ChemSystemsChem最新文献

The Front Cover represents an energy landscape of kinetically trapped chemical-fueled fibers, which reminds of a mountain landscape. Our work unravels how tuning the kinetic trapping in chemical-fueled self-assemblies can recover dynamic instabilities, such as microtubule-like growth and shrinkage. This opens the door to the creation of new adaptive nanotechnologies. More information can be found in the Research Article by Job Boekhoven and co-workers.

The quest to understand life and recreate it in vitro has been undertaken through many different routes. These different approaches for experimental investigation of life aim to piece together the puzzle either by tracing life's origin or by synthesizing life-like systems from non-living components. Unlike efforts to define life, these experimental inquiries aim to recapture specific features of living cells, such as reproduction, self-organization or metabolic functions that operate far from thermodynamic equilibrium. As such, these efforts have generated significant insights that shed light on crucial aspects of biological functions. For observers outside these specific research fields, it sometimes remains puzzling what properties an artificial system would need to have in order to be recognized as most similar to life. In this Perspective, we discuss properties whose realization would, in our view, allow the best possible experimental emulation of a minimal form of biological life.

Hydrogen ion autocatalytic reactions, especially in combination with an appropriate negative feedback process, show a wide range of dynamical phenomena, like clock behavior, bistability, oscillations, waves, and stationary patterns. The temporal or spatial variation of pH caused by these reactions is often significant enough to control the actual state (geometry, conformation, reactivity) or drive the mechanical motion of coupled pH-sensitive physico-chemical systems. These autonomous operating systems provide nonlinear chemistry's most reliable applications, where the hydrogen ion autocatalytic reactions act as engines. This review briefly summarizes the nonlinear dynamics of these reactions and the different approaches developed to properly couple the pH-sensitive units (e. g., pH-sensitive equilibria, gels, molecular machines, colloids). We also emphasize the feedback of the coupled processes on the dynamics of the hydrogen ion autocatalytic reactions since the way of coupling is a critical operational issue.

The catalytic action of invertase generates bilayer asymmetry that stabilises membrane curvature. The driving mechanism for the generation of membrane curvature by invertase is investigated using giant unilamellar vesicles (GUVs). The invertase cleaves the sucrose in the exterior compartment, thereby creating a sugar asymmetry across the bilayer membrane that is measured for GUV membranes consisting of the lipid Dioleoylphosphatidylcholine (DOPC). Finally, the advantage of this method to control membrane curvature and to stabilize multi-sphere morphologies is demonstrated. The GUV system in the presence of invertase is beneficial as a tool to generate multiple on-demand compartments with more extended stability after the enzymatic activity has established the asymmetry.

Systems chemistry represents a shift from studying molecules in isolation to studying the collective behavior of mixtures or ensembles of reacting and interacting molecules. This research direction provides new ways to build and understand collective chemical properties and emergent functions that are inaccessible using conventional, reductionist, chemistry approaches. This field exemplifies fundamental connections between chemistry and biology, and has the potential to give rise to completely new ways for chemists to approach and resolve wide-ranging issues related to all aspects of living systems, that themselves are complex systems. Short peptides, while simple in design, carry rich and versatile information encoded in sequence specific side-chain interactions, that makes it possible to access a high level of complex, information rich systems with emergent properties from Life's simplified building blocks. This review focuses on recent developments in the synthesis of complex adaptive systems based on peptides, where multiple components are designed to cooperatively interact, react and collectively adapt to their context.

The front cover artwork is provided by the Hartley group at Miami University. The image shows a cartoon of transient molecular cages generated through the action of a chemical fuel on macrocycles with pendant groups. The cages are able to bind ions. Read the full text of the Research Article at 10.1002/syst.202200016.

The Cover Feature shows puzzle pieces that initially change their shape, and consequently their interconnection, to eventually go back to their initial state, resembling the behavior of the components in a dissipative dynamic combinatorial library. Design by Daniele Del Giudice. More information can be found in the Concept by Gianfranco Ercolani, Stefano Di Stefano and co-workers.

The Front Cover illustrates the formation of molecular cages through the action of a chemical “fuel” on macrocyclic precursors. The cages exist for only a short time but are able to bind appropriate cations. More information can be found in the Research Article by C. Scott Hartley and co-workers.

Peptides have essential structural and catalytic functions in living organisms. The formation of peptides requires the overcoming of thermodynamic and kinetic barriers. In recent years, various formation scenarios that may have occurred during the origin of life have been investigated, including iron(III)-catalyzed condensations. However, iron(III)-catalysts require elevated temperatures and the catalytic activity in peptide bond forming reactions is often low. It is likely that in an anoxic environment such as that of the early Earth, reduced iron compounds were abundant, both on the Earth's surface itself and as a major component of iron meteorites. In this work, we show that reduced iron activated by acetic acid mediates efficiently peptide formation. We recently demonstrated that, compared to water, liquid sulfur dioxide (SO₂) is a superior reaction medium for peptide formations. We thus investigated both and observed up to four amino acid/peptide coupling steps in each solvent. Reaction with diglycine (G₂) formed 2.0 % triglycine (G₃) and 7.6 % tetraglycine (G₄) in 21 d. Addition of G₃ and dialanine (A₂) yielded 8.7 % G₄. Therefore, this is an efficient and plausible route for the formation of the first peptides as simple catalysts for further transformations in such environments.

Nature uses dynamic, molecular self-assembly to create cellular architectures that adapt to their environment. For example, a guanosine triphosphate (GTP)-driven reaction cycle activates and deactivates tubulin for dynamic assembly into microtubules. Inspired by dynamic self-assembly in biology, recent studies have developed synthetic analogs of assemblies regulated by chemically fueled reaction cycles. A challenge in these studies is to control the interplay between rapid disassembly and kinetic trapping of building blocks known as dynamic instabilities. In this work, we show how molecular design can tune the tendency of molecules to remain trapped in their assembly. We show how that design can alter the dynamic of emerging assemblies. Our work should give design rules for approaching dynamic instabilities in chemically fueled assemblies to create new adaptive nanotechnologies.