MOOC时代下化学分析课堂的改革

大型开放式网络课程(MOOC,译为慕课)的提出对化学分析课堂改革提供了新的思路,MOOC的实践显现了有待解决的问题;针对化学分析课堂现状,拟采用线上与线下结合的混合教学模式推进课堂改革,对具体的方案进行了讨论。此计划有望提高化学分析课堂教学质量、培养师生在网络时代下的信息素质,改进人才的培养模式。     

Performance validation of neural network based (13)c NMR prediction using a publicly available data source

The validation of the performance of a neural network based 13C NMR prediction algorithm using a test set available from an open source publicly available database, NMRShiftDB, is described. The validation was performed using a version of the database containing ca. 214,000 chemical shifts as well as for two subsets of the database to compare performance when overlap with the training set is taken into account. The first subset contained ca. 93,000 chemical shifts that were absent from the ACD\CNMR DB, the "excluded shift set" used for training of the neural network and the ACD\CNMR prediction algorithm, while the second contained ca. 121,000 shifts that were present in the ACD\CNMR DB training set, the "included shift set". This work has shown that the mean error between experimental and predicted shifts for the entire database is 1.59 ppm, while the mean deviation for the subset with included shifts is 1.47 and 1.74 ppm for excluded shifts. Since similar work has been reported online for another algorithm we compared the results with the errors determined using Robien's CNMR Neural Network Predictor using the entire NMRShiftDB for program validation.     

Selection of appropriate training and validation set chemicals for modelling dermal permeability by U-optimal design

Quantitative structure-activity relationship (QSAR) models are being used increasingly in skin permeation studies. The main idea of QSAR modelling is to quantify the relationship between biological activities and chemical properties, and thus to predict the activity of chemical solutes. As a key step, the selection of a representative and structurally diverse training set is critical to the prediction power of a QSAR model. Early QSAR models selected training sets in a subjective way and solutes in the training set were relatively homogenous. More recently, statistical methods such as D-optimal design or space-filling design have been applied but such methods are not always ideal. This paper describes a comprehensive procedure to select training sets from a large candidate set of 4534 solutes. A newly proposed ‘Baynes’ rule’, which is a modification of Lipinski's ‘rule of five’, was used to screen out solutes that were not qualified for the study. U-optimality was used as the selection criterion. A principal component analysis showed that the selected training set was representative of the chemical space. Gas chromatograph amenability was verified. A model built using the training set was shown to have greater predictive power than a model built using a previous dataset [1].     

Effectiveness of a short training session for improving pipetting accuracy

The quality of diagnostic tests conducted by the Animal Quarantine Service (AQS) is critical to the safety of national livestock production. In procedures for tests such as polymerase chain reaction and enzyme-linked immunosorbent assay, measurement of tiny quantities of samples or reagents is quite common. Therefore, many efforts have been made to maintain the quality of micropipette operations, including routine calibration of equipment and training programs for operators. In this study, we developed a pilot training program to analyze the effects of training on pipetting accuracy, i.e., trueness and precision. The program involved a self-instruction A4-sized leaflet describing how to improve pipetting technique. Thirty-three staff members from seven AQS laboratories participated in the program. Each participant repeated sampling of 300 μL of distilled water 10 times before and after reading the leaflet, and the effects of training on the trueness and precision of the pipetting results were analyzed. To determine pipetting trueness, we examined the variation of the delivered volume from the target volume (300 μL) using the proportional odds mixture model. Our data demonstrated that participation in the training program and the level of experience with pipetting significantly improved trueness. Analysis of standard deviations of the ten samplings, as an indicator of precision, also showed that participation in the training program improves pipetting precision. Thus, our data supported the implementation of such simple, quick training sessions to improve pipetting trueness and precision in diagnostic laboratories.     

利用在线加压溶剂提取-超高效液相色谱-离子阱-飞行时间-质谱法定性分析片仔癀化学成分组

片仔癀(Pien-Tze-Huang)是由三七、牛黄、蛇胆、麝香等名贵中药经加工精制而成的中药制剂.片仔癀中的三七皂苷、胆汁酸以及麝香酮等主要化学成分已被深入研究,然而其全方化学成分组成尚未被整体阐明.该文建立了在线加压溶剂提取-超高效液相色谱-离子阱-飞行时间质谱(online PLE-UHPLC-IT-TOF-MS...     

