Spectroscopy among the stars

The space between the stars is not void, but filled with interstellar matter, mainly composed of dust and gas, which gather in large interstellar clouds. In our Galaxy these interstellar clouds are distributed along a thin, but extended layer which basically traces out the spiral distribution of matter: the stars, the gas, and the dust component. Up to the present time more than 100 different molecules have been identified in interstellar molecular clouds. The majority of the interstellar molecules constitute carbon containing organic substances. During the past years, overwhelming evidence has been gathered, mainly through spectroscopic observations, that interstellar molecular clouds provide the birthplaces for stars. In fact detailed high spectral and spatial resolution spectroscopic measurements reveal physical and chemical processes of the intricate star formation process.     

Spectroscopy among the stars

The space between the stars is not void, but filled with interstellar matter, mainly composed of dust and gas, which gather in large interstellar clouds. In our Galaxy these interstellar clouds are distributed along a thin, but extended layer which basically traces out the spiral distribution of matter: the stars, the gas, and the dust component. Up to the present time more than 100 different molecules have been identified in interstellar molecular clouds. The majority of the interstellar molecules constitute carbon containing organic substances. During the past years, overwhelming evidence has been gathered, mainly through spectroscopic observations, that interstellar molecular clouds provide the birthplaces for stars. In fact detailed high spectral and spatial resolution spectroscopic measurements reveal physical and chemical processes of the intricate star formation process.     

The Chemistry of Interstellar Space

Within the last ten to twenty years, radioastronomers have discovered the existence of almost 100 different molecules in interstellar space. Ranging in complexity from two to thirteen atoms, these molecules are found in cold, rarefied regions called interstellar clouds, which are giant accumulations of gas and dust located in our galaxy as well as many others. Interstellar clouds are also the birthplaces of future generations of stars and are of great interest to astronomers. The observation of the large sample of gaseous molecules, detected mainly via their rotational spectral patterns, tells astronomers about the detailed physical conditions in interstellar clouds, and tells chemists about the extent of molecular synthesis possible under the seemingly harsh conditions of low temperature and density. The molecules are mainly organic in nature and comprise species known to be both stable and common in the laboratory as well as those both unstable and uncommon under terrestrial conditions, including radicals and molecular ions. Although the gas phase of interstellar clouds is well studied via spectroscopic techniques, the dust particles are much more poorly characterized via their scattering and absorption of visible radiation as well as some broad resonances in the ultraviolet and infrared regions of the spectrum. It is normally thought that these submicron-sized particles consist of cores that are composites of silicate and carbonaceous materials with mantles that contain material deposited from the gas such as ices of water, ammonia, and methane. In addition to the dust particles and gaseous molecules, there is some evidence for very large aromatic molecules (the so-called polycyclic aromatic hydrocarbons or PAH's) which occupy a nether region in between large gas-phase species and small dust particles. As our understanding of the chemical processes in interstellar clouds increases, it may be possible to speculate how large interstellar molecules can come into existence and whether or not there is a clear connection between interstellar chemistry and the start of life on earth.     

学科能力导向的“物质构成的奥秘”教学研究

以王磊提出的化学学科能力框架为理论依据,对“物质构成的奥秘”主题进行分析,从核心知识经验、认识角度思路、认识对象及问题、能力活动要素等4个维度构建了“物质构成的奥秘”主题的学科能力模型。运用实验法进行教学实践,证实了本研究设计的教学方式更有利于学生学科能力的发展提升。最后提出学科能力导向的“物质构成的奥秘”教学设计模式和教学实施的有效策略:(1)单元整体系统化设计,有层次有梯度的发展学生学科能力;(2)侧重应用实践型任务的解决,外显知识的输出性功能和价值;(3)重视核心知识和认识角度的建立过程;(4)追问、外显学生的认识角度和认识思路。     

