & Sons, Inc.

Microwave-assisted preparation of 2-methallyloxyphenol

Catechol reacted with beta-methallyl chloride in the presence of base and phase transfer catalyst under microwave irradiation and gave 2-methallyloxyphenol within 1 similar to 2 minutes. The yield of 2-methallyloxyphenol varied from 64%similar to 68%.

A simple preparation of stationary phase of alkylamide reversed-phase liquid chromatograph for the separation of basic substances

A simple preparation process of alkylamide phase for reversed-phase HPLC (RP-HPLC) is described. The process includes aminopropyltrimethoxysilane firstly reacted with octanoyl chloride, then the intermediate was coupled onto porous silica. The resultant bonded silica has a reproducible ligand surface concentration and homogenous bonded ligand distribution on the porous silica. Characterization of prepared packing was carried out with elemental analysis, solid-state C-13 NMR and Fourier transform infrared (FT-IR). Chromatographic evaluations were carried out by using a mixture of organic compounds including acidic, basic and neutral analytes under methanol/water as binary mobile phase. The results showed that the stationary phase have excellent chromatographic properties and can be efficiently used for the separation of basic compounds.

Preparation and characterization of a novel macrocyclic ligand—dinitro-tetraazacyclotetradeca-tetraene—and application as a highly selective extractant for copper(II)

A novel tetraaza macrocyclic Schiff base ligand, 6,13-dinitro-5,7,12,14-tetramethyl-1,4,8,11-tetraazacyclotetradeca-1,5,7,-12-tetraene, was prepared and its copper(II) and nickel(II) complexes were characterized. This ligand was found to be an excellent extractant for copper(II).

一种Post-WIMP界面：PGIS的实现

随着计算机应用从桌面环境扩展到移动环境，计算机用户从专业化走向大 众化，传统的 WIMP界面的缺点逐渐体现出来。笔式用户界面作为 Post-WIMP 界面的一种重要形式，具有自然、和谐的交互特性，成为当前研究的热点之一。 针对这一方向，本文对笔式用户界面范式展开了研究。首先，本文阐述了一种 新的基于笔交互的界面范式 PGIS，定义了纸、小工具等交互组件，以及各种组 件的显示形态及交互形式。然后，实现了 PGIS 界面，包括交互对象的管理、 显示等内容。最后，详细介绍了 PGIS 界面的使用过程，并用一个应用实例加 以验证。为了支持上层应用程序的可移植性和可维护性，PGIS界面的使用采用 了模型驱动构架的开发思想。目前，我们基于 PGIS 界面开发了几款优秀的笔 式交互软件，如幼儿教学系统、便签本系统、篮球战术板系统等。这些系统完 全满足用户对笔交互应用程序的需求，目前可在 Linux 系统、Windows 系统等 多种系统上运行。PGIS界面范式的可行性也因此得到了很好的验证。 本文的主要内容有以下几点： 1. 阐述了一种 Post-WIMP范畴下的新的界面范式：PGIS。 本文在对Post-WIMP界面做了充分地理解和分析的基础上，阐述了一种新 的界面范式：PGIS。这是一种基于笔交互的界面范式，文中对该范式的纸笔隐 喻方式、所包含的内容、各交互组件的表现形式、以及各组件间的静态及动态 关系做出了详细的描述。 2. 实现了PGIS界面。 为了验证PGIS界面范式的可行性，并直接支持基于 PGIS范式的应用程序 开发，本文详细介绍了PGIS界面的实现细节，其中包括PGIS界面中所包含的 元素、PGIS界面中交互对象的显示、交互对象的管理、以及交互对象对基本原 语的转换和响应。 3. 介绍了 PGIS界面的使用过程。 整个使用过程采用模型驱动架构的思想，引入对以下三个子模块的调用： 与平台相关的底层核心库和 PGIS 引擎、与平台无关的场景设计工具。这三个 子模块决定了上层应用程序的可移植性和可维护性。另外，场景设计工具提供 了代码自动生成的功能，大幅度缩短了应用程序的开发周期。 4. 实现了一个基于 PGIS界面的幼儿教学系统。 为了说明 PGIS界面的使用流程，本文设计并实现了一个基于PGIS界面的 幼儿教学系统。在开发过程中，大部分工作在场景设计工具中快速完成，小部 分工具集中在数据管理库、场景任务库的开发上。该系统的评估结果很好地验 证了 PGIS界面范式的可行性。

Preparation and Characterization of BaLiF3:Er3+ Nanoparticles by the Hydrothermal Microemulsion Synthesized Method

Nanoparticles of BaLiF3:Er3+ were prepared from the quaternary microemulsions of Cetyltrim-Enthyl Ammonium Bromide (CTAB), n-butanol, n-octane, and water, using the hydrothermal-microemulsion technique. The complex fluorides were characterized by means of X-ray power diffraction, Environmental Scanning Electron Microscopy (ESEM), and fluorescence spectra.

Preparation and characterization of Gd2O3:Eu3+ luminescence nanotubes

The size controllable Gd2O3:Eu3+ luminescence nanotubes were successfully prepared using a simple method by coating gadolinium compounds on the carbon nanotubes and then firing the carbon nanotubes. The morphology of the obtained Gd2O3:Eu3+ nanotubes was determined by transmission electron microscopy (TEM). It was found that the obtained nanotubes have the outer diameters of similar to 100 nm, the inner diameters of similar to 50 nm, and the lengths of several tens of microns. The sizes of Gd2O3:Eu3+ nanotubes can be easily controlled by changing the reaction times and the concentration of reactants.