Oleksandr

Nature Materials, Published online: 28 June 2023; doi:10.1038/s41563-023-01602-4

Synthetic oligosaccharides and microED analysis enable the molecular level characterization of carbohydrate materials. The local crystal organization is correlated to the supramolecular architecture, allowing for the design of helical structures as well as flat lamellae.

Abstract

Hierarchical carbohydrate architectures serve multiple roles in nature. Hardly any correlations between the carbohydrate chemical structures and the material properties are available due to the lack of standards and suitable analytic techniques. Therefore, designer carbohydrate materials remain highly unexplored, as compared to peptides and nucleic acids. A synthetic D‐glucose disaccharide, DD, was chosen as a model to explore carbohydrate materials. Microcrystal electron diffraction (MicroED), optimized for oligosaccharides, revealed that DD assembled into highly crystalline left‐handed helical fibers. The supramolecular architecture was correlated to the local crystal organization, allowing for the design of the enantiomeric right‐handed fibers, based on the L‐glucose disaccharide, LL, or flat lamellae, based on the racemic mixture. Tunable morphologies and mechanical properties suggest the potential of carbohydrate materials for nanotechnology applications.

Nature, Published online: 20 November 2020; doi:10.1038/d41586-020-03300-6

Nature Catalysis, Published online: 12 November 2020; doi:10.1038/s41929-020-00536-3

RNA‐catalyzed RNA ligation is widely believed to be a key reaction for primordial biology. However, since typical chemical routes towards activating RNA substrates are incompatible with ribozyme catalysis, it remains unclear how prebiotic systems generated and sustained pools of activated building blocks needed to form increasingly larger and complex RNA. Herein, we demonstrate in situ activation of RNA substrates under reaction conditions amenable to catalysis by the hairpin ribozyme. We found that diamidophosphate (DAP) and imidazole drive the formation of 2’,3’‐cyclic phosphate RNA mono‐ and oligonucleotides from monophosphorylated precursors in frozen water‐ice. This long‐lived activation enables iterative enzymatic assembly of long RNAs. Our results provide a plausible scenario for the generation of higher‐energy substrates required to fuel ribozyme‐catalyzed RNA synthesis in the absence of a highly evolved metabolism.

The development of highly selective adsorbents for aromatics/cyclic aliphatics separation is highly desired and urgently needed. In this communication, a solid–liquid host–guest separation method is presented, which can efficiently extract three kinds of dimethylbenzene molecules from their corresponding hydrogenation products by using a newly designed and synthesized macrocyclic arene, namely elongated‐geminiarene.

Abstract

Energy‐saving separation and purification of industrially important compounds with similar physical and chemical properties by novel molecular crystalline materials are of great importance and highly desired. Here a newly enlarged version of geminiarene, namely elongated‐geminiarene (ElGA), is first designed and synthesized. Taking advantages of both geminiarenes and biphenarenes, ElGA shows great features including scalable synthesis, nanometer‐sized cavity, rich blend of conformational features, and excellent solid‐state host–guest properties. Significantly, the functional crystalline materials of ElGA are highly effective in the separation of aromatics and cyclic aliphatics, showing a preference for dimethylbenzene over its corresponding hydrogenation products and paving a new avenue for separation science and industry.

Atomically precise graphene nanoribbons (GNRs) attract great interest because of their highly tunable electronic, optical, and transport properties. However, on-surface synthesis of GNRs is typically based on metal surface–assisted chemical reactions, where metallic substrates strongly screen their designer electronic properties and limit further applications. Here, we present an on-surface synthesis approach to forming atomically precise GNRs directly on semiconducting metal oxide surfaces. The thermally triggered multistep transformations preprogrammed in our precursors’ design rely on highly selective and sequential activations of carbon-bromine (C-Br) and carbon-fluorine (C-F) bonds and cyclodehydrogenation. The formation of planar armchair GNRs terminated by well-defined zigzag ends is confirmed by scanning tunneling microscopy and spectroscopy, which also reveal weak interaction between GNRs and the rutile titanium dioxide substrate.

Nature, Published online: 28 July 2020; doi:10.1038/d41586-020-02235-2

Nature Communications, Published online: 15 July 2020; doi:10.1038/s41467-020-17321-2

An old phenomenon in a new light : In this brief Essay, the currently highly recognized aggregation‐induced emission (AIE) phenomenon is discussed in a broader perspective by illustrating its roots in earlier work.

Abstract

Aggregation‐induced emission (AIE) has attracted considerable interest over the last twenty years. In contrast to the large number of available reviews focusing specifically on AIE, this Essay discusses the AIE phenomenon from a broader perspective, with an emphasis on early observations related to AIE made long before the term was coined. Illustrative examples are highlighted from the 20th century where fluorescence enhancement upon rigidification of dyes in viscous or solid environments or J‐aggregate formation was studied. It is shown that these examples already include typical AIE luminogens such as tetraphenylethylene (TPE) as well as stilbenes and oligo‐ or polyphenylenevinylenes and ‐ethynylenes, which became important fluorescent solid‐state materials in OLED research in the 1990s. Further examples include cyanine dyes such as thiazole orange (TO) or its dimers (TOTOs), which have been widely applied as molecular probes in nucleic acid research. The up to 10 000‐fold fluorescence enhancement of such dyes upon intercalation into double‐stranded DNA, attributable to the restricted intramolecular motion (RIM) concept, afforded commercial products for bioimaging and fluorescence sensing applications already in the early 1990s.

Nature Reviews Chemistry, Published online: 01 July 2020; doi:10.1038/s41570-020-0196-x

Non‐enzymatic RNA Copying: Enhanced non‐enzymatic ligation allows the rapid copying of long RNA template and short RNA splinted templates, thus suggesting a potential route to the assembly of artificial systems capable of evolution.

Abstract

The non‐enzymatic replication of the primordial genetic material is thought to have enabled the evolution of early forms of RNA‐based life. However, the replication of oligonucleotides long enough to encode catalytic functions is problematic due to the low efficiency of template copying with mononucleotides. We show that template‐directed ligation can assemble long RNAs from shorter oligonucleotides, which would be easier to replicate. The rate of ligation can be greatly enhanced by employing a 3′‐amino group at the 3′‐end of each oligonucleotide, in combination with an N‐alkyl imidazole organocatalyst. These modifications enable the copying of RNA templates by the multistep ligation of tetranucleotide building blocks, as well as the assembly of long oligonucleotides using short splint oligonucleotides. We also demonstrate the formation of long oligonucleotides inside model prebiotic vesicles, which suggests a potential route to the assembly of artificial cells capable of evolution.

Shaping amphiphile assemblies into a novel class of tubular architectures has been realized by programming an unconventional amphiphilic molecule with directional Watson–Crick hydrogen‐bonding interactions that are shielded from the aqueous environment. These self‐assembled nanotubes have chiral lipophilic pores about 2 nm in diameter that are able to encapsulate molecules that are complementary in size and chemical affinity.

Abstract

Despite the central importance of aqueous amphiphile assemblies in science and industry, the size and shape of these nano‐objects is often difficult to control with accuracy owing to the non‐directional nature of the hydrophobic interactions that sustain them. Here, using a bioinspired strategy that consists of programming an amphiphile with shielded directional Watson–Crick hydrogen‐bonding functions, its self‐assembly in water was guided toward a novel family of chiral micelle nanotubes with partially filled lipophilic pores of about 2 nm in diameter. Moreover, these tailored nanotubes are successfully demonstrated to extract and host molecules that are complementary in size and chemical affinity.