Au(I)/Sc(III)-co-catalyzed tandem spiroannulation/cycloisomerization of 3-(2-ethynylaryl)-N-tosylaziridines with indoles to access 5H-benzo[b]carbazoles.

An unusual spiroannulation/cycloisomerization cascade of 3-(2-ethynylaryl)-N-tosylaziridines with indoles enabled by cooperative gold/scandium catalysis is presented, which facilitates the synthesis of 5H-benzo[b]carbazoles in moderate to excellent yields. This protocol features a broad substrate scope and good functional-group compatibility. Additionally, the resulting 5H-benzo[b]carbazoles exhibit good fluorescence properties, demonstrating the synthetic practicality of this method. Moreover, control experiments were performed to illustrate the reaction mechanism.

Lipid osmosis, membrane tension, and other mechanochemical driving forces of lipid flow.

Nonvesicular lipid transport among different membranes or membrane domains plays crucial roles in lipid homeostasis and organelle biogenesis. However, the forces that drive such lipid transport are not well understood. We propose that lipids tend to flow towards the membrane area with a higher membrane protein density in a process termed lipid osmosis. This process lowers the membrane tension in the area, resulting in a membrane tension difference called osmotic membrane tension. We examine the thermodynamic basis and experimental evidence of lipid osmosis and osmotic membrane tension. We predict that lipid osmosis can drive bulk lipid flows between different membrane regions through lipid transfer proteins, scramblases, or similar barriers that selectively pass lipids but not membrane proteins. We also speculate on the biological functions of lipid osmosis. Finally, we explore other driving forces for lipid transfer and describe potential methods and systems to further test our theory.

A DNA-based molecular clamp for probing protein interactions and structure under force.

Cellular mechanotransduction, a process central to cell biology, embryogenesis, adult physiology and multiple diseases, is thought to be mediated by force-driven changes in protein conformation that control protein function. However, methods to study proteins under defined mechanical loads on a biochemical scale are lacking. We report the development of a DNA based device in which the transition between single-stranded and double-stranded DNA applies tension to an attached protein. Using a fragment of the talin rod domain as a test case, negative-stain electron microscopy reveals programmable extension while pull down assays show tension-induced binding to two ligands, ARPC5L and vinculin, known to bind to cryptic sites inside the talin structure. These results demonstrate the utility of the DNA clamp for biochemical studies and potential structural analysis.

Channel width modulates the permeability of DNA origami based nuclear pore mimics.

Nucleoporins (nups) in the central channel of nuclear pore complexes (NPCs) form a selective barrier that suppresses the diffusion of most macromolecules while enabling rapid transport of nuclear transport receptors (NTRs) with bound cargos. The complex molecular interactions between nups and NTRs have been thought to underlie the gatekeeping function of the NPC. Recent studies have shown considerable variation in NPC diameter but how altering NPC diameter might impact the selective barrier properties remains unclear. Here, we build DNA nanopores with programmable diameters and nup arrangement to mimic NPCs of different diameters. We use hepatitis B virus (HBV) capsids as a model for large-size cargos. We find that Nup62 proteins form a dynamic cross-channel meshwork impermeable to HBV capsids when grafted on the interior of 60-nm wide nanopores but not in 79-nm pores, where Nup62 cluster locally. Furthermore, importing substantially changes the dynamics of Nup62 assemblies and facilitates the passage of HBV capsids through NPC mimics containing Nup62 and Nup153. Our study shows the transport channel width is critical to the permeability of nup barriers and underscores the role of NTRs in dynamically remodeling nup assemblies and mediating the nuclear entry of viruses.

Lipid osmosis, membrane tension, and other mechanochemical driving forces of lipid flow.

Nonvesicular lipid transport among different membranes or membrane domains plays crucial roles in lipid homeostasis and organelle biogenesis. However, the forces that drive such lipid transport are not well understood. We propose that lipids tend to flow towards the membrane area with a higher membrane protein density in a process termed lipid osmosis. This process lowers the membrane tension in the area, resulting in a membrane tension difference called osmotic membrane tension. We examine the thermodynamic basis and experimental evidence of lipid osmosis and osmotic membrane tension. We predict that lipid osmosis can drive bulk lipid flows between different membrane regions through lipid transfer proteins, scramblases, or other similar barriers that selectively pass lipids but not membrane proteins. We also speculate on the biological functions of lipid osmosis. Finally, we explore other driving forces for lipid transfer and describe potential methods and systems to further test our theory.