Polymersomes in "gelly" polymersomes: toward structural cell mimicry

We demonstrate here the formation of compartmentalized polymersomes with an internal "gelly" cavity using an original and versatile process. Nanosize polymersomes of poly(trimethylene carbonate)-b-poly(L-glutamic acid) (PTMC-b-PGA), formed by a solvent displacement method are encapsulated with a rough "cytoplasm mimic" in giant polymersomes of poly(butadiene)-b-poly(ethylene oxide) PB-b-PEO by emulsion-centrifugation. Such a system constitutes a first step toward the challenge of structural cell mimicry with both "organelles" and "cytoplasm mimics". The structure is demonstrated with fluorescence labeling and confocal microscopy imaging with movies featuring the motion of the inner nanosize polymersomes in larger vesicles. Without "cytoplasm mimic", the motion was confirmed to be Brownian by particle tracking analysis. The inner nanosize polymersomes motion was blocked in the presence of alginate, but only hindered in the presence of dextran. With the use of such high molecular weight and concentrated polysaccharides, the crowded internal volume of cells, responsible for the so-called "macromolecular crowding" effect influencing every intracellular macromolecular association, seems to be efficiently mimicked. This study constitutes major progress in the field of structural biomimicry and will certainly enable the rise of new, highly interesting properties in the field of high-added value soft matter.     

Rotational Signatures of Dispersive Stacking in the Formation of Aromatic Dimers

The aggregation of aromatic species is dictated by inter‐ and intramolecular forces. Not only is characterizing these forces in aromatic growth important for understanding grain formation in the interstellar medium, but it is also imperative to comprehend biological functions. We report a combined rotational spectroscopic and quantum‐chemical study on three homo‐dimers, comprising of diphenyl ether, dibenzofuran, and fluorene, to analyze the influence of structural flexibility and the presence of heteroatoms on dimer formation. The structural information obtained shows clear similarities between the dimers, despite their qualitatively different molecular interactions. All dimers are dominated by dispersion interactions, but the dibenzofuran dimer is also influenced by repulsion between the free electron pairs of the oxygen atoms and the π‐clouds. This study lays the groundwork for understanding the first steps of molecular aggregation in systems with aromatic residues.     

Chemical reactions in clouds

Summary In contrast to a fairly extensive knowledge of gas phase chemical reactions in the atmosphere, our current understanding of the chemistry in the aqueous phase of clouds is still inadequate. Particularly for continental clouds the difficulties arise primarily from uncertainties in reaction mechanisms for the oxidation of various sulfur(IV) species originating from the dissolution of sulfur dioxide in cloud water and the role of the ions of transition metals in this oxidation process. The importance of OH and other radicals in gas-phase reactions has led to models, in which radical reactions are held responsible for much of the chemical change also in the liquid phase. This viewpoint has gained support specifically from the identification of iron(III)-hydroxo complexes as a photochemical source of OH radicals in continental clouds. Their reactions with sulfur(IV) compounds in the aqueous phase initiate chain processes, which are currently being examined by laboratory studies.     

Holographic electron density shape theorem and its role in drug design and toxicological risk assessment

Each complete, boundaryless molecular electron density is fully determined by any nonzero volume piece of the electron density cloud. This inherent feature of molecules, called the "holographic" property of molecular electron densities, provides a strong foundation for the local, quantum chemical shape analysis of various functional groups, pharmacophores, and other local molecular moieties. A proof is presented for the relevant molecular shape theorem, the "holographic electron density shape theorem", and the role of this theorem in quantum chemical, quantitative shape-activity relations (QShAR) is discussed. The quantum chemical methods of molecular shape analysis can be extended to ab initio quality electron densities of macromolecules, such as proteins, as well as to local molecular moieties, such as functional groups or pharmacophores, based on the transferability and additivity of local, fuzzy density fragments and the associated local density matrixes within the framework of the ADMA (Adjustable Density Matrix Assembler) approach. In addition to new results on chemical bonding and the development of macromolecular force methods, the new methodologies are also applicable to QShAR studies in computer-aided drug discovery and in toxicological risk assessment.     

