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In type II CRISPR systems, the guide RNA (gRNA) comprises a CRISPR RNA (crRNA) and a hybridized trans-acting CRISPR RNA (tracrRNA), both being essential in guided DNA targeting functions. Here the authors investigate the programmability of crRNA-tracrRNA hybridization for Cas9 and apply this to biosensing.

Abstract The chiral charge density wave is a many-body collective phenomenon in condensed matter that may play a role in unconventional superconductivity and topological physics. Two-dimensional chiral charge density waves provide the building blocks for the fabrication of various stacking structures and chiral homostructures, in which physical properties such as chiral currents and the anomalous Hall effect may emerge. Here, we demonstrate the phase manipulation of two-dimensional chiral charge density waves and the design of in-plane chiral homostructures in 1T-TaS2. We use chiral Raman spectroscopy to directly monitor the chirality switching of the charge density wave—revealing a temperature-mediated reversible chirality switching. We find that interlayer stacking favours homochirality configurations, which is confirmed by first-principles calculations. By exploiting the interlayer chirality-locking effect, we realise in-plane chiral homostructures in 1T-TaS2. Our results provide a versatile way to manipulate chiral collective phases by interlayer coupling in layered van der Waals semiconductors.

Radialenes have distinct structural, electronic and chemical properties from other hydrocarbons, but their synthesis remains a challenge. Here, the authors report a copper catalyzed one-step synthetic protocol of [4]radialene via the cyclotetramerization of phenylacetylene molecules upon thermal activation.

Graphene nanoribbons consist of carbon atoms arranged in a hexagonal lattice. Despite non-hexagonal rings generally being more unstable, the authors demonstrate the successful synthesis of graphene-like nanoribbons with periodically embedded four- and eight-membered carbon rings, with tailored electronic properties.