Autocatalytic System Research Articles

Oxylipin affects ethylene metabolism and ethylene receptor gene expression levels in peach fruit (Prunus persica L. Batsch)

ABSTRACTThe effects of two oxylipins – jasmonic acid (JA) and 9, 10-ketol-octadecadienoic acid (KODA) – on ethylene metabolism and ethylene receptor genes were examined in peach fruit (Prunus persica L.) harvested at 88 days after full bloom (DAFB), in the pre-climacteric stage, and at 102 DAFB, at the beginning of the climacteric stage. Immediate post-harvest applications of either n-propyl dihydrojasmonate (PDJ) (a JA analog) or KODA stimulated ethylene production and 1-aminocyclopropane-1-carboxylate (ACC) concentrations in fruit that were harvested at 88 and 102 DAFB. KODA application significantly increased levels of ACC oxidase (PpACO1) expression at 5 and 8 days after treatment (DAT) in 88-DAFB-harvested fruit, and at 1 DAT in 102-DAFB-harvested fruit. Expression levels of ethylene response factors (PpERS1) were not influenced by either PDJ or KODA applications at 88 or 102 DAFB. In contrast, levels of ethylene-receptor-coding genes (PpETR1) expression in 88-DAFB KODA-treated fruit increased at 8 and 14 DAT. Expression levels of constitutive triple response (PpCTR1) in the untreated control fruit decreased with DAT in both 88- and 102-DAFB-harvested fruit.These results suggest that certain oxylipins may promote ethylene production in peach fruit, and that PpETR1 and PpCTR1 may be associated with the autocatalytic system of ethylene production.

Autocatalytic degradation of perfluorooctanoic acid in a permanganate-ultrasonic system

An autocatalytic system, permanganate-ultrasonic (PM-US) system, was applied to degrade perfluorooctanoic acid (PFOA) in aqueous solutions. After a 120-min ultrasonication, a PM dosage of 6 mM increased the pseudo first-order rate constant (k1) for PFOA decomposition from 3.5 × 10−3 to 13.0 × 10−3 min−1 and increased the pseudo zeroth-order rate constant (k2) for PFOA defluorination from 1.5 × 10−3 to 7.9 × 10−3 mM·min−1, respectively. The PFOA degradation rates increased proportionally with the enhanced production rates of MnO2 particles. An initial pH 4 condition was optimal for the PFOA degradation compared to highly acidic and neutral conditions. PFOA degradation could be significantly facilitated by increasing power density of ultrasonication from 60 to 180 W·L−1. While increasing solution temperature to 50 °C only slightly promoted the PFOA decomposition and defluorination to 1.15 and 1.07 times of that at 30 °C, respectively. The solution saturated with argon was more favorable for the PFOA degradation in the PM-US system than that saturated with air and oxygen. Co-dissolved Cu(II), Fe(II) and Fe(III) ions inhibited the PFOA degradation by forming metal-PFOA complexes. Based on the experimental results and intermediates analysis, mechanisms and pathways of PFOA decomposition and defluorination in the PM-US system were proposed.

Comparing the Caputo, Caputo-Fabrizio and Atangana-Baleanu derivative with fractional order: Fractional cubic isothermal auto-catalytic chemical system

In this work we extend the standard model for a cubic isothermal auto-catalytic chemical system (CIACS) to a new model of a fractional cubic isothermal auto-catalytic chemical system (FCIACS) based on Caputo (C), Caputo-Fabrizio (CF) and Atangana-Baleanu in the Liouville-Caputo sense (ABC) fractional time derivatives, respectively. We present approximate solutions for these extended models using the q -homotopy analysis transform method (q -HATM). We solve the FCIACS with the C derivative and compare our results with those obtained using the CF and ABC derivatives. The ranges of convergence of the solutions are found and the optimal values of h , the auxiliary parameter, are derived. Finally, these solutions are compared with numerical solutions of the various models obtained using finite differences and excellent agreement is found.

