Mutual Catalysis Research Articles

Kinetics and coexistence of autocatalytic reaction cycles

Biological reproduction rests ultimately on chemical autocatalysis. Autocatalytic chemical cycles are thought to have played an important role in the chemical complexification en route to life. There are two, related issues: what chemical transformations allow such cycles to form, and at what speed they are operating. Here we investigate the latter question for solitary as well as competitive autocatalytic cycles in resource-unlimited batch and resource-limited chemostat systems. The speed of growth tends to decrease with the length of a cycle. Reversibility of the reproductive step results in parabolic growth that is conducive to competitive coexistence. Reversibility of resource uptake also slows down growth. Unilateral help by a cycle of its competitor tends to favour the competitor (in effect a parasite on the helper), rendering coexistence unlikely. We also show that deep learning is able to predict the outcome of competition just from the topology and the kinetic rate constants, provided the training set is large enough. These investigations pave the way for studying autocatalytic cycles with more complicated coupling, such as mutual catalysis.

Study on the pyrolysis mechanism of unsaturated fatty acid: A combined density functional theory and experimental study

In this study, oleic acid was used as a model compound to discuss the mechanism of thermal conversion of unsaturated fatty acids to hydrocarbons, so as to promote the goal of obtaining renewable chemicals and fuels from unsaturated fatty acids. In-situ detection techniques such as TG-FTIR and Py-GC/MS combined with density functional theory were applied to study the reaction mechanism of oleic acid molecules in the conditions of slow pyrolysis and fast pyrolysis. As the temperature rises, the hydrogen bond is broken, and the vibration peak of oleic acid shows obvious dehydrogenation under slow pyrolysis, and the same situation exists under fast pyrolysis. As the temperature increases, the pyrolysis process of oleic acid molecules changed from the dominant role of bimolecular mutual catalysis to that of free radical reaction. The results of Py-GC/MS showed that methyl, ethyl, and hydrogen radicals are the main active substances under the conditions of high temperature and fast pyrolysis of unsaturated fatty acid. This work demonstrates the feasibility of producing renewable hydrocarbons by pyrolysis of unsaturated fatty acids and proposed influenced factors to control product distribution. Novelty Statement Density functional theory (DFT) combined with experiments was used in present study to supplement the understanding of the pyrolysis mechanism of fatty acids in bio oil pyrolysis, and the control factors of controlling the distribution of fatty acid pyrolysis products were proposed.

Chemical Ecosystem Selection on Mineral Surfaces Reveals Long-Term Dynamics Consistent with the Spontaneous Emergence of Mutual Catalysis.

How did chemicals first become organized into systems capable of self-propagation and adaptive evolution? One possibility is that the first evolvers were chemical ecosystems localized on mineral surfaces and composed of sets of molecular species that could catalyze each other’s formation. We used a bottom-up experimental framework, chemical ecosystem selection (CES), to evaluate this perspective and search for surface-associated and mutually catalytic chemical systems based on the changes in chemistry that they are expected to induce. Here, we report the results of preliminary CES experiments conducted using a synthetic “prebiotic soup” and pyrite grains, which yielded dynamical patterns that are suggestive of the emergence of mutual catalysis. While more research is needed to better understand the specific patterns observed here and determine whether they are reflective of self-propagation, these results illustrate the potential power of CES to test competing hypotheses for the emergence of protobiological chemical systems.

The cathedral’s ivory tower and the open education bazaar – catalyzing innovation in the higher education sector

ABSTRACT Will open education replace traditional higher education, or augment it? Digital innovation in the higher education sector is fuelling speculation about the transformation of higher education and the future role of universities. Much of the speculation makes questionable implicit assumptions about current and future business models in the higher education sector. This conceptual paper applies an innovation management perspective to critically examine the use and misuse of the business model concept in the context of digital innovation in the higher education sector. Using Raymond’s metaphor of the cathedral and the bazaar which contrasted traditional commercial software development (the cathedral) with open source software development (the bazaar). We analogise this relationship with the relationship between ‘cathedral-type’ business models in traditional higher education (e.g. universities) and ‘bazaar-type’ business models in open education (e.g. open educational resource publishers). Using the historical perspective we now have on the software industry’s evolution we critique the ubiquitous replacement narrative of destruction and disruption of the sector, and propose an alternative narrative of interdependence and mutual innovative catalysis. We predict that higher education ecosystems will be based on synergistic relationships between organisations that represent many gradations on the continuum between ‘cathedral-type’ and ‘bazaar-type’ organisations.

