Die tödliche Brechnuss. Strychnin – von der Isolierung zur Totalsynthese

Strychnine, one of the most poisonous alkaloids, has fascinated scientists since its first isolation in 1818. It took over 130 years until its chemical structure was unequivocally determined and another 7 years until the first total synthesis by Robert B. Woodward was finished. Nowadays scientists are still developing new strategies for the synthesis of this fascinating complex compound. Some chemical aspects and personal accounts of synthesis #17 from 2010 are given.     

Xylene-stream method for obtaining thin polyethylene specimens for electron microscopy

A new technique is described for obtaining thin specimens from melt-crystallized polyethylene surface for studying the lamellar structure with the electron microscope. The specimen was first backed with carbon–gelatin backing and then the polyethylene side was exposed to a temperature-controlled xylene stream. After dissolving most of the specimen, a very thin layer of polyethylene which shows certain aspects of the original lamellar structure was obtained. Stereoscopic micrographs revealed the structure of polyethylene consisting of curved layers, concave, convex and other forms. These curved layers were identified by analysis of the Bragg fringes to be the crystalline lamellae. A special pattern resembling a spider in shape caused by a spherical crystal was investigated.     

Chemical control of electronic structure and superconductivity in layered borides and borocarbides: understanding the absence of superconductivity in LixBC

The synthetic search for materials related to the 39 K superconductor MgB2 has been difficult. The most promising theoretical suggestion, hole doping of LiBC, does not lead to a new superconductor. We show here that a combination of density functional theory (DFT) calculations, materials synthesis, and structural characterization reveals the origin of the puzzling absence of superconductivity in Li1/2BC as a subtle change in the electronic structure driven by structural response to the introduction of holes. This indicates that the unique aspects of the electronic structure of MgB2 will be demanding to replicate in other systems.     

Middle-infrared Second-order Nonlinear Optical Chalcogenides and Halides Containing Multiple Anions

The second-order nonlinear optical(NLO) materials play an important role in the application and development of laser techniques. For various candidates, those in the middle infrared(MIR) region are far from the market's requirement. Therefore, it is necessary to explore new ones with better performance. For their exploration, the inclusion of multiple anions in one structure has been proved to be a successful strategy. The NLO property contains several aspects, and different anions may contribute to different aspects. Therefore, the multiple anions' combination may give an opportunity to obtain NLO materials with desirable properties. Here, we make a short but clear summary on the MIR NLO-active chalcogenides and halides containing multiple anions, as most of them exhibit nice NLO performances.     

Critical aspects in the development of lithium–air batteries

Intensive research has been done on lithium–air batteries, especially in the last few years. Due to their very high theoretical specific energy, lithium–air batteries are one of the most promising candidates to power future electric vehicles. However, this new technology is in a very early stage of development, and several challenges must be overcome before there will be a commercially viable product. This review describes the most important critical aspects in the development of lithium–air batteries: the electrocatalysis of the oxygen electrode reactions, the degradation of the electrolyte and the oxygen electrode components, the structure of the oxygen electrode, and the passivation of the oxygen electrode during the discharge of the battery. Recent works in these areas are critically reviewed, and suitable research strategies to address these issues are discussed.     

Quantum phenomena in small semiconductor structures and devices

The ability to artificially structure new semiconductor materials on an atomic scale, using advanced crystal growth methods such as molecular beam epitaxy and metal organic chemical vapor deposition, has led recently to the observation of new physical phenomena as well as the creation of entirely new classes of devices based on band gap and wave function engineering. In these lectures an elementary introduction is given to the quantum aspects of these new structures.     

