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Dedicated assembly factors orchestrate the stepwise production of many molecular machines, including the 28-subunit proteasome core particle (CP) that mediates protein degradation. Here we report cryo-electron microscopy reconstructions of seven recombinant human subcomplexes that visualize all five chaperones and the three active site propeptides across a wide swath of the assembly pathway. Comparison of these chaperone-bound intermediates and a matching mature CP reveals molecular mechanisms determining the order of successive subunit additions, as well as how proteasome subcomplexes and assembly factors structurally adapt upon progressive subunit incorporation to stabilize intermediates, facilitate the formation of subsequent intermediates and ultimately rearrange to coordinate proteolytic activation with gated access to active sites. This work establishes a methodologic approach for structural analysis of multiprotein complex assembly intermediates, illuminates specific functions of assembly factors and reveals conceptual principles underlying human proteasome biogenesis, thus providing an explanation for many previous biochemical and genetic observations.

Ubiquitin ligation is typically executed by hallmark E3 catalytic domains. Two such domains, ‘cullin–RING’ and ‘RBR’, are individually found in several hundred human E3 ligases, and collaborate with E2 enzymes to catalyze ubiquitylation. However, the vertebrate-specific CUL9 complex with RBX1 (also called ROC1), of interest due to its tumor suppressive interaction with TP53, uniquely encompasses both cullin–RING and RBR domains. Here, cryo-EM, biochemistry and cellular assays elucidate a 1.8-MDa hexameric human CUL9–RBX1 assembly. Within one dimeric subcomplex, an E2-bound RBR domain is activated by neddylation of its own cullin domain and positioning from the adjacent CUL9–RBX1 in trans. Our data show CUL9 as unique among RBX1-bound cullins in dependence on the metazoan-specific UBE2F neddylation enzyme, while the RBR domain protects it from deneddylation. Substrates are recruited to various upstream domains, while ubiquitylation relies on both CUL9’s neddylated cullin and RBR domains achieving self-assembled and chimeric cullin–RING/RBR E3 ligase activity.

In this letter, we apply an oxidation technique for p-GaN to a normally-off p-GaN /AlGaN/GaN HEMT to improve the threshold voltage and gate reliability. Oxygen-plasma and low-temperature Oxygen post-annealing treatment (OPAT) of p-GaN before the deposition of gate metal has introduced a 5 nm oxidation interlayer, resulting in a significant improvement in gate breakdown voltage, from 10.4 V to 20.6 V. Thanks to this interlayer, the threshold voltage of p-GaN gate HEMTs is increased from 1.9 V to 4.6 V, while an almost same on- state resistance and a higher drain breakdown voltage are obtained. Time-dependent gate breakdown measurement shows OPAT-HEMTs have a maximum on- state gate drive voltage of 9.2 V for a 10-year lifetime with a 63 % gate failure rate. In addition, a more stable threshold voltage under gate stress indicates the promising application of this technology in GaN power devices.

Three-dimensional covalent organic frameworks (3D COFs) have emerged as a promising class of crystalline materials due to large surface areas, interconnected porosity, and accessible active sites. Their structural versatility, enabled by the judicious selection of organic building blocks, allows for precise tuning of pore size, architecture, and functionality. These unique attributes position 3D COFs as ideal candidates for the development of tailored membrane materials capable of high-performance separations. This review provides a comprehensive overview of the synthesis methodologies and applications of 3D COF-based membranes. The critical role of their pore size, topology, stability, hydrophilicity/hydrophobicity and surface charge on membrane structure and performance is examined. In addition, various fabrication methods for 3D COF-based membranes (e.g., blending, in situgrowth, and interfacial polymerization) are presented. The usage of 3D COF-based membranes in diverse fields such as gas separation, water treatment, organic solvent nanofiltration, pervaporation, and proton exchange is also outlined. The review concludes by identifying key challenges and outlining future research directions for advancing the field of 3D COF-based membranes.

In the emerging 5G and beyond 5G (B5G) era, the spotlight is sharply focused on the power amplifier, a critical component with stringent specification requirements that dictates the performance of the transmitter. The gallium nitride (GaN) device, with its superior inherent properties, is surfacing as a front-runner for power amplifier applications. The increasing demand for high frequency, high linearity, and cost-effective GaN power amplifiers is driven by anticipated traffic surges and the need for extensive 5G deployment. This paper offers a thorough review and future perspective on research developments in RF GaN device technology. It encompasses critical issues in advanced device and circuit technology, with a focus on high frequency, high linearity, cost-effective GaN-on-Si high electron mobility transistors (HEMTs), and compact modeling. This work aims to serve as a guide for the utilization of GaN HEMTs in 5G communication applications.