Role of post-translational modifications on the alpha-synuclein aggregation-related pathogenesis of Parkinson's disease.

Together with neuronal loss, the existence of insoluble inclusions of alpha-synuclein (α-syn) in the brain is widely accepted as a hallmark of synucleinopathies including Parkinson's disease (PD), multiple system atrophy, and dementia with Lewy body. Because the α-syn aggregates are deeply involved in the pathogenesis, there have been many attempts to demonstrate the mechanism of the aggregation and its potential causative factors including post-translational modifications (PTMs). Although no concrete conclusions have been made based on the previous study results, growing evidence suggests that modifications such as phosphorylation and ubiquitination can alter α-syn characteristics to have certain effects on the aggregation process in PD; either facilitating or inhibiting fibrillization. In the present work, we reviewed studies showing the significant impacts of PTMs on α-syn aggregation. Furthermore, the PTMs modulating α-syn aggregation-induced cell death have been discussed. [BMB Reports 2022; 55(7): 323-335].

Development of a fluorescent nanoprobe based on an amphiphilic single-benzene-based fluorophore for lipid droplet detection and its practical applications.

Lipid droplets (LDs) are crucial biological organelles connected with metabolic pathways in biological systems and diseases. To monitor the locations and accumulation of LDs in lipid-related diseases, the development of a visualization tool for LDs has gained importance. In particular, LD visualization using fluorescent probes has gained attention. Herein, a new fluorescent nanoprobe, BMeS-Ali, is developed that can sense LDs based on an amphiphilic single benzene-based fluorophore (SBBF). BMeS-Ali consists of hydrophilic (-NH2) and hydrophobic (-C12H25) moieties and exists as a micelle nanostructure in aqueous media. BMeS-Ali has a weak fluorescence, but its emission was dramatically enhanced upon exposure to the LD components such as oleic acids (OA) by reassembling its nano-formulation. BMeS-Ali showed a selective LD staining ability and great biocompatibility in cells (cancer cells and stem cells). It also showed a practical sensing ability towards biologically derived lipids and can be applied to the visualization of human fingerprints. We found that the nanoprobe BMeS-Ali has significant potential to serve as a practical dye and sensor for lipids, especially for LD imaging in the biomedical research area and broader industrial applications.

Orientation-Controllable ZnO Nanorod Array Using Imprinting Method for Maximum Light Utilization in Dye-Sensitized Solar Cells.

We present a holey titanium dioxide (TiO2) film combined with a periodically aligned ZnO nanorod layer (ZNL) for maximum light utilization in dye-sensitized solar cells (DSCs). Both the holey TiO2 film and the ZNL were simultaneously fabricated by imprint technique with a mold having vertically aligned ZnO nanorod (NR) array, which was transferred to the TiO2 film after imprinting. The orientation of the transferred ZNL such as laid, tilted, and standing ZnO NRs was dependent on the pitch and height of the ZnO NRs of the mold. The photoanode composed of the holey TiO2 film with the ZNL synergistically utilized the sunlight due to enhanced light scattering and absorption. The best power conversion efficiency of 8.5 % was achieved from the DSC with the standing ZNL, which represented a 33 % improvement compared to the reference cell with a planar TiO2.

Palladium-decorated hydrogen-gas sensors using periodically aligned graphene nanoribbons.

Polymer residue-free graphene nanoribbons (GNRs) of 200 nm width at 1 µm pitch were periodically generated in an area of 1 cm(2) via laser interference lithography using a chromium interlayer prior to photoresist coating. High-quality GNRs were evidenced by atomic force microscopy, micro-Raman spectroscopy, and X-ray photoelectron spectroscopy measurements. Palladium nanoparticles were then deposited on the GNRs as catalysts for sensing hydrogen gases, and the GNR array was utilized as an electrically conductive path with less electrical noise. The palladium-decorated GNR array exhibited a rectangular sensing curve with unprecedented rapid response and recovery properties: 90% response within 60 s at 1000 ppm and 80% recovery within 90 s in nitrogen ambient. In addition, reliable and repeatable sensing behaviors were revealed when the array was exposed to various gas concentrations even at 30 ppm.

Transfer printing of metal nanoring and nanodot arrays for use in catalytic reactions.

Nanoscale metal ring and dot catalyst arrays are printed over large substrate areas using vertically aligned carbon-based stamps with the ring- and dot-shaped tips. The fundamental nature of these ring and dot catalysts is successfully compared by applying them in diverse electrocatalytic reactions in acidic and alkaline media.

