ChemSystemsChem最新文献

Absorption of ultraviolet (UV) radiation can trigger a variety of photophysical and photochemical reactions in nucleic acids. In the prebiotic era, on the surface of the early Earth, UV light could have played a major role in the selection of the building blocks of life via a balance between synthetic and destructive pathways. As nucleic acid monomers assembled into polymers, their survival and facility for non-enzymatic replication hinged on their photostability and the ability for self-repair of lesions, e. g., by UV-induced charge transfer. Such photoprocesses are known to be sequence-dependent and could have led to an additional prebiotic selection of the genetic sequence pools available to the earliest life forms. This review summarizes the photophysical processes in nucleic acids upon the absorption of a UV photon and their implications for chemical and genetic selection at the emergence of life and the origin of translation.

For the emergence of life, the abiotic synthesis of RNA from its monomers is a central step. We found that in alkaline, drying conditions in bulk and at heated air-water interfaces, 2′,3′-cyclic nucleotides oligomerised without additional catalyst, forming up to 10-mers within a day. The oligomerisation proceeded at a pH range of 7–12, at temperatures between 40–80 °C and was marginally enhanced by K⁺ ions. Among the canonical ribonucleotides, cGMP oligomerised most efficiently. Quantification was performed using HPLC coupled to ESI-TOF by fitting the isotope distribution to the mass spectra. Our study suggests a oligomerisation mechanism where cGMP aids the incorporation of the relatively unreactive nucleotides C, A and U. The 2′,3′-cyclic ribonucleotides are byproducts of prebiotic phosphorylation, nucleotide syntheses and RNA hydrolysis, indicating direct recycling pathways. The simple reaction condition offers a plausible entry point for RNA to the evolution of life on early Earth.

This Concept is focused on the key features of dissipative dynamic combinatorial chemistry (DDCC). DDCC deals with transient libraries of compounds, maintained out-of-equilibrium by the consumption of a fuel, whose composition changes upon the selection pressure of kinetic and/or thermodynamic processes. Concepts and definitions of kinetic and thermodynamic dissipative dynamic libraries (“KDDL” and “TDDL”), are introduced and illustrated by a number of actual cases, thus showing the consistency of the present approach. Such concepts and definitions can help establish a common language for this emerging field, which, in our view, has the potential to become highly relevant to supramolecular chemistry.

Metabolites are the set of substances produced or utilized in the biochemical process of metabolism known to perform diverse physiological functions in every living organism. As very simple molecules, metabolites can self-assemble into functional materials for biomedical and nanotechnology applications. Simple amino acid-based crystals exhibit interesting physicochemical properties of piezoelectricity, fluorescence and optical waveguiding. Combinations of metal-coordinated metabolites display catalytic properties mimicking natural enzymes for chemical reactions and environmental remediation. Furthermore, excessive accumulation of metabolites spontaneously forms toxic assemblies implicated in the pathogenesis of metabolic and neurodegenerative diseases. Herein, we mainly review the progress of recent three years on the assembly of minimalistic metabolite-based building blocks into bionanomaterials and their potential applications in energy harvesting, optical waveguiding, enzymatic catalysis, and biomedicine. We hope this review can promote the understanding and development of metabolite materials to meet functional requirements.

The front cover artwork is provided by Wolfgang Weigand's group at Friedrich Schiller University Jena and was designed by Mario Grosch. The image shows a hypothetical version of the Earth's early surface, where mackinawite produced from the reaction between iron and sulfur in water can react with C₁ substrates like HCN to form CH₄, NH₃, CH₃SH and CH₃CHO. Read the full text of the Research Article at 10.1002/syst.202200010.

The Front Cover shows a possible version of Earth's early surface, where mackinawite formed by the reaction between iron and sulfur can subsequently reduce HCN into organic compounds like CH₄, NH₃, CH₃SH and CH₃CHO and thereby provide important precursors for the origin of life. Design by Mario Grosch. More information can be found in the Research Article by Markus Ribbe, Yilin Hu, Oliver Trapp, Christian Robl, Wolfgang Weigand and co-workers.

The use of “fuel” compounds to drive chemical systems out of equilibrium is currently of interest because of the potential for temporally controlled, responsive behavior. We have recently shown that transiently formed crown ethers exhibit counterintuitive templation effects when generated in the presence of alkali metal cations: “matched” cations, such as K⁺ with an 18-crown-6 analogue, suppress the formation of the macrocycles (negative templation). In this work, we describe two macrocyclic diacids that, on treatment with carbodiimides, give transient macrobicyclic cages analogous to polyether cages. Negative templation effects are observed for the smaller cage when generated in the presence of K⁺ and Na⁺, but there is a weak, but reproducible, positive templation effect in the presence of Li⁺. The larger cage behaves similarly in the presence of Li⁺, K⁺, Rb⁺, and Cs⁺, but differently with Na⁺, which appears to bind to both the cage and the initial macrocycle.

Nucleotides play a fundamental role in organisms, from adenosine triphosphate (ATP), the body‘s main source of energy, to cofactors of enzymatic reactions (e. g. coenzyme A), to nucleoside monophosphates as essential building blocks of deoxyribonucleic acid (DNA) and ribonucleic acid (RNA). Although nucleotides play such an elemental role, there is no pathway to date for the selective formation of nucleoside 5′-monophosphates. Here, we demonstrate a selective reaction pathway for 5’ mono-phosphorylation for all canonical purine and pyrimidine bases under exceptionally mild prebiotic relevant conditions in water and without using a condensing agent. The pivotal reaction step involves activated imidazolidine-4-thione phosphates. The selective formation of non-cyclic mono-phosphorylated nucleosides represents a novel and unique route to nucleotides and opens exciting perspectives in the study of the origins of life.

Block copolymer-based polymersomes are important building blocks for the bottom-up design of protocells and are considered advantageous over liposomes due to their higher mechanical stability and chemical versatility. Endowing both types of vesicles with capabilities for transmembrane transport is important for creating nanoreactor functionality and has been achieved by insertion of protein nanopores, even into comparably thick polymersome membranes. Still, the design space for protein nanopores is limited and higher flexibility might be accessible by de novo design of DNA nanopores, which have thus far been limited largely to liposome systems. Here, we introduce the successful insertion of two different 3D DNA origami nanopores into PMOXA-b-PDMS-b-PMOXA polymersomes, and confirm pore formation by dye influx studies and microscopy. This research thus opens the further design space of this versatile class of large DNA origami nanopores for polymersome-based functional protocells.

The Front Cover shows a light microscopy image of metabolite coacervates. A graphic representation of a metabolic network is projected over the coacervate protocells, containing illustrations that depict different steps in the emergence of life on Earth. Small molecules react to form more complex molecules, which eventually partake in reaction networks. This work shows how metabolites present in these early networks are able to phase separate and form stable coacervate droplets. The coacervates are able to compartmentalize metabolites and increase reaction rates, providing an attractive model for the first generation of protocells. More information can be found in the Research Article by Evan Spruijt and co-workers.