Oleksandr

Mechanically interlocked molecules are likely candidates for the design and synthesis of artificial molecular machines. Although polyrotaxanes have already found niche applications in exotic materials with specialized mechanical properties, efficient synthetic protocols to produce them with precise numbers of rings encircling their polymer dumbbells are still lacking. We report the assembly line–like emergence of poly[n]rotaxanes with increasingly higher energies by harnessing artificial molecular pumps to deliver rings in pairs by cyclical redox-driven processes. This programmable strategy leads to the precise incorporation of two, four, six, eight, and 10 rings carrying 8+, 16+, 24+, 32+, and 40+ charges, respectively, onto hexacationic polymer dumbbells. This strategy depends precisely on the number of redox cycles applied chemically or electrochemically, in both stepwise and one-pot manners.

The addition of chain stoppers significantly improves carbon nanotube (CNT) sorting with an H‐bonding supramolecular polymer. In‐depth characterization reveals that this supramolecular polymer exhibits ring–chain equilibrium, and that stoppers skew the distribution toward chains, which can wrap CNTs more effectively. Careful selection of the stopper–monomer ratio results in doubling of the sorting yield without compromising the purity or properties of sorted CNTs.

Abstract

Supramolecular polymer sorting is a promising approach to separating single‐walled carbon nanotubes (CNTs) by electronic type. Unlike conjugated polymers, they can be easily removed from the CNTs after sorting by breaking the supramolecular bonds, allowing for isolation of electronically pristine CNTs as well as facile recycling of the sorting polymer. However, little is understood about how supramolecular polymer properties affect CNT sorting. Herein, chain stoppers are used to engineer the conformation of a supramolecular sorting polymer, thereby elucidating the relationship between sorting efficacy and polymer conformation. Through NMR and UV–vis spectroscopy, small‐angle X‐ray scattering (SAXS), and thermodynamic modeling, it is shown that this supramolecular polymer exhibits ring–chain equilibrium, and that this equilibrium can be skewed toward chains by the addition of chain stoppers. Furthermore, by controlling the stopper–monomer ratio, the sorting yield can be doubled from 7% to 14% without compromising the semiconducting purity (>99%) or properties of sorted CNTs.

Whole living cells were used as the template in a dynamic combinatorial chemistry system. The amplified member of the dynamic library showed strong and selective binding to the main glycosaminoglycan of the extracellular matrix of the corresponding cell. This work demonstrates the power of dynamic covalent screening in chemical biology, even in highly challenging biorelevant media.

Abstract

Dynamic covalent chemistry combines in a single step the screening and synthesis of ligands for biomolecular recognition. In order to do that, a chemical entity is used as template within a dynamic combinatorial library of interconverting species, so that the stronger binders are amplified due to the efficient interaction with the target. Here we employed whole A549 living cells as template in a dynamic mixture of imines, for which amplification reflects the efficient and selective interaction with the corresponding extracellular matrix. The amplified polyamine showed strong interaction with the A549 extracellular matrix in on‐cell NMR experiments, while combination of NMR, SPR, and molecular dynamics simulations in model systems provided insights on the molecular recognition event. Notably, our work pioneers the use of whole living cells in dynamic combinatorial chemistry, which paves the way towards the discovery of new bioactive molecules in a more biorelevant environment.

Transcription polymerases can exhibit an unusual mode of regenerating certain RNA templates from RNA, yielding systems that can replicate and evolve with RNA as the information carrier. Two classes of pathogenic RNAs (hepatitis delta virus in animals and viroids in plants) are copied by host transcription polymerases. Using in vitro RNA replication by the transcription polymerase of T7 bacteriophage as an experimental model, we identify hundreds of new replicating RNAs, define three mechanistic hallmarks of replication (subterminal de novo initiation, RNA shape-shifting, and interrupted rolling-circle synthesis), and describe emergence from DNA seeds as a mechanism for the origin of novel RNA replicons. These results inform models for the origins and replication of naturally occurring RNA genetic elements and suggest a means by which diverse RNA populations could be propagated as hereditary material in cellular contexts.

The simple combination of DMPC and DHPC resulted in various lipid nanostructures with distinct structure–function relationships, differing in uptake, drug encapsulation efficacy, and in vivo anti‐tumor therapy.

Abstract

Structural morphology is the key parameter for efficacy of nanomedicine. To date, lipid‐based nanomaterial has been the most widely used material in nanomedicine and many other biomedical applications. However, to the best of our knowledge, there has not been an in‐depth or systematic investigation of the structure–function relationship of lipid‐based nanostructures. In this report, we investigated the formulation of novel lipid‐based nanostructures via simple tuning of lipid combinations. To prove this concept, we used a combination of various ratios of simple and common phospholipids with different chain lengths (14‐carbon chain DMPC: 6‐carbon chain DHPC) to find out whether a myriad of novel lipid nanostructures could be obtained. Interestingly, many combinations resulted in distinct lipid nanostructures. Drug encapsulation tests confirmed that they are able to load large amounts of drugs for biological application. In vivo anti‐tumor efficacy revealed that certain lipid nanostructures possessed superior tumor retardation effects.