说“弛豫”

"弛豫"是高分子物理课程中最重要的概念之一。作为"弛豫"的同义语,"松弛"一词应用更为普遍。与"弛豫"或"松弛"相关的术语有多个,如弛豫过程、松弛时间谱、力学松弛、介电松弛、应力松弛和次级松弛等。本文将这些术语集中在一起,分别阐释了其内涵。通过辨析,学习者就可以很好地理解这些概念,从而不会因其名称相近而造成混淆。弛豫现象是物质内部的分子运动在宏观上的一种表现,从绝对的意义上来说,任何物质都存在弛豫现象。但是,在所有的物质中,聚合物的弛豫现象表现最为突出。文章最后揭示了聚合物弛豫现象的分子机理。     

蛋白–配体复合物的结构及其相互作用分子机制的虚拟仿真实验项目的建设与教学实践——COVID-19肺炎疫情防控时期线上教学的案例

The scale gap between the macro world and the micro world makes it impossible to directly observe the micro-structure, but chemical researchers must elucidate the properties of macro matter based on the micro-structure. Therefore, characterizing the micro-structure through the X-ray diffraction and other instruments is an important means to understand the micro world. However, it is hard for undergraduates to learn and understand the microstructure by using these scientific instruments due to the high instrumental running cost, complicated operation procedure and radiation safety issue. By integrating the construction concept of "combination of reality and practice", protein-ligand complexes crystallography research, the latest results of the theory of accurate prediction of ligand binding conformation, and the basic theoretical knowledge in the "Structural Chemistry Curriculum Group", we developed this virtual simulation experimental project by using modern information technology such as "3D virtual reality". This project will provide a useful method for the study of the theoretical foundation of chemistry, and development of thinking with chemical knowledge, scientific expression, and application abilities.     

An introduction to bubble dynamics

The creation, understanding and control of mesoscopic chemical objects are at the core of many areas of chemistry and physics. Their preparation depends on a variety of nucleation and aggregation processes and they are exploitable for practical purposes, including fabrication techniques. At the opposite end, are cavitation phenomena. They also originate from a nucleation event, but result in the formation of a bubble. In recent years, bubbles have ceased to be a problem and have become increasingly more attractive for medical and industrial applications. Our understanding of bubble dynamics has steadily increased and we believe that it is timely to attempt to summarize in simple terms the knowledge accumulated in this area for a chemical audience. In this introduction, we focus on the nature of bubble formation, evolution and collapse. We discuss the macroscopic models that were developed at the beginning of the 20th century and accompany them with the results of more detailed molecular dynamics simulations.     

Understanding chemical reactivity: the case for atom, proton and methyl transfers

The concept of "chemical reactivity" assumes that atoms and molecules contain the necessary information to describe their evolution over time as they transform from reactants to products. This concept was useful in the past to rationalize reactivity trends and predict the behavior of new systems. Free-energy relationships have played a central role in this field. However, electronic effects often counter the energetic effects and give rise to "anomalies" or separate correlations. We discuss a quantification of the concept of "chemical reactivity", emphasizing the role of molecular and electronic factors in chemistry.     

化学品安全知识与应急科普宣传研究

Based on the theme of "chemical awareness and safety accident response capability", this paper conducts a questionnaire survey for college students. In response to the survey results, scientific, popular, and novel offline activities/online publicity will be used to popularize chemical basics, relevant laws and regulations, and chemical safety accident emergency response methods for university students. The aim is to improve the level of understanding of various types of chemicals among college students. In the event of sudden chemical safety incidents, corrective measures can be taken, and useful information can be accurately identified after a chemical accident.     

“高分子材料合成创新实验”线上教学探索与实践

Based on the platform of "QQ share screen + video live broadcast", through the combination of "online theory teaching", "development of home alternative experiment", "game type" experimental operation and "virtual simulation experiment", we carried out the online teaching of polymer material synthesis innovation laboratories, integrating "theory + practice" and "virtual + reality", which is also a good opportunity for labor education. These explorations and practices are expected to provide some references for online teaching of chemical laboratory courses during the COVID-19 epidemic.     

Gas Phase Formation of the Interstellar Molecule Methyltriacetylene

Methyltriacetylene – the largest methylated polyacetylene detected in deep space – has been synthesized in the gas phase via the bimolecular reaction of the 1-propynyl radical with diacetylene under single-collision conditions. The barrier-less route to methyltriacetylene represents a prototype of a polyyne chain extension through a radical substitution mechanism and provides a novel low temperature route, in which the propynyl radical piggybacks a methyl group to be incorporated into methylated polyynes. This mechanism overcomes a key obstacle in previously postulated reactions of methyl radicals with unsaturated hydrocarbon, which fail the inclusion of methyl groups into hydrocarbons due to insurmountable entrance barriers thus providing a fundamental understanding on the electronic structure, chemical bonding, and formation of methyl-capped polyacetylenes. These species are key reactive intermediates leading to carbonaceous nanostructures in molecular clouds like TMC-1.     

