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Unlike acoustic metasurfaces that rely solely on phase gradients, acoustic metagratings (AMs) operate based on both phase gradients and grating diffraction, thus further extending the generalized Snell's law (GSL). In particular, AMs can achieve reversal of refraction and reflection based on the parity of the number of wave propagations inside the AMs. So far, discussions of this GSL extension have largely been applied to one-dimensional periodic AMs, while the designs of two-dimensional (2D) periodic AMs and their performance in three-dimensional (3D) space have been quite limited. Here, we study the GSL extension in 3D space and experimentally demonstrate a series of functional 2D periodic AMs. The designed AMs can achieve sound refraction/reflection under any incidence angle in 3D space, without restrictions to certain critical ranges; adjusting incident angles only enables the reversal of refraction and reflection. Additionally, we demonstrate two types of dual-layer sound lenses based on two AMs, whose reversal of refraction and reflection can be realized by simply attaching or separating the two AMs. Our work paves the way to complex 3D wavefront manipulation of AMs, which may find potential use in practical acoustic devices. [ABSTRACT FROM AUTHOR]

The prevalence of multidrug resistance among clinically significant bacteria calls for the urgent development of new antibiotics with novel mechanisms of action. In this study, a new small molecule exhibiting excellent inhibition of bacterial cell division with potent antibacterial activity was discovered through cell-based screening. The compound exhibits a broad spectrum of bactericidal activity, including the methicillin-resistant Staphylococcus aureus, vancomycin-resistant Enterococcus and NDM-1 Escherichia coli. The in vitro and in vivo results suggested that this compound disrupts the dynamic assembly of FtsZ protein and Z-ring formation through stimulating FtsZ polymerization. Moreover, this compound exhibits no activity on mammalian tubulin polymerization and shows low cytotoxicity on mammalian cells. Taken together, these findings could provide a new chemotype for development of antibacterials with FtsZ as the target.

Recently, acoustic vortices with orbital angular momentum (OAM) have attracted great attention and interest owing to their extensive applications. Based on the generalized Snell's law (GSL), acoustic vortex beams can be observed by constructing different types of acoustic metasurfaces immersed into cylindrical waveguides. However, owing to the restrictions of the phase gradient of metasurface structures and the critical order of propagating vortex beams, there exist great challenges in realizing complex modulation of vortex beams and designing advanced multifunctional sound devices. Here, we theoretically study and experimentally demonstrate the extended GSL in designing a mode converter of vortex beams based on phase-gradient acoustic metagratings (AMs). We demonstrate that the extended GSL can not only accurately predict the transmitted or reflected orders of vortex beams created by a series of AMs with arbitrary phase gradient ξ, but also effectively overcome the limitations of both the phase gradient and the critical order. More importantly, we design a type of mode converter of vortex beams and realize the mode conversion of output vortex beams by simply modulating the orders of input vortex beams. To present it, we experimentally demonstrate the switch between the output vortex beams with the orders of −2 and 2 through the same phase-gradient AM by using the input vortex beams with the orders of 1 and −1, respectively, which can be separately predicted by the GSL and the extended GSL. Our work paves a way for the complex modulation of acoustic vortex beams and the design of multifunctional OAM-based sound devices with practical applications. [ABSTRACT FROM AUTHOR]

Inhibition of the functional activity of Filamenting temperature-sensitive mutant Z (FtsZ) protein, an essential and highly conserved bacterial cytokinesis protein, is a promising approach for the development of a new class of antibacterial agents. Berberine, a benzylisoquinoline alkaloid widely used in traditional Chinese and native American medicines for its antimicrobial properties, has been recently reported to inhibit FtsZ. Using a combination of in silico structure-based design and in vitro biological assays, 9-phenoxyalkyl berberine derivatives were identified as potent FtsZ inhibitors. Compared to the parent compound berberine, the derivatives showed a significant enhancement of antibacterial activity against clinically relevant bacteria, and an improved potency against the GTPase activity and polymerization of FtsZ. The most potent compound 2 strongly inhibited the proliferation of Gram-positive bacteria, including methicillin-resistant S. aureus and vancomycin-resistant E. faecium, with MIC values between 2 and 4 µg/mL, and was active against the Gram-negative E. coli and K. pneumoniae, with MIC values of 32 and 64 µg/mL respectively. The compound perturbed the formation of cytokinetic Z-ring in E. coli. Also, the compound interfered with in vitro polymerization of S. aureus FtsZ. Taken together, the chemical modification of berberine with 9-phenoxyalkyl substituent groups greatly improved the antibacterial activity via targeting FtsZ.

The development of site‐specific, target‐selective and biocompatible small molecule ligands as a fluorescent tool for real‐time study of cellular functions of RNA G‐quadruplexes (G4s), which are associated with human cancers, is of significance in cancer biology. We report a fluorescent ligand that is a cytoplasm‐specific and RNA G4‐selective fluorescent biosensor in live HeLa cells. The in vitro results show that the ligand is highly selective targeting RNA G4s including VEGF, NRAS, BCL2 and TERRA. These G4s are recognized as human cancer hallmarks. Moreover, intracellular competition studies with BRACO19 and PDS, and the colocalization study with G4‐specific antibody (BG4) in HeLa cells may support that the ligand selectively binds to G4s in cellulo. Furthermore, the ligand was demonstrated for the first time in the visualization and monitoring of dynamic resolving process of RNA G4s by the overexpressed RFP‐tagged DHX36 helicase in live HeLa cells. [ABSTRACT FROM AUTHOR]