scholarly journals A chemical reaction controlled by light-activated molecular switches based on hetero-cyclopentanediyls

2019 ◽  
Vol 10 (12) ◽  
pp. 3486-3493 ◽  
Author(s):  
Jonas Bresien ◽  
Thomas Kröger-Badge ◽  
Stefan Lochbrunner ◽  
Dirk Michalik ◽  
Henrik Müller ◽  
...  
Keyword(s):  
Small Molecules ◽  
Computational Methods ◽  
Chemical Reactions ◽  
Chemical Reaction ◽  
Molecular Switches ◽  
Control Chemical

Biradicals were applied as molecular switches to control chemical reactions that involve the activation of small molecules. The mechanism was studied by experimental and computational methods.

Normal approximations for distributions arising in the stochastic approach to chemical reaction kinetics

1981 ◽  
Vol 18 (01) ◽  
pp. 263-267 ◽  
Author(s):  
F. D. J. Dunstan ◽  
J. F. Reynolds
Keyword(s):  
Reaction Kinetics ◽  
Chemical Reactions ◽  
Chemical Reaction ◽  
Stochastic Approach ◽  
Algebraic Functions ◽  
Chemical Reaction Kinetics ◽  
Normal Approximations ◽  
Formal Solutions

Earlier stochastic analyses of chemical reactions have provided formal solutions which are unsuitable for most purposes in that they are expressed in terms of complex algebraic functions. Normal approximations are derived here for solutions to a variety of reactions. Using these, it is possible to investigate the level at which the classical deterministic solutions become inadequate. This is important in fields such as radioimmunoassay.

scholarly journals Mapping the Space of Chemical Reactions using Attention-Based Neural Networks

2020 ◽  
Author(s):  
Philippe Schwaller ◽  
Daniel Probst ◽  
Alain C. Vaucher ◽  
Vishnu H Nair ◽  
David Kreutter ◽  
...  
Keyword(s):  
Neural Networks ◽  
Reaction Center ◽  
Chemical Reactions ◽  
Chemical Reaction ◽  
Classification Accuracy ◽  
Similarity Searching ◽  
Reaction Space ◽  
Fine Grained ◽  
Visual Clustering ◽  
Better Than

<div><div><div><p>Organic reactions are usually assigned to classes grouping reactions with similar reagents and mechanisms. Reaction classes facilitate communication of complex concepts and efficient navigation through chemical reaction space. However, the classification process is a tedious task, requiring the identification of the corresponding reaction class template via annotation of the number of molecules in the reactions, the reaction center and the distinction between reactants and reagents. In this work, we show that transformer-based models can infer reaction classes from non-annotated, simple text-based representations of chemical reactions. Our best model reaches a classification accuracy of 98.2%. We also show that the learned representations can be used as reaction fingerprints which capture fine-grained differences between reaction classes better than traditional reaction fingerprints. The unprecedented insights into chemical reaction space enabled by our learned fingerprints is illustrated by an interactive reaction atlas providing visual clustering and similarity searching. </p><p><br></p><p>Code: https://github.com/rxn4chemistry/rxnfp</p><p>Tutorials: https://rxn4chemistry.github.io/rxnfp/</p><p>Interactive reaction atlas: https://rxn4chemistry.github.io/rxnfp//tmaps/tmap_ft_10k.html</p></div></div></div>

scholarly journals Mass transfer with complex reversible chemical reactions—I. Single reversible chemical reaction

1989 ◽  
Vol 44 (10) ◽  
pp. 2295-2310 ◽  
Author(s):  
G.F. Versteeg ◽  
J.A.M. Kuipers ◽  
F.P.H. Van Beckum ◽  
W.P.M. Van Swaaij
Keyword(s):  
Mass Transfer ◽  
Chemical Reactions ◽  
Chemical Reaction ◽  
Reversible Chemical Reaction

Kinetic study of key species and reactions of atmospheric pressure pulsed corona discharge in humid air

2021 ◽  
Author(s):  
Yongkang Peng ◽  
Xiaoyue Chen ◽  
Yeqiang Deng ◽  
Lan Lei ◽  
Zhan Haoyu ◽  
...  
Keyword(s):  
Chemical Reactions ◽  
Chemical Reaction ◽  
Atmospheric Pressure ◽  
Discharge Plasma ◽  
Reaction Rates ◽  
Global Model ◽  
Discharge Process ◽  
Humid Air ◽  
Pressure Discharge ◽  
Atmospheric Pressure Discharge

Abstract The traditional corona discharge fluid model considers only electrons, positive and negative ions, and the discharge parameters are determined using the simplified weighting method involving the partial pressure ratio. Atmospheric pressure discharge plasma in humid air involves three main neutral gas molecule types: N2, O2, and H2O(g). However, in these conditions, the discharge process involves many types of particles and chemical reactions, and the charge and substance transfer processes are complex. At present, the databases of plasma chemical reaction equations are still expanding based on scholarly research. In this study, we examined the key particles and chemical reactions that substantially influence plasma characteristics. In summarizing the chemical reaction model for the discharge process of N2–O2–H2O(g) mixed gases, 65 particle types and 673 chemical reactions were investigated. On this basis, a global model of atmospheric pressure humid air discharge plasma was developed, with a focus on the variation of charged particles densities and chemical reaction rates with time under the excitation of a 0–200 Td pulsed electric field. Particles with a density greater than 1% of the electron density were classified as key particles. For such particles, the top ranking generation or consumption reactions (i.e., where the sum of their rates was greater than 95% of the total rate of the generation or consumption reactions) were classified as key chemical reactions On the basis of the key particles and reactions identified, a simplified global model was derived. A comparison of the global model with the simplified global model in terms of the model parameters, particle densities, reaction rates (with time), and calculation efficiencies demonstrated that both models can adequately identify the key particles and chemical reactions reflecting the chemical process of atmospheric pressure discharge plasma in humid air. Thus, by analyzing the key particles and chemical reaction pathways, the charge and substance transfer mechanism of atmospheric pressure pulse discharge plasma in humid air was revealed, and the mechanism underlying water vapor molecules’ influence on atmospheric pressure air discharge was elucidated.

