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Two-dimensional (2D) materials.sup.1,2 and the associated van der Waals (vdW) heterostructures.sup.3-7 have provided great flexibility for integrating distinct atomic layers beyond the traditional limits of lattice-matching requirements, through layer-by-layer mechanical restacking or sequential synthesis. However, the 2D vdW heterostructures explored so far have been usually limited to relatively simple heterostructures with a small number of blocks.sup.8-18. The preparation of high-order vdW superlattices with larger number of alternating units is exponentially more difficult, owing to the limited yield and material damage associated with each sequential restacking or synthesis step.sup.8-29. Here we report a straightforward approach to realizing high-order vdW superlattices by rolling up vdW heterostructures. We show that a capillary-force-driven rolling-up process can be used to delaminate synthetic SnS.sub.2/WSe.sub.2 vdW heterostructures from the growth substrate and produce SnS.sub.2/WSe.sub.2 roll-ups with alternating monolayers of WSe.sub.2 and SnS.sub.2, thus forming high-order SnS.sub.2/WSe.sub.2 vdW superlattices. The formation of these superlattices modulates the electronic band structure and the dimensionality, resulting in a transition of the transport characteristics from semiconducting to metallic, from 2D to one-dimensional (1D), with an angle-dependent linear magnetoresistance. This strategy can be extended to create diverse 2D/2D vdW superlattices, more complex 2D/2D/2D vdW superlattices, and beyond-2D materials, including three-dimensional (3D) thin-film materials and 1D nanowires, to generate mixed-dimensional vdW superlattices, such as 3D/2D, 3D/2D/2D, 1D/2D and 1D/3D/2D vdW superlattices. This study demonstrates a general approach to producing high-order vdW superlattices with widely variable material compositions, dimensions, chirality and topology, and defines a rich material platform for both fundamental studies and technological applications. A simple but flexible technique based on a capillary-force-driven rolling-up process produces high-order van der Waals superlattices that are hard to produce with existing fabrication techniques., Author(s): Bei Zhao [sup.1] , Zhong Wan [sup.2] , Yuan Liu [sup.1] [sup.3] , Junqing Xu [sup.4] , Xiangdong Yang [sup.1] , Dingyi Shen [sup.1] , Zucheng Zhang [sup.1] , [...]

The [alpha][beta] T cell receptor (TCR), in association with the CD3[gamma][epsilon]-CD3[delta][epsilon]-CD3[zeta][zeta] signalling hexamer, is the primary determinant of T cell development and activation, and of immune responses to foreign antigens. The mechanism of assembly of the TCR-CD3 complex remains unknown. Here we report a cryo-electron microscopy structure of human TCR[alpha][beta] in complex with the CD3 hexamer at 3.7 Å resolution. The structure contains the complete extracellular domains and all the transmembrane helices of TCR-CD3. The octameric TCR-CD3 complex is assembled with 1:1:1:1 stoichiometry of TCR[alpha][beta]:CD3[gamma][epsilon]:CD3[delta][epsilon]:CD3[zeta][zeta]. Assembly of the extracellular domains of TCR-CD3 is mediated by the constant domains and connecting peptides of TCR[alpha][beta] that pack against CD3[gamma][epsilon]-CD3[delta][epsilon], forming a trimer-like structure proximal to the plasma membrane. The transmembrane segment of the CD3 complex adopts a barrel-like structure formed by interaction of the two transmembrane helices of CD3[zeta][zeta] with those of CD3[gamma][epsilon] and CD3[delta][epsilon]. Insertion of the transmembrane helices of TCR[alpha][beta] into the barrel-like structure via both hydrophobic and ionic interactions results in transmembrane assembly of the TCR-CD3 complex. Together, our data reveal the structural basis for TCR-CD3 complex assembly, providing clues to TCR triggering and a foundation for rational design of immunotherapies that target the complex. A high-resolution cryo-electron microscopy structure of the human octameric T cell receptor-CD3 complex, including the complete extracellular and transmembrane domains, reveals the structural basis for TCR-CD3 assembly and provides insights into T cell receptor activation., Author(s): De Dong [sup.1] , Lvqin Zheng [sup.2] [sup.3] , Jianquan Lin [sup.1] , Bailing Zhang [sup.1] , Yuwei Zhu [sup.1] , Ningning Li [sup.2] , Shuangyu Xie [sup.1] , [...]

The CRISPR-Cas systems, as exemplified by CRISPR-Cas9, are RNA-guided adaptive immune systems used by bacteria and archaea to defend against viral infection (1-7). The CRISPR-Cpf1 system, a new class 2 CRISPR-Cas system, mediates robust DNA interference in human cells (1,8-10). Although functionally conserved, Cpf1 and Cas9 differ in many aspects including their guide RNAs and substrate specificity. Here we report the 2.38 Å crystal structure of the CRISPR RNA (crRNA)-bound Lachnospiraceae bacterium ND2006 Cpf1 (LbCpf1). LbCpf1 has a triangle-shaped architecture with a large positively charged channel at the centre. Recognized by the oligonucleotide-binding domain of LbCpf1, the crRNA adopts a highly distorted conformation stabilized by extensive intramolecular interactions and the [(Mg[([H.sub.2]0).sub.6]).sup.2+] ion. The oligonucleotide-binding domain also harbours a looped-out helical domain that is important for LbCpf1 substrate binding. Binding of crRNA or crRNA lacking the guide sequence induces marked conformational changes but no oligomerization of LbCpf1. Our study reveals the crRNA recognition mechanism and provides insight into crRNA-guided substrate binding of LbCpf1, establishing a framework for engineering LbCpf1 to improve its efficiency and specificity for genome editing., After integration of short segments of invader-derived DNA (known as a protospacer) into a CRISPR array within the host genome, expression and processing of the precursor crRNAs produces mature crRNAs. [...]

The human immunodeficiency virus (HIV)-1 protein Vif has a central role in the neutralization of host innate defences by hijacking cellular proteasomal degradation pathways to subvert the antiviral activity of [...]

A Correction to this paper has been published: https://doi.org/10.1038/s41586-021-03245-4., Author(s): De Dong [sup.1] , Lvqin Zheng [sup.2] [sup.3] , Jianquan Lin [sup.1] , Bailing Zhang [sup.1] , Yuwei Zhu [sup.1] , Ningning Li [sup.2] , Shuangyu Xie [sup.1] , [...]