An effective homotopy analysis method to solve the cubic isothermal auto-catalytic chemical system

We established an effective algorithm for the homotopy analysis method (HAM) to solve a cubic isothermal auto-catalytic chemical system (CIACS). Our solution comes in a rapidly convergent series where the intervals of convergence given by h-curves and to find the optimal values of h, we used the averaged residual errors. The HAM solutions are compared with the solutions obtained by Mathematica in-built numerical solver. We also show the behavior of the HAM solution.

Self-reproducing micelles coupled to a secondary catalyst.

We report a physical autocatalytic system where micelles self-reproduce via a copper-catalyzed azide-alkyne cycloaddition in a biphasic reaction mixture. The coupling of a secondary catalyst to an autocatalytic cycle opens up new opportunities to control and probe autocatalytic processes.

Coupled autocatalytic reactions: Interconversion and extinction of species

An autocatalytic reaction involves a species catalyzing its own formation and can be viewed as a mechanism to explain self-replication. This class of chemical reactions can be used to model phenomena across a wide cross-section of disciplines, i.e chemical reaction engineering, biology, ecology, social sciences and economics. Here, we study a system of two species undergoing autocatalysis. Each species participates in the autocatalysis of the other. The autocatalytic reactions can represent interconversion of two social groups or isomers into each other. The two autocatalytic steps are assumed to be elementary and follow cubic and quadratic laws. We examine the behavior of this coupled autocatalytic system at steady state. Specifically, singularity theory and bifurcation theory are applied to classify the bifurcation behavior of the system. The focus of the work is to obtain the conditions for extinction or complete conversion of one of the species. We analyze the system for all combinations of generation and decay reactions. We find the common features and dominant factors in the different combinations analyzed.

Reactor dynamics investigation based on calorimetric data

A simple and general procedure has been developed to determine the thermal behaviour of a reactor based on heat balance, PID temperature control, and jacket behaviour. Using only temperature heating/cooling ramps followed by isothermal stages, such a procedure was tested at laboratory and industrial scale, respectively in a 0.5 L Mettler‐Toledo RC1e and a 100 L industrial reactor. The obtained model was demonstrated to be in good accordance with the measurements. The consistency and robustness of the model were assessed by imposing an external heat profile based on an autocatalytic reaction system. The results have proven that even under perturbations, the retrieved parameters remain correct. In summary, the thermal behaviour of a chemical reactor can be defined through the reactor dynamic investigation procedure and can be used to identify the optimal operating conditions.

Visualization of the spontaneous emergence of a complex, dynamic, and autocatalytic system

Autocatalytic chemical reactions are widely studied as models of biological processes and to better understand the origins of life on Earth. Minimal self-reproducing amphiphiles have been developed in this context and as an approach to de novo "bottom-up" synthetic protocells. How chemicals come together to produce living systems, however, remains poorly understood, despite much experimentation and speculation. Here, we use ultrasensitive label-free optical microscopy to visualize the spontaneous emergence of an autocatalytic system from an aqueous mixture of two chemicals. Quantitative, in situ nanoscale imaging reveals heterogeneous self-reproducing aggregates and enables the real-time visualization of the synthesis of new aggregates at the reactive interface. The aggregates and reactivity patterns observed vary together with differences in the respective environment. This work demonstrates how imaging of chemistry at the nanoscale can provide direct insight into the dynamic evolution of nonequilibrium systems across molecular to microscopic length scales.

A novel method to compute the time dependence of state distributions in the stochastic kinetic description of an autocatalytic system

A novel method is introduced to estimate the solution of the stochastic kinetic master equation of an autocatalytic reaction scheme. The method first computes an accurate probability master distribution for relatively low particle numbers, then uses a time shift property of the distributions to extend this solution to the entire state space and time scale. A limited comparison with accurately calculated probability distributions suggests that the approximation works exceptionally well and is able to provide a very reliable way to obtain the solution of the stochastic master equation of a system without any limitation on its size. The method will most probably be applicable with minor modifications for the stochastic kinetic description of other irreversible reactions as well.