Why relevant chemical information cannot be exchanged without disclosing structures

Both society and industry are interested in increasing the safety of pharmaceuticals. Potentially dangerous compounds could be filtered out at early stages of R&D by computer prediction of biological activity and ADMET characteristics. Accuracy of such predictions strongly depends on the quality & quantity of information contained in a training set. Suggestion that some relevant chemical information can be added to such training sets without disclosing chemical structures was generated at the recent ACS Symposium. We presented arguments that such safety exchange of relevant chemical information is impossible. Any relevant information about chemical structures can be used for search of either a particular compound itself or its close analogues. Risk of identifying such structures is enough to prevent pharma industry from relevant chemical information exchange.     

Obtaining Kinetic Parameters by Modulated Thermogravimetry

A new technique, called modulated thermogravimetry, is introduced as a tool for obtaining continuous kinetic information for decomposition and volatilization reactions. The approach makes use of an oscillatory temperature program to obtain kinetic parameters during a mass loss. MTGA™ may be used under quasi-isothermal conditions to observe a single mass loss or may be combined with linear heating rate or Hi-Res™ controlled rate thermogravimetry to scan from one mass loss region to another. Results obtained are in agreement with those obtained by other kinetic methods. This revised version was published online in July 2006 with corrections to the Cover Date.     

Using sheath‐liquid reagents for capillary electrophoresis‐mass spectrometry: Application to the analysis of phenolic plant extracts

The combination of CE and MS is now a widely used tool that can provide a combination of high resolution separations with detailed structural information. Recently, we highlighted the benefits of an approach to add further functionality to this well‐established hyphenated technique, namely the possibility to perform chemical reactions within the sheath‐liquid of the CE‐MS interface 1 . Apart from using hydrogen/deuterium exchange for online determination of numbers of exchangeable protons, the addition of DPPH? (2,2‐diphenyl‐1‐picrylhydrazyl) to the sheath‐liquid can be used as a fast screening tool for studying antioxidant characteristics of individual components. Such a CE‐MS methodology allows rapid and information‐rich analysis with minimal reagent and sample consumption to be performed. In the present work, we demonstrate the applicability of this approach for the characterization of phenolic plant extracts from the Labiatae family, namely Rosmarinus officinalis and Melissa officinalis. Using the described approach, a wide range of compounds (15 and 13 phenolic compounds, respectively) could be confidently identified using a combination of high resolution CE‐MS separations with implementation of online deuterium exchange and DPPH? reactions. These compounds included polyphenols, phenolic acids, and triterpene acids. In conjunction with online MS/MS experiments, extensive structural information for aglyconic and glycosylated antioxidants present in the extracts could be obtained using simple experimental changes, which can be carried out prior to the purchasing of expensive chemical standards or the time‐consuming preparative isolation of individual compounds.     

从能源产业发展和人才需求浅谈“能源化学”新工科改造

Based on building emerging engineering education of "energy chemistry", we investigated the state key petro-chemical enterprises according to the industrial development and the demand of professional talents. The research report summarizes, analyzes and discusses the current priority development fields of industry, the talent training status, curriculum structure and education program of the chemistry and chemical engineering in universities. The ideas on emerging engineering education of "energy chemistry" have been proposed, and it will be beneficial to building a novel education program for talents training, which integrates the principle of chemistry, energy conversion and information science, etc.     

CheD: chemical database compilation tool, Internet server, and client for SQL servers

An efficient program, which runs on a personal computer, for the storage, retrieval, and processing of chemical information, is presented, The program can work both as a stand-alone application or in conjunction with a specifically written Web server application or with some standard SQL servers, e.g., Oracle, Interbase, and MS SQL. New types of data fields are introduced, e.g., arrays for spectral information storage, HTML and database links, and user-defined functions. CheD has an open architecture; thus, custom data types, controls, and services may be added. A WWW server application for chemical data retrieval features an easy and user-friendly installation on Windows NT or 95 platforms.     

