Dendritic Encapsulation of Function: Applying Nature's Site Isolation Principle from Biomimetics to Materials Science

The convergence of our understanding of structure-property relationships for selected biological macromolecules and our increased ability to prepare large synthetic macromolecules with a structural precision that approaches that of proteins have spawned a new area of research where chemistry and materials science join with biology. While evolution has enabled nature to perfect processes involving energy transfer or catalysis by incorporating functions such as self-replication and repair, synthetic macromolecules still depend on our synthetic skills and abilities to mesh structure and function in our designs. Clearly, we can take advantage of our understanding of natural systems to mimic the structural features that lead to optimized function. For example, numerous biological systems make use of the concept of site isolation whereby an active center or catalytic site is encapsulated, frequently within a protein, to afford properties that would not be encountered in the bulk state. The ability of the dendritic shell to encapsulate functional core moieties and to create specific site-isolated nanoenvironments, and thereby affect molecular properties, has been explored. By utilizing the distinct properties of the dendrimer architecture active sites that have either photophysical, photochemical, electrochemical, or catalytic functions have been placed at the core. Applying the general concept of site isolation to problems in materials research is likely to prove extremely fruitful in the long term, with short-term applications in areas such as the construction of improved optoelectronic devices. This review focuses on the evolution of a natural design principle that contributes to bridging the gap between biology and materials science. The recent progress in the synthesis of dendrimer-encapsulated molecules and their study by a variety of techniques is discussed. These investigations have implications that range from the preliminary design of artificial enzymes, catalysts, or light-harvesting systems to the construction of insulated molecular wires, light-emitting diodes, and fiber optics.     

Self‐Assembled Cage‐Like Protein Structures

Proteins and protein‐based assemblies represent the most structurally and functionally diverse molecules found in nature. Protein cages, viruses and bacterial microcompartments are highly organized structures that are composed primarily of protein building blocks and play important roles in molecular ion storage, nucleic acid packaging and catalysis. The outer and inner surface of protein cages can be modified, either chemically or genetically, and the internal cavity can be used to template, store and arrange molecular cargo within a defined space. Owing to their structural, morphological, chemical and thermal diversity, protein cages have been investigated extensively for applications in nanotechnology, nanomedicine and materials science. Here we provide a concise overview of the most common icosahedral viral and nonviral assemblies, their role in nature, and why they are highly attractive scaffolds for the encapsulation of functional materials.     

Microfabrication of three-dimensional bioelectronic architectures

The functionality and structural diversity of biological macromolecules has motivated efforts to exploit proteins and DNA as templates for synthesis of electronic architectures. Although such materials offer promise for numerous applications in the fabrication of cellular interfaces, biosensors, and nanoelectronics, identification of techniques for positioning and ordering bioelectronic components into useful patterns capable of sophisticated function has presented a major challenge. Here, we describe the fabrication of electronic materials using biomolecular scaffolds that can be constructed with precisely defined topographies. In this approach, a tightly focused pulsed laser beam capable of promoting protein photo-cross-linking in specified femtoliter volume elements is scanned within a protein solution, creating biomolecular matrices that either remain in integral contact with a support surface or extend as free-standing structures through solution, tethered at their ends. Once fabricated, specific protein scaffolds can be selectively metallized via targeted deposition and growth of metal nanoparticles, yielding high-conductivity bioelectronic materials. This aqueous fabrication strategy opens new opportunities for creating electronic materials in chemically sensitive environments and may offer a general approach for creating microscopically defined inorganic landscapes.     

Applications of inductively coupled plasma mass spectrometry and laser ablation inductively coupled plasma mass spectrometry in materials science

Inductively coupled plasma mass spectrometry (ICP-MS) and laser ablation ICP-MS (LA-ICP-MS) have been applied as the most important inorganic mass spectrometric techniques having multielemental capability for the characterization of solid samples in materials science. ICP-MS is used for the sensitive determination of trace and ultratrace elements in digested solutions of solid samples or of process chemicals (ultrapure water, acids and organic solutions) for the semiconductor industry with detection limits down to sub-picogram per liter levels. Whereas ICP-MS on solid samples (e.g. high-purity ceramics) sometimes requires time-consuming sample preparation for its application in materials science, and the risk of contamination is a serious drawback, a fast, direct determination of trace elements in solid materials without any sample preparation by LA-ICP-MS is possible. The detection limits for the direct analysis of solid samples by LA-ICP-MS have been determined for many elements down to the nanogram per gram range. A deterioration of detection limits was observed for elements where interferences with polyatomic ions occur. The inherent interference problem can often be solved by applying a double-focusing sector field mass spectrometer at higher mass resolution or by collision-induced reactions of polyatomic ions with a collision gas using an ICP-MS fitted with collision cell. The main problem of LA-ICP-MS is quantification if no suitable standard reference materials with a similar matrix composition are available. The calibration problem in LA-ICP-MS can be solved using on-line solution-based calibration, and different procedures, such as external calibration and standard addition, have been discussed with respect to their application in materials science. The application of isotope dilution in solution-based calibration for trace metal determination in small amounts of noble metals has been developed as a new calibration strategy. This review discusses new analytical developments and possible applications of ICP-MS and LA-ICP-MS for the quantitative determination of trace elements and in surface analysis for materials science.     

