In living organisms, protein functions are constantly evolving over generations throughout the history. Through iterative rounds of genetic mutations and natural selection of fit phenotypes, protein functions have been gradually optimized. This process could be mimicked and even greatly accelerated in the laboratory, when the selection pressure is directly applied to biomolecules of interest, which forms the basis of a technique called directed evolution. The Nobel Prize in chemistry 2018 was awarded jointly to Frances Arnold, George Smith and Gregory P. Winter for their pioneering contributions to the development and applications of directed evolution. Here we briefly review the history of this technique and its impact on renewable energy and pharmaceutical industry.
This paper introduces new practices in improving laboratory management system for teaching laboratory in universities. The novel practices are based on GB/T19001-2016 quality management system (QMS). The first principle as well as the term 9.1.2 and 10.3 of QMS are used to optimize laboratory management. Laboratory managers and technicians are advised to transform their ideas with the principles of "engagement of all people" and "continuous improvement". The goal is to increase laboratory operation efficiency and management level step by step by applying these proposed techniques in this paper.
The construction of teaching resources is an important work in university teaching reform. Aiming at improving the quality of laboratory teaching and cultivating students' creative ability, the discussion on the teaching resources of organic chemistry laboratory in our university was conducted and provided by network platform as assistant teaching. The effect of preview before class was improved by the video resources. The experiment design idea and creative ability were cultivated for college students by courseware resources. The students' view was broadened and the interest in chemical experiment was inspired by supplementary resources. The basic theoretical knowledge was tested accurately by examination resources database online. After the application of teaching resources, both the teaching effect and teaching quality were improved effectively.
High quality laboratory teaching material is an important guarantee for undergraduate laboratory teaching and plays an important role in the cultivation of innovative talents. The article introduces the construction of comprehensive experimental teaching material of chemical biology course from the fields as follows:writing background, guiding ideology, projects writing and revision, etc. This teaching material has been through more than 10 years' test of laboratory teaching, and can better meet the needs of cultivating students' related disciplines.
The manuscript starts from fundamental knowledge of amino acid metabolism, followed by the analysis of how and why we incorporate it into current biochemistry education. These metabolic processes containing different biochemical reaction mechanisms are generally fascinating, and thus can be selected as good study materials for undergraduate education to attract their attention. Based on the discussion of various amino acid examples, the significance is demonstrated in different aspects as diversity, complexity, attractivity and inseparability. It is a meaningful trial of installing frontier research into fundamental knowledge to deepen amino acid metabolic contents in biochemistry education.
Low friction is the most outstanding feature of ice surface. The existence of liquid water on ice surface, which serves as lubricant, has been taken as the main cause for its low friction. Three main hypotheses for the formation of liquid water on ice surface were introduced and analyzed. It was found that the pressure-melting, friction heat-melting and pre-melting theories cannot give satisfactory explanation to all facts. Based on the previous studies, it was clear that the formation of liquid water was not the only reason for explaining the low friction of ice. A new model that there is a transition layer with small ice particles and liquid water forming a gel-like amorphous structure on the ice surface is proposed. Owing to the weak interaction between these small ice particles, they can easily slide or rotate along the shear direction and thus reduce friction. Both the rotation of ice particles and lubrication of liquid water benefit excellent slipperiness of ice surface.
Carboranes exhibit three-dimensional aromaticity as well as stable physical and chemical properties due to their unique molecular cages, which not only enable the wide application in organoboron and organometallic chemistry, but also result in increasing potential applications in fields such as biology and materials science. This article briefly describes the development of carborane chemistry and the structural properties of carboranes, in particular reviewing recent progresses of carboranes in biomedicine, luminescent material, and catalysis. The authors hope to give a hand to readers in a quick scan of the most recent progresses in carborane chemistry.
Tetraphenylethylene and its derivatives with propeller structure have excellent fluorescence properties, which can be applied to the fields of organic photo-electric materials, fluorescence sensing and biological imaging due to the aggregation-induced fluorescence property. In this experiment, tetraphenylethylene was synthesized by McMurry coupling reaction using benzophenone as starting materials. The target compound was separated and purified by extraction, drying and column chromatography, and its structure was characterized by the melting point measurement, 1H NMR, 13C NMR, and MS. The fluorescence detection limit for explosives was determined by fluorescence spectra using picric acid as a model compound. This experiment with the research focuses can improve the students' experimental skills, help students to understand the current status and applications of tetraphenylethylene and its derivatives with aggregation-induced fluorescence property, and stimulate students' interest in scientific research and innovation consciousness.
By using the light sensor of smartphone, a simple photometer was designed. Also, an Android APP was developed to show the online signal and calculate the absorbance automatically. This photometer uses a flow cell of HPLC UV-detector as sample absorption cell and an optical fiber to transfer the light signal. The mobile-phone photometer can greatly reduce the amount of reagents used. Only 200 μL sample is needed to run a test, which effectively reduces laboratory waste. There is a good linear relationship with R2 value 0.9991 while using the photometer to measure the iron ion standard solution, which means it can replace the traditional spectrophotometer in chemical experiments. Students can enhance their understanding of the instrument principles and inspire their creativity by using this DIY photometer.
