IntroductionReceptor activator of NF-B (nuclear factor-B) ligand (RANKL; also called TRANCE [tumor necrosis factor (TNF) activationinduced cytokine], ODF [osteoclast differentiation factor], and OPGL [osteoprotegerin ligand]) 1-4 is a key factor stimulating the differentiation and activation of osteoclasts and, therefore, is essential for bone remodeling. 5 The binding of RANKL to its receptor RANK leads to recruitment of TNF receptor-associated factor 6 (TRAF6) to the cytoplasmic domain of RANK, thereby resulting in the activation of distinct signaling cascades mediated by mitogen-activated protein (MAP) kinases, including c-Jun N-terminal kinase (JNK), p38 MAP kinase (p38), and extracellular signal-regulated kinase (ERK). 6 It has been shown that JNK1-activated c-Jun signaling in cooperation with nuclear factor of activated T cells (NFAT) is key to RANKL-regulated osteoclast differentiation. 7 In addition, stimulation of p38 results in the downstream activation of the mi/Mitf (microphthalmia/microphthalmia transcription factor), which controls the expression of the genes encoding tartrate-resistant acid phosphatase (TRAP) and cathepsin K, indicating the importance of p38 signaling cascades. 6 Although our understanding of signaling pathways associated with osteoclast differentiation has advanced considerably recently, the mechanism of RANKL-mediated osteoclastogenesis, specifically the molecular linkage between TRAF6 and MAP kinases, is still unknown.At high concentrations, reactive oxygen species (ROSs) cause oxidative stress that has been viewed as deleterious phenomena, including inflammatory response, apoptosis, or ischemia. 8 Recent studies, however, indicate that small nontoxic amounts of ROS may play a role as a second messenger in the various receptor signaling pathways. [9][10][11][12][13] Osteoclasts have shown to be activated by ROSs to enhance bone resorption, 14 but little attention has been given to the role of ROSs in differentiation of macrophages and monocytes into osteoclasts. Signaling molecules such as JNK and p38, which are known to be essential for osteoclast differentiation, 6,7 are sensitive to activation by ROSs. 11,12 Thus, we hypothesized that signaling cascade(s) can be modulated by ROSs in bone marrow monocyte-macrophage lineage (BMM) cells.Here, we show that RANKL generates ROSs in BMM cells. Examination of the mechanism by which RANKL generates ROSs revealed the involvement of TRAF6, Rac1, and NADPH (nicotinamide adenine dinucleotide phosphate) oxidase 1 (Nox1). These data suggest that RANKL-mediated ROS production serves to regulate RANKL signaling pathways, including JNK and p38 activation required for osteoclast differentiation. Materials and methods Reagents and plasmids2Ј,7Ј-dichlorofluorescein diacetate (DCFH-DA) was purchased from Molecular Probes (Leiden, The Netherlands); all other chemicals and FLAG (five NH2-terminally deleted epitope-tagged) epitope (M2) were from Expression constructs encoding FLAG-tagged wild-type RANK, HAtagged TRAF6 (amino acids [aa] 289-530), and...

High-entropy alloy nanoparticles (HEA-NPs) are important class of materials with significant technological potential. However, the strategies for synthesizing uniformly dispersed HEA-NPs on granular supports such as carbon materials, γ-Al 2 O 3 , and zeolite, which is vital to their practical applications, are largely unexplored. Herein, we present a fast moving bed pyrolysis strategy to immobilize HEA-NPs on granular supports with a narrow size distribution of 2 nm up to denary (MnCoNiCuRhPdSnIrPtAu) HEA-NPs at 923 K. Fast moving bed pyrolysis strategy ensures the mixed metal precursors rapidly and simultaneously pyrolyzed at high temperatures, resulting in nuclei with a small size. The representative quinary (FeCoPdIrPt) HEA-NPs exhibit high stability (150 h) toward hydrogen evolution reaction with high mass activity, which is 26 times higher than the commercial Pt/C at an overpotential of 100 mV. Our strategy provides an improved methodology for synthesizing HEA-NPs on various supports.

Attractive hydrogen production? The amorphous Fe nanoparticles prepared following a simple but very efficient method possess high catalytic activity (see picture) for the generation of hydrogen from an aqueous solution of ammonia borane, even in air, and can readily be recycled with no obvious loss of catalytic activity.

The oxidation of CO to CO 2 by metal catalysts has been intensively investigated; for example, gold nanoparticles have exhibited excellent properties. 1 The metal catalysts are often dispersed on a solid support, such as oxide, zeolite, and so on. Exposed to heating during vehicle use, these metal particles trend to agglomerate and grow, which causes their overall surface area to decrease. As a result, catalyst activity deteriorates. 2 These metal catalysts are also very easily poisoned by exposing them to moisture or organic compounds. On the other hand, the newly developed microporous metal-organic polymers (MMOPs) have recently

Carbon-supported Fe@Pt core-shell nanoparticle (NP) catalysts with Fe cores in different crystal states have been successfully synthesized by a sequential reduction process. Unexpectedly, in contrast to its crystallized counterpart, iron in the amorphous state exerts a distinct and powerful ability as the core for the Fe@Pt NPs. The resultant NPs are far more active for ammonia borane oxidation (by up to 354%) than the commercial Pt/C catalysts. Furthermore, these NPs combine low cost, long-term stability, and easy recovery functions.

For the first time, a single crystalline FeTiO 3 nanodisc in the ilmenite phase has been synthesized by a hydrothermal reaction at 220 °C. The prepared FeTiO 3 was a hexagonal disk-like structure with an average diameter of ∼400 nm and a thickness of ∼70 nm, while its hexagonal face was oriented in (001) plane and grown to (110) direction. The heterojunction structure was formed between the as-prepared FeTiO 3 nanodisc and Degussa P25 with an average particle size of ∼25 nm by employing maleic acid as an organic linker. The prepared FeTiO 3 /TiO 2 coupled at a nanoscale demonstrated greatly enhanced photocatalytic activity in removing 2-propanol and evolving CO 2 in gas phase under visible light irradiation (λ g 420 nm). Its degradation constant (k) in removing 2-propanol was ∼25 times that of Degussa P25, which suggests that its catalytic efficiency is comparable to that of a typical N-doped TiO 2 . The remarkable photocatalytic activity of FeTiO 3 / TiO 2 could be explained by the intersemiconductor hole-transfer mechanism caused by the unique relative band positions of these two semiconductors.

In this paper, two kinds of Ni nanoparticles have been successfully synthesized without and with starch as the "green" protective material and investigated as catalysts for generating hydrogen from ammonia borane (NH(3)BH(3), AB). Experimental investigations have demonstrated that both of the Ni nanoparticles possess high catalytic activities for H(2) generation from aqueous solution of AB. However, the catalytic activities of Ni nanoparticles without starch decrease seriously in the course of the lifetime tests. In contrast, the catalytic activities of the Ni nanoparticles with starch almost keep unchanged even after 240 h. Moreover, the XPS results show that the surface of the Ni nanoparticles in starch solution is still metallic Ni even after 240 h, while that in pure water is nickel oxide. This means that starch can successfully keep the Ni nanoparticles in aqueous solution from the oxidation in air. The present efficient, low-cost, and longtime water/air stable Ni catalyst represents a promising step toward the development of AB as a viable on-board hydrogen storage and supply material.

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