The Use of Structural Templates in Protein Backbone Modeling

The procedures used to model a protein structure are well established when the novel protein has high sequence similarity to a protein of known structure. Many proteins of interest have low (i.e. <50%) sequence similarity to any known structure. In these cases new approaches to prediction of structure are required.The use of sequence profiles which relate sequence to known structure has been proposed as one method to assign local regions of structure. As a first stage, templates or “icons” of the many relevant substructural motifs found in proteins must be defined. The sequences which gave rise to these structures are then aligned and a weighted profile obtained.Average structures of the 8 and 12 residue helix-turn and turn-helix motifs have been prepared. These coordinate templates were then used to scan through the Brookhaven protein structural database for similar, superimposable fragments. A composite template of 100 similar fragments for each element was found to be internally consistent to a rmsd=0.92 Å for HT8, 1.54 Å for HT12, 0.41 Å for TH8 and 1.40 Å for TH12. All of the sequences, from these structures, were then used to create an overall sequence profile.The four sequence profiles were scanned against the amino acid sequences of the proteins in the Brookhaven database: tertiary structure was correctly identified only about 10% of the time. This value is too low for predictive purposes. However, it could be increased by checking for multiple occurrences of the template in one protein.     

Biocompatibility Pathways in Tissue-Engineering Templates

Tissue engineering, which involves the creation of new tissue by the deliberate and controlled stimulation of selected target cells through a systematic combination of molecular and mechanical signals, usually involves the assistance of biomaterials-based structures to deliver these signals and to give shape to the resulting tissue mass. The specifications for these structures, which used to be described as scaffolds but are now more correctly termed templates, have rarely been defined, mainly because this is difficult to do. Primarily, however, these specifications must relate to the need to develop the right microenvironment for the cells to create new tissue and to the need for the interactions between the cells and the template material to be consistent with the demands of the new viable tissues. These features are encompassed by the phenomena that are collectively called biocompatibility. However, the theories and putative mechanisms of conventional biocompatibility (mostly conceived through experiences with implantable medical devices) are inadequate to describe phenomena in tissue-engineering processes. The present author has recently redefined biocompatibility in terms of specific materials- and biology-based pathways; this opinion paper places tissue-engineering biocompatibility mechanisms in the context of these pathways.     

Isosonic Templates for Plant Layout

Using critical noise lines of equal loudness surrounding production equipment, the best relative position of such equipment can be determined to ensure an acceptable noise level environment. In the facilities design stage, noise levels can be optimized along with all the other plant layout objectives. As a corrective measure, isosonic templates can indicate the minimal relocation necessary, and identify the points at which further noise control measures must be taken. By recording the percentage of time an operator spends in each noise zone, and considering the additive effect of adjacent noise sources, the total cumulative operator noise exposure can be determined.     

Gadolinium-Loaded Nanoparticles Engineered from Microemulsion Templates

ABSTRACT

Microemulsions (oil-in-water) have been used as templates to engineer stable emulsifying wax and Brij 72 (polyoxyl 2 stearyl ether) nanoparticles. The technique is simple, reproducible, and amenable to large-scale production of stable nanoparticles having diameters below 100 nm. Investigation of the process variables showed that the amount of surfactant used in the preparation of microemulsion templates had the greatest influence on the microemulsion window, as well as the properties and stability of the cured nanoparticles. Emulsifying wax and Brij 72 nanoparticles (2 mg/mL) made with 3 mM polyoxyl 20 stearyl ether and 2.3 mM polysorbate 80, respectively, were the most stable based on retention of nanoparticle size over time. Gadolinium acetylacetonate (GdAcAc), a potential anticancer agent for neutron capture therapy (NCT), was entrapped in stable nanoparticles. The apparent water solubility of GdAcAc was increased more than 2000-fold by entrapment into nanoparticles. The entrapment efficiency of GdAcAc was about 100% for emulsifying wax nanoparticles and 86% for Brij 72 nanoparticles, as determined by gel permeation chromatography (GPC). Elution profiles were obtained with light scattering (counts per second) to detect nanoparticles and ultraviolet (UV) absorption of GdAcAc at 288 nm. Challenges of these cured nanoparticles in biologically relevant media such as 10% fetal bovine serum, 10 mM phosphate-buffered saline, 150 mM NaCl, and 10% lactose at 37°C for 60 min demonstrated that these nanoparticles are stable. The ease of preparation of these very small and stable nanoparticles, and the ability to entrap lipophilic drugs such as GdAcAc with high efficiency, suggested that these systems may have potential in cell targeting, especially for specific delivery to tumor cells for NCT.     