Biopolymers for surface engineering of paper-based products

The combination of biopolymer science and technology with surface engineering of paper-based cellulosic materials has a lot of potential in stepping forward to a sustainable future. Various biopolymers such as oxidized starch, carboxymethyl cellulose, and polylatic acid have been commercially used to engineer paper surface. The paper-based cellulosic products are widely used for printing/writing and packaging applications. However, the production of these products are currently dependent mainly upon the use of petroleum-based materials including synthetic pigment coating latexes and barrier coating materials. The major challenges associated with some biopolymers are their relatively high costs and unsatisfactory performances. Continuing efforts are being made to enable the increased and value-added use of various biopolymers in paper surface engineering. These polymers can be based on cellulose, hemicelluloses, chitosan, alginate, protein, polylactic acid, and polyhydroxyalkanoate. The biopolymer-engineered paper products can be tailored for use as substitutes for various non-renewable materials including plastics and metals as well. Future development in the area of biopolymers for paper surface engineering is likely to lead to new possibilities and breakthroughs, paving the way for a substantially sustainable and green future.     

基于催化应用调控氧化铈纳米材料的形貌

催化剂的设计、合成和结构调控是获得优异性能的关键.传统的策略主要是尽量减小催化剂颗粒尺寸以增加活性中心的数目,即尺寸效应.近年来,材料科学的快速发展使得在纳米尺度上调变催化剂的尺寸和形貌成为可能,特别是通过形貌调控可暴露更多的高活性晶面,大幅度提高催化性能,即纳米催化中的形貌效应.因此,调节催化剂的尺寸与形貌可以单独或协同优化材料的性能.氧化铈作为催化剂的重要组分与结构、电子促进剂被广泛应用于多相催化剂体系.本文总结了近期氧化铈材料形貌可控合成的进展,包括主要的合成策略和表征方法; 进而分析了氧化铈和金-氧化铈催化材料的形貌效应,指出金-氧化铈之间独特的相互作用与载体形貌密切相关; 阐述了氧化铈纳米材料因暴露晶面的差异而获得不同催化性能的化学机制.     

Unleashing chemical power from protein sequence space toward genetically encoded “click” chemistry

We propose the concept of genetically encoded “click” chemistry (GECC) to describe the “perfect” peptide-protein reactive partners and use SpyTag/SpyCatcher chemistry as a prototype to illustrate their structural plasticity, robust interaction, and versatile applications.     

A view on future directions for macromolecular science

Polymer science has in recent years become one of the most dynamic components of materials science [1, 2, 3], which in turn is a powerful bridge between basic science and advanced technology. The National Science Foundation (NSF) has periodically reviewed the status of polymer science and engineering to ensure that this important field continues to develop in an appropriate fashion. Thus, the NSF asked the U.S. National Academy of Sciences on two previous occasions, in 1981 and again in 1994, to assess progress in polymer science and engineering and to make recommendations for the future. The resulting reports [4, 5] received wide circulation in many countries and helped to focus attention on the changing nature of the polymer field. A clear trend that was identified in these reports is the greater commonality with other materials‐related disciplines [1‐3] and with the biological sciences [1‐5]. Increasingly, these changes are being reflected in the programs of government agencies funding polymer research which are tending to be broader and more interdisciplinary than in the past.     