Diastereoselective Access to Seven-Membered Benzosultams via Palladium-Catalyzed Ring-Opening [3 + 2]-Annulation.

A palladium-catalyzed ring-opening [3 + 2]-annulation of spirovinylcyclopropanyl oxindoles with seven-membered cyclic N-sulfonylimines has been developed. A wide range of seven-membered benzosultams featuring both a quaternary center and axially chiral biaryl scaffolds have been afforded in an average yield of 87% with moderate to excellent diastereoselectivities. The enantioenriched benzosultams were also accessed successfully in good yields with excellent atropoenantioselectivities enabled by the Pd2(dba)3/(S,S,S)-SKP ligand. The practical utility of this protocol was further demonstrated by the gram-scale reaction and diversified synthetic transformations of the desired seven-membered benzosultam.

Photothermal-driven disassembly of naphthalocyanine nano-photosensitizers for photothermal and photodynamic therapy.

The disassembly of nanomaterials is of particular interest for high-quality imaging and targeted therapies in the field of nanomedicine. In this study, we developed a novel strategy for fabricating self-assembled naphthalocyanine photosensitizers (SiNc@CEL) with intrinsically unique photochemical and photophysical properties. SiNc@CEL could be disassembled under the photothermal effect, and its photoactivity could be enhanced by 780 nm laser irradiation. Moreover, SiNc@CEL generates reactive oxygen species, including superoxide radicals (O2•-) and singlet oxygen (1O2), as well as good photothermal properties, facilitating the application of multifunctional phototherapy. In vitro evaluation indicated that SiNc@CEL possesses an excellent bactericidal effect under a combination of photodynamic (PDT) and photothermal therapy (PTT). The in vivo treatment of a full-layer skin defect model of Escherichia coli (E. coli) infection showed that SiNc@CEL had superior antibacterial and wound-healing abilities. These results provide the basis for a feasible strategy to enhance the phototherapeutic effect of photosensitizer (PS) systems.

The capsid lattice engages a bipartite NUP153 motif to mediate nuclear entry of HIV-1 cores.

Increasing evidence has suggested that the HIV-1 capsid enters the nucleus in a largely assembled, intact form. However, not much is known about how the cone-shaped capsid interacts with the nucleoporins (NUPs) in the nuclear pore for crossing the nuclear pore complex. Here, we elucidate how NUP153 binds HIV-1 capsid by engaging the assembled capsid protein (CA) lattice. A bipartite motif containing both canonical and noncanonical interaction modules was identified at the C-terminal tail region of NUP153. The canonical cargo-targeting phenylalanine-glycine (FG) motif engaged the CA hexamer. By contrast, a previously unidentified triple-arginine (RRR) motif in NUP153 targeted HIV-1 capsid at the CA tri-hexamer interface in the capsid. HIV-1 infection studies indicated that both FG- and RRR-motifs were important for the nuclear import of HIV-1 cores. Moreover, the presence of NUP153 stabilized tubular CA assemblies in vitro. Our results provide molecular-level mechanistic evidence that NUP153 contributes to the entry of the intact capsid into the nucleus.

Recent Advances in DNA Origami-Engineered Nanomaterials and Applications.

DNA nanotechnology is a unique field, where physics, chemistry, biology, mathematics, engineering, and materials science can elegantly converge. Since the original proposal of Nadrian Seeman, significant advances have been achieved in the past four decades. During this glory time, the DNA origami technique developed by Paul Rothemund further pushed the field forward with a vigorous momentum, fostering a plethora of concepts, models, methodologies, and applications that were not thought of before. This review focuses on the recent progress in DNA origami-engineered nanomaterials in the past five years, outlining the exciting achievements as well as the unexplored research avenues. We believe that the spirit and assets that Seeman left for scientists will continue to bring interdisciplinary innovations and useful applications to this field in the next decade.

Modeling HIV-1 nuclear entry with nucleoporin-gated DNA-origami channels.

