ChemSystemsChem最新文献

The Front Cover depicts a microfluidic channel with multilayer polylysine surfaces, which provide the potential to bestow an acid–base equilibrium with the capacity of signal transduction. Cover design by Niels van der Velde (University of Twente, NL). More information can be found in the Research Article by Jurriaan Huskens, Albert S. Y. Wong, and co-workers.

Rotaxanes are interlocked molecules that consist of a macrocycle encircling a stoppered thread. The ability to control relative component positions makes rotaxanes ideal building blocks for constructing functional and responsive molecular machines. Despite the potential of rotaxanes, their challenging synthesis limits their application. One approach to construct rotaxanes is to use an active template synthesis, where a reaction that forms the thread is accelerated in the cavity of a macrocycle. An emerging method of active template synthesis that exploits the ability of crown ether macrocycles to accelerate simple organic reactions is discussed herein. Crown ether active template synthesis (CEATS) permits the rapid and simple synthesis of rotaxanes containing a wide range of functionality. Integrating rotaxane formation with chemical reaction networks has permitted the construction of molecular machines. The simplification of rotaxane synthesis will facilitate their widespread study and application.

An analysis of an out-of-equilibrium cyclic reaction network which continuously converts a minor undesired product enantiomer to the desired major enantiomer by irreversible addition of chemical fuel and irreversible elimination of spent fuel is presented. The reaction network is maintained as long as fuel is added; interrupted fuel addition drives the system towards equilibrium, but the cyclic process restarts upon resumed fuel addition, as demonstrated by three consecutive fuel cycles. The process is powered by the hydrolysis of methyl cyanoformate to HCN and monomethyl carbonic acid, which decomposes to CO₂ and MeOH. The time it takes to reach steady state depends on the rate of conversion of the fuel and decreases with increased conversion rate. Three catalysts, one metal catalyst and two enzymes, together constitute an efficient regulation system allowing control of the forward, backward and waste-forming steps, thereby assuring the production of high yields of products with high enantiopurity.

The bottom-up fabrication of compartmentalized cell-like entities represents a promising avenue for reconstituting hierarchical organization within cells and emulating life-like behaviors. Integrating the creation of semipermeable membranes and membraneless artificial organelles has recently garnered significant attention, aiming to achieve cytomimetic properties. We briefly describe the concept of liquid-liquid phase separation and review approaches for the fabrication of cell-sized membranous protocells (e. g., giant unilamellar vesicles, polymersomes and proteinosomes). Three strategies are emphasized for the construction of advanced cell-like structures consisting of liquid-like subcompartments enclosed by a membrane: (i) adsorption and assembly of organic or inorganic species onto the surface of preformed coacervate microdroplets; (ii) interfacial assembly of a lipid or polymer bilayer on the surface of an aqueous pool containing preformed microdroplets; and (ii) triggering phase separation within a preformed semipermeable membrane with chemical or physical stimuli. This review underscores the significance of the hierarchical organization of these synthetic cellular structures in mimicking cytomimetic functions, including transmembrane signaling, protocell communication, prototissue formation, and their compelling biomedical applications.

Artificial cell and organelle construction has recently gained substantial attention to generate simplified models for understanding of biological phenomena, or micro- and nanomachines for biomedical and biotechnological applications. A wide array of building blocks has been employed to build these systems as membraneless structures with the ability to compartmentalize chemical reactions by enhanced partitioning, or as membrane-defined entities that provide a physical barrier that inhibits the interference of external factors. While these systems present unique properties that enable high fidelity to biological processes, they present limited ability to recreate the high selectivity and specificity of small molecule trafficking observed in biological membranes. Owing to their high chemical versatility, polymers can be leveraged to generate 3D structures that resemble biological membranes while providing transmembrane chemical motifs that enable responsiveness to a wide array of stimuli. This Concept Article discusses the ability to control membrane transport facilitating the emergence of out-of-equilibrium feedback mechanisms that ultimately modulate enzymatic rates. This can be employed to engineer future artificial cells and organelles that display homeostasis as a mechanism of self-adaptation to continuously evolving environments.

The front cover artwork is provided by David T. Gonzales of the Max Planck Institute of Molecular Cell Biology and Genetics. The image shows a collection of aqueous water-in-oil droplets with lipid bilayer interfaces. Inside each droplet is a cell-free expression system that is capable of gene expression or intercellular communication. Read the full text of the Research Article at 10.1002/syst.202300029.

Implementation of new activated carboxylic acids is crucial to switch reversibly chemical systems over time in a safer manner. By applying cheap 1,3-acetonedicarboxylic acid, the pH of aqueous solutions can be decreased before autonomously evolving over time back again to a higher value upon diacid decarboxylation. This decarboxylation can be catalysed by different species such as simple amines or simple metals such as iron and copper salts. This process generates 2 molecules of CO₂ and acetone as single waste, considerably decreasing the toxicity associated with such activated acids. The potential of this weak diacid was confirmed by reversibly disrupting a strong gel upon diacid addition and opens the way to the application in complex chemically fuelled systems.

This work describes a competing activation network, which is regulated by chemical feedback at the liquid-surface interface. Feedback loops dynamically tune the concentration of chemical components in living systems, thereby controlling regulatory processes in neural, genetic, and metabolic networks. Advances in systems chemistry demonstrate that chemical feedback could be designed based on similar concepts of using activation and inhibition processes. Most efforts, however, are focused on temporal feedback whereas biological networks are maintained by the interplay between temporal and spatial organization. Here, we designed a feedback system comprising a simple acid-base equilibrium that can be perturbed by two opposing activation processes. Crucially, one of the processes is immobilized on the surface of a microfluidic channel using poly-l-lysine (PLL). We measured the capacity of the PLL-coated channels to resist changes in pH in flow using a pH-sensitive indicator, phenol red, and showed that this capacity can be increased by employing polyelectrolyte multilayers. Specifically, we found that the rate of local activation (i. e., the deprotonation of the immobilized lysine residues) could be significantly increased to delay the otherwise fast equilibrium. This effect allowed for encoding read and write operations, providing the potential to bestow CRNs with the capacity of molecular information processing.

The Front Cover shows collections of communicating synthetic cells composed of water-in-oil droplets separated and stabilized by lipid bilayer interfaces and containing cell-free expression system with quorum sensing gene circuits. Cover design by David T. Gonzales. More information can be found in the Research Article by T.-Y. Dora Tang and co-worker.

The Cover Feature illustrates three strategies for the generation of dynamic combinatorial libraries (DCLs) of peptide or peptidomimetic-based assemblies. Exploring their self-adaptative potential can lead to the discovery of smart nanomaterials, drug nanocarriers or drugs for untreated diseases. Cover design by Ashmi Rodrigues. More information can be found in the Review by Ashmi Rodrigues, Lou Rocard and Roba Moumné.