以学生为中心的物理化学远程教学初探

During the fight against the new coronavirus epidemic, the "Physical Chemistry" team of Beijing Normal University used various network platforms and tools, such as MOOC of China University, Rain Classroom and WeChat Group in the teaching process. The exploration and practice of online learning of "Physical Chemistry" is carried out based on MOOC teaching, with student learning as the center and teacher guidance as the support. Taking the most difficult chapter of "fundamentals for statistical thermodynamic" as an example, we designed a complex teaching program that includes previews, watching MOOC videos in class, real-time online exercises, teachers' answers, and after-class reflection and questioning. The students were encouraged to learn independently through the reserved information, designed activities and assignments. Practice shows that the online course has cultivated the students' self-management ability, trained their critical thinking skills, and achieved good teaching results.     

Computer-Assisted Solution of Chemical Problems—The Historical Development and the Present State of the Art of a New Discipline of Chemistry

The topic of this article is the development and the present state of the art of computer chemistry, the computer-assisted solution of chemical problems. Initially the problems in computer chemistry were confined to structure elucidation on the basis of spectroscopic data, then programs for synthesis design based on libraries of reaction data for relatively narrow classes of target compounds were developed, and now computer programs for the solution of a great variety of chemical problems are available or are under development. Previously it was an achievement when any solution of a chemical problem could be generated by computer assistance. Today, the main task is the efficient, transparent, and non-arbitrary selection of meaningful results from the immense set of potential solutions—that also may contain innovative proposals. Chemistry has two aspects, constitutional chemistry and stereochemistry, which are interrelated, but still require different approaches. As a result, about twenty years ago, an algebraic model of the logical structure of chemistry was presented that consisted of two parts: the constitution-oriented algebra of be- and r-matrices, and the theory of the stereochemistry of the chemical identity group. New chemical definitions, concepts, and perspectives are characteristic of this logic-oriented model, as well as the direct mathematical representation of chemical processes. This model enables the implementation of formal reaction generators that can produce conceivable solutions to chemical problems—including unprecedented solutions—without detailed empirical chemical information. New formal selection procedures for computer-generated chemical information are also possible through the above model. It is expedient to combine these with interactive methods of selection. In this review, the Munich project is presented and discussed in detail. It encompasses the further development and implementation of the mathematical model of the logical structure of chemistry as well as the experimental verification of the computer-generated results. The article concludes with a review of new reactions, reagents, and reaction mechanisms that have been found with the PC-programs IGOR and RAIN.     

Radiotracer investigation of phosphoric acid and phosphatic fertilizers production process

In the phosphoric acid production process, the time a particle spends inside the chemical reactor (residence time) is of paramount importance to process engineers. Residence time distribution (RTD) gives information on the efficiency of the chemical reactor, on the efficiency of the process, and also the availabilities of the reactive volume for the reaction (active volume vs. dead volume). Traditionally, chemical engineers used chemical tracer to determine the RTD. However, first disadvantage is that the chemical tracer could not allow an online diagnosis: the samples containing chemical tracer have to go to a lab for analysis, second disadvantage is that the chemical tracer is less sensitive than radioactive ones because of its adsorption onto strata or its retention in rocks. Consequently, chemical tracer results are not always precise and cannot convincingly explain the multiple flow-path model. Radioactive tracers are the only tracers capable of measuring the active RTD with high degree of precision and give information on the internal recirculation rate. In this work, we will describe the application of radiotracer method for RTD measurement in the phosphoric acid production process and give results and discussion of each case encountered.     