Excellent hydrolysis performances of Mg3RE hydrides

Hydrogenated Mg3Mm (where Mm denotes La-rich and Ce-rich misch metal) has been identified as an excellent hydrolysis material for the first time. Hydrolysis of the as-hydrogenated Mg3Mm produced 695 mL g−1 hydrogen in 5 min, 828 mL g−1 hydrogen in 15 min, and the highest hydrogen yield reached 9.79 wt.% at 298 K. Compared to hydrogenated Mg3La, Mg3Ce, Mg3Pr, and Mg3Nd, hydrogenated Mg3Mm displayed the fastest hydrolysis rate due to mutual catalysis of LaH3, CeH3, PrH3, and Nd2H5. The hydrolysis mechanisms of hydrogenated Mg3RE are also discussed herein.

Excess Mutual Catalysis Is Required for Effective Evolvability

It is widely accepted that autocatalysis constitutes a crucial facet of effective replication and evolution (e.g., in Eigen's hypercycle model). Other models for early evolution (e.g., by Dyson, Gánti, Varela, and Kauffman) invoke catalytic networks, where cross-catalysis is more apparent. A key question is how the balance between auto- (self-) and cross- (mutual) catalysis shapes the behavior of model evolving systems. This is investigated using the graded autocatalysis replication domain (GARD) model, previously shown to capture essential features of reproduction, mutation, and evolution in compositional molecular assemblies. We have performed numerical simulations of an ensemble of GARD networks, each with a different set of lognormally distributed catalytic values. We asked what is the influence of the catalytic content of such networks on beneficial evolution. Importantly, a clear trend was observed, wherein only networks with high mutual catalysis propensity (p(mc)) allowed for an augmented diversity of composomes, quasi-stationary compositions that exhibit high replication fidelity. We have reexamined a recent analysis that showed meager selection in a single GARD instance and for a few nonstationary target compositions. In contrast, when we focused here on compotypes (clusters of composomes) as targets for selection in populations of compositional assemblies, appreciable selection response was observed for a large portion of the networks simulated. Further, stronger selection response was seen for high p(mc) values. Our simulations thus demonstrate that GARD can help analyze important facets of evolving systems, and indicate that excess mutual catalysis over self-catalysis is likely to be important for the emergence of molecular systems capable of evolutionlike behavior.

Simulations, models, and testbeds: A mutual catalysis

Recent developments in the area of decentralized and infrastructureless systems opened avenues for novel applications. Along with these new technologies, new questions regarding their operational bounds in terms of e.g. scalability and security arose. Due to the sparse presence of real-world decentralized and infrastructureless systems, new protocols and applications have to be scrutinized by means of simulation, in (small-scale) testbeds, and by analytical models. In this paper, we discuss challenges of evaluating security mechanisms for mobile ad hoc networks and peer-to-peer systems. We focus on harmonizing predictions of analytical models and results obtained from simulation studies and testbed experiments.

Dehydrogenation in lithium borohydride/conventional metal hydride composite based on a mutual catalysis

The dehydrogenation of LiBH4 ball-milled with hydrogenated 40Ti–15Mn–15Cr–30V alloy was investigated. It was found that there is a mutual catalysis between the two hydrides, lowering the temperature of hydrogen release from both hydrides. In the case of 1 h milled LiBH4/40Ti–15Mn–15Cr–30V with a mass ratio of 1:4, the peak temperatures of 40Ti–15Mn–15Cr–30V and LiBH4 were decreased to 195 and 390 °C, respectively, which are 77 and 50 °C lower than the respective hydride on its own.

