A Chemically Driven Rotary Molecular Motor Based on Reversible Lactone Formation with Perfect Unidirectionality

A chemically driven molecular motor has been designed, which proceeds through stepwise movements fueled by chemical energy and undergoes full 360° unidirectional rotation. A record, nearly 100% unidirectionality is realized during the whole rotary process

Intrinsically unidirectional chemically fuelled rotary molecular motors

Biological systems mainly utilize chemical energy to fuel autonomous molecular motors, enabling the system to be driven out of equilibrium1. Taking inspiration from rotary motors such as the bacterial flagellar motor2 and adenosine triphosphate synthase3, and building on the success of light-powered unidirectional rotary molecular motors4–6, scientists have pursued the design of synthetic molecular motors solely driven by chemical energy7–13. However, designing artificial rotary molecular motors operating autonomously using a chemical fuel and simultaneously featuring the intrinsic structural design elements to allow full 360° unidirectional rotary motion like adenosine triphosphate synthase remains challenging. Here we show that a homochiral biaryl Motor-3, with three distinct stereochemical elements, is a rotary motor that undergoes repetitive and unidirectional 360° rotation of the two aryl groups around a single-bond axle driven by a chemical fuel. It undergoes sequential ester cyclization, helix inversion and ring opening, and up to 99% unidirectionality is realized over the autonomous rotary cycle. The molecular rotary motor can be operated in two modes: synchronized motion with pulses of a chemical fuel and acid–base oscillations; and autonomous motion in the presence of a chemical fuel under slightly basic aqueous conditions. This rotary motor design with intrinsic control over the direction of rotation, simple chemical fuelling for autonomous motion and near-perfect unidirectionality illustrates the potential for future generations of multicomponent machines to perform mechanical functions

The band gap and nonlinear optical susceptibility of SrSn1-xVxO3 films

Perovskite-type oxide SrSn1-xVxO3 thin films with different concentrations x = 0.1–0.9 were fabricated by using pulsed-laser deposition, and the effects of V doping on the structure, optical band gap and the third-order optical nonlinearity were systematically investigated. With the increase of x value, the lattice parameters of SrSn1-xVxO3 decrease from 3.997 to 3.862 Å gradually, while the optical band gaps firstly increase and then decrease with boundary at x = 0.3. The third-order nonlinear optical responses were studied via the z-scan technique. The closed-aperture measurements show a negative nonlinear refractive index n2, and the open-aperture measurements demonstrate a saturable absorption β. Both the n2 and β responses vary with the increase of V doping level. The metal-oxygen chemical bond along with the localized V5+Sn2+V5+ complex contribute to the enhancement of optical nonlinearity, and the highest value of third-order susceptibility χ(3) is observed in SrSn0.5V0.5O3 film

Asymmetric synthesis of N,O-heterocycles via enantioselective iridium-catalysed intramolecular allylic amidation

Chiral N,O-heterocycles were synthesized in high yields and excellent enantioselectivity up to 97% ee via iridium-catalysed intramolecular allylic substitution with nucleophilic attack by the amide oxygen atom. The resulting benzoxazine derivatives were further transformed into challenging chiral N,O-ketals bearing both a tertiary and a quaternary center with excellent diastereoselectivities

In situ control of polymer helicity with a non-covalently bound photoresponsive molecular motor dopant

The transfer of chirality from a molecular motor to a dynamic helical polymer via ionic interactions was investigated. A dopant with photoswitchable chirality was able to induce a preferred helicity in a poly(phenylacetylene) polymer and the helicity is inverted upon irradiation. The findings described herein will advance the development of functional and responsive polymeric systems

Solvent mixing to induce molecular motor aggregation into bowl-shaped particles:underlying mechanism, particle nature and application to control motor behavior