IR Spectrum Data Bank System

The infrared spectra of pure compounds of ninety thousands, poly compounds of twelve thousand, drugs of one thousand were included in the data bank. All of them can be searched out according to their serial number, chemical name, commercial name, amount of each atoms, or molecular formula, as well as their spectrum peak appearances. Program for spectrum information inputting, program for spectrum information search and program for spectrum peak appearance search were included in the system; in addition, spectrum information data bank, spectrum peak code data bank and spectrum figure data bank were attached to the system. System program was written by Visial Basic, and run under Windows system. The spectrum information data bank and spectrum figure data bank were administrated by Microsoft Access.The program for spectrum message inputting can be used to add message data and spectrum figure of some new compounds into the data banks by users themselves. The program for spectrum message search was designed to find out all the message data and spectrum figure of interested compound according to someone of the message data. The program for spectrum peak search was designed to find out some spectra most similar in peak shape with unknown spectrum by peak to peak comparison. When the wavenumbers and transmittances of main peaks in the spectrum of unknown sample were entered, the spectrum peak search was performed and several hits with higher similarity were reported including their similarity scores, spectrum serial numbers, sample's states,melt points, molecular formulas as well as spectrum images. If the search result was not satisfactory,some methods to modify spectrum parameters were reminded and search was performed again.     

QSPR modelling of the soil sorption coefficient from training sets of different sizes

Quantitative structure–property relationship (QSPR) modelling has been used in many scientific fields. This approach has been extensively applied in environmental research to predict physicochemical properties of compounds with potential environmental impact. The soil sorption coefficient is an important parameter for the evaluation of environmental risks, and it helps to determine the final fate of substances in the environment. In the last few years, different QSPR models have been developed for the determination of the sorption coefficient. In this study, several QSPR models were generated and evaluated for the prediction of log K_oc from the relationship with log P. These models were obtained from an extensive and diverse training set (n = 639) and from subsets of this initial set (i.e. halves, fourths and eighths). The aim of this study was to investigate whether the size of the training set affects the statistical quality of the obtained models. Furthermore, statistical equivalence was verified between the models obtained from smaller sets and the model obtained from the total training set. The results confirmed the equivalence between the models, thus indicating the possibility of using smaller training sets without compromising the statistical quality and predictive capability, as long as most chemical classes in the test set are represented in the training set.     

The computer processing and interpretation of mass spectral information. VII—identification of ions in terms of structural symbols

A new version of the AELITA-F program for computation of a monoisotopic spectrum and identification of the ion composition as a collection of elements or as structural fragments is described. A technique is proposed for specifying a priori information on the compound in a ‘hybrid’ form which combines structural fragments of the molecule and individual chemical elements. This version permits the elimination of redundant information and reduces the requirements of computer resources. The program effectiveness is increased by reducing the number of ions to be generated. The format in which the mass spectral information is read out is more comprehensible to a chemist.     

The SFU/TRIUMF Radiochemistry Institute an intensive training program for radiopharmaceutical chemistry

An institute for the training of radiochemist was proposed in 1989 by scientists/educators from Simon Fraser University (SFU) and the TRIUMF Nuclear Research Facility in Canada. The intensive program spans 6 weeks and includes seminars and problem sesssions as well as practical laboratory experience. Topics include health physics, synthesis of short lived radiopharmaceuticals, automation and quality control. The first offering was in May–June 1990. Based on this experience a textbook on Radiochemistry and Radiopharmaceutical Chemistry has been initiated. Parts of the program may be implemented into a credit course to be offered through the Department of Chemistry at SFU.     

Rational selection of training and test sets for the development of validated QSAR models

Quantitative Structure–Activity Relationship (QSAR) models are used increasingly to screen chemical databases and/or virtual chemical libraries for potentially bioactive molecules. These developments emphasize the importance of rigorous model validation to ensure that the models have acceptable predictive power. Using k nearest neighbors (kNN) variable selection QSAR method for the analysis of several datasets, we have demonstrated recently that the widely accepted leave-one-out (LOO) cross-validated R² (q²) is an inadequate characteristic to assess the predictive ability of the models [Golbraikh, A., Tropsha, A. Beware of q2! J. Mol. Graphics Mod. 20, 269-276, (2002)]. Herein, we provide additional evidence that there exists no correlation between the values of q ² for the training set and accuracy of prediction (R ²) for the test set and argue that this observation is a general property of any QSAR model developed with LOO cross-validation. We suggest that external validation using rationally selected training and test sets provides a means to establish a reliable QSAR model. We propose several approaches to the division of experimental datasets into training and test sets and apply them in QSAR studies of 48 functionalized amino acid anticonvulsants and a series of 157 epipodophyllotoxin derivatives with antitumor activity. We formulate a set of general criteria for the evaluation of predictive power of QSAR models.