Unlike the unstable black phosphorous, another two-dimensional group-VA material, antimonene, was recently predicted to exhibit good stability and remarkable physical properties. However, the synthesis of high-quality monolayer or few-layer antimonenes, sparsely reported, has greatly hindered the development of this new field. Here, we report the van der Waals epitaxy growth of few-layer antimonene monocrystalline polygons, their atomical microstructure and stability in ambient condition. The high-quality, few-layer antimonene monocrystalline polygons can be synthesized on various substrates, including flexible ones, via van der Waals epitaxy growth. Raman spectroscopy and transmission electron microscopy reveal that the obtained antimonene polygons have buckled rhombohedral atomic structure, consistent with the theoretically predicted most stable β-phase allotrope. The very high stability of antimonenes was observed after aging in air for 30 days. First-principle and molecular dynamics simulation results confirmed that compared with phosphorene, antimonene is less likely to be oxidized and possesses higher thermodynamic stability in oxygen atmosphere at room temperature. Moreover, antimonene polygons show high electrical conductivity up to 104 S m−1 and good optical transparency in the visible light range, promising in transparent conductive electrode applications.

Arrestins bind active phosphorylated G protein-coupled receptors, precluding G protein activation and channeling signaling to alternative pathways. Arrestins also function as mitogen-activated protein kinase (MAPK) scaffolds, bringing together three components of MAPK signaling modules. Here we have demonstrated that all four vertebrate arrestins interact with JNK3, MKK4, and ASK1, but only arrestin3 facilitates JNK3 activation. Thus, the functional specificity of arrestins is not determined by differential binding of the kinases. Using receptor binding-impaired mutant, we have shown that free arrestin3 readily promotes JNK3 phosphorylation. We identified key arrestin-binding elements in JNK3 and ASK1 and investigated the molecular interactions of arrestin2 and arrestin3 and their individual domains with the components of the two MAPK cascades, ASK1-MKK4-JNK3 and c-Raf-1-MEK1-ERK2. We found that both arrestin domains interact with all six kinases. These findings shed new light on the mechanism of arrestin-mediated MAPK activation and the spatial arrangement of the three kinases on arrestin molecule.Arrestins are multifunctional regulators of cell signaling (1, 2). Arrestins, which bind active phosphorylated G protein-coupled receptors (GPCRs), 2 which play a major role in receptor desensitization and internalization (3, 4). With the identification of numerous non-receptor binding partners, the classical paradigm of arrestin function has been expanded, implicating arrestins in mitogen-activated protein kinase (MAPK) activation, protein ubiquitination, chemotaxis, apoptosis, and other cellular functions (2, 5-11).The first indication that arrestins function as signaling adapters came from the studies of arrestin-dependent c-Src recruitment to the receptors, which results in the activation of extracellular signal-regulated kinases (ERK1/2) (10, 12, 13).Subsequently, arrestin2 and arrestin3 in complex with different receptors were reported to scaffold JNK3 (9), ERK1/2 (8, 14), and p38 (15, 16) activation cascades. Although arrestins play an important role in regulating different MAPK pathways, the mechanism of arrestin-dependent assembly of MAP kinases into a signaling complex remains largely unexplored. Existing models have limited predictive value. For example, the idea that JNK3 is activated solely by arrestin3 because this arrestin subtype has unique ability to bind JNK3 (9, 17) was not supported by further experimentation (18 -20). Similarly, the hypothesis that only receptor-bound arrestins interact with MAP kinases (8, 9) was not confirmed (17-20).Here we addressed several key mechanistic issues in arrestindependent MAPK signaling. First, we show that the scaffolding function is not limited to receptor-bound arrestin; free arrestin3 facilitates ASK1-mediated JNK3 activation, indicating that arrestins are not exclusively receptor-regulated adapters as thought previously. Second, we show that all four mammalian arrestins bind each component of the JNK3 cascade with comparable affinity, demonstrating that bindin...

SummaryArrestins regulate the activity and subcellular localization of G protein-coupled receptors and other signaling molecules. Here we demonstrate that arrestins bind microtubules (MTs) in vitro and in vivo. The MT-binding site on arrestins significantly overlaps with the receptor-binding site, but the conformations of MT-bound and receptor-bound arrestin are different. Arrestins recruit ERK1/2 and the E3 ubiquitin ligase Mdm2 to microtubules in cells, similar to the arrestin-dependent mobilization of these proteins to the receptor. Arrestin-mediated sequestration of ERK to MTs reduces the level of ERK activation. In contrast, recruitment of Mdm2 to microtubules by arrestin channels Mdm2 activity toward cytoskeleton-associated proteins, dramatically increasing their ubiquitination. The mobilization of signaling molecules to microtubules is a novel biological function of arrestin proteins.

Graphene with a sp 2 -honeycomb carbon lattice has drawn a large amount of attention due to its excellent properties and potential applications in many fields. Similar to the structure of graphene, two-dimensional semiconductors are its two-dimensional and isostructural counterparts based on the typical layerstructured semiconductors, such as boron nitride (h-BN) and transition metal dichalcogenides (e.g. MoS 2 and WS 2 ), whose layers are bound by weak van der Waals forces. Unlike the semi-metal features of graphene, the two-dimensional semiconductors are natural semiconductors with thicknesses on the atomic scale. When one of the dimensions is extremely reduced, the two-dimensional semiconductors exhibit some unique properties, such as a transition from indirect to direct semiconductor properties, and hence have great potential for applications in electronics, energy storage, sensors, catalysis and composites, which arise both from the dimension-reduced effect and from the modified electronic structure. In this feature article, recent developments in the synthesis, properties and applications of two-dimensional semiconductors are discussed. The reported virtues and novelties of two-dimensional semiconductors are highlighted and the current problems in their developing process are clarified, in addition to their challenges and future prospects.