The control over dynamic functions in larger assemblies is key to many molecular systems ranging from responsive materials to molecular machines. Here we report a molecular motor that forms bowl-shaped particles in water and how confinement of the molecular motor effects rotary motion. Studying the aggregation process in a broader context we provide evidence that in the case of bowl-shaped particles the structures are not the product of self-assembly, but a direct result of the mixing a good solvent and a (partial) non-solvent and highly independent of the molecular design. Under influence of the non-solvent, droplets are formed, of which the exterior is hardened due to the increased glass-transition temperature by the external medium, while the interior of the droplets remains plasticized by the solvent resulting in the formation of stable bowl-shaped particles with a fluid interior, a glass-like exterior and a very specific shape; dense spheres with a hole in their side. Applying this to a bulky first generation molecular motor allowed us to change its isomerization behavior. Furthermore, the motor shows in situ photo-switchable aggregation-induced emission (AIE). Strong confinement prohibits the thermal helix inversion step while altering the energy barriers that determine the rotary motion, such that it introduces a reverse trans-cis isomerization by heating. These studies show a remarkable control of forward and backward rotary motion by simple changing solvent ratios and extend of confinement

Layer-by-Layer Epitaxy of Multilayer MoS2 Wafers

Two-dimensional (2D) semiconductor of MoS2 has great potential for advanced electronics technologies beyond silicon1-9. So far, high-quality monolayer MoS2 wafers10-12 are already available and various demonstrations from individual transistors to integrated circuits have also been shown13-15. In addition to the monolayer, multilayers have narrower band gaps but improved carrier mobilities and current capacities over the monolayer5,16-18. However, achieving high-quality multilayer MoS2 wafers remains a challenge. Here we report the growth of high quality multilayer MoS2 4-inch wafers via the layer-by-layer epitaxy process. The epitaxy leads to well-defined stacking orders between adjacent epitaxial layers and offers a delicate control of layer numbers up to 6. Systematic evaluations on the atomic structures and electronic properties were carried out for achieved wafers with different layer numbers. Significant improvements on device performances were found in thicker-layer field effect transistors (FETs), as expected. For example, the average field-effect mobility ({\mu}FE) at room temperature (RT) can increase from ~80 cm2V-1s-1 for monolayer to ~110/145 cm2V-1s-1 for bilayer/trilayer devices. The highest RT {\mu}FE=234.7 cm2V-1s-1 and a record-high on-current densities of 1.704 mA{\mu}m-1 at Vds=2 V were also achieved in trilayer MoS2 FETs with a high on/off ratio exceeding 107. Our work hence moves a step closer to practical applications of 2D MoS2 in electronics.Comment: 13 pages,4 Figure

The Genome of Ganderma lucidum Provide Insights into Triterpense Biosynthesis and Wood Degradation

BACKGROUND: Ganoderma lucidum (Reishi or Ling Zhi) is one of the most famous Traditional Chinese Medicines and has been widely used in the treatment of various human diseases in Asia countries. It is also a fungus with strong wood degradation ability with potential in bioenergy production. However, genes, pathways and mechanisms of these functions are still unknown. METHODOLOGY/PRINCIPAL FINDINGS: The genome of G. lucidum was sequenced and assembled into a 39.9 megabases (Mb) draft genome, which encoded 12,080 protein-coding genes and ∼83% of them were similar to public sequences. We performed comprehensive annotation for G. lucidum genes and made comparisons with genes in other fungi genomes. Genes in the biosynthesis of the main G. lucidum active ingredients, ganoderic acids (GAs), were characterized. Among the GAs synthases, we identified a fusion gene, the N and C terminal of which are homologous to two different enzymes. Moreover, the fusion gene was only found in basidiomycetes. As a white rot fungus with wood degradation ability, abundant carbohydrate-active enzymes and ligninolytic enzymes were identified in the G. lucidum genome and were compared with other fungi. CONCLUSIONS/SIGNIFICANCE: The genome sequence and well annotation of G. lucidum will provide new insights in function analyses including its medicinal mechanism. The characterization of genes in the triterpene biosynthesis and wood degradation will facilitate bio-engineering research in the production of its active ingredients and bioenergy

Phylogenomic analyses provide insights into primate evolution

Comparative analysis of primate genomes within a phylogenetic context is essential for understanding the evolution of human genetic architecture and primate diversity. We present such a study of 50 primate species spanning 38 genera and 14 families, including 27 genomes first reported here, with many from previously less well represented groups, the New World monkeys and the Strepsirrhini. Our analyses reveal heterogeneous rates of genomic rearrangement and gene evolution across primate lineages. Thousands of genes under positive selection in different lineages play roles in the nervous, skeletal, and digestive systems and may have contributed to primate innovations and adaptations. Our study reveals that many key genomic innovations occurred in the Simiiformes ancestral node and may have had an impact on the adaptive radiation of the Simiiformes and human evolution