全新设计蛋白质的折叠机制

蛋白质全新设计和折叠研究是从两个不同的方向来理解蛋白质序列-结构-功能关系这一结构生物学重要问题. 蛋白质全新设计取得的成功实例一定程度上检验了人们对蛋白质结构和相互作用理解的准确性, 但它们中多数所表现的不同于天然蛋白质的折叠动力学特征也表明, 要达到最终的功能化实现目标还面临着不少的挑战. 本文综述了蛋白质全新设计的发展过程及现状, 蛋白质折叠研究在实验、理论及模拟方面的研究进展, 以及全新设计蛋白质的折叠机制的研究现状. 阐述了深入了解全新设计蛋白质与天然蛋白质折叠机制的不同, 可以为进一步有效地合理化设计蛋白质提供有益的参考.     

Carbon–fluorine compounds as battery materials

Historical aspects on the syntheses and structure models of carbon–fluorine compounds, discharge reaction and characteristics of Li/(CF)_n batteries, and syntheses and electrochemical behavior of new alternating cathode materials have been reviewed.     

表面活性剂的绿色化学进展

表面活性剂领域的绿色化学进展，主要体现在根据结构性能关系的研究进行分子设计，开发易生物降解，对人体温和的表面活性剂，降低现有产品中有害物质的含量，推进产品的环境友好化，在其生产过程中推进化学反应的绿色化及原料的绿色化，同时根据表面活性剂能对界面过程产生影响，起到功能助剂作用的特点，大力开展表面活性剂在节能增效，改进质量，改善环境方面的应用，并对上述进展进行了简单介绍。     

解吸电喷雾电离技术

本文介绍了一种新近发展起来的质谱离子化方法——解吸电喷雾电离（desorption electrospray ionization, DESI）及其最新研究进展。该方法首次于2004年提出后,由于其具有样品无需前处理就可以在常压条件下从各种载物表面直接分析固相,或凝固相样品等优势而得到了迅速的发展。本文描述了DESI的基本原理、离子源的结构和相关优化的参数,并对该离子化方法中所用的载物表面进行了总结。在实际应用方面,本文综述了DESI技术在常压气相化学反应产物监测,合成高聚物表征,爆炸物和化学战毒剂检测,以及在药品,生物代谢产物和生物组织表面分析方面的应用成果,同时对DESI的基础应用研究方向进行了分析和展望。     

Phorbasins G-K: new cytotoxic diterpenes from a southern Australian marine sponge, Phorbas sp

Fractionation of a cytotoxic extract obtained from a southern Australian marine sponge, Phorbas sp., yielded the known diterpenes phorbasins B-F () together with five new members of the phorbasin family, phorbasins G-K (). Structures were assigned to the new phorbasins based on detailed spectroscopic analysis. A preliminary structure activity relationship (SAR) evaluation based on the co-metabolites phorbasins B-K () revealed aspects of the phorbasin pharmacophore.     

Analysis of food proteins and peptides by mass spectrometry-based techniques

Mass spectrometry has arguably become the core technology for the characterization of food proteins and peptides. The application of mass spectrometry-based techniques for the qualitative and quantitative analysis of the complex protein mixtures contained in most food preparations is playing a decisive role in the understanding of their nature, structure, functional properties and impact on human health. The application of mass spectrometry to protein analysis has been revolutionized in the recent years by the development of soft ionization techniques such as electrospray ionization and matrix assisted laser desorption/ionization, and by the introduction of multi-stage and ‘hybrid’ analyzers able to generate de novo amino acid sequence information. The interfacing of mass spectrometry with protein databases has resulted in entirely new possibilities of protein characterization, including the high sensitivity mapping (femtomole to attomole levels) of post-translational and other chemical modifications, protein conformations and protein–protein and protein–ligand interactions, and in general for proteomic studies, building up the core platform of modern proteomic science. MS-based strategies to food and nutrition proteomics are now capable to address a wide range of analytical questions which include issues related to food quality and safety, certification and traceability of (typical) products, and to the definition of the structure/function relationship of food proteins and peptides. These different aspects are necessarily interconnected and can be effectively understood and elucidated only by use of integrated, up-to-date analytical approaches. In this review, the main aspects of current and perspective applications of mass spectrometry and proteomic technologies to the structural characterization of food proteins are presented, with focus on issues related to their detection, identification, and quantification, relevant for their biochemical, technological and toxicological aspects.     