Enhanced light absorption of silicon nanotube arrays for organic/inorganic hybrid solar cells.

By combining nanoimprint lithography technique and a two-step lift-off process, a Si nanotube array is fabricated and applied as a light absorber for n-Si/PEDOT:PSS hybrid solar cells. The light is effectively trapped within the nanotubes and the device reveals a Jsc of 29.9 mA · cm(-2) and a power conversion efficiency of 10.03%, which is an enhancement of 13.4% compared to the cell having the best-known Si architecture of nanocones as a light absorber to date.

Nanoslit Confined DNA at Low Ionic Strengths.

We present nanoslit confined DNA conformations at very low ionic strengths and a theory to explain most measurements for single DNA molecule size under strong nanoslit confinement. Very low ionic strength conditions not only increase the DNA persistence length dramatically, but also cause DNA molecules to swell to the extent that the effective diameter of DNA becomes larger than the nanoslit height. By accounting for these effects, our results and theory provide a reasonable clue for a current controversy regarding the dependence of the DNA conformation on slit height (h), persistence length (p), and effective diameter (w).

3D Branched nanowire photoelectrochemical electrodes for efficient solar water splitting.

We report the systematic study of 3D ZnO/Si branched nanowire (b-NW) photoelectrodes and their application in solar water splitting. We focus our study on the correlation between the electrode design and structures (including Si NW doping, dimension of the trunk Si and branch ZnO NWs, and b-NW pitch size) and their photoelectrochemical (PEC) performances (efficiency and stability) under neutral conditions. Specifically, we show that for b-NW electrodes with lightly doped p-Si NW core, larger ZnO NW branches and longer Si NW cores give a higher photocathodic current, while for b-NWs with heavily doped p-Si NW trunks smaller ZnO NWs and shorter Si NWs provide a higher photoanodic current. Interestingly, the photocurrent turn-on potential decreases with longer p-Si NW trunks and larger ZnO NW branches resulting in a significant photocathodic turn-on potential shift of ~600 mV for the optimized ZnO/p-Si b-NWs compared to that of the bare p-Si NWs. A photocathode energy conversion efficiency of greater than 2% at -1 V versus Pt counter electrode and in neutral solution is achieved for the optimized ZnO/p-Si b-NW electrodes. The PEC performances or incident photon-to-current efficiency are further improved using Si NW cores with smaller pitch size. The photoelectrode stability is dramatically improved by coating a thin TiO2 protection layer using atomic-layer deposition method. These results provide very useful guidelines in designing photoelectrodes for selective solar water oxidation/reduction and overall spontaneous solar fuel generation using low cost earth-abundant materials for practical clean solar fuel production.

Printable nanoscale metal ring arrays via vertically aligned carbon nanotube platforms.

This paper reports a novel and efficient strategy for fabricating sub-100 nm metal ring arrays using a simple printing process. Vertically aligned carbon nanotubes that are supported by hexagonally ordered channels of alumina matrices are used as a stamp to print nanoscale ring patterns, which is a very unique stamping platform that has never been reported. Using this strategy, uniform nanoring patterns of various metals can be directly printed onto a wide range of substrate surfaces under ambient conditions. Significantly, the size and interval of the printed nanorings can be systematically tuned by controlling the ring-shaped tip dimensions of the pristine stamps. An advanced example of these printable nanoscale metal ring arrays is explicitly embodied in this work by investigation of the plasmon resonances of metal nanorings with different sizes and intervals.

Tailoring n-ZnO/p-Si branched nanowire heterostructures for selective photoelectrochemical water oxidation or reduction.

We report the fabrication of three-dimensional (3D) branched nanowire (NW) heterostructures, consisting of periodically ordered vertical Si NW trunks and ZnO NW branches, and their application for solar water splitting. The branched NW photoelectrodes show orders of magnitudes higher photocurrent compared to the bare Si NW electrodes. More interestingly, selective photoelectrochemical cathodic or anodic behavior resulting in either solar water oxidation or reduction was achieved by tuning the doping concentration of the p-type Si NW core. Specifically, n-ZnO/p-Si branched NW array electrodes with lightly doped core show broadband absorption from UV to near IR region and photocathodic water reduction, while n-ZnO/p(+)-Si branched NW arrays show photoanodic water oxidation with photoresponse only to UV light. The photoelectrochemical stability for over 24 h under constant light illumination and fixed biasing potential was achieved by coating the branched NW array with thin layers of TiO2 and Pt. These studies not only reveal the promise of 3D branched NW photoelectrodes for high efficiency solar energy harvesting and conversion to clean chemical fuels, but also developing understanding enabling rational design of high efficiency robust photocathodes and photoanodes from low-cost and earth-abundant materials allowing practical applications in clean renewable energy.