Elucidation of the Structures of Asymmetric Autocatalyst Based on X-ray Crystallography

Abstract Much interest has been paid to the origin of homochirality, such as that of l-amino acids. The proposed origins of chirality have usually induced only low enantiomeric excess. Thus, asymmetric amplification by asymmetric autocatalysis has been invoked. Asymmetric autocatalysis of 5-pyrimidyl alkanol in the enantioselective addition of diisopropylzinc to pyrimidine-5-carbaldehyde is a unique example of amplification of chirality. Crystallization of possible intermediates, specifically zinc alkoxides of this 5-pyrimidyl alkanol, was investigated to obtain mechanistic insights into this reaction. Single-crystal X-ray crystallography of the formed zinc alkoxide crystals shows the existence of tetramer or higher oligomer structures in this asymmetric autocatalytic system.

Theoretical Analysis of a Self-Replicator With Reduced Template Inhibition Based on an Informational Leaving Group.

The first non-enzymatic self-replicating systems, as proposed by von Kiedrowski (Angew Chem Int Ed Engl 25(10):932-935, 1986) and Orgel (Nature 327(6120):346-347, 1987), gave rise to the analytical background still used today to describe artificial replicators. What separates a self-replicating from an autocatalytic system is the ability to pass on structural information (Orgel, Nature 358(6383):203-209, 1992). Utilising molecular information, nucleic acids were the first choice as prototypical examples. But early self-replicators showed parabolic over exponential growth due to the strongly bound template duplex after template-directed ligation of substrates. We propose a self-replicating scheme with a weakly bound template duplex, using an informational leaving group. Such a scheme is inspired by the role of tRNA as leaving group and information carrier during protein synthesis, and is based on our previous experience with nucleotide chemistry. We analyse theoretically this scheme and compare it to the classical minimal replicator model. We show that for an example hexanucleotide template mirroring that is used by von Kiedrowski (Bioorganic chemistry frontiers, 1993) for the analysis of the classical minimal replicator, the proposed scheme is expected to result in higher template self-replication rate. The proposed self-replicating scheme based on an informational leaving group is expected to outperform the classical minimal replicator because of a weaker template duplex bonding, resulting in reduced template inhibition.

Crystal Structure of the Isopropylzinc Alkoxide of Pyrimidyl Alkanol: Mechanistic Insights for Asymmetric Autocatalysis with Amplification of Enantiomeric Excess

Asymmetric amplification during self-replication is a key feature that is used to explain the origin of homochirality. Asymmetric autocatalysis of pyrimidyl alkanol in the asymmetric addition of diisopropylzinc to pyrimidine-5-carbaldehyde is a unique example of this phenomenon. Crystallization of zinc alkoxides of this 5-pyrimidyl alkanol and single-crystal X-ray diffraction analysis of the alkoxide crystals reveal the existence of tetramer or higher oligomer structures in this asymmetric autocatalytic system.

Crystal Structure of the Isopropylzinc Alkoxide of Pyrimidyl Alkanol: Mechanistic Insights for Asymmetric Autocatalysis with Amplification of Enantiomeric Excess.

Asymmetric amplification during self-replication is a key feature that is used to explain the origin of homochirality. Asymmetric autocatalysis of pyrimidyl alkanol in the asymmetric addition of diisopropylzinc to pyrimidine-5-carbaldehyde is a unique example of this phenomenon. Crystallization of zinc alkoxides of this 5-pyrimidyl alkanol and single-crystal X-ray diffraction analysis of the alkoxide crystals reveal the existence of tetramer or higher oligomer structures in this asymmetric autocatalytic system.

An Autocatalytic System of Photooxidation‐Driven Substitution Reactions on a FeII4L6 Cage Framework

AbstractThe functions of life are accomplished by systems exhibiting nonlinear kinetics: autocatalysis, in particular, is integral to the signal amplification that allows for biological information processing. Novel synthetic autocatalytic systems provide a foundation for the design of artificial chemical networks capable of carrying out complex functions. Here we report a set of FeII4L6 cages containing BODIPY chromophores having tuneable photosensitizing properties. Electron‐rich anilines were observed to displace electron‐deficient anilines at the dynamic‐covalent imine bonds of these cages. When iodoaniline residues were incorporated, heavy‐atom effects led to enhanced 1O2 production. The incorporation of (methylthio)aniline residues into a cage allowed for the design of an autocatalytic system: oxidation of the methylthio groups into sulfoxides make them electron‐deficient and allows their displacement by iodoanilines, generating a better photocatalyst and accelerating the reaction.