Analysis of Enzyme Structure and Activity by Protein Engineering

Structure-activity relationships of enzymes can now be analyzed for the first time by the systematic alteration of protein structure. Recent developments in the chemical synthesis of DNA fragments and recombinant DNA technology enable the facile modification of proteins by highly specific mutagenesis of their genes. Kinetic analysis of the mutant enzymes combined with high-resolution structural data from protein X-ray crystallography allow direct measurements on the relationships between structure and function. In particular, the strength and nature of enzyme-substrate interactions and their detailed roles in catalysis and specificity can now be studied. We have developed such analysis of enzyme structure-function by site-directed mutagenesis of the tyrosyl-tRNA synthetase from Bacillus stearothermophilus, concentrating so far on the subtle role of hydrogen bonding in both substrate specificity and catalysis. We find that the energetics of tyrosine and ATP binding must be analyzed in terms of an exchange reaction with solvent water. Based on this idea and structural data, we have engineered an enzyme of improved enzyme-substrate affinity, and there thus appear to be real prospects of engineering proteins of new specificities, activities, and structural properties. We are also using protein engineering to gather direct information on the nature of enzyme catalysis. For example, we find the catalysis of formation of Tyr-AMP from Tyr and ATP is due largely to electrostatic and hydrogen bonding interactions that are stronger in the transition state than in the ground state—a “strain” mechanism rather than acid-base or covalent catalysis.     

Ordered mesoporous materials in the context of drug delivery systems and bone tissue engineering

Chemistry, materials science and medicine are research areas that converge in the field of drug delivery systems and tissue engineering. This paper tries to introduce an example of such an interaction, aimed at solving health issues within the world of biomaterials. Ordered mesoporous materials can be loaded with different organic molecules that would be released afterwards, in a controlled fashion, inside a living body. These materials can also react with the body fluids giving rise to carbonated nanoapatite particles as the products of such a chemical interaction; these particles, equivalent to biological apatites, enable the regeneration of bone tissue.     

Review on the Use of Artificial Intelligence to Predict Fire Performance of Construction Materials and Their Flame Retardancy

The evaluation and interpretation of the behavior of construction materials under fire conditions have been complicated. Over the last few years, artificial intelligence (AI) has emerged as a reliable method to tackle this engineering problem. This review summarizes existing studies that applied AI to predict the fire performance of different construction materials (e.g., concrete, steel, timber, and composites). The prediction of the flame retardancy of some structural components such as beams, columns, slabs, and connections by utilizing AI-based models is also discussed. The end of this review offers insights on the advantages, existing challenges, and recommendations for the development of AI techniques used to evaluate the fire performance of construction materials and their flame retardancy. This review offers a comprehensive overview to researchers in the fields of fire engineering and material science, and it encourages them to explore and consider the use of AI in future research projects.     

Using small angle scattering (SAS) to structurally characterise peptide and protein self-assembled materials

In the past 20 years protein and peptide self-assembly has attracted material scientists' interest due to the possibility to exploit such molecular mechanism to create novel biomaterials including hydrogels. One of the main challenges when dealing with "soft" biological materials is their structural and morphological characterisation. Small angle scattering (SAS) can be a highly complementary tool to microscopy for the characterisation of such materials as it allows the investigation of samples in their wet-state without the need for any sample preparation such as drying and/or freezing. In this tutorial review we introduce briefly the SAS technique to the non-expert and through selected examples from the literature show how SAS can be readily used thanks to existing analytical approaches developed by a number of authors to extract structural information on the self-assembly of peptide and proteins.     

Transient behavior at the nanoscale

Transient and steady state responses of a system to an input are well-known features of materials and systems in science and engineering. These responses depend on the intrinsic parameters of the system and on the nature of the input. We find that a system comprised of nanosized features no longer shows the typical stationary characteristics as their microscopic or solid-state counterparts. Interestingly, because of the chemistry of the nanostructure, thermal motion of the atoms, and external fields, the nanosized system shows extended electrical transient behavior, compatible with highly nonlinear features such a negative differential resistance and hysteresis.     

Functionalized Conducting Polymers—Towards Intelligent Materials

Organic conjugated polymers and oligomers constitute a three-dimensional network of molecular wires, in which all monomeric units can be functionalized with various prosthetic groups. By varying the nature of these groups, specific interactions with external physical or chemical phenomena can be developed in these materials, leading to molecular devices such as sensors, transducers, memories and logic operators. Chemists have already mastered the realization of many of these functional elements, which mimic those existing in organized beings.The further assembly of these elements in multifunctionalized organic conducting polymers and oligomers will represent the next step towards intelligent materials.     

缺陷位工程在二维材料电催化析氢反应中的研究进展

面对不可再生资源的快速消耗和环境污染的日益加重,寻找清洁可再生能源势在必行.氢能是一种清洁可再生的能源,是目前最有希望替代化石燃料的一种能源.电化学水分解可用来产生高纯氢气,其中析氢催化剂起着至关重要的作用.尽管贵金属铂基催化剂表现出优异的析氢性能,然而稀缺性和高成本限制了其大规模应用.因此,开发高效和地球存量丰富的电...     