Nanoparticle Assemblies on Nanoinjection-Molded Polymer Templates

A mass-producible method for fabricating nanoparticle assemblies using nanoinjection-molded polymer templates with deposition and selective removal has been developed and characterized in this work. Results are demonstrated for assembly of multiple nanoparticle sizes and types in 1-D and 2-D formats over large areas. Template dimensions such as width and depth are used to control the assembled structures, including the quantity and type of nanoparticles in the assembly. This method offers a high-throughput, low-cost approach to nanoscale assembly for applications in optical, electronic, and biomedical devices.      

聚合物模板法制备介孔材料

聚合物模板剂因其能够自组装成形态不同、尺寸可调的纳米单元,且在反应后易于除去等特点而在介孔材料的合成过程中起着重要的作用。本文中对近几年聚合物模板制备介孔材料的研究做了简要的回顾与总结,介绍了交联及嵌段共聚物、乳液及微乳液以及生物大分子作为模板制备介孔材料的研究进展,对现代物理测试技术如TEM、SEM、XRD和N2吸附-脱附曲线等在介孔材料的制备表征中的应用做了较详细的分析与探讨。     

应用DNA模版自组装CdS纳米线

近年来,由于具有双螺旋补偿结构,DNA分子作为智能模版被广泛应用于设计棒状或管状类的纳米结构.本文报道了应用DNA双螺旋模版将CdS纳米粒子自组装为CdS纳米线.制备的CdS纳米线由几根纳米线紧密缠绕在一起,也呈螺旋形结构,该结构在无机材料中是很少见的.该结构形成的主要原因归功于CdS纳米粒子和DNA分子间的强烈静电互作用,由于含自由基的CdS纳米粒子带负电荷,而氨基的DNA核酸根带正电荷.研究结果表明应用DNA模版制备纳米线是一种简便、高效的技术和方法.同时,DNA模版法也为从底上制备纳米级的材料和物体提供了广阔的空间.     

模板技术在纳米材料制备中的应用与发展

模板法制备的纳米材料具有形貌、结构、尺寸、取向等可控的特点,是一种简便有效的方法.介绍了在纳米材料合成中常见的几种模板,包括多孔阳极氧化铝模板、痕迹刻蚀聚合物模板、共聚物模板、中孔材料、碳纳米管、生物模板、聚集体模板与混合模板;论述了利用模板技术可以制备材料的类型及模板技术在核壳结构材料、空心微球材料、生物技术方面的新进展.     

Surface Influences on the Electrodiffusive Behavior in Mesoporous Templates

The physicochemical details of the well‐established template‐assisted electrodeposition process for metal nanowire fabrication are investigated with respect to the physical origination for template geometry limitation. The overall process of metal reduction inside anodized Al₂O₃ (AAO) is divided into three parts: i) the electrochemical reduction at the pore bottom, ii) the diffusion of the electrolytic species, and iii) the capacitive interaction between pore surface and electrolyte. The results show that the reduction of Ni is controlled by the degree of electrode recession, i.e., the pore depth. Applying Cottrell's equation to pulsed electrodeposition enables experimental access to diffusion coefficients (). This gives a gradient in along with the filling process. The switch‐over from crystallization to diffusion control is investigated to depend on temperature and pore length. Additionally, the electrode surface capacitance scales non‐linearly with the pore depth. This is deduced as a consequence of electrostatic surface–electrolyte interaction. A minimum in the electrode capacitance at a pore length of 48 μm is identified as the point with maximum thickness of a double‐layer‐type surface effect to the electrolyte. The results extend the template's role from simply geometrically limiting metal growth and explain occurring process issues when filling especially high‐aspect‐ratio pores.