An Autocatalytic System of Photooxidation-Driven Substitution Reactions on a Fe(II)4L6 Cage Framework.

The functions of life are accomplished by systems exhibiting nonlinear kinetics: autocatalysis, in particular, is integral to the signal amplification that allows for biological information processing. Novel synthetic autocatalytic systems provide a foundation for the design of artificial chemical networks capable of carrying out complex functions. Here we report a set of Fe(II)4L6 cages containing BODIPY chromophores having tuneable photosensitizing properties. Electron-rich anilines were observed to displace electron-deficient anilines at the dynamic-covalent imine bonds of these cages. When iodoaniline residues were incorporated, heavy-atom effects led to enhanced (1)O2 production. The incorporation of (methylthio)aniline residues into a cage allowed for the design of an autocatalytic system: oxidation of the methylthio groups into sulfoxides make them electron-deficient and allows their displacement by iodoanilines, generating a better photocatalyst and accelerating the reaction.

Distinguishing between discreteness effects in stochastic reaction processes.

The effect of discreteness on stochastic dynamics of chemically reacting systems is studied analytically. We apply the scheme bridging the chemical master equation and the chemical Fokker-Planck equation by a parameter representing the degree of discreteness previously proposed by the author for two concrete systems. One is an autocatalytic reaction system, and the other is a branching-annihilation reaction system. It is revealed that the change in characteristic time scales when discreteness is decreased is yielded between the two systems for different reasons. In the former system, it originates from the boundaries where one of the chemical species is zero, whereas in the latter system, it is due to modification of the most probable extinction path caused by discreteness loss.

Ebola-challenge and revival of theoretical epidemiology: Why Extrapolations from early phases of epidemics are problematic.

Ebola-challenge and revival of theoretical epidemiology: Why Extrapolations from early phases of epidemics are problematic.

Autocatalytic Production of 5-Hydroxymethylfurfural from Fructose-Based Carbohydrates in a Biphasic System and Its Purification

An efficient autocatalytic process for the production of 5-hydroxymethylfurfural (HMF) from fructose-based carbohydrates has been investigated without the addition of any external catalysts in a methyl isobutyl ketone/water biphasic system, leading to elevated HMF yield through continuous extraction of HMF from an aqueous solution. The results show that both the reaction temperature and time have significant effects on fructose conversion and HMF yield; 96.8% of fructose can be converted into 73.6% of HMF with a small amount of levulinic acid and formic acid formed at a point of compromise between the reaction temperature and time (160 °C for 2 h). In addition, this autocatalytic system is suitable for other fructose-based feedstocks, such as sucrose and inulin, to achieve acceptable HMF yield. Moreover, a simple and efficient purification strategy for as-prepared HMF, viz., the NaOH neutralization method, has also been tested, achieving more than 99% of HMF recovery with more than 98% of purity correspon...

Autocatalytic amplified detection of DNA based on a CdSe quantum dot/folic acid electrochemiluminescence energy transfer system.

In this work, electrochemiluminescence energy transfer (ECL-ET) from CdSe quantum dots (QDs) to folic acid is reported for the first time and applied for amplified detection of DNA by using a novel DNAzyme-mediated autocatalytic system.

Emergence of single-molecular chirality from achiral reactants.

The synthesis of enantiopure molecules from achiral precursors without the need for pre-existing chirality is a major challenge associated with the origin of life. We here show that an enantiopure product can be obtained from achiral starting materials in a single organic reaction. An essential characteristic of this reaction is that the chiral product precipitates from the solution, introducing a crystal–solution interface which functions as an asymmetric autocatalytic system that provides sufficient chiral amplification to reach an enantiopure end state. This approach not only provides more insight into the origin of life but also offers a pathway to acquire enantiopure compounds for industrial applications.