Arc Synthesis, Crystal Structure, and Photoelectrochemistry of Copper(I) Tungstate

A little-studied p-type ternary oxide semiconductor, copper(I) tungstate (Cu2WO4), was assessed by a combined theoretical/experimental approach. A detailed computational study was performed to solve the long-standing debate on the space group of Cu2WO4, which was determined to be triclinic P1. Cu2WO4 was synthesized by a time-efficient, arc-melting method, and the crystalline reddish particulate product showed broad-band absorption in the UV–visible spectral region, thermal stability up to ∼260 °C, and cathodic photoelectrochemical activity. Controlled thermal oxidation of copper from the Cu(I) to Cu(II) oxidation state showed that the crystal lattice could accommodate Cu2+ cations up to ∼260 °C, beyond which the compound was converted to CuO and CuWO4. This process was monitored by powder X-ray diffraction and X-ray photoelectron spectroscopy. The electronic band structure of Cu2WO4 was contrasted with that of the Cu(II) counterpart, CuWO4 using spin-polarized density functional theory (DFT). Finally, the compound Cu2WO4 was determined to have a high-lying (negative potential) conduction band edge underlining its promise for driving energetic photoredox reactions

Evidence that Proteasome-Dependent Degradation of the Retinoblastoma Protein in Cells Lacking A-Type Lamins Occurs Independently of Gankyrin and MDM2

A-type lamins, predominantly lamins A and C, are nuclear intermediate filaments believed to act as scaffolds for assembly of transcription factors. Lamin A/C is necessary for the retinoblastoma protein (pRB) stabilization through unknown mechanism(s). Two oncoproteins, gankyrin and MDM2, are known to promote pRB degradation in other contexts. Consequently, we tested the hypothesis that gankyrin and/or MDM2 are required for enhanced pRB degradation in Lmna-/- fibroblasts. Principal Findings. To determine if gankyrin promotes pRB destabilization in the absence of lamin A/C, we first analyzed its protein levels in Lmna-/- fibroblasts. Both gankyrin mRNA levels and protein levels are increased in these cells, leading us to further investigate its role in pRB degradation. Consistent with prior reports, overexpression of gankyrin in Lmna+/+ cells destabilizes pRB. This decrease is functionally significant, since gankyrin overexpressing cells are resistant to p16(ink4a)-mediated cell cycle arrest. These findings suggest that lamin A-mediated degradation of pRB would be gankyrin-dependent. However, effective RNAi-enforced reduction of gankyrin expression in Lmna-/- cells was insufficient to restore pRB stability. To test the importance of MDM2, we disrupted the MDM2-pRB interaction by transfecting Lmna-/- cells with p14(arf). p14(arf) expression was also insufficient to stabilize pRB or confer cell cycle arrest, suggesting that MDM2 also does not mediate pRB degradation in Lmna-/- cells.Our findings suggest that pRB degradation in Lmna-/- cells occurs by gankyrin and MDM2-independent mechanisms, leading us to propose the existence of a third proteasome-dependent pathway for pRB degradation. Two findings from this study also increase the likelihood that lamin A/C functions as a tumor suppressor. First, protein levels of the oncoprotein gankyrin are elevated in Lmna-/- fibroblasts. Second, Lmna-/- cells are refractory to p14(arf)-mediated cell cycle arrest, as was previously shown with p16(ink4a). Potential roles of lamin A/C in the suppression of tumorigenesis are discussed

Crystal growth, characterization and physical properties of PrNiSb 3, NdNiSb 3 and SmNiSb 3

The crystal structures of three new intermetallic ternary compounds in the LnNiSb 3 (Ln=Pr, Nd and Sm) family have been characterized by single crystal X-ray diffraction. PrNiSb 3, NdNiSb 3 and SmNiSb 3 all crystallize in an orthorhombic space group, Pbcm (No. 57), Z=12, with a=12.5700(2)Å, b=6.2010(4)Å, c=18.670(6)Å, and V=1431.64(11)Å3; a=12.5090(2)Å, b=6.1940(3)Å, c=18.3350(6)Å, and V=1420.61(9)Å3; and a=12.3900(1)Å, b=6.1760(3)Å, c=18.2650(6)Å, and V=1397.65(8)Å3, for Ln=Pr, Nd and Sm, respectively. These compounds consist of rare-earth atoms located above and below layers of nearly square, buckled Sb nets, along with layers of highly distorted edge- and face-sharing NiSb 6 octahedra. Resistivity data indicate metallic behavior for all three compounds. Magnetization measurements show antiferromagnetic behavior with TN=4.5K (PrNiSb 3), 4.6 K (NdNiSb 3), and 2.9 K (SmNiSb 3). Effective moments of 3.62 μ B, 3.90 μ B and 0.80 μ B are found for PrNiSb 3, NdNiSb 3 and SmNiSb 3, respectively, and are consistent with Pr 3+ (f 2), Nd 3+ (f 3), and Sm 3+ (f 4). Structure of PrNiSb 3 viewed down the b-axis containing Pr atoms (gray circles) located between layers of nearly square Sb nets and highly distorted Ni-centered octahedra. © 2004 Elsevier Inc. All rights reserved