Catalytic effects of histidine enantiomers and glycine on the formation of dileucine and dimethionine in the salt-induced peptide formation reaction

The salt-induced peptide formation (SIPF) reaction takes place readily under mild reaction conditions and proceeds via a copper complex. Its ease of reaction and the universality for prebiotic scenarios add weights to the arguments in favour of the importance of peptide and proteins in the tug of war with the RNA world hypothesis. In addition, the SIPF reaction has a preference for L-form amino acids in dipeptide formation, casting light on the puzzle of biohomochirality, especially for the amino acids with aliphatic side chains. A detailed investigation on the behaviour of aliphatic leucine in the SIPF reaction is presented in this paper, including the catalytic effects of glycine, L- and D-histidine as well as the stereoselectivity under all the reaction conditions above. The results show a relatively low reactivity and stereoselectivity of leucine in the SIPF reaction, while both glycine and histidine enantiomers remarkably increase the yields of dileucine by factors up to 40. Moreover, a comparative study of the effectiveness of L- and D-histidine in catalysing the formation of dimethionine was also carried out and extends the scope of mutual catalysis by amino acid enantiomers in the SIPF reaction.

The origin of the RNA world: Co-evolution of genes and metabolism

Discoveries demonstrating that RNA can serve genetic, catalytic, structural, and regulatory roles have provided strong support for the existence of an RNA World that preceded the origin of life as we know it. Despite the appeal of this idea, it has been difficult to explain how macromolecular RNAs emerged from small molecules available on the early Earth. We propose here a mechanism by which mutual catalysis in a pre-biotic network initiated a progression of stages characterized by ever larger and more effective catalysts supporting a proto-metabolic network, and the emergence of RNA as the dominant macromolecule due to its ability to both catalyze chemical reactions and to be copied in a template-directed manner. This model suggests that many features of modern life, including the biosynthetic pathways leading to simple metabolites, the structures of organic and metal ion cofactors, homochirality, and template-directed replication of nucleic acids, arose long before the RNA World and were retained as pre-biotic systems became more sophisticated.

Partial recovery of quantum entanglement

Suppose Alice and Bob try to transform an entangled state shared between them into another one by local operations and classical communications. Then in general a certain amount of entanglement contained in the initial state will decrease in the process of transformation. However, an interesting phenomenon called partial entanglement recovery shows that it is possible to recover some amount of entanglement by adding another entangled state and transforming the two entangled states collectively. In this paper, we are mainly concerned with the feasibility of partial entanglement recovery. The basic problem we address is whether a given state is useful in recovering entanglement lost in a specified transformation. In the case where the source and target states of the original transformation satisfy the strict majorization relation, a necessary and sufficient condition for partial entanglement recovery is obtained. For the general case we give two sufficient conditions. We also give an efficient algorithm for the feasibility of partial entanglement recovery in polynomial time. As applications, we establish some interesting connections between partial entanglement recovery and the generation of maximally entangled states, quantum catalysis, mutual catalysis, and multiple-copy entanglement transformation.

Mutual catalysis of entanglement transformations for pure entangled states

We study the mutual catalysis of entanglement transformations, which refers to the fact that each of the two entanglement transformations cannot occur with certainty by local operations and classical communication independently, but both can occur jointly if collective local operations are performed on both of the initial entangled states. We surprisingly find that mutually catalyzed transformations can be realized even in the case when the standard entanglement catalyzed transformations [D. Jonathan and M. B. Plenio, Phys. Rev. Lett. 83, 3566 (1999)] are forbidden.

The lipid world.

The continuity of abiotically formed bilayer membranes with similar structures in contemporary cellular life, and the requirement for microenvironments in which large and small molecules could be compartmentalized, support the idea that amphiphilic boundary structures contributed to the emergence of life. As an extension of this notion, we propose here a 'Lipid World' scenario as an early evolutionary step in the emergence of cellular life on Earth. This concept combines the potential chemical activities of lipids and other amphiphiles, with their capacity to undergo spontaneous self-organization into supramolecular structures such as micelles and bilayers. In particular, the documented chemical rate enhancements within lipid assemblies suggest that energy-dependent synthetic reactions could lead to the growth and increased abundance of certain amphiphilic assemblies. We further propose that selective processes might act on such assemblies, as suggested by our computer simulations of mutual catalysis among amphiphiles. As demonstrated also by other researchers, such mutual catalysis within random molecular assemblies could have led to a primordial homeostatic system displaying rudimentary life-like properties. Taken together, these concepts provide a theoretical framework, and suggest experimental tests for a Lipid World model for the origin of life.

