ChemSystemsChem最新文献

Iron-sulfur clusters are ancient cofactors that could have played a role in the prebiotic chemistry leading to the emergence of protometabolism. Previous research has shown that certain iron-sulfur clusters can form from prebiotically plausible components, such as cysteine-containing oligopeptides. However, it is unclear if these iron-sulfur clusters could have survived in prebiotically plausible environments. To begin exploring this possibility, we tested the stability of iron-sulfur clusters coordinated to a tripeptide and to N-acetyl-L-cysteine methyl ester in a variety of solutions meant to mimic prebiotically plausible environments. We also assessed the impact of individual chemical components on stability. We find that iron-sulfur clusters form over a wide variety of conditions but that the type of iron-sulfur cluster formed is strongly impacted by the chemical environment and the coordinating scaffold. These findings support the general hypothesis that iron-sulfur clusters were present on the prebiotic Earth and that different types of iron-sulfur cluster predominated in different environments.

The cover picture shows a scanning electron micrograph of self-organized chemical garden tubes. These calcium-based hollow structures are composed of porous walls separating an alkaline exterior liquid and acidic, metal salt interior solution. Natural analogs to this classic chemistry experiment are hydrothermal vents found at the base of the ocean. Their structures are composed of mineral walls which separate two disparate chemical environments maintaining a far-from-equilibrium setting. More in theResearch Article by Pamela Knoll and Corentin C. Loron.

Asymmetric chemical reactions on the surfaces of colloidal particles are known to propel them into directional motion. The dynamics of such chemical micromotors are sensitive to their local chemical environments, which also continually evolve with the reactions on motor surfaces. This two-way coupling between the motor dynamics and the local environment may result in complex nonlinear behaviors. As an example, we report that Janus Ag microspheres, which self-propel in hydrogen peroxide (H₂O₂), spontaneously reverse their direction of motion two or more times. We hypothesize that two distinct chemical reactions between Ag and H₂O₂ drive the micromotor in opposite directions, and which reaction dominates depends on the local pH. Interestingly, the local pH near a Ag micromotor oscillates spontaneously in H₂O₂, likely due to a complex interplay between the kinetics of the reaction between Ag and H₂O₂ and the diffusion of chemical species. Consequently, the pH-sensitive Ag micromotor reverses its direction of motion in response to these pH oscillations. This study introduces a new mechanism for regulating the speed and directionality of micromotors, highlights the potential of Ag micromotors in chemical sensing, and sheds new light on the interplay between chemical kinetics and micromotor dynamics.

The injection of rare-earth metal salt solutions into sodium silicate solution results in vertically growing tubular precipitate structures. At low input concentrations reaction kinetics is the rate-detemining process, leading to linear growth rates independent of injection rates. At higher concentrations, flow drives the precipitate growth, characterized by jetting mechanism. Among the studied rare-earth metal silicates, dysprosium silicate is found to have the most rigid structure with visible growth even at higher injection rates. The outer surface of the hollow tubes is smooth, on which rare-earth hydroxide – based on the result of the energy dispersive X-ray spectroscopy measurements – aggregates into globules.

Belousov−Zhabotinsky (BZ) self-oscillating gels exhibit periodic volumetric swelling−deswelling, providing the basis for autonomous soft robots without external control. However, traditional BZ self-oscillating gels suffer from degradation and slow chemo−mechanical response. Here, three types of BZ self-oscillating gels were prepared by adjusting the monomer/crosslinker ratio and using N-isopropylacrylamide nanogels as crosslinker. Compared with traditional gels, the toughness of nanopolymerized and entangled gels was markedly improved and their response to the Ru (III)/Ru (II) alternation was accelerated. The three self-oscillating gels showed different periodic responses in a BZ reaction solution. Entangled gels, as a result of their greater spatial uniformity in energy dissipation and enhanced interconnection between mesopores, respectively, showed the longest lifetime and shortest chemo-mechanical oscillation delay. The synthesis of tougher and faster responding entangled gels expands the function and application of BZ self-oscillating gels.