This paper designed a facile comprehensive experiment based on the frontier research topic of gold nanoparticles. The well-dispersed gold suspensions were synthesized by the reduction of chloroauric acid with sodium citrate and their size-dependent optical properties were discussed. Moreover, the gold nanoparticles were explored as primary electrolyte sensors because the addition of electrolytes induced aggregation of the nanoparticles and caused color changes.
Advanced network technology can help form an effective closed loop for the management of hazardous wastes in universities, reduce the harm to chemistry from chemistry teaching and research activities, and roughly understand the teaching and research work of each laboratory through the dynamic monitoring of laboratory hazardous wastes. This will give reasonable suggestions to promote the environmental protection and safety work that universities and colleges laboratories need to solve urgently.
Hot pot is a famous traditional Chinese cuisine. During hot pot, people usually judge whether or not the meat is well done by observation. This way for making judgement lacks scientific support and may possibly cause safety risks. In this paper, we set up two models for meat slice and ball, respectively, and treated the heat transfer from soup to the very center of meat based on these unsteady state heat transfer models. The temperature of very center of meat is plotted against time, and the time required for heating the very center of meat to ca. 100℃ was determined. It was found that the time required for the center temperature to attain 100℃ is ca. 15 s for meat slice of 1.8 mm thick, and more than 8 min for meat ball of 2.6 cm in diameter. The discussion and conclusion are helpful for food safety.
Two different kinds of expressions about freezing point depression were shown in current college chemistry textbooks, leading to the confusion of teachers and students in teaching and learning. Suggestions were put forward with graphic analysis and interpretation of the definition.
Proton nuclear magnetic resonance spectroscopy is one of the most commonly used spectral methods for the characterization of organic compounds. It provides proton information on chemical shifts, integral areas, and coupling splits of organic compounds. The common active hydrogen is a hydrogen atom covalently linked to oxygen, nitrogen, or sulfur. There is rapid active proton exchange which makes significant difference from other carbon-linked hydrogen. Under different conditions, the chemical shift of active hydrogen is not fixed, the peak shape is variable and the coupling split is complicated. In order to cultivate students' practical ability on observing, analyzing and structure characterizing, active hydrogen identification by proton nuclear magnetic resonance spectroscopy was discussed in the article.
Extraction separation is a common operation in chemical experiments. According to the distribution law, the Lagrangian multiplier method is used to derive and prove that the extraction efficiency can be optimized only in the case of using same aliquots of solvent. The limit extraction residual rate of the extraction is related to the physical properties and the dose of the solvent used, as well as other factors. This paper provides reference and guidance on designing extraction method for those engaged in chemical synthesis, analysis, separation, and chemical industry and can be extended to the fields of dilution and solid phase separation.
Colligative properties of dilute strong electrolyte solution, i.e., freezing point depression, boiling point elevation and osmotic pressure, are discussed. As an example, the freezing point depression equation of dilute strong electrolyte solution is derived with the help of Gibbs-Duhem equation. This equation is verified with the freezing point depression experiments of aqueous sodium chloride solutions.
This paper proposes a method of using free software on mobile phones or tablets to remotely control and monitor laboratory equipment. The Ezviz Studio video software is used to monitor laboratory environment and the surrounding of equipment, which provides real-time information on the remotely controlled equipment and operation, and it is also possible to use this software to conduct audio communications with the personnel onsite. The Teamviewer software can be used to monitor the progress of experiments at any time, to remotely control the starting time and finishing time of an experiment or to change the experimental parameters; remotely controlled intelligent switches can be used to control lighting and electricity, which also helps with monitoring the laboratory during night time and turning off unnecessary power consumption. This will help with reducing work loads of laboratory personnel, increasing work efficiency, providing real-time information on the laboratory and functioning of the equipment, enabling timely adjustment of experimental parameters and reducing energy consumption. This paper also introduces the application of Teamviewer on data processing.
This paper discussed the differences between intermolecular interactions and van der Waals force. Based on the physical models of different interactions, some important and confusing concepts were clarified.
Currently, the interpretation of the location effect of electrophilic substitution reaction on benzene ring is mainly based on the qualitative explanation of the experiment. In this paper, we chose five typical mono-substituted benzene molecules (including aniline, toluene, chlorobenzene, nitrobenzene, benzaldehyde) as the representative, and carried out a study on the electrophilic substitution reaction sites of those molecules by quantum chemical methods (including electrostatic potential, atomic charges, frontier molecular orbital theory, Fukui function and dual descriptor, etc.). Through quantitative data and visual graphics, this paper reveals the nature of the orientation of benzene molecular electrophilic substitution reaction, and makes up for the shortcomings in teaching and teaching materials. The results of this study can provide useful reference for the compilation of the organic chemistry textbook and teaching of the organic chemistry course.
This paper introduces the skillful calculation formula and application scope of multi-equilibrium standard equilibrium constant. It is a simple, fast and accurate approach to solve problems. Moreover, it can also intuitively estimate the directionality and extent of reactions using this formula.