Delivering the virus genome into the host nucleus through the nuclear pore complex (NPC) is pivotal in human immunodeficiency virus 1 (HIV-1) infection. The mechanism of this process remains mysterious owing to the NPC complexity and the labyrinth of molecular interactions involved. Here we built a suite of NPC mimics-DNA-origami-corralled nucleoporins with programmable arrangements-to model HIV-1 nuclear entry. Using this system, we determined that multiple cytoplasm-facing Nup358 molecules provide avid binding for capsid docking to the NPC. The nucleoplasm-facing Nup153 preferentially attaches to high-curvature regions of the capsid, positioning it for tip-leading NPC insertion. Differential capsid binding strengths of Nup358 and Nup153 constitute an affinity gradient that drives capsid penetration. Nup62 in the NPC central channel forms a barrier that viruses must overcome during nuclear import. Our study thus provides a wealth of mechanistic insight and a transformative toolset for elucidating how viruses like HIV-1 enter the nucleus.

CLASP2 recognizes tubulins exposed at the microtubule plus-end in a nucleotide state-sensitive manner.

CLASPs (cytoplasmic linker-associated proteins) are ubiquitous stabilizers of microtubule dynamics, but their molecular targets at the microtubule plus-end are not understood. Using DNA origami-based reconstructions, we show that clusters of human CLASP2 form a load-bearing bond with terminal non-GTP tubulins at the stabilized microtubule tip. This activity relies on the unconventional TOG2 domain of CLASP2, which releases its high-affinity bond with non-GTP dimers upon their conversion into polymerization-competent GTP-tubulins. The ability of CLASP2 to recognize nucleotide-specific tubulin conformation and stabilize the catastrophe-promoting non-GTP tubulins intertwines with the previously underappreciated exchange between GDP and GTP at terminal tubulins. We propose that TOG2-dependent stabilization of sporadically occurring non-GTP tubulins represents a distinct molecular mechanism to suppress catastrophe at the freely assembling microtubule ends and to promote persistent tubulin assembly at the load-bearing tethered ends, such as at the kinetochores in dividing cells.

Collaborative hydrothermal and calcination fabrication of ZnOS heterostructures for visible-light-driven H2 production.

Photocatalytic water splitting is forecasted as a promising strategy for H2 production. In this work, novel zinc oxide/zinc sulfide (ZnOS-x) (x = 1, 2, 3 and 4) heterostructures were fabricated by a collaborative hydrothermal and calcination method with different amounts of trithiocyanuric acid. The formation of ZnOS-x heterostructures was confirmed by PXRD, XPS, and HRTEM. Moreover, ZnOS-3 nanoparticles exhibited homogeneous and smooth surface morphology structure. ZnOS-3 displayed efficient charge separation and transfer efficiency upon photoinduction. ZnOS-3 showed the highest average H2 evolution reaction rate (78.87 µmol h-1) under visible-light irradiation, which increased with increase in the ratio of trithiocyanuric acid in the ZnOS-x series. This work provides a new insight to prepare uniformly integrated heterostructures of metal oxides/sulfides for visible-light-driven H2 generation.

Functionalized DNA-Origami-Protein Nanopores Generate Large Transmembrane Channels with Programmable Size-Selectivity.

The DNA-origami technique has enabled the engineering of transmembrane nanopores with programmable size and functionality, showing promise in building biosensors and synthetic cells. However, it remains challenging to build large (>10 nm), functionalizable nanopores that spontaneously perforate lipid membranes. Here, we take advantage of pneumolysin (PLY), a bacterial toxin that potently forms wide ring-like channels on cell membranes, to construct hybrid DNA-protein nanopores. This PLY-DNA-origami complex, in which a DNA-origami ring corrals up to 48 copies of PLY, targets the cholesterol-rich membranes of liposomes and red blood cells, readily forming uniformly sized pores with an average inner diameter of ∼22 nm. Such hybrid nanopores facilitate the exchange of macromolecules between perforated liposomes and their environment, with the exchange rate negatively correlating with the macromolecule size (diameters of gyration: 8-22 nm). Additionally, the DNA ring can be decorated with intrinsically disordered nucleoporins to further restrict the diffusion of traversing molecules, highlighting the programmability of the hybrid nanopores. PLY-DNA pores provide an enabling biophysical tool for studying the cross-membrane translocation of ultralarge molecules and open new opportunities for analytical chemistry, synthetic biology, and nanomedicine.

Synergistic Sc(III)/Au(I)-Catalyzed Dearomative Spiroannulation of 2-(Ethynyl)aryl Cyclopropanes with 2-Aryl Indoles.