Graded Autocatalysis Replication Domain (GARD): kinetic analysis of self-replication in mutually catalytic sets.

A Graded Autocatalysis Replication Domain (GARD) model is proposed, which provides a rigorous kinetic analysis of simple chemical sets that manifest mutual catalysis. It is shown that catalytic closure can sustain self-replication up to a critical dilution rate, λc, related to the graded extent of mutual catalysis. We explore the behavior of vesicles containing GARD species whose mutual catalysis is governed by a previously published statistical distribution. In the population thus generated, some GARD vesicles display a significantly higher replication efficiency than most others. GARD thus represents a simple model for primordial chemical selection of mutually catalytic sets.

Mutual catalysis in sets of prebiotic organic molecules: Evolution through computer simulated chemical kinetics

A thorough outlook on the origin of life needs to delineate a chemically rigorous, self-consistent path from highly heterogeneous, random ensembles of relatively simple organic molecules, to an entity that has rudimentary life-like characteristics. Such entity should be endowed with a capacity to express variation, undergo mutation-like changes and manifest a simple evolutionary process. For simulating such system we developed the Graded Autocatalysis Replication Domain (GARD) model for explicit kinetic analysis of mutual catalysis in sets of random oligomers derived from energized precursor monomers. The kinetic properties of the GARD model are based on vesicle enclosure and expansion. With the additional assumption of spontaneous vesicle splitting, a GARD evolution scenario is envisaged as a consequence of pure chemical kinetics. Here we show how the GARD model can serve as a platform for investigating the dynamics of self-organization mechanisms in molecular evolutionary processes.

Catalysis of dialanine formation by glycine in the salt-induced peptide formation reaction.

Mutual catalysis of amino acids in the salt-induced peptide formation (SIPF) reaction is demonstrated for the case of glycine/alanine. The presence of glycine enhances dialanine formation by a factor up to 50 and enables dialanine formation at much lower alanine concentrations. The actual amounts of glycine play an important role for this catalytic effect, the optimal glycine concentration is 1/8 of the alanine concentration. The mechanism appears to be based on the formation of the intermediate Gly-Ala-Ala tripeptide, connected to one coordination site of copper(II) ion, and subsequent hydrolysis to dialanine and glycine.

Self replication and chemical selection in primordial mutually catalytic sets

Template-mediated replication of individual molecules has been pursued as the basis for primordial chemical evolution. In parallel, it has been suggested that sets of mutually catalytic molecules could undergo replication, even if none of their individual components is autocatalytic, thus constituting a primitive metabolism without a genome (1). In support of the latter concept, we describe here an explicit kinetic model for a Graded Autocatalysis Replication Domain (GARD), in which mutual catalysis in a set of N types of molecules (Ai) derived from a common precursor (A0), can sustain self-replication of the entire ensemble. The components of GARD may be any organic molecules, endowed with sufficient complexity to allow for structural diversity and mutual complementarity. The mutual catalytic rate enhancement exerted on the species Ai by the species Aj is denoted by a matrix element

Mutual Catalysis of Neutral and Anionic Cobalt Carbonyls in Their CO Scrambling Reactions

Redox‐condensation equilibria, probably with the participation of [Co3(CO)10]− as intermediate, and not ion pairing as previously postulated, explain the acceleration of the CO scrambling in [Co(CO)4]− by alkali metal counterions. The studies described here show that neutral carbonyl complexes catalyze the CO scrambling for anionic metal carbonyls and vice versa, and that the catalysis is less effective in the presence of free CO. The latter is in agreement with [Co3(CO)10]− as the intermediate. These results are important mainly because neutral and anionic metal carbonyls frequently exist together as a result of side reactions.

Mutual Catalysis in the Chromium(III)–EDTA–Hydrogen Peroxide System

Abstract Hydrogen peroxide catalyzes the reaction between hexaaquachromium(III) and ethylenediaminetetraacctic acid, while chromium(III)–EDTA complex accelerates the decomposition of hydrogen peroxide. A mechanism is suggested for the reaction on the basis of gasvolumetric and spectrophotometric experiments.