Structure and function of the N-terminal domain of the human mitochondrial calcium uniporter.

The mitochondrial calcium uniporter (MCU) is responsible for mitochondrial calcium uptake and homeostasis. It is also a target for the regulation of cellular anti-/pro-apoptosis and necrosis by several oncogenes and tumour suppressors. Herein, we report the crystal structure of the MCU N-terminal domain (NTD) at a resolution of 1.50 Å in a novel fold and the S92A MCU mutant at 2.75 Å resolution; the residue S92 is a predicted CaMKII phosphorylation site. The assembly of the mitochondrial calcium uniporter complex (uniplex) and the interaction with the MCU regulators such as the mitochondrial calcium uptake-1 and mitochondrial calcium uptake-2 proteins (MICU1 and MICU2) are not affected by the deletion of MCU NTD. However, the expression of the S92A mutant or a NTD deletion mutant failed to restore mitochondrial Ca(2+) uptake in a stable MCU knockdown HeLa cell line and exerted dominant-negative effects in the wild-type MCU-expressing cell line. These results suggest that the NTD of MCU is essential for the modulation of MCU function, although it does not affect the uniplex formation.

Constructing inverse opal structured hematite photoanodes via electrochemical process and their application to photoelectrochemical water splitting.

In this study, we constructed an inverse opal structured hematite (IOS α-Fe2O3) as the photoanode of a photoelectrochemical (PEC) cell for efficient solar water splitting via a simple electrochemical process. At the same time, a series of affecting factors (template particle size, electrodeposition time and annealing temperature) to construct the IOS α-Fe2O3 photoanode on the photoelectrochemical water splitting were considered. Optimized PEC efficiency was observed for the IOS α-Fe2O3 photoanode annealed at 400 °C using the 250 nm sized-polystyrene (PS) colloid template and 9 minutes of electrodeposition time for the given specific Fe precursor solution. This resulted in the highest photocurrent density compared to other crossed conditions, which significantly achieved 3.1 mA cm(-2) at 0.5 V vs. Ag/AgCl reference electrode. The synthesis of the IOS α-Fe2O3 via an easy-to-control electrochemical process is described for first time that opens a possibility for constructing other oxide semiconductor photoanodes (not only well-known Si, Ti and Zr) with inverse opal structure.

Enhanced photocurrent density of tungsten oxide hollow particle arrays produced by colloidal template synthesis.

Tungsten oxide hollow particle arrays were fabricated for use as the photoanode in photoelectrochemical cells. These arrays were constructed through an electrochemical infiltration method in a three-dimensional colloidal array template. The enhanced contact area between the tungsten oxide and the electrolyte resulted in an increase in photocurrent when compared to a cell prepared with no template. The porous structures were greatly influenced by the temperature used during the thermal annealing step. This simple and cost-effective approach resulted in photocatalytic activity for hydrogen production that was three times higher than that of tungsten oxide prepared without the template.

Effect of incorporation of TiO2 nanoparticles into oriented TiO2 nanotube based dye-sensitized solar cells.

The authors present the first reported use of vertically oriented titanium oxide nanotube/titanium oxide nanoparticle nanocomposites to improve the efficiency of TiO2 based dye-sensitized solar cells (DSSCs). Titanium oxide nanotubes incorporating titanium oxide nanoparticles were prepared to harvest more solar light, and their solar-to-electric conversion efficiency was characterized. The incorporation of the titanium oxide nanoparticles increased the visible light absorption of the titanium oxide nanotube based DSSC system because of the increased light absorption resulting from the increased surface area. However, the photocurrent enhancement was more obvious under the illumination of visible light with a wavelength longer than 550 nm owing to the light scattering effect of the titanium oxide nanoparticles.

Highly Transparent Dual-Sensitized Titanium Dioxide Nanotube Arrays for Spontaneous Solar Water Splitting Tandem Configuration.

Vertically aligned one-dimensional (1D) titanium dioxide (TiO2) arrays on transparent conducting oxide (TCO) substrates, which can act as host electron transport materials for low bandgap materials, were synthesized via a hydrothermal reaction combined with a controlled chemical etching process. By controlling the chemical etching conditions, we can maximize the light transmission properties of the 1D TiO2 arrays, which is beneficial for the front electrode in photoelectrochemical (PEC) tandem configurations. As a result, dual sensitization to form 1D TiO2@CdS@CdSe (CdS and CdSe coated 1D TiO2) results in excellent photocurrent density, as well as transparency, and the resulting material is able to pass unabsorbed photons through the front electrode into the rear bias solar cell. Owing to the improved light transmission in combination with the increased specific surface area of the obtained 1D TiO2 arrays from the controlled etching process, a high-efficiency PEC tandem device with ∼2.1% was successfully fabricated for unassisted hydrogen evolution. Efficient PEC tandem device was fabricated for unassisted solar hydrogen generation using highly transparent composite electrode composed of dual sensitization to form 1D TiO2@CdS@CdSe.

Controlled synthesis of skein shaped TiO2-B nanotube cluster particles with outstanding rate capability.

Herein, we first report a facile synthetic route for preparing micron-sized particles comprising TiO(2)-B nanotubes, namely, skein shaped TiO(2)-B nanotube cluster particles with an ultra high surface area of 257 m(2) g(-1). The galvanostatic charge-discharge test showed that the hierarchical micron-sized particles composed of TiO(2)-B nanotubes with approximately 10 nm in diameter exhibited outstanding rate capability as well as high specific capacity.

Controlled synthesis of vertically aligned hematite on conducting substrate for photoelectrochemical cells: nanorods versus nanotubes.

This paper describes two different processes to synthesize vertically aligned hematite nanorod and nanotube arrays, respectively, on a conductive substrate by the electrochemical deposition method with the help of an anodized aluminum oxide nanotemplate. The two types of nanostructured hematite were used as the photoanode for photoelectrochemical cells. The hematite nanotubes exhibited much higher photoelectrochemical activity than the hematite nanorods, including an improved photocurrent density, more negative onset potential, better photon harvesting, and better charge carrier transfer ability. The observed behavior may offer new information to enhance the photocatalytic ability of hematite, which is considered to be one of the best photoanode materials in the research field of photoelectrochemical cells.

CdS or CdSe decorated TiO2 nanotube arrays from spray pyrolysis deposition: use in photoelectrochemical cells.

In the present work we report on an investigation of TiO(2) nanotube arrays sensitized by low band-gap materials, such as CdS and CdSe, prepared by the one-step spray pyrolysis deposition method, which is very suitable for mass production, and their performance in photoelectrochemical cells.