The diastereoselective assembly of spiroindolenines via a synergistic scandium/gold-catalyzed dearomative spiroannulation is herein described. This protocol offers access to a wide variety of spiroindolenine derivatives in 86% average yield with moderate to excellent diastereoselectivities (up to 97:3 dr). The control experimental studies lend support to the bimetallic relay catalysis. Moreover, the scale-up reaction and synthetic transformations of spiroindolenine product further demonstrate its synthetic utility.

Actuating tension-loaded DNA clamps drives membrane tubulation.

Membrane dynamics in living organisms can arise from proteins adhering to, assembling on, and exerting force on cell membranes. Programmable synthetic materials, such as self-assembled DNA nanostructures, offer the capability to drive membrane-remodeling events that resemble protein-mediated dynamics but with user-defined outcomes. An illustrative example is the tubular deformation of liposomes by DNA nanostructures with purposely designed shapes, surface modifications, and self-assembling properties. However, stimulus-responsive membrane tubulation mediated by DNA reconfiguration remains challenging. Here, we present the triggered formation of membrane tubes in response to specific DNA signals that actuate membrane-bound DNA clamps from an open state to various predefined closed states, releasing prestored energy to activate membrane deformation. We show that the timing and efficiency of vesicle tubulation, as well as the membrane tube widths, are modulated by the conformational change of DNA clamps, marking a solid step toward spatiotemporal control of membrane dynamics in an artificial system.

Rose bengal-modified gold nanorods for PTT/PDT antibacterial synergistic therapy.

In this study, Rose Bengal (RB) was loaded onto mesoporous silica coated gold nanorods (AuNR@SiO2-NH2) to form a novel multifunctional platform for antimicrobial therapy (AuNR@SiO2-NH2-RB). The platform combines the photothermal functions of AuNR and the photodynamic functions of RB to effectively inactivate bacteria under irradiation. Moreover, AuNR@SiO2-NH2-RB showed negligible cytotoxicity and good blood compatibility. Therefore, this work has potential significance for the development of new antibacterial agents.

Frame-Guided Assembly of Amphiphiles.

Amphiphiles tend to self-assemble into various structures and morphologies in aqueous environments (e.g., micelles, tubes, fibers, vesicles, and lamellae). These assemblies and their properties have made significant impact in traditional chemical industries, e.g., increasing solubility, decreasing surface tension, facilitating foaming, etc. It is well-known that the molecular structure and its environment play a critical role in the assembly process, and many theories, including critical packing factor, thermodynamic models, etc., have been proposed to explain and predict the assembly morphology. It has been recognized that the morphology of the amphiphilic assembly plays important roles in determining the functions, such as curvature-dependent biophysical (e.g., liposome fusion and fission) and biochemical (e.g., lipid metabolism and membrane protein trafficking) processes, size-related EPR (enhanced permeability and retention) effects, etc. Meanwhile, various nanomaterials have promised great potential in directing the arrangement of molecules, thus generating unique functions. Therefore, control over the amphiphilic morphology is of great interest to scientists, especially in nanoscale with the assistance of functional nanomaterials. However, how to precisely manipulate the sizes and shapes of the assemblies is challenged by the entropic nature of the hydrophobic interaction. Inspired by the "cytoskeleton-membrane protein-lipid bilayer" principle of the cell membrane, a strategy termed "frame-guided assembly (FGA)" has been proposed and developed to direct the arrangement of amphiphiles. The FGA strategy welcomes various nanomaterials with precisely controlled properties to serve as scaffolds. By introducing scattered hydrophobic molecules, which are defined as either leading hydrophobic groups (LHGs) or nucleation seeds onto a selected scaffold, a discontinuous hydrophobic trace along the scaffold can be outlined, which will further guide the amphiphiles in the system to grow and form customized two- or three-dimensional (2D/3D) membrane geometries.Topologically, the supporting frame can be classified as three types including inner-frame, outer-frame, and planar-frame. Each type of FGA assembly possesses particular advantages: (1) The inner-frame, similar to endoskeletons of many cellular structures, steadily supports the membrane from the inside and exposes the full surface area outside. (2) The outer-frame, on the other hand, molds and constrains the membrane-wrapped vesicles to regulate their size and shape. It also allows postengineering of the frame to precisely decorate and dynamically manipulate the membrane. (3) The planar-frame mediates the growth of the 2D membrane that profits from the scanning-probe microscopic characterization and benefits the investigation of membrane proteins.In this Account, we introduce the recent progress of frame-guided assembly strategy in the preparation of customized amphiphile assemblies, evaluate their achievements and limitations, and discuss prospective developments and applications. The basic principle of FGA is discussed, and the morphology controllability is summarized in the inner-, outer-, and planar-frame categories. As a versatile strategy, FGA is able to guide different types of amphiphiles by designing specific LHGs for given molecular structures. The mechanism of FGA is then discussed systematically, including the driving force of the assembly, density and distribution of the LHGs, amphiphile concentration, and the kinetic process. Furthermore, the applications of FGA have been developed for liposome engineering, membrane protein incorporation, and drug delivery, which suggest the huge potential of FGA in fabricating novel and functional complexes.