Chemical Reaction Kinetics in Solution

2004 ◽  
Author(s):  
W. Ronald Fawcett
Keyword(s):  
Reaction Kinetics ◽  
Chemical Reactions ◽  
Chemical Reaction ◽  
Physical Property ◽  
Theoretical Description ◽  
Time Range ◽  
Chemical Changes ◽  
Elementary Reactions ◽  
Chemical Reaction Kinetics ◽  
Liquid Solutions

The kinetics of chemical reactions were first studied in liquid solutions. These experiments involved mixing two liquids and following the change in the concentration of a reactant or product with time. The concentration was monitored by removing a small sample of the solution and stopping the reaction, for example, by rapidly lowering the temperature, or by following a physical property of the system in situ, for example, its color. Although the experiments were initially limited to slow reactions, they established the basic laws governing the rate at which chemical changes occur. The variables considered included the concentrations of the reactants and of the products, the temperature, and the pressure. Thus, the reacting system was examined using the variables normally considered for a system at equilibrium. Most reactions were found to be complex, that is, to be made up of several elementary steps which involved one or two reactants. As the fundamental concepts of chemical kinetics developed, there was a strong interest in studying chemical reactions in the gas phase. At low pressures the reacting molecules in a gaseous solution are far from one another, and the theoretical description of equilibrium thermodynamic properties was well developed. Thus, the kinetic theory of gases and collision processes was applied first to construct a model for chemical reaction kinetics. This was followed by transition state theory and a more detailed understanding of elementary reactions on the basis of quantum mechanics. Eventually, these concepts were applied to reactions in liquid solutions with consideration of the role of the non-reacting medium, that is, the solvent. An important turning point in reaction kinetics was the development of experimental techniques for studying fast reactions in solution. The first of these was based on flow techniques and extended the time range over which chemical changes could be observed from a few seconds down to a few milliseconds. This was followed by the development of a variety of relaxation techniques, including the temperature jump, pressure jump, and electrical field jump methods. In this way, the time for experimental observation was extended below the nanosecond range.

scholarly journals VIII. On the apparent change in weight during chemical reaction

1913 ◽  
Vol 212 (484-496) ◽  
pp. 227-260
Keyword(s):  
Chemical Reactions ◽  
Chemical Reaction ◽  
Experimental Work ◽  
Total Mass ◽  
Apparent Change ◽  
Chemically Reacting

During the year 1890 the late Prof. Landolt inaugurated his prolonged researches upon the apparent alteration in the total mass of chemically reacting substances. From the time of its inception until it was brought to a conclusion in 1907, the experimental work was freely varied both as regards the conditions and the nature of the chemical reactions involved. The methods and precautions adopted, together with the final results obtained, are to be found embodied and set forth in detail in Landolt’s important memoir, “Über die Erhaltung der Masse hei Chemischen Umsetzungen.”* Before proceeding to deal with my own investigations in this field of research, it may not be inappropriate first very briefly to recall the chief features of Landolt’s work and conclusions.

Emerging concepts in pseudoenzyme classification, evolution, and signaling

2019 ◽  
Vol 12 (594) ◽  
pp. eaat9797 ◽  
Author(s):  
António J. M. Ribeiro ◽  
Sayoni Das ◽  
Natalie Dawson ◽  
Rossana Zaru ◽  
Sandra Orchard ◽  
...  
Keyword(s):  
Small Molecules ◽  
A Priori ◽  
Molecular Switches ◽  
Regulatory Mechanisms ◽  
Signaling Networks ◽  
Control Assembly ◽  
Experimental Approaches ◽  
Catch Up ◽  
Enzyme Families ◽  
Selection Of

The 21st century is witnessing an explosive surge in our understanding of pseudoenzyme-driven regulatory mechanisms in biology. Pseudoenzymes are proteins that have sequence homology with enzyme families but that are proven or predicted to lack enzyme activity due to mutations in otherwise conserved catalytic amino acids. The best-studied pseudoenzymes are pseudokinases, although examples from other families are emerging at a rapid rate as experimental approaches catch up with an avalanche of freely available informatics data. Kingdom-wide analysis in prokaryotes, archaea and eukaryotes reveals that between 5 and 10% of proteins that make up enzyme families are pseudoenzymes, with notable expansions and contractions seemingly associated with specific signaling niches. Pseudoenzymes can allosterically activate canonical enzymes, act as scaffolds to control assembly of signaling complexes and their localization, serve as molecular switches, or regulate signaling networks through substrate or enzyme sequestration. Molecular analysis of pseudoenzymes is rapidly advancing knowledge of how they perform noncatalytic functions and is enabling the discovery of unexpected, and previously unappreciated, functions of their intensively studied enzyme counterparts. Notably, upon further examination, some pseudoenzymes have previously unknown enzymatic activities that could not have been predicted a priori. Pseudoenzymes can be targeted and manipulated by small molecules and therefore represent new therapeutic targets (or anti-targets, where intervention should be avoided) in various diseases. In this review, which brings together broad bioinformatics and cell signaling approaches in the field, we highlight a selection of findings relevant to a contemporary understanding of pseudoenzyme-based biology.

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