Crystal growth, characterization and physical properties of PrNiSb 3, NdNiSb 3 and SmNiSb 3

The crystal structures of three new intermetallic ternary compounds in the LnNiSb 3 (Ln=Pr, Nd and Sm) family have been characterized by single crystal X-ray diffraction. PrNiSb 3, NdNiSb 3 and SmNiSb 3 all crystallize in an orthorhombic space group, Pbcm (No. 57), Z=12, with a=12.5700(2)Å, b=6.2010(4)Å, c=18.670(6)Å, and V=1431.64(11)Å3; a=12.5090(2)Å, b=6.1940(3)Å, c=18.3350(6)Å, and V=1420.61(9)Å3; and a=12.3900(1)Å, b=6.1760(3)Å, c=18.2650(6)Å, and V=1397.65(8)Å3, for Ln=Pr, Nd and Sm, respectively. These compounds consist of rare-earth atoms located above and below layers of nearly square, buckled Sb nets, along with layers of highly distorted edge- and face-sharing NiSb 6 octahedra. Resistivity data indicate metallic behavior for all three compounds. Magnetization measurements show antiferromagnetic behavior with TN=4.5K (PrNiSb 3), 4.6 K (NdNiSb 3), and 2.9 K (SmNiSb 3). Effective moments of 3.62 μ B, 3.90 μ B and 0.80 μ B are found for PrNiSb 3, NdNiSb 3 and SmNiSb 3, respectively, and are consistent with Pr 3+ (f 2), Nd 3+ (f 3), and Sm 3+ (f 4). Structure of PrNiSb 3 viewed down the b-axis containing Pr atoms (gray circles) located between layers of nearly square Sb nets and highly distorted Ni-centered octahedra. © 2004 Elsevier Inc. All rights reserved

Crystal structure and physical properties of polymorphs of LnAlB 4 (Ln = Yb, Lu)

Single crystals of YbAlB4 were grown in excess Al flux. Plate- and needle-shaped crystals were found. The plates are found to be ß-YbAlB4, which crystallizes with the ThMoB4 structure type in space group Cmmm (No. 65), Z = 4, with lattice parameters of a = 7.3080(4), b = 9.3150(5), and c = 3.4980(2) Å. The needle-shaped crystals were identified as the first form of YbAlB4 which crystallizes with the YCrB4 structure type in space group Pbam (No. 55), Z = 4, with lattice parameters of a = 5.9220(2), b = 11.4730(3), and c = 3.5060(5) Å. While both compounds have heavy fermion ground states with Isinglike magnetic anisotropy, the electronic specific heat coefficients (γ) differ. The ß-phase has a γ value near 300 mJ mol -1 K-2, more than twice that of the α-phase, γ = 130 mJ mol-1 K-2. A comparison of the structures and physical properties of both polymorphs is presented. © 2007 American Chemical Society

A comparison of the structure and localized magnetism in Ce 2PdGa12 with the heavy fermion CePdGa6

Single crystals of Ce2PdGa12 have been synthesized in Ga flux and characterized by X-ray diffraction. This compound crystallizes in the tetragonal P4/nbm space group, Z=2 with lattice parameters of a=6.1040(2)Å and c=15.5490(6)Å. It shows strongly anisotropic magnetism and orders antiferromagnetically at TN∼11 K. A field-induced metamagnetic transition to the ferromagnetic state is observed below TN. Structure-property relationships with the related heavy-fermion antiferromagnet CePdGa6 are discussed. © 2005 Elsevier Inc. All rights reserved

Crystal structure and physical properties of polymorphs of LnAlB 4 (Ln = Yb, Lu)

Single crystals of YbAlB were grown in excess Al flux. Plate- and needle-shaped crystals were found. The plates are found to be ß-YbAlB , which crystallizes with the ThMoB structure type in space group Cmmm (No. 65), Z = 4, with lattice parameters of a = 7.3080(4), b = 9.3150(5), and c = 3.4980(2) Å. The needle-shaped crystals were identified as the first form of YbAlB which crystallizes with the YCrB structure type in space group Pbam (No. 55), Z = 4, with lattice parameters of a = 5.9220(2), b = 11.4730(3), and c = 3.5060(5) Å. While both compounds have heavy fermion ground states with Isinglike magnetic anisotropy, the electronic specific heat coefficients (γ) differ. The ß-phase has a γ value near 300 mJ mol K , more than twice that of the α-phase, γ = 130 mJ mol K . A comparison of the structures and physical properties of both polymorphs is presented. © 2007 American Chemical Society. 4 4 4 4 4 -1 -2 -1 -