Molecules can be designed to interact with one another and form assemblies. Biology also uses molecular self-assembly to create its structural components. However, this biological process is tightly regulated by chemical reaction cycles that operate out of equilibrium. If we want to create life-like materials or even synthetic life, we should use an approach similar to molecular self-assembly. The focus of this review is to lay out design strategies toward the synthesis of molecular assemblies regulated by chemical reaction cycles.

Self‐assembly is a bioinspired strategy to create soft materials for renewable and clean energy technologies. The field of supramolecular energy materials is described, covering work on self‐assembling molecules to craft light harvesting systems for photocatalysis and photovoltaics. Also, pathways to use supramolecular phases as templates for inorganic structures and electrodeposition for the synthesis of energy materials are discussed.

Abstract

Self‐assembly is a bioinspired strategy to craft materials for renewable and clean energy technologies. In plants, the alignment and assembly of the light‐harvesting protein machinery in the green leaf optimize the ability to efficiently convert light from the sun to form chemical bonds. In artificial systems, strategies based on self‐assembly using noncovalent interactions offer the possibility to mimic this functional correlation among molecules to optimize photocatalysis, photovoltaics, and energy storage. One of the long‐term objectives of the field described here as supramolecular energy materials is to learn how to design soft materials containing light‐harvesting assemblies and catalysts to generate fuels and useful chemicals. Supramolecular energy materials also hold great potential in the design of systems for photovoltaics in which intermolecular interactions in self‐assembled structures, for example, in electron donor and acceptor phases, maximize charge transport and avoid exciton recombination. Possible pathways to integrate organic and inorganic structures by templating strategies and electrodeposition to create materials relevant to energy challenges including photoconductors and supercapacitors are also described. The final topic discussed is the synthesis of hybrid perovskites in which organic molecules are used to modify both structure and functions, which may include chemical stability, photovoltaics, and light emission.

Play with Lego: A modular synthetic strategy for macrocycles with functional skeletons was demonstrated, involving one‐pot and high‐yielding condensation between bis(2,4‐dimethoxyphenyl)arene monomers and paraformaldehyde. By changing the blocks, variously functional units can be conveniently introduced into the backbone of macrocycles.

Abstract

Reported here is a molecule‐Lego synthetic strategy for macrocycles with functional skeletons, involving one‐pot and high‐yielding condensation between bis(2,4‐dimethoxyphenyl)arene monomers and paraformaldehyde. By changing the blocks, variously functional units (naphthalene, pyrene, anthraquinone, porphyrin, etc.) can be conveniently introduced into the backbone of macrocycles. Interestingly, the macrocyclization can be tuned by the geometrical configuration of monomeric blocks. Linear (180°) monomer yield cyclic trimers and pentamers, while V‐shaped (120°, 90° and 60°) monomers tend to form dimers. More significantly, even heterogeneous macrocycles are obtained in moderate yield by co‐oligomerization of different monomers. This series of macrocycles have the potential to be prosperous in the near future.

Targeting soft‐matter chemists and beginning structural biologists, this work aims to give a concise background into electron microscopy, including topics like image formation, microscope composition, and processing possibilities. Furthermore, it discusses technical developments that have been implemented in the field of biology and are also of interest to the field of soft‐matter chemistry.

Abstract

With a significant role in material sciences, physics, (soft matter) chemistry, and biology, the transmission electron microscope is one of the most widely applied structural analysis tool to date. It has the power to visualize almost everything from the micrometer to the angstrom scale. Technical developments keep opening doors to new fields of research by improving aspects such as sample preservation, detector performance, computational power, and workflow automation. For more than half a century, and continuing into the future, electron microscopy has been, and is, a cornerstone methodology in science. Herein, the technical considerations of imaging with electrons in terms of optics, technology, samples and processing, and targeted soft materials are summarized. Furthermore, recent advances and their potential for application to soft matter chemistry are highlighted.

Nature, Published online: 28 February 2020; doi:10.1038/d41586-020-00599-z

Three searchable databases provide information on global opportunities for graduate students, postdocs and junior faculty members.

There is a need to make and break covalent bonds under the same reaction conditions to devise new chemical reaction cycles that can power dissipative self‐assembly. The progress of the past ten years toward this goal is reviewed, and two new chemistries that could be used in future reaction cycles are proposed.

Abstract

Fuel‐driven reaction cycles are found in biological systems to control the assembly and disassembly of supramolecular materials such as the cytoskeleton. Fuel molecules can bind noncovalently to a self‐assembling building block or they can react with it, resulting in covalent modifications. Overall the fuel can either switch the self‐assembly process on or off. Here, a closer look is taken at artificial systems that mimic biological systems by making and breaking covalent bonds in a self‐assembling motif. The different chemistries used so far are highlighted in chronological order and the pros and cons of each system are discussed. Moreover, the desired traits of future reaction cycles, their fuels, and waste management are outlined, and two chemistries that have not been explored up to now in chemically fueled dissipative self‐assembly are suggested.

