The severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), the causative agent of COVID-19 illness, has caused millions of infections worldwide. In SARS coronaviruses, the non-structural protein 16 (nsp16), in conjunction with nsp10, methylates the 5′-end of virally encoded mRNAs to mimic cellular mRNAs, thus protecting the virus from host innate immune restriction. We report here the high-resolution structure of a ternary complex of SARS-CoV-2 nsp16 and nsp10 in the presence of cognate RNA substrate analogue and methyl donor, S-adenosyl methionine (SAM). The nsp16/nsp10 heterodimer is captured in the act of 2′-O methylation of the ribose sugar of the first nucleotide of SARS-CoV-2 mRNA. We observe large conformational changes associated with substrate binding as the enzyme transitions from a binary to a ternary state. This induced fit model provides mechanistic insights into the 2′-O methylation of the viral mRNA cap. We also discover a distant (25 Å) ligand-binding site unique to SARS-CoV-2, which can alternatively be targeted, in addition to RNA cap and SAM pockets, for antiviral development.

A graphene and zinc oxide nanowires (G/ZnO NWs) based ultraviolet (UV) photodetector presents excellent responsivity and photocurrent gain with detectivity. Graphene due to higher charge carrier transport mobility induces faster response to UV illumination at the interface between ZnO and graphene with improved response and decay times as compared to a ZnO NWs device alone. A linear increase is revealed for both the responsivity and photocurrent gain of the G/ZnO NWs device with the applied bias. These results suggest that the G/ZnO NWs device exhibits great promise for highly efficient UV photodetectors.

Growth of highly dense ZnO nanowires (ZnO NWs) is demonstrated on three-dimensional graphene foam (GF) using resistive thermal evaporation technique. Photoresponse of the as-grown hybrid structure of ZnO NWs on GF (ZnO NWs/GF) is evaluated for ultraviolet (UV) detection. Excellent photoresponse with fast response and recovery times of 9.5 and 38 s with external quantum efficiency of 2490.8% is demonstrated at low illumination power density of 1.3 mW/cm(2). In addition, due to excellent charge carrier transport, mobility of graphene reduces the recombination rate of photogenerated charge carriers, hence the lifetime of photogenerated free charge carriers enhances in the photodetectors.

Super-compressible foam-like carbon nanotube films [1][2][3][4][5][6][7] have been reported to exhibit highly nonlinear viscoelastic behavior in compression similar to soft tissue. [4] Their unique combination of light weight and exceptional electrical, thermal, and mechanical properties have helped identify them as viable building blocks for more complex nanosystems and as stand-alone structures for a variety of different applications. In the as-grown state, their mechanical performance is limited by the weak adhesion between the tubes, controlled by van der Waals forces, and the substrate allowing the forests to split easily and to have low resistance in shear.[5] Under axial compression loading carbon nanotubes have demonstrated bending, buckling, [8] and fracture [9] (or a combination of the above) depending on the loading conditions and the number of loading cycles. [4] In this work, we study the strain rate effects on the mechanical properties of carbon nanotube forests and report several related interesting new phenomena. We partially anchor [10] dense vertically aligned foam-like forests of carbon nanotubes on a thin, flexible polymer layer to provide structural stability, particularly at the higher strain rates. The goal of the anchoring was also to create versatile nanosystems, which integrate the excellent nanotube properties in a light-weight portable system. We test the sample under quasi-static indentation loading and under impact loading and report a variable nonlinear response and different elastic recoveries with varying strain rates. A Bauschinger-like effect is observed at very low strain rates while buckling and the formation of permanent defects in the tube structure is reported at very high strain rates. Using high-resolution transmission microscopy we observe for the first time the delamination and crumbling of carbon nanotube walls. These polymer-anchored CNT foams are reported to behave as conductive nanostructured layers, suitable as fundamental building blocks for a variety of different applications, or as new self-standing application-ready materials with potential employment as actuators, impact absorbers, or as layered components for the creation of acoustic dampers.Because of the excellent thermal, electronic and mechanical properties, vertically aligned carbon nanotube (CNT) arrays have been proposed for several potential applications, ranging from biomimetic adhesives similar to spider's and gecko's feet, [11] to nanobrushes, [12] vibration damping layers, [6] and multifunctional composites, [13] but their development into successful commercial applications has been limited by their weak adhesion to the growth substrate, resulting in poor resistance to shear. In the present work we grew long, vertically-aligned multiwall CNTs (Fig. 1a), transferred and anchored them in thin polymer layers (Fig. 1b), and tested their mechanical response. While the nanotubes appear to be vertically aligned throughout the entire thickness of the sample (Fig. 1b), scanning electron microscopy (SEM) im...

Inhibition of human islet amyloid polypeptide (hIAPP) fibrillisation by peptides incorporating a helicogenic amino acid, dehydrophenylalanine: implications for Type-2 diabetes.

A heterostructure of graphene and zinc oxide (ZnO) nanowires (NWs) is fabricated by sandwiching an array of ZnO NWs between two graphene layers for an ultraviolet (UV) photodetector. This unique structure allows NWs to be in direct contact with the graphene layers, minimizing the effect of the substrate or metal electrodes. In this device, graphene layers act as highly conducting electrodes with a high mobility of the generated charge carriers. An excellent sensitivity is demonstrated towards UV illumination, with a reversible photoresponse even for a short period of UV illumination. Response and recovery times of a few milliseconds demonstrated a much faster photoresponse than most of the conventional ZnO nanostructure-based photodetectors. It is shown that the generation of a built-in electric field between the interface of graphene and ZnO NWs effectively contributes to the separation of photogenerated electron-hole pairs for photocurrent generation without applying any external bias. Upon application of external bias voltage, the electric field further increases the drift velocity of photogenerated electrons by reducing the charge recombination rates, and results in an enhancement of the photocurrent. Therefore, the graphene-based heterostructure (G/ZnO NW/G) opens avenues to constructing a novel heterostructure with a combination of two functionally dissimilar materials.

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Figure-Mechanical response of as-grown carbon nanotubes, (a) Elastic modulus and (b) Peak stress plotted for four different strain rates, 50% s -1 (blue squares), 3% s -1 (red triangles), 0.3% s -1 (green circles) and 0.03% s -1 (yellow diamonds) as a function of samples' density. The data points for each strain rate were fitted with a linear function.