Phase-separated compartments can localize (bio)chemical reactions and influence their kinetics. They are believed to play an important role both in extant life in the form of biomolecular condensates and at the origins of life as coacervate protocells. However, experimentally testing the influence of coacervates on different reactions is challenging and time-consuming. We therefore use a numerical model to explore the effect of phase-separated droplets on the kinetics and outcome of different chemical reaction systems, where we vary the coacervate volume and partitioning of reactants. We find that the rate of bimolecular reactions has an optimal dilute/coacervate phase volume ratio for a given reactant partitioning. Furthermore, coacervates can accelerate polymerization and self-replication reactions and lead to formation of longer polymers. Lastly, we find that coacervates can ‘rescue’ oscillating reaction networks in concentration regimes where sustained oscillations do not occur in a single-phase system. Our results indicate that coacervates can direct the outcome of a wide range of reactions and impact fundamental aspects such as yield, reaction pathway selection, product length and emergent functions. This may have far-reaching implications for origins of life, synthetic cells and the fate and function of biological condensates.

The origin of life, being one of the most fascinating questions in science, is increasingly addressed by interdisciplinary research. In addition to developing plausible chemical models for synthesizing the first biomolecules from prebiotic building blocks, searching for suitable and plausible non-equilibrium boundary conditions that drive such reactions is thus a central task in this endeavor. This perspective highlights the remarkably simple yet versatile scenario of heat flows in geologically plausible crack-like compartments as a habitat for prebiotic chemistry. Based on our recent findings, it is discussed how thermophoretically driven systems offer insights into solving key milestones in the origin of life research, such as the template inhibition problem, prebiotic symmetry breaking, and the promotion of prebiotic chemistry by selective enrichment of biochemical precursors. Our results on molecular-selective thermogravitational accumulation, heat flow-induced pH gradients, and environmental cycles are put in the context of other approaches to non-equilibrium systems and prebiotic chemistry. The coupling of heat flows to chemical and physical boundary conditions thus opens up numerous future experimental research avenues, such as the extraction of phosphate from geomaterials or the integration of chemical reaction networks into thermal non-equilibrium systems, offering a promising framework for advancing the field of prebiotic chemistry.

Owing to their property to alter their surface-activity upon the irradiation with light, photoswitchable surfactants have gained tremendous interest in colloidal science. Their mere addition to a colloidal system allows, e. g., to obtain control over polyelectrolytes, micro- and nanoscale particles or emulsions. Most literature examples focus on azobenzene-based, or related, systems, which employ a photoisomerization reaction for switching. Other structures, such as spiropyrans, play a subordinate role, although they have gained increasing attention over the past few years. In this perspective article, we want to provide an overview about existing systems of photoswitchable surfactants. We address the issue that alternative photoswitches are given less attention, and what benefits surfactants could possess that are based on said switchable units. With our contribution, we want to broaden the view on stimuli-responsive surfactants – and to provide a guideline for the design of novel structures.

Biomembranes wrapping cells and organelles are not only the partitions that separate the insides but also dynamic fields for biological functions accompanied by membrane shape changes. In this review, we discuss the spatiotemporal patterns and fluctuations of membranes under nonequilibrium conditions. In particular, we focus on theoretical analyses and simulations. Protein active forces enhance or suppress the membrane fluctuations; the membrane height spectra are deviated from the thermal spectra. Protein binding or unbinding to the membrane is activated or inhibited by other proteins and chemical reactions, such as ATP hydrolysis. Such active binding processes can induce traveling waves, Turing patterns, and membrane morphological changes. They can be represented by the continuum reaction-diffusion equations and discrete lattice/particle models with state flips. The effects of structural changes in amphiphilic molecules on the molecular-assembly structures are also discussed.

Biochemical communication is ubiquitous in life. Biology uses chemical reaction networks to regulate concentrations of myriad signaling molecules. Recent advances in supramolecular and systems chemistry demonstrate that feedback mechanisms of such networks can be rationally designed but strategies to transmit and process information encoded in molecules are still in their infancy. Here, we designed a polyelectrolyte reaction network maintained under out-of-equilibrium conditions using pH gradients in flow. The network comprises two weak polyelectrolytes (polyallylamine, PAH, and polyacrylic acid, PAA) in solution and one immobilized on the surface (poly-l-lysine, PLL). We chose PAH and PAA as their complexation process is known to be history-dependent (i. e., the preceding state of the system can determine the next state). Surprisingly, we found that the hysteresis diminished as the PLL-coated surface supported rather than perturbed the formation of the complex. PLL-coated surfaces are further exploited to establish that reversible switching between the assembled and disassembled state of polyelectrolytes can process signals encoded in the frequency and duration of pH pulses. We envision that the strategy employed to modulate information in this polyelectrolyte reaction network could open novel routes to transmit and process molecular information in biologically relevant processes.