The COVID-19 (Coronavirus disease-2019) pandemic, caused by the SARS-CoV-2 coronavirus, is a significant threat to public health and the global economy. SARS-CoV-2 is closely related to the more lethal but less transmissible coronaviruses SARS-CoV-1 and MERS-CoV. Here, we have carried out comparative viral-human protein-protein interaction and viral protein localization analysis for all three viruses. Subsequent functional genetic screening identified host factors that functionally impinge on coronavirus proliferation, including Tom70, a mitochondrial chaperone protein that interacts with both SARS-CoV-1 and SARS-CoV-2 Orf9b, an interaction we structurally characterized using cryo-EM. Combining genetically-validated host factors with both COVID-19 patient genetic data and medical billing records identified important molecular mechanisms and potential drug treatments that merit further molecular and clinical study.

The current simple nanofluid flooding method for tertiary or enhanced oil recovery is inefficient, especially when used with low nanoparticle concentration. We have designed and produced a nanofluid of graphene-based amphiphilic nanosheets that is very effective at low concentration. Our nanosheets spontaneously approached the oil-water interface and reduced the interfacial tension in a saline environment (4 wt % NaCl and 1 wt % CaCl 2 ), regardless of the solid surface wettability. A climbing film appeared and grew at moderate hydrodynamic condition to encapsulate the oil phase. With strong hydrodynamic power input, a solid-like interfacial film formed and was able to return to its original form even after being seriously disturbed. The film rapidly separated oil and water phases for slug-like oil displacement. The unique behavior of our nanosheet nanofluid tripled the best performance of conventional nanofluid flooding methods under similar conditions. nanofluid flooding | amphiphilic Janus nanosheets | enhanced oil recovery | climbing film | interfacial film F inding economically viable and environmentally friendly methods to extract the huge amount of residual oil after primary and secondary recovery remains challenging for the oil and gas industry and is also of significant importance in efforts to satisfy the world's increasing energy demand. Nanofluid flooding as an alternative tertiary oil recovery method has been recently reported (1-5). Obviously, simple nanofluid flooding (containing only nanoparticles) at low concentration (0.01 wt % or less) shows the greatest potential from the environmental and economic perspective. Several corresponding oil displacement mechanisms have also been introduced, including reduction of oil-water interfacial tension (6, 7), alteration of rock surface wettability (8-10), and generation of structural disjoining pressure (11-13). However, the oil recovery factor is below 5% with 0.01% nanoparticle loading in core flooding tests in a saline environment (2 wt % or higher NaCl content). Here we show that an oil recovery factor of 15.2% is achieved by using a simple nanofluid of graphene-based Janus amphiphilic nanosheets. To our knowledge, this is the first report of applying nanofluid of amphiphilic Janus two-dimensional materials in tertiary or enhanced oil recovery. We found that in a saline environment, the nanosheets spontaneously approach the oil-water interface, reducing the interfacial tension. A climbing film emerges and encapsulates the oil phase and may carry it forward. Furthermore, we found that a solid-like film forms with strong hydrodynamic power. The film rapidly separates oil and water for slug-like oil displacement. Even though there are ways to achieve 20% enhanced recovery by complicated alkali/surfactant/polymer flooding (14) or by surfactants with added nanoparticles (5), the necessary concentrations of the chemicals and nanoparticles are much higher than 0.01 wt %. Our results provide a nanofluid flooding method for tertiary oil recovery that is compar...

Graphene oxide (GO) sheets have been used successfully as a supporting substrate film in several recent cryogenic electron-microscopy (cryo-EM) studies of challenging biological macromolecules. However, difficulties in preparing GO-covered holey carbon EM grids have limited their widespread use. Here, we report a simple and robust method for covering holey carbon EM grids with GO sheets and demonstrate that these grids can be used for high-resolution single particle cryo-EM. GO substrates adhere macromolecules, allowing cryo-EM grid preparation with lower specimen concentrations and provide partial protection from the air-water interface. Additionally, the signal of the GO lattice beneath the frozen-hydrated specimen can be discerned in many motion-corrected micrographs, providing a high-resolution fiducial for evaluating beam-induced motion correction.

