ChemSystemsChem最新文献

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.

The front cover illustrates cell-like functional molecular systems based on DNA nanotechnology and lipid vesicles. The base-specific interactions of DNA enable the construction of various functional components that can be integrated into lipid vesicles, aiming to create artificial molecular systems comparable to, or even surpassing, natural molecular systems, such as living cells. The Review by Y. Sato describes the latest achievements in functions realized through the combination of DNA nanotechnology and lipid vesicles.

Understanding the emergence of complex properties in dissipative non-equilibrium systems is crucial for unraveling the mysteries of life processes. The review focuses on the documented research on chemically fueled autonomous systems, self-sorting towards compartmentalization, self-replication via autocatalysis, and rhythmic chemical oscillators. In addition to that, the review also discusses newly introduced reactions and dynamic combinatorial libraries in dissipative systems.

We previously reported collective behavior in colloidal aggregates of silver phosphate in H₂O₂ and under UV light. Diffusiophoretic interactions between aggregates lead to non-linear behavior such as oscillations and synchronization, in which oscillation frequencies increase with H₂O₂ concentration. The aggregates transition between schooling and dispersed behaviors with incipient spatiotemporal correlations. We identified a kinetic model that maps the chemical species that are thought to underlie non-linear phenomena in the colloidal aggregates, i. e. adsorbed oxygen species *OOH⁻ and *O. We investigate the emergent dynamics for the simplest case, the coupling of two otherwise bistable clusters. Two coupling schemes are proposed and we find that – depending on whether the coupling is excitatory or inhibitory – the clusters may oscillate with zero or π phase shift.

In supramolecular chemistry, photostimulants are generally combined with a static solution under thermodynamic equilibrium with no time progression. After reaching the thermodynamic state, self-assembly events contain various species–a mixture of component molecules, intermediate species, and completed assemblies–which light reaches uniformly. In this study, snapshot control of supramolecular polymerization was first combined with pinpoint photoirradiation using a microflow system. Employing the azobenzene derivative trans-C3NO as a monomer, a snapshot moment of supramolecular polymerization along a microflow channel was selectively irradiated with UV light at 365 nm in a space-resolved manner, so that the monomers, intermediates (oligomers), or extended supramolecular polymers were selectively exposed to light stimuli. We found that a pinpoint photostimulus to each snapshot moment had a pronounced effect on the kinetic pathway by tuning the timing at which the snapshot moment of cis-C3NO was generated. Upon irradiation in the upstream region, in the very early stages before initiating polymerization, supramolecular polymerization was suppressed by generating a less reactive cis-C3NO monomer. However, photoirradiation does not affect the supramolecular polymers in the downstream region because of their stiff nature. Remarkably, when irradiating the middle stream region involving a soft-natured intermediate species, supramolecular copolymerization occurred through in situ conversion from trans- and cis-C3NO inside the primitive supramolecular polymer. Loose monomer stacking in the primitive aggregate endows it with mechanoresponsiveness. Under the influence of shear force in a Hagen–Poiseuille flow, the resultant supramolecular copolymers containing geometrically different cis-isomers were rolled up and transformed into a micrometer-sized disk-like structure. During the in situ supramolecular copolymerization and transformation to the disk structure, a liquid–liquid interface generated in the laminar flow acted as a template to fix the orientation of the monomers and supramolecular polymers, leading to the uniform disk formation. Furthermore, monomers’ orientation in the aligned supramolecular polymers are fixed on the interface, on which light is always irradiated in an anisotropic manner. This results in both complexity at the molecular level and long-range structural order such as regular rolling up at the micrometer range over the molecular scale. By incorporating the photostimulus system, microflow extends its potential for supramolecular chemistry.