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"Kinetics"
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Correction: Growth and Nitrogen Uptake Kinetics in Cultured Prorocentrum donghaiense
[...]this work was supported by NOAA and NSF grants to MRM, and Natural Science Foundation of China (NSFC) (Grant Numbers 40776078, 40876074, 41176104, U1133003). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.”
Journal Article
Ozawa’s kinetic method for analyzing thermoanalytical curves
By reviewing the history of thermal analysis and its application to the kinetic analysis of the solid-state processes, we investigate the theoretical basis and historical perspective of Ozawa’s kinetic method for analyzing thermoanalytical curves. Ozawa’s nonisothermal kinetic method is demonstrated using thermoanalytical data for the thermal decomposition of sodium hydrogencarbonate and the crystallization of anhydrous magnesium acetate glass as examples. Through investigating recent theoretical advancements in nonisothermal kinetic analysis in view of the theoretical fundamentals of Ozawa’s kinetic method, it is indicated that they are in line with Ozawa’s kinetic theory. On the basis of the above investigations, we discuss the role of Ozawa’s kinetic theory in advancing the analysis of complex reaction kinetics.
Journal Article
Velocity-resolved kinetics of site-specific carbon monoxide oxidation on platinum surfaces
Catalysts are widely used to increase reaction rates. They function by stabilizing the transition state of the reaction at their active site, where the atomic arrangement ensures favourable interactions
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. However, mechanistic understanding is often limited when catalysts possess multiple active sites—such as sites associated with either the step edges or the close-packed terraces of inorganic nanoparticles
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–
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—with distinct activities that cannot be measured simultaneously. An example is the oxidation of carbon monoxide over platinum surfaces, one of the oldest and best studied heterogeneous reactions. In 1824, this reaction was recognized to be crucial for the function of the Davy safety lamp, and today it is used to optimize combustion, hydrogen production and fuel-cell operation
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,
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. The carbon dioxide products are formed in a bimodal kinetic energy distribution
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–
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; however, despite extensive study
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, it remains unclear whether this reflects the involvement of more than one reaction mechanism occurring at multiple active sites
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,
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. Here we show that the reaction rates at different active sites can be measured simultaneously, using molecular beams to controllably introduce reactants and slice ion imaging
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,
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to map the velocity vectors of the product molecules, which reflect the symmetry and the orientation of the active site
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. We use this velocity-resolved kinetics approach to map the oxidation rates of carbon monoxide at step edges and terrace sites on platinum surfaces, and find that the reaction proceeds through two distinct channels
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–
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: it is dominated at low temperatures by the more active step sites, and at high temperatures by the more abundant terrace sites. We expect our approach to be applicable to a wide range of heterogeneous reactions and to provide improved mechanistic understanding of the contribution of different active sites, which should be useful in the design of improved catalysts.
The catalytic oxidation of carbon monoxide over platinum proceeds through two distinct channels: it is dominated at low temperatures by the more active step sites and at high temperatures by the more abundant terrace sites of the platinum surface.
Journal Article
Standardized assays for determining the catalytic activity and kinetics of peroxidase-like nanozymes
Nanozymes are nanomaterials exhibiting intrinsic enzyme-like characteristics that have increasingly attracted attention, owing to their high catalytic activity, low cost and high stability. This combination of properties has enabled a broad spectrum of applications, ranging from biological detection assays to disease diagnosis and biomedicine development. Since the intrinsic peroxidase activity of Fe3O4 nanoparticles (NPs) was first reported in 2007, >40 types of nanozymes have been reported that possess peroxidase-, oxidase-, haloperoxidase- or superoxide dismutase–like catalytic activities. Given the complex interdependence of the physicochemical properties and catalytic characteristics of nanozymes, it is important to establish a standard by which the catalytic activities and kinetics of various nanozymes can be quantitatively compared and that will benefit the development of nanozyme-based detection and diagnostic technologies. Here, we first present a protocol for measuring and defining the catalytic activity units and kinetics for peroxidase nanozymes, the most widely used type of nanozyme. In addition, we describe the detailed experimental procedures for a typical nanozyme strip–based biological detection test and demonstrate that nanozyme-based detection is repeatable and reliable when guided by the presented nanozyme catalytic standard. The catalytic activity and kinetics assays for a nanozyme can be performed within 4 h.
Journal Article
Kinetics of liquid phase batch adsorption experiments
Batch adsorption experiments are carried out by adding a known amount of adsorbent to a liquid solution at a known initial concentration and following the evolution in time of the concentration of the adsorbate. This is a very common method to obtain equilibrium and kinetic information in liquid systems, but in most cases kinetic results are analysed on the basis of empirical models. Two phenomenological models based on macropore diffusion in beads and shrinking core kinetics are used to generate data that are then interpreted with the widely used unconstrained linear regression methods. The results show that for both cases R2 values close to unity are obtained leading to the incorrect interpretation of the mechanism of mass transport. It is recommended that batch adsorption experiments should be analysed using phenomenological models to obtain physical parameters that are applicable to other systems and to reduce the experiments required to characterise fully the kinetics of adsorption.
Journal Article
DNA as a universal substrate for chemical kinetics
Molecular programming aims to systematically engineer molecular and chemical systems of autonomous function and ever-increasing complexity. A key goal is to develop embedded control circuitry within a chemical system to direct molecular events. Here we show that systems of DNA molecules can be constructed that closely approximate the dynamic behavior of arbitrary systems of coupled chemical reactions. By using strand displacement reactions as a primitive, we construct reaction cascades with effectively unimolecular and bimolecular kinetics. Our construction allows individual reactions to be coupled in arbitrary ways such that reactants can participate in multiple reactions simultaneously, reproducing the desired dynamical properties. Thus arbitrary systems of chemical equations can be compiled into real chemical systems. We illustrate our method on the Lotka-Volterra oscillator, a limit-cycle oscillator, a chaotic system, and systems implementing feedback digital logic and algorithmic behavior.
Journal Article
Bridging Disciplines in Enzyme Kinetics: Understanding Steady-State, Transient-State and Performance Parameters
Enzyme kinetics is fundamental across diverse fields—from enzymology and medicine to biocatalysis and metabolic engineering. Analyses of enzyme kinetics provide insights into catalytic rates, substrate affinities, inhibition patterns, productivities and mechanistic pathways, which are critical for areas such as drug development, industrial biocatalysis and mechanistic enzymology. However, each research field emphasizes different types of kinetic parameters, leading to challenges in establishing a common ground for understanding and interpreting enzyme properties. This review covers interpretation of enzyme kinetic parameters under three main categories—steady-state, transient-state and performance metrics—in a descriptive way and discusses their relevance with respect to different scientific and applied fields that investigate and utilize enzymes. By comparatively defining key kinetic and thermodynamic parameters, the review aims to help researchers interpret and report enzyme behavior more effectively, bridging gaps across interdisciplinary fields.
Journal Article