DIAR成色剂的最新进展

本文分别从定时基团、抑制基团、成色母体和分子结构这4方面介绍了近十几年来DIAR成色剂的最新进展,特别介绍了一些具有新结构和新功能的DIAR成色剂的情况.抑制基团是这几年发展最快的,一些具有好的照相性能的抑制基团被合成;为了提高DIAR成色剂的层间效应,设计出了双定时的DIAR成色剂;溶出型的DIAR成色剂得到进一步的改进,从而能够被广泛地应用.     

The impact of the discovery of stereoregular polymers in macromolecular science

The paper recalls some aspects of the fascinating history of the discovery by Giulio Natta and his coworkers of the stereospecific polymerization of α-olefins and of the determination of the structure of synthetic stereoregular polymers. The most relevant recent advances in the comprehension of the mechanisms regulating their synthesis with heterogeneous supported catalysts and with the newly discovered homogeneous metallocene-based catalysts are briefly outlined.     

Protein unfolding and refolding under force: methodologies for nanomechanics.

An increasing number of inter- and intramolecular interactions can nowadays be probed using single-molecule manipulation techniques. Protein unfolding and refolding is the most representative--though complex--of these interactions. Herein, we review the main modes of performing a force unfolding experiment: the velocity clamp and the new force clamp mode. We also compare some of the physical aspects behind the two most frequently used single-molecule manipulation instrumentations: optical tweezers and atomic force microscopes.     

Propellane, 11. Mitt.: Synthese von Dioxa[4.3.3]propellanen aus vicinalen Tetrakis(hydroxymethyl)cycloalkanen

Summary The synthesis of two new [4.3.3]propellanes is described. The structure of the compounds was determined by chemical and spectroscopic methods. Some aspects of the conformation of the propellanes were studied using¹H NMR.

     

Synthesis of the bicyclo[6.2.1]undecane ring system by a solvent-free Diels–Alder reaction

A bicyclo[6.2.1]undecane model compound of the core structure of the biologically active furanoheliangolide sesquiterpene was synthesized. This new and short route was developed by using a solvent-free Diels–Alder reaction between cyclopentadiene and 3-nitro-2-cyclohexenone, followed by simple transformations. Theoretical calculations were performed in order to understand reactivity aspects of the cycloaddition.     

Fucoidan: structure and bioactivity

Fucoidan refers to a type of polysaccharide which contains substantial percentages of L-fucose and sulfate ester groups, mainly derived from brown seaweed. For the past decade fucoidan has been extensively studied due to its numerous interesting biological activities. Recently the search for new drugs has raised interest in fucoidans. In the past few years, several fucoidans' structures have been solved, and many aspects of their biological activity have been elucidated. This review summarizes the research progress on the structure and bioactivity of fucoidan and the relationships between structure and bioactivity.     

Structural bases for the catalytic mechanism of Ni-containing carbon monoxide dehydrogenases

Significant progress has been made recently in our understanding of the structure/function relationships of the catalytic C-cluster of carbon monoxide dehydrogenases. Several structures of this enzyme have been reported, some of them at very high resolution. One recurrent problem, however, is the high degree of heterogeneity within each structure, as well as between the different X-ray models. Here, we have tried to relate the structural data with the wealth of spectroscopic and biochemical information gathered over many years. As a result, we propose a catalytic cycle that is consistent with both observations and stereochemistry. We also give alternatives to one of the most difficult aspects of the cycle, namely, the location of the two electrons in the most reduced state of the C-cluster.     

Characterization of LC Stationary Phases by Inverse Size Exclusion Chromatography

Abstract

The most efficient use of a porous particulate stationary phase can only be made when the material in the column is fully characterized. While complete characterization includes both chemical and physical aspects, the macro structure provides the framework for the microscopic chemical interactions. The physical analysis is therefore critically important for a more complete calibration of the chromatographic effects.