Curcumin tautomerization in the mechanism of pentameric amyloid- β42 oligomers disassembly.

Alzheimer\u27s disease is a neurologic disorder characterized by the accumulation of extracellular deposits of amyloid-β (Aβ) fibrils in the brain of patients. The key etiologic agent in Alzheimer\u27s disease is not known; however oligomeric Aβ appears detrimental to neuronal functions and increases Aβ fibrils deposition. Previous research has shown that curcumin, a phenolic pigment of turmeric, has an effect on Aβ assemblies, although the mechanism remains unclear. In this study, we demonstrate that curcumin disassembles pentameric oligomers made from synthetic Aβ42 peptides (pentameric oAβ42), using atomic force microscopy imaging followed by Gaussian analysis. Since curcumin shows keto-enol structural isomerism (tautomerism), the effect of keto-enol tautomerism on its disassembly was investigated. We have found that curcumin derivatives capable of keto-enol tautomerization also disassemble pentameric oAβ42, while, a curcumin derivative incapable of tautomerization did not affect the integrity of pentameric oAβ42. These experimental findings indicate that keto-enol tautomerism plays an essential role in the disassembly. We propose a mechanism for oAβ42 disassembly by curcumin based on molecular dynamics calculations of the tautomerism. When curcumin and its derivatives bind to the hydrophobic regions of oAβ42, the keto-form changes predominantly to the enol-form; this transition is associated with structural (twisting, planarization and rigidification) and potential energy changes that give curcumin enough force to act as a torsion molecular-spring that eventually disassembles pentameric oAβ42. This proposed mechanism sheds new light on keto-enol tautomerism as a relevant chemical feature for designing such novel therapeutic drugs that target protein aggregation

A Compact Ultrafast Electron Diffractometer with Relativistic Femtosecond Electron Pulses

We have developed a compact relativistic femtosecond electron diffractometer with a radio-frequency photocathode electron gun and an electron lens system. The electron gun generated 2.5-MeV-energy electron pulses with a duration of 55 ± 5 fs containing 6.3 × 104 electrons per pulse. Using these pulses, we successfully detected high-contrast electron diffraction images of single crystalline, polycrystalline, and amorphous materials. An excellent spatial resolution of diffraction images was obtained as 0.027 ± 0.001 Å−1. In the time-resolved electron diffraction measurement, a laser-excited ultrafast electronically driven phase transition in single-crystalline silicon was observed with a temporal resolution of 100 fs. The results demonstrate the advantages of the compact relativistic femtosecond electron diffractometer, including access to high-order Bragg reflections, single shot imaging with the relativistic femtosecond electron pulse, and the feasibility of time-resolved electron diffraction to study ultrafast structural dynamics

A new indicator of forest fire risk for Indonesia based on peat soil reflectance spectra measurements.

Conventional fire risk prediction using vegetation indexes is inappropriate because changes in soil moisture caused by plant drought stress have a 1 to 2 month time lag, which is too long for fire risk management. Further, soil and water indices used for traditional bare land assessments are also unsuitable because Indonesia is partially covered by peat soil, which has different reflection characteristics compared to typical agricultural and field soils. Here we describe a new index for estimating peat soil moisture using satellite remote sensing data. The method was developed using the ultra-blue band (435 to 451 nm) of the Land Remote-Sensing Satellite (Landsat 8) and is based on the moisture dependence of the reflected spectra measured directly. Our developed index showed a relatively strong correlation (r = 0.56 to 0.63) with real wildfire points and was a more reliable index than conventional measures used for fire risk management

Resistive switching memory performance in oxide hetero-nanocrystals with well-controlled interfaces

For realization of new informative systems, the memristor working like synapse has drawn much attention. We developed isolated high-density Fe3O4 nanocrystals on Ge nuclei/Si with uniform and high resistive switching performance using low-temperature growth. The Fe3O4 nanocrystals on Ge nuclei had a well-controlled interface (Fe3O4/GeOx/Ge) composed of high-crystallinity Fe3O4 and high-quality GeOx layers. The nanocrystals showed uniform resistive switching characteristics (high switching probability of ~90%) and relatively high Off/On resistance ratio (~58). The high-quality interface enables electric field application to Fe3O4 and GeOx near the interface, which leads to effective positively charged oxygen vacancy movement, resulting in high-performance resistive switching. Furthermore, we successfully observed memory effect in nanocrystals with well-controlled interface. The experimental confirmation of the memory effect existence even in ultrasmall nanocrystals is significant for realizing non-volatile nanocrystal memory leading to neuromorphic devices

Quantitative spatial mapping of distorted state phases during the metal-insulator phase transition for nanoscale VO2 engineering

ABSTRACT Vanadium dioxide (VO2) material, known for changing physical properties due to metal-insulator transition (MIT) near room temperature, has been reported to undergo a phase change depending on the strain. This fact can be a significant problem for nanoscale devices in VO2, where the strain field covers a large area fraction, spatially non-uniform, and the amount of strain can vary during the MIT process. Direct measurement of the strain field distribution during MIT is expected to establish a methodology for material phase identification. We have demonstrated the effectiveness of geometric phase analysis (GPA), high-resolution transmission electron microscopy techniques, and transmission electron diffraction (TED). The GPA images show that the nanoregions of interest are under tensile strain conditions of less than 0.4% as well as a compressive strain of about 0.7% (Rutile phase VO2[100] direction), indicating that the origin of the newly emerged TED spots in MIT contains a triclinic phase. This study provides a substantial understanding of the strain-temperature phase diagram and strain engineering strategies for effective phase management of nanoscale VO2