Nature, Published online: 05 February 2020; doi:10.1038/d41586-020-00309-9

Research involves deep discussions between authors and reviewers. Starting this week, readers of some Nature Research journals will be able to see this up close.

All systems go : Increased research on large molecules will reveal construction principles dictated by recurring motifs that govern structure formation through folding and self‐assembly. These principles are comparable to the organization of atoms in the Periodic Table of Chemical Elements and could lead to the establishment of a Periodic System of Supramolecular Elements.

Abstract

Chemistry “beyond the molecule” is based on weak, noncovalent, and reversible interactions. As a consequence of these bonds being weak, structural organization by folding and self‐assembly can only be fully exploited with larger molecules that can provide multiple binding sites. Such “supramolecules” can now be synthesized and their folding into desired conformations predicted. A new level of chemistry can now be realized through the creation of non‐natural entities composed of molecular building blocks with defined secondary structures. Herein we define these building blocks as “supramolecular elements”. We anticipate that further research on such large molecules will reveal construction principles dictated by recurring motifs that govern structure formation through folding and self‐assembly. These principles are comparable to the organization of atoms in the Periodic Table of Chemical Elements and may lead to the establishment of a Periodic System of Supramolecular Elements.

We advocate an integrative approach between laboratory experiments in prebiotic chemistry and geologic, geochemical, and astrophysical observations to help assemble a robust chemical pathway to life that can be reproduced in the laboratory. The cyanosulfidic chemistry scenario described here was developed by such an integrative iterative process. We discuss how it maps onto evolving planetary surface environments on early Earth and Mars and the value of comparative planetary evolution. The results indicate that Mars can offer direct evidence for geochemical conditions similar to prebiotic Earth, whose early record has been erased. The Jezero crater is now the chosen landing site for NASA’s Mars 2020 rover, making this an extraordinary opportunity for a breakthrough in understanding life’s origins.

Nature, Published online: 27 January 2020; doi:10.1038/s41586-020-1938-0

Flash Joule heating of inexpensive carbon sources is used to produce gram-scale quantities of high-quality graphene in under a second, without the need for a furnace, solvents or reactive gases.

The right channels: A novel class of foldamer‐based pore‐forming helically folded polyhydrazides, having hydrophobic cavities of about a 6.5 Å diameter, promote transport of anions, rather than cations, across membranes, with iodide as the preferred transport species. The best channel, having a helical height of 3.6 nm, exhibits the highest recorded iodide transport activity (EC ₅₀=0.042 μm or 0.028 mol % relative to lipid) and high I⁻/Cl⁻ selectivity of 11, in terms of EC ₅₀ values, or 42 based on initial rate constants.

Abstract

Reported herein is a series of pore‐containing polymeric nanotubes based on a hydrogen‐bonded hydrazide backbone. Nanotubes of suitable lengths, possessing a hollow cavity of about a 6.5 Å diameter, mediate highly efficient transport of diverse types of anions, rather than cations, across lipid membranes. The reported polymer channel, having an average molecular weight of 18.2 kDa and 3.6 nm in helical height, exhibits the highest anion‐transport activities for iodide (EC ₅₀=0.042 μm or 0.028 mol % relative to lipid), whcih is transported 10 times more efficiently than chlorides (EC ₅₀=0.47 μm). Notably, even in cholesterol‐rich environment, iodide transport activity remains high with an EC ₅₀ of 0.37 μm. Molecular dynamics simulation studies confirm that the channel is highly selective for anions and that such anion selectivity arises from a positive electrostatic potential of the central lumen rendered by the interior‐pointing methyl groups.

aza‐BODIPY comes alive! Living supramolecular polymerization was demonstrated by aza‐BODIPY 1 bearing hydrogen‐bond accepting triazole units that can be facilely constructed through click chemistry. The H‐bonding unit of amide‐linked triazole in dye 1 could be employed as a general motif for encoding conformational information and developing polymorphic supramolecular systems.

Abstract

An aza‐BODIPY dye 1 bearing two hydrophobic fan‐shaped tridodecyloxybenzamide pendants through 1,2,3‐triazole linkages was synthesized by a click reaction and characterized. ¹H NMR studies indicated that dye 1 exhibited variable conformations through intramolecular H‐bonding interaction, which is beneficial for the polymorphism of aggregation. The thermodynamic, structural, and kinetic aspect of the supramolecular polymerization of dye 1 was investigated by UV/Vis absorption spectroscopy, IR spectroscopy, AFM, TEM, and SEM. Biphasic aggregation pathways of dye 1, leads to the formation of off‐pathway, metastable Agg. I and thermodynamically stable Agg. II with distinct H‐aggregation spectra and nanoscale morphology. The living manner of the supramolecular polymerization of dye 1 was demonstrated in seeded polymerization experiments with temperature‐modulated successive cooling–heating cycles.