Omicron-specific mRNA vaccination alone and as a heterologous booster against SARS-CoV-2.

The Omicron variant of SARS-CoV-2 recently swept the globe and showed high level of immune evasion. Here, we generate an Omicron-specific lipid nanoparticle (LNP) mRNA vaccine candidate, and test its activity in animals, both alone and as a heterologous booster to WT mRNA vaccine. Our Omicron-specific LNP-mRNA vaccine elicits strong antibody response in vaccination-naïve mice. Mice that received two-dose WT LNP-mRNA show a > 40-fold reduction in neutralization potency against Omicron than WT two weeks post boost, which further reduce to background level after 3 months. The WT or Omicron LNP-mRNA booster increases the waning antibody response of WT LNP-mRNA vaccinated mice against Omicron by 40 fold at two weeks post injection. Interestingly, the heterologous Omicron booster elicits neutralizing titers 10-20 fold higher than the homologous WT booster against Omicron variant, with comparable titers against Delta variant. All three types of vaccination, including Omicron alone, WT booster and Omicron booster, elicit broad binding antibody responses against SARS-CoV-2 WA-1, Beta, Delta variants and SARS-CoV. These data provide direct assessments of an Omicron-specific mRNA vaccination in vivo, both alone and as a heterologous booster to WT mRNA vaccine.

Variant-specific vaccination induces systems immune responses and potent in vivo protection against SARS-CoV-2.

Lipid nanoparticle (LNP)-mRNA vaccines offer protection against COVID-19; however, multiple variant lineages caused widespread breakthrough infections. Here, we generate LNP-mRNAs specifically encoding wild-type (WT), B.1.351, and B.1.617 SARS-CoV-2 spikes, and systematically study their immune responses. All three LNP-mRNAs induced potent antibody and T cell responses in animal models; however, differences in neutralization activity have been observed between variants. All three vaccines offer potent protection against in vivo challenges of authentic viruses of WA-1, Beta, and Delta variants. Single-cell transcriptomics of WT- and variant-specific LNP-mRNA-vaccinated animals reveal a systematic landscape of immune cell populations and global gene expression. Variant-specific vaccination induces a systemic increase of reactive CD8 T cells and altered gene expression programs in B and T lymphocytes. BCR-seq and TCR-seq unveil repertoire diversity and clonal expansions in vaccinated animals. These data provide assessment of efficacy and direct systems immune profiling of variant-specific LNP-mRNA vaccination in vivo.

Fluorogenic DNA-PAINT for faster, low-background super-resolution imaging.

DNA-based points accumulation for imaging in nanoscale topography (DNA-PAINT) is a powerful super-resolution microscopy method that can acquire high-fidelity images at nanometer resolution. It suffers, however, from high background and slow imaging speed, both of which can be attributed to the presence of unbound fluorophores in solution. Here we present two-color fluorogenic DNA-PAINT, which uses improved imager probe and docking strand designs to solve these problems. These self-quenching single-stranded DNA probes are conjugated with a fluorophore and quencher at the terminals, which permits an increase in fluorescence by up to 57-fold upon binding and unquenching. In addition, the engineering of base pair mismatches between the fluorogenic imager probes and docking strands allowed us to achieve both high fluorogenicity and the fast binding kinetics required for fast imaging. We demonstrate a 26-fold increase in imaging speed over regular DNA-PAINT and show that our new implementation enables three-dimensional super-resolution DNA-PAINT imaging without optical sectioning.