Multifunctional hybrid organic-inorganic catalytic materials with a hierarchical system of well-defined micro- and mesopores

Novel layered zeolitic organic-inorganic materials (MWW-BTEB) have been synthesized by intercalation and stabilization of arylic silsesquioxane molecules between inorganic zeolitic MWW layers. The organic linkers are conformed by two condensed silyl-arylic groups from disilane molecules, such as 1,4-bis(triethoxysilyl)benzene (BTEB), which react with the external silanol groups of the zeolitic layers. The hybrids contain micropores within the inorganic layers and a well-defined mesoporous system in between the organic linkers. An amination post-treatment introduces basic groups in the organic linkers close to the acid sites present in the structural inorganic counterpart. Through this methodology it has been possible to prepare bifunctional acid-base catalysts where the acid sites are of zeolitic nature located in the inorganic building blocks and the basic sites are part of the organic structure. The resultant materials can act as bifunctional catalysts for performing a two-step cascade reaction that involves the catalytic conversion of benzaldehyde dimethylacetal into benzylidene malononitrile.     

Controlling membrane permeability with bacterial porins: application to encapsulated enzymes

Recent achievements of membrane protein science allow easy protein modification by genetic engineering and, for some proteins, their production in large quantities. We regard these features as the basic requirements for applications of membrane proteins in materials science. Here, we demonstrate a possible application of membrane proteins, inserting porins from the outer cell wall of Escherichia coli into the walls of liposomes. Encapsulation of enzymes into liposomes or polymer nanocapsules protects them against proteases and denaturation. Functional reconstitution of porins into the capsule shell allows to control the rate and selectivity of substrate permeation, and thus to control the enzyme reaction kinetics. We suggest that this technique can prove to be useful in the area of biosensors, providing enzymatic stability while keeping the functionality or even enhancing the sensitivity by substrate preselection. Another application of this kind of stabilisation is in the field of single enzyme activity recording.     

冷冻扫描电子显微镜冷冻断裂法在生物样品观察中的应用

冷冻扫描电子显微镜(Cryo-SEM)具有能在高真空状态下观察含水样品、分辨率高、制样简单快速、可对样品进行断裂刻蚀等优点,是生命科学研究中的有力工具.利用Cryo-SEM冷冻断裂法进行生物类样品表面形貌观察,既能观察到表面结构信息,又可观察样品内部结构信息.以沙漠梭梭成熟分支中上部同化枝的植物样品和乳清蛋白纤维(WPIF)的液体样品为试验材料,对样品进行冷冻断裂处理,观察并对比冷冻断裂处理前后样品的结构.结果表明:植物样品冷冻断裂后在升华温度为-100℃、升华时间10 min、冷台温度为-175℃、观察电压5 kV的试验条件下可以观察到植物细胞的叶绿体和细胞之间的细毛组织. WPIF冷冻断裂后在升华温度为-100℃、升华时间5 min、冷台温度为-175℃、观察电压5 kV的试验条件下可以观察到中链甘油三酯和蛋白纤维堆积而成的片层结构.未冷冻断裂处理的样品无法观察到以上结果.     

冶金标准物质的作用及其发展

经过几代人的共同努力,我国的冶金标准物质已经达到了相当高的水平。品种齐全、数量充足、质量上接近或达到了世界先进水平。本文从八个方面论述了冶金标准物质对冶金科学技术的发展、冶金产品及其品种和质量的提高所发挥的重要作用。冶金科学技术和现代分析技术的发展又推动了冶金标准物质的发展。用统一、提高、拓宽六个字可概括九十年代冶金标准物质的发展趋势。     

仿病毒衣壳自组装体及其生物医学应用

仿病毒衣壳结构自组装体具有重要的基础研究和应用价值,是化学、材料、生物医学等多学科前沿交叉领域.本文从天然病毒衣壳的基本结构和特征出发,立足于从结构仿生到功能仿生的角度,综述了以天然病毒衣壳蛋白质和人工合成材料为组装基元构建仿病毒衣壳自组装体的策略,及其形态结构的调控和功能优化等.重点论述了近年来合成肽类分子在仿病毒衣壳自组装体结构和功能方面的进展.同时,就仿病毒衣壳自组装体在药物控释、基因传递等生物医学领域的应用也做了论述.