Expression, purification and microscopic characterization of human ATP-binding cassette sub-family B member 7 protein.

The ATP-binding cassette sub-family B member 7 (ABCB7) is a membrane transport protein located on the inner membrane of mitochondria, which could be involved in the transport of heme from the mitochondria to the cytosol. ABCB7 also plays a central role in the maturation of cytosolic iron-sulfur (Fe/S) cluster-containing proteins, and mutations can cause a series of mitochondrial defects. X-linked sideroblastic anemia and ataxia (XLSA-A) is a rare cause of early onset ataxia, which may be overlooked due to the usually mild asymptomatic anemia. The genetic defect has been identified as a mutation in the ABCB7 gene at Xq12-q13. Here, we report the expression, purification and the 2D projections derived from negatively stained electron micrographs of recombinant H. sapiens ABCB7 (hABCB7), paving the way from an atomic structure determination of ABCB7.

Quantitative analysis of the effect of radiation on mitochondria structure using coherent diffraction imaging with a clustering algorithm.

Radiation damage and a low signal-to-noise ratio are the primary factors that limit spatial resolution in coherent diffraction imaging (CDI) of biomaterials using X-ray sources. Introduced here is a clustering algorithm named ConvRe based on deep learning, and it is applied to obtain accurate and consistent image reconstruction from noisy diffraction patterns of weakly scattering biomaterials. To investigate the impact of X-ray radiation on soft biomaterials, CDI experiments were performed on mitochondria from human embryonic kidney cells using synchrotron radiation. Benefiting from the new algorithm, structural changes in the mitochondria induced by X-ray radiation damage were quantitatively characterized and analysed at the nanoscale with different radiation doses. This work also provides a promising approach for improving the imaging quality of biomaterials with XFEL-based plane-wave CDI.

Support interactions dictated active edge sites over MoS2-carbon composites for hydrogen evolution.

The rational design and synthesis of MoS2-based electrocatalysts with desirable active sites for the hydrogen evolution reaction have been actively pursued. Herein, we demonstrate a microwave-assisted steam heating method for the rapid and efficient synthesis of lamellar MoS2-based materials with favorable exposed active edge sites. Based on this new strategy, we have further separately introduced reduced graphene oxide (rGO) and carbon nanotubes (CNTs), two typical carbon allotropes widely used to boost the electrocatalytic activity of MoS2, to comparatively assess the support interactions and their effects on the electrocatalytic activity of MoS2. It was found that as compared to rGO, the CNTs afford favorable support interactions, which not only benefit to suppress the oriented in-plane growth of MoS2 to maximize the exposed edge sites but also ensure the maintainence of their intrinsic activity, thereby synergistically facilitating the exertion of the potential of MoS2 for HER. Our work conceptually highlights the importance of the support interactions for taming the active edge sites of MoS2 and is expected to inspire the rational design of layered metal dichalcogenide-based electrocatalysts with favorable active edges for HER.

Nitrogen-doped Carbon with Modulated Surface Chemistry and Porous Structure by a Stepwise Biomass Activation Process towards Enhanced Electrochemical Lithium-Ion Storage.

Controllable conversion of biomass to value-added carbon materials is attractive towards a wide variety of potential applications. Herein, hydrothermal treatment and KOH activation are successively employed to treat the cheap and abundant camellia oleifera shell as a new carbon raw material. It is shown that this stepwise activation process allows the production of porous nitrogen-doped carbon with optimized surface chemistry and porous structure compared to the counterparts prepared by a single activation procedure. Benefiting from the modulated porous structure, the as-produced porous nitrogen-doped carbon electrode delivered a high reversible capacity of 1080 mAh g-1 at a current density of 100 mA g-1, which is 3.3 and 5.8 times as high as that of the carbon materials prepared by bare hydrothermal treatment or KOH activation, respectively. Moreover, the optimized surface composition of the porous nitrogen-doped carbon endows it with a highest initial Coulombic efficiency among the three samples, showing great potentials for practical applications. This work is expected to pave a new avenue to upgrade biomass to carbon materials with tunable surface properties and microstructures for target applications.

Dimerization of MICU Proteins Controls Ca2+ Influx through the Mitochondrial Ca2+ Uniporter.

The mitochondrial Ca2+ uniporter complex (MCUC) is responsible for Ca2+ influx into the mitochondrial matrix, playing critical roles in various mitochondrial functions. Eukaryotic MCUC consists of multiple subunits, and its Ca2+ influx activity is controlled by regulatory subunits, including mitochondrial Ca2+ uptake 1 (MICU1) and its paralogs (MICU2 and MICU3). However, the underlying mechanism remains unclear. Here, we determined multiple crystal structures of MICU2 and MICU3 from Homo sapiens. Our data demonstrate that distinct MICU protein N-domains determine the specific type of MICU dimers that perform the opposing roles in mitochondrial Ca2+ uptake at low cytosolic Ca2+ levels. In contrast, at high cytosolic Ca2+ levels, all MICU proteins undergo dimer rearrangement induced by Ca2+ binding, which releases the suppression of the MCUC pore-forming subunit and promotes the influx of large amounts of Ca2+. Altogether, our results elucidate the delicate mechanism of mitochondrial Ca2+ uptake regulation by MICU proteins.

Facile synthesis of Camellia oleifera shell-derived hard carbon as an anode material for lithium-ion batteries.

A comparatively facile and ecofriendly process has been developed to synthesize porous carbon materials from Camellia oleifera shells. Potassium carbonate solution (K2CO3) impregnation is introduced to modify the functional groups on the surface of Camellia oleifera shells, which may play a role in promoting the development of pore structure during carbonization treatment. Moreover, a small amount of naturally embedded nitrogen and sulfur in the Camellia oleifera shells can also bring about the formation of pores. The Camellia oleifera shell-derived carbon has a large specific surface area of 1479 m2 g-1 with a total pore volume of 0.832 cm3 g-1 after being carbonized at 900 °C for 1 h. Furthermore, when used as an anode for lithium-ion batteries, the sample shows superior electrochemical performance with a specific capacity of 483 mA h g-1 after 100 cycles measured at 200 mA g-1 current density. Surprisingly, the specific capacity is even gradually increased with cycling. In addition, this sample exhibits almost 100% retention capacity after 250 cycles at a current density of 200 mA g-1.