Etiology of potentially primordial biomolecular structures: from vitamin B12 to the nucleic acids and an inquiry into the chemistry of life's origin: a retrospective

"We'll never be able to know" is a truism that leads to resignation with respect to any experimental effort to search for the chemistry of life's origin. But such resignation runs radically counter to the challenge imposed upon chemistry as a natural science. Notwithstanding the prognosis according to which the shortest path to understanding the metamorphosis of the chemical into the biological is by way of experimental modeling of "artificial chemical life", the scientific search for the route nature adopted in creating the life we know will arguably never truly end. It is, after all, part of the search for our own origin.     

卤化银彩色成像体系中染料云形态的优化

本文为验证彩色卤化银体系中染料云形成的动力学模型而设计了实验,实验验证是采用一种“三明治”结构的彩色卤化银涂层,以保证其在曝光和彩色显影后所形成的染料云基本上不重叠,然后测量其染料云的尺寸分布和平均尺寸并与彩色卤化银体系中染料云形成的动力学模型计算所得的染料云的平均尺寸进行比较,结果证实了模型的适用性,在此基础上利用模型研究了各种因素对染料云形态、尺寸的影响,并综合各因素进行体系的优化。     

Materials Studio软件在“金属”教学中的应用*

以中学化学所涉及的“金属”物质教学内容为例,运用MS分子模拟软件内嵌的Visualizer,Build 及Symmetry property 等3个功能模块,在不同尺度(从埃、纳米、微米到厘米)范围内,实现对“金属原子结构”“金属晶体”及“金属性质(密度)”的连续性可视化展示,帮助学生从原子的视角深入理解化学物质微观结构与宏观性质之间的本质相关性。     

Comparison of the structural and chemical composition of giant T-even phage heads.

A study has been made of the structure of the capsids of T4D giant phage produced from mutants in gene 23 and temperature-sensitive mutants in gene 24, and T4D and T2L giant phage formed by the addition of L-canavanine followed by an Larginine chase in the growth medium. All the giant phage capsids have been shown to be built according to the same geometrical architecture. This consists of a near-hexagonal surface net, lattice constant 129.5 A, folded into a left-handed T = 13 prolate icosahedron elongated along one of its fivefold symmetry axes. Their only apparent difference from wild-type T-even phage capsids is their abnormally elongated tubular part. A comparison of the capsomere morphologies and protein compositions of the giant phage capsids showed that all T4D giants are identical but differ from T2L: The T4D capsomere has a complex (6 + 6 + 1)-type morphology, whereas the T2L has a simple 6-type. T2L phage, however, lack two capsid proteins, "soc" and "hoc", present in T4D. The difference in capsomere morphology can therefore be related to the difference in the protein compositions of these two phage. Possible differences between the initiation and means of length regulation of giant phage heads and the aberrant polyheads are discussed.     

极地平流层云及其非均相化学

南极臭氧洞的形成与南极平流层云及其非均相化学过程有很大关系.南极平流层云中存在着硫酸气溶胶粒子、与硫酸/硝酸/水有关的固体或液体粒子以及水的冰晶粒子等,在其表面上可以发生非均相化学反应,一方面使本来比较惰性的硝酸氯(ClONO₂)具有相当大的活性,另一方面可以把NO₂或硝酸以硝酸固体粒子的形式从平流层中移走.由非均相化学产生的HOCl和Cl₂发生光离解,产生活性氯,加强了与ClO的二聚物或者与ClO-BrO互反应有关的破坏臭氧的催化循环圈的进行,加快南极臭氧洞的形成.本文重点介绍极地平流层云及其非均相化学在极地平流层臭氧消耗过程中的作用,使人们对加重平流层臭氧消耗的非均相化学有所了解。