Affinity grids have great potential to facilitate rapid preparation of even quite impure samples in single-particle cryo-electron microscopy (EM). Yet despite the promising advances of affinity grids over the past decades, no single strategy has demonstrated general utility. Here we chemically functionalize cryo-EM grids coated with mostly one or two layers of graphene oxide to facilitate affinity capture. The protein of interest is tagged using a system that rapidly forms a highly specific covalent bond to its cognate catcher linked to the grid via a polyethylene glycol (PEG) spacer. Importantly, the spacer keeps particles away from both the air–water interface and the graphene oxide surface, protecting them from potential denaturation and rendering them sufficiently flexible to avoid preferential sample orientation concerns. Furthermore, the PEG spacer successfully reduces nonspecific binding, enabling high-resolution reconstructions from a much cruder lysate sample.

Stretchable transparent electrodes are key elements in flexible electronics and e-skins. However, existing stretchable transparent electrodes, including graphene sheets, carbon nanotube, and metal nanowire networks, weakly adheres to the substrate by van der Waals forces. Such electrodes suffer from poor scratch-resistance or poor durability, and this issue has been one of the biggest problems for their applications in industry. Here we show that, by introducing a Au–S bond between a Au nanomesh (AuNM) and the underlying elastomeric substrate, the AuNM strongly adheres to the substrate and can withstand scratches of a pressure of several megapascals. We find that the strong chemical bond, on the other hand, leads to a stiffening effect and localized rupture of the AuNM upon stretching; thus the stretchability is poor. A prestraining process is applied to suppress the localized rupture and has successfully improved the stretchability: electrical resistance of the prestrained AuNM exhibits modest change by one-time stretching to 160%, or repeated stretching to 50% for 25 000 cycles. This conductor is an ideal platform for robust stretchable photoelectronics. The idea of introducing a covalent bond to improve the scratch-resistance may also be applied to other systems including Ag nanowire films, carbon nanotube films, graphene, and so forth.

Motile cilia power cell locomotion and drive extracellular fluid flow by propagating bending waves from their base to tip. The coordinated bending of cilia requires mechanoregulation by the radial spoke (RS) protein complexes and the microtubule central pair (CP). Despite their importance for ciliary motility across eukaryotes, the molecular function of the RSs is unknown. Here, we reconstituted the Chlamydomonas reinhardtii RS head that abuts the CP and determined its structure using single-particle cryo-EM to 3.1 Å resolution, revealing a flat, negatively-charged surface supported by a rigid core of tightly intertwined proteins. Mutations in this core, corresponding to those involved in human ciliopathies, compromised stability of the recombinant complex, providing a molecular basis for disease. Partially reversing the negative charge on the RS surface impaired motility in C. reinhardtii . We propose that the RS head architecture is well-suited for mechanoregulation of ciliary beating through physical collisions with the CP.

No abstract

Despite their great potential to facilitate rapid preparation of quite impure samples, affinity gridshave not yet been widely employed in single particle cryo-EM. Here, we chemically functionalize graphene oxide coated grids and use a highly specific covalent affinity tag system. Importantly, our polyethylene glycol spacer keeps particles away from the air-water interface and graphene oxide surface, protecting them from denaturation or aggregation and permits high-resolution reconstructions of small particles. MainOwing to a series of technological breakthroughs, cryo-electron microscopy (cryo-EM) is fast becoming the method of choice for determining protein structures at a near-atomic or atomic resolution 1, 2 . By contrast with the rapidity of data collection and processing, sample preparation remains slow and, in many cases, has become rate-limiting. Cryo-EM specimens are typically prepared by depositing purified proteins onto cryo-EM grids, which are usually a metal grid covered with continuous perforated carbon or gold films.