All-solution-processed transparent thin film transistor and its application to liquid crystals driving.

All-solution-processed transparent thin film transistors (TTFTs) are demonstrated with silver grid source/drain electrodes, which are fabricated by printing and subsequent silver nanoparticles solution coating, which allows continuous processing without using high vacuum systems. The silver grid electrode shows a reasonable transmittance in visible range, moderate electrical conductance and mechanical strength. The TTFTs are employed to drive liquid crystal cells and demonstrate a successful switching operation.

A simple self-assembly route to single crystalline SnO2 nanorod growth by oriented attachment for dye sensitized solar cells.

One-dimensional (1-D) SnO(2) nanorods (NRs) with a rutile structure are grown on various substrates regardless of the lattice-mismatch by using a new nutrient solution based on tin oxalate, which generated supersaturated Sn(2+) sources. These affluent sources are appropriate for producing a large number of SnO(2) nanoparticles, sufficient for stacking on a substrate surface by gravity, which then acts as a seed layer for subsequent nanorod growth. Single crystalline nanorods are grown along the [001] direction by the oriented attachment phenomenon in which the attached nanoparticles were rearranged to reduce the overall surface energy through sharing thermodynamically unstable crystal (001) planes. Furthermore, the grown SnO(2) NRs are covered with a TiO(2) particulate film and utilized as a photoanode in DSSCs. The power conversion efficiency is 8.61%, enhanced by 14.2% compared to the photoanode with only a TiO(2) particulate film.

Large-area fabrication of periodic sub-15 nm-width single-layer graphene nanorings.

A periodically aligned array of graphene nanorings (GRNRs) with a sub-15 nm linewidth at a pitch of 450 nm is fabricated with a large area, 9 cm(2) , through conventional nanoimprint lithography coupled with sophisticated metal deposition and plasma-etching processes. The existence of the single-layer GRNRs is verified by various techniques.

Printing of sub-100-nm metal nanodot arrays by carbon nanopost stamps.

This work reports an efficient method to fabricate hexagonally patterned metal nanodot arrays at the sub-100-nm scale, which is based on contact printing via novel nanometer-scaled stamps. Vertically aligned carbon nanoposts, supported by hexagonally ordered nanochannels of anodic aluminum oxide templates, are employed as the stamping platform to directly transfer controlled metal nanodot arrays. Using the fabrication platform, a number of patterned metal nanodot arrays made of Au, Cu, Ni, Ag, Pt, Al, and Ti can be contact-printed over large substrate areas in ambient conditions. The size, density, and interdistance of the printed nanodots are controllable with a tight correspondence to the mother stamp geometries, which can be precisely tuned by modifying the pore dimensions of the alumina matrixes. An advanced example of contact printing of metal nanoparticles is successfully demonstrated by the controlled formation of nanodot arrays in a specific area.

A crossbar-type high sensitivity ultraviolet photodetector array based on a one hole-one nanorod configuration via nanoimprint lithography.

Single crystalline vertical ZnO nanorods were grown in a one hole-one rod configuration using a hydrothermal method with a patterned polymer template generated by nanoimprint lithography, allowing precise control over the position and density of the ZnO nanorods. An 8×8 ZnO nanorod-based ultraviolet photodetector array is demonstrated, in which a well-confined number of ZnO nanorods are sandwiched between crossbar-type platinum and indium tin oxide electrodes (e.g. 16 nanorods in a 2×2 µm2 area). A high photocurrent/dark current ratio of 3×10(3) at a reverse bias of 1.5 V under UV illumination at room temperature, a responsivity of 4381.4 A W(-1) at 365 nm, and an ultraviolet-to-visible rejection ratio of 83 are obtained and maintained, irrespective of pixel size. A uniform photoresponse is achieved in each of the pixels, indicating the scalability with this technique for fabricating an integrated UV photodetector array circuit.