The effect of the stacking fault on the diffusion of chemisorbed hydrogen atoms inside few-layered graphene

We examined the diffusion of hydrogen atoms in mono-, bi- and tetralayer graphene with AB stacking and two bilayer graphene with stacking faults using density functional theory. The bi- and tetralayer graphene provide diffusion pathways with lower energy barriers inside the interlayer space. Inside the bi- and tetralayer graphene with AB stacking, the in-plane diffusion is more favorable than the inter-plane jumping. However, the stacking faults made by sliding layer planes lowers the energy barrier of the inter-plane jumping and the effective frequency of the inter-plane jump is larger than that of the in-plane diffusion inside the graphene layers with the stacking faults. This suggests that hydrogen atoms can diffuse over a long distance inside few-layered graphene with stacking faults jumping consecutively between adjacent layers.close0

Cystamine induces AIF-mediated apoptosis through glutathione depletion

AbstractCystamine and its reduced form cysteamine showed protective effects in various models of neurodegenerative disease, including Huntington's disease and Parkinson's disease. Other lines of evidence demonstrated the cytotoxic effect of cysteamine on duodenal mucosa leading to ulcer development. However, the mechanism for cystamine cytotoxicity remains poorly understood. Here, we report a new pathway in which cystamine induces apoptosis by targeting apoptosis-inducing factor (AIF). By screening of various cell lines, we observed that cystamine and cysteamine induce cell death in a cell type-specific manner. Comparison between cystamine-sensitive and cystamine-resistant cell lines revealed that cystamine cytotoxicity is not associated with unfolded protein response, reactive oxygen species generation and transglutaminase or caspase activity; rather, it is associated with the ability of cystamine to trigger AIF nuclear translocation. In cystamine-sensitive cells, cystamine suppresses the levels of intracellular glutathione by inhibiting γ-glutamylcysteine synthetase expression that triggers AIF translocation. Conversely, glutathione supplementation completely prevents cystamine-induced AIF translocation and apoptosis. In rats, cysteamine administration induces glutathione depletion and AIF translocation leading to apoptosis of duodenal epithelium. These results indicate that AIF translocation through glutathione depletion is the molecular mechanism of cystamine toxicity, and provide important implications for cystamine in the neurodegenerative disease therapeutics as well as in the regulation of AIF-mediated cell death

Extracellular Transglutaminase 2 Is Catalytically Inactive, but Is Transiently Activated upon Tissue Injury

Transglutaminase 2 (TG2) is a multifunctional mammalian protein with transamidase and signaling properties. Using selective TG2 inhibitors and tagged nucleophilic amine substrates, we show that the majority of extracellular TG2 is inactive under normal physiological conditions in cell culture and in vivo. However, abundant TG2 activity was detected around the wound in a standard cultured fibroblast scratch assay. To demonstrate wounding-induced activation of TG2 in vivo, the toll-like receptor 3 ligand, polyinosinic-polycytidylic acid (poly(I:C)), was injected in mice to trigger small intestinal injury. Although no TG2 activity was detected in vehicle-treated mice, acute poly(I:C) injury resulted in rapid TG2 activation in the small intestinal mucosa. Our findings provide a new basis for understanding the role of TG2 in physiology and disease

Theoretical study on porphyrin based covalent organic polyhedra as a hydrogen storage

We introduce a new covalent organic polyhedron (COP) containing porphyrinyl groups. The porphyrin based COP (PCOP) is designed by modeling and simulation using 6 tetraaldehyde molecules and 8 triamine molecules combined by 24 imine bonds. Probable molecular crystal structures of the modeled PCOP are suggested by the simulated annealing Monte Carlo simulation method. We found that the predicted crystal structures show large surface areas up to over 6000 m(2)/g and the surface area depends on how to pack PCOP molecules and the resulting pore structure. Grand canonical Monte Carlo simulations predict the hydrogen uptakes of these polymorphs of PCOP and the values are from 98 to 262 mg/g for gravimetric uptake and from 45 to 50 kg/m(3) for volumetric uptake at 77 K. Hydrogen uptakes of PCOP crystals are comparable to the best records of metal-organic frameworks (164.1 mg/g for NU-100 and 176 mg/g for MOF-210 at 77 K). Hence, PCOP is expected to be applicable to hydrogen storage.close

Extracellular Transglutaminase 2 Is Catalytically Inactive, but Is Transiently Activated upon Tissue Injury

Transglutaminase 2 (TG2) is a multifunctional mammalian protein with transamidase and signaling properties. Using selective TG2 inhibitors and tagged nucleophilic amine substrates, we show that the majority of extracellular TG2 is inactive under normal physiological conditions in cell culture and in vivo. However, abundant TG2 activity was detected around the wound in a standard cultured fibroblast scratch assay. To demonstrate wounding-induced activation of TG2 in vivo, the toll-like receptor 3 ligand, polyinosinic-polycytidylic acid (poly(I:C)), was injected in mice to trigger small intestinal injury. Although no TG2 activity was detected in vehicle-treated mice, acute poly(I:C) injury resulted in rapid TG2 activation in the small intestinal mucosa. Our findings provide a new basis for understanding the role of TG2 in physiology and disease.</p