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Successive cleavages of amyloid precursor protein C-terminal fragment with 99 residues (APP-C99) by γ-secretase result in amyloid-β (Ab) peptides of varying lengths. Most cleavages have a step size of three residues. To elucidate the underlying mechanism, we determined the atomic structures of human γ-secretase bound individually to APP-C99, Ab49, Ab46, and Ab43. In all cases, the substrate displays the same structural features: a transmembrane α-helix, a three-residue linker, and a β-strand that forms a hybrid β-sheet with presenilin 1 (PS1). Proteolytic cleavage occurs just ahead of the substrate β-strand. Each cleavage is followed by unwinding and translocation of the substrate α-helix by one turn and the formation of a new β-strand. This mechanism is consistent with existing biochemical data and may explain the cleavages of other substrates by β-secretase. [ABSTRACT FROM AUTHOR]

Ag@C core-shell structures were prepared using hydrothermal methods by AgNO3 reduction with ascorbic acid in the presence of polyacrylamide (PAM). Temperature plays a key role in the formation of the core-shell structures. The roles of reactants, surfactant concentrations and reaction time on the morphologies of core-shell nanoparticles were investigated in detail. This synthetic method is one-pot synthesis, which is fast, high-yield and environmental-friendly for fabrication of Ag@C core-shell structures. The surface properties of core-shell Ag@C nanoparticles were characterized by Raman spectroscopy. [ABSTRACT FROM AUTHOR]

One-step synthetic route has been developed for the preparation of Nd(OH)3 nanorods in the presence of n-butylamine. The as-prepared sample is in hexagonal phase with good crystallinity, and made up of highly dispersed nanorods of 14-15 nm in diameter and up to 40-50 nm in length at 120°C for 24 h. Optical measurements show that these nanorods have intensive photoluminescence (PL) at room temperature and have the potential to become optical materials. Thermogravimetric analysis (TGA) of the Nd(OH)3 nanorods reveals that the nanorods remain stable up to 220°C and decompose to the derived oxide of Nd2O3 at higher temperatures. The derived oxides show the promise active catalyst for the oxidation of carbon monoxide. In addition, this synthetic route has been developed for the synthesis of a series of other lanthanide hydroxides nanorods including Pr(OH)3, Sm(OH)3, Eu(OH)3, Gd(OH)3, Tb (OH)3 and Dy(OH)3, and their PL properties, thermostability and catalytic properties are investigated. [ABSTRACT FROM AUTHOR]

The flower-like Cu2O nanostructures were hydrothermally synthesized without using any template or surfactant. The influences of hydrothermal temperature, reaction time and reactants concentrations on the growth of nanostructures were investigated in detail. The samples were characterized by scanning electron microscope (SEM) and X-ray powder diffraction (XRD). Cu2O crystals with different shapes, i.e., flower-like (F-product) cubic box (CB-product) and cubic box with holes in each face (CBH-product), were synthesized by controlling the synthesis parameters and explored for CO catalytic oxidation. It was found that F-product showed higher catalytic than others. [ABSTRACT FROM AUTHOR]

A label-free biosensor for Escherichia coli (E. coli) ORN 178 based on faradaic electrochemical impedance spectroscopy (EIS) was developed. a-Mannoside or ß-galactoside was immobilized on a gold disk electrode using a self-assembled monolayer (SAM) via a spacer terminated in a thiol functionality. Impedance measurements (Nyquist plot) showed shifts due to the binding of E. coli ORN 178, which is specific for a-mannoside. No significant change in impedance was observed for E. coli ORN 208, which does not bind to a-mannoside. With increasing concentrations of E. coli ORN 178, electron-transfer resistance (Ret) increases before the sensor is saturated. After the Nyquist plot of E. coli/mixed SAM/gold electrode was modeled, a linear relationship between normalized Ret and the logarithmic value of E. coli concentrations was found in a range of bacterial concentration from 102 to 103 CFU/mL. The combination of robust carbohydrate ligands with EIS provides a label-free, sensitive, specific, user-friendly, robust, and portable biosensing system that could potentially be used in a point-of-care or continuous environmental monitoring setting. [ABSTRACT FROM AUTHOR]

A Nation film loaded with novel catalyst-free multhvalled carbon nanotubes (MWCNTs) was used to modify a glassy carbon (GC) electrode to detect trace concentrations of metal ions, with europium ion (Eu3+) as a model. The interaction between the sidewalls of MWCNTs and the hydrophobic backbone of Nation allows die MWCNTs to be dispersed in Nafion, which was then coated as a thin film on the GC electrode surface- The electrochemical response to Eu3+ was found to be ~10 times improved by MWCNT concentrations between 0.5 and 2 mg/mL, which effectively expanded the electrode surface into the Nafion film and thereby reduced the diffusion distance of Bo to the electrode surface. At low MWCNT concentrations of 0.25 and 0.5 mg/mL, no significant improvement in signal was obtained compared with Nafion alone. Scanning electron microscopy and electrochemical impedance spectroscopy were used to characterize the structure of the MWCNT-Nafion film, followed by electrochemical characterization with Eu3+ via cyclic voltammetry and preconcentration voltammetry. Under the optimized conditions, a linear range of 1 - 100 nM with a calculated detection limit of 0.37 nM (signal/noise = 3) was obtained for determination of Eu3+ by Osteryoung square-wave voltammetry after a preconcentration time of 480 s. [ABSTRACT FROM AUTHOR]

Aberrant cleavage of amyloid precursor protein (APP) by γ-secretase is closely associated with Alzheimer’s disease (AD). γ-secretase activating protein (GSAP) specifically promotes γ-secretase–mediated cleavage of APP. However, the underlying mechanism remains enigmatic. Here, we demonstrate that the 16-kDa C-terminal fragment of GSAP (GSAP-16K) undergoes phase separation in vitro and forms puncta-like condensates in cells. GSAP-16K exerts dual modulation on γ-secretase cleavage; GSAP-16K in dilute phase increases APP–C-terminal 99-residue fragment (C99) cleavage toward preferred production of β-amyloid peptide 42 (Aβ42), but GSAP-16K condensates reduce APP-C99 cleavage through substrate sequestration. Notably, the Aβ42/Aβ40 ratio is markedly elevated with increasing concentrations of GSAP-16K. GSAP-16K stably associates with APP-C99 through specific sequence elements. These findings mechanistically explain GSAP-mediated modulation of γ-secretase activity that may have ramifications on the development of potential therapeutics. [ABSTRACT FROM AUTHOR]

How superconductivity interacts with charge or nematic order is one of the great unresolved issues at the center of research in quantum materials. Ba1-xSrxNi2As2 (BSNA) is a charge ordered pnictide superconductor recently shown to exhibit a sixfold enhancement of superconductivity due to nematic fluctuations near a quantum phase transition (at xc=0.7) [1]. The superconductivity is, however, anomalous, with the resistive transition for 0.4