Fabrication of inverse opal molybdenum sulfide and its use as a catalyst for H2 evolution.

Amorphous molybdenum sulfide (MoSx) and crystalline molybdenum disulfide (MoS2) are attractive noble-metal-free electrocatalysts for the H2 evolution reaction from water. Their actual activities depend on the quantity of active sites which are exposed to the electrolyte, which in turn, is influenced by their specific electrochemical surface area. Herein we report on the fabrication of regular inverse opal MoSx and MoS2 films by employing polystyrene nanoparticles with diameters in the range of 30-90 nm as hard templates. The use of these catalysts for the H2 evolution reaction in an acidic electrolyte solution is also presented. Impacts of the regular porous structure, the film thickness as well as the chemical nature of the catalyst (MoS2versus MoSx) are discussed. It shows a catalytically-effective-thickness of ca. 300 nm where the electrolyte can fully penetrate the catalyst macropores, thus all the catalytic active sites can be exposed to the electrolyte to achieve the maximal catalytic operation.

Exploring the Sub-nanoscale Structure of Cobalt Molybdenum Sulfide and the Role of a Cobalt Promoter in Catalytic Hydrogen Evolution.

Cobalt-promoted molybdenum sulfide (CoMoS) is known as a promising catalyst for H2 evolution reaction and hydrogen desulfurization reaction. This material exhibits superior catalytic activity as compared to its pristine molybdenum sulfide counterpart. However, revealing the actual structure of cobalt-promoted molybdenum sulfide as well as the plausible contribution of a cobalt promoter is still challenging, especially when the material has an amorphous nature. Herein, we report, for the first time, on the use of positron annihilation spectroscopy (PAS), being a nondestructive nuclear radiation-based method, to visualize the position of a Co promoter within the structure of MoS at the atomic scale, which is inaccessible by conventional characterization tools. It is found that at low concentrations, a Co atom occupies preferably the Mo-vacancies, thus generating the ternary phase CoMoS whose structure is composed of a Co-S-Mo building block. Increasing the Co concentration, e.g., a Co/Mo molar ratio of higher than 1.12/1, leads to the occupation of both Mo-vacancies and S-vacancies by Co. In this case, secondary phases such as MoS and CoS are also produced together with the CoMoS one. Combining the PAS and electrochemical analyses, we highlight the important contribution of a Co promoter to enhancing the catalytic H2 evolution activity. Having more Co promoter in the Mo-vacancies promotes the H2 evolution rate, whereas having Co in the S-vacancies causes a drop in H2 evolution ability. Furthermore, the occupation of Co to the S-vacancies leads also to the destabilization of the CoMoS catalyst, resulting in a rapid degradation of catalytic activity.

Albumin in immunohistochemistry: Foe and friend.

Immunohistochemical procedures constitute a high methodological value in both pathologic diagnostics and research. Staining quality depends on a large variety of interference factors. Primarily, background staining reduces the quality of evaluation by reducing the chromatic discrimination. For the identification of important interference factors, various incubation steps and composition of solutions recommended in routine protocols were altered or omitted in our study. Surprisingly, the most important effect concerning background staining reduction could be significantly attributed to the omission of albumin which usually is recommended as a reducer of background stainings. However, in contrast to this negative effect, albumin could also increase specific staining intensity. These findings lead to the recommendation of a careful use of albumin in immunohistochemistry because of the dichotomous effects mentioned above. Furthermore, these results imply that in case of a good specific staining pattern, the use of albumin in immunohistochemical solutions merely exerts significant negative background staining effects.

Intracellular sequestration of hetero-oligomers formed by wild-type and glaucoma-causing myocilin mutants.

PURPOSE: To investigate mechanism(s) by which mutations in the olfactomedin domain of myocilin (MYOC), also known as the trabecular meshwork-induced glucocorticoid response (TIGR) gene, cause autosomal dominant open-angle glaucoma, the structure and properties of wild-type (WT) MYOC protein were examined, when expressed alone or simultaneously with the Q368X or K423E disease-associated polypeptides. METHODS: Myocilin was analyzed in human aqueous humor and human trabecular meshwork (HTM) tissues. COS-7 and immortalized human trabecular meshwork (iHTM) cell lines were transfected with expression vectors encoding WT MYOC, mutated, and/or epitope-tagged cDNAs. MYOC proteins were characterized by double-epitope tagging procedures and/or Western blot analysis. RESULTS: MYOC polypeptides formed highly similar oligomers in aqueous humor, HTM tissues, transfected COS-7, and iHTM cell lines. These complexes ranged in size from 116 kDa to more than 200 kDa. The smallest complex, approximately 116 kDa, resulted from dimerization between two MYOC monomers. Expression of a 150-kDa complex was strongest in aqueous humor. Cotransfections of the WT construct with either the Q368X or K423E cDNA produced MYOC(WT)/MYOC(mutant) heterodimers and higher molecular weight hetero-oligomeric complexes. WT homo-oligomeric complexes were secreted in the extracellular media of both cell lines whereas the Q368X and K423E mutant/mutant homomultimers and heteromeric WT/mutant oligomers remained sequestered intracellularly. CONCLUSIONS: Formation of heteromeric WT/mutant complexes may provide a critical mechanism by which mutant myocilin polypeptides produce autosomal dominant open-angle glaucoma. The intracellular sequestration of abnormal WT/mutant complexes could lead to the malfunction of MYOC-expressing cells and to POAG potentially involving a dominant negative effect.

TIGR is upregulated in the chronic glial scar in response to central nervous system injury and inhibits neurite outgrowth.

Reactive astrocytes respond to central nervous system (CNS) injury and disease by elaborating a glial scar that is inhibitory to axonal regeneration. To identify genes that may be involved in the astrocytic response to injury, we used differential display polymerase chain reaction and an in vivo model of the CNS glial scar. Expression of the trabecular meshwork inducible glucocorticoid response (TIGR) gene was increased in gliotic tissue compared with the uninjured cerebral cortex. Increased TIGR expression by reactive astrocytes was confirmed by in situ hybridization, quantitative reverse transcriptase-polymerase chain reaction, immunoblot analysis, and immunohistochemistry. Although mutations of the TIGR gene have been implicated in glaucoma, a function for TIGR has not been reported. Since TIGR is secreted, we assessed a possible role in inhibition of neuronal regeneration with an in vitro bioassay and found that this protein is a potent inhibitor of neurite outgrowth. Thus, TIGR is a newly identified component of the CNS glial scar that is likely to contribute to neuronal regenerative failure characteristic of the mammalian CNS.

CD14 expression by activated parenchymal microglia/macrophages and infiltrating monocytes following human traumatic brain injury.

The immune response in the central nervous system (CNS) is under tight control of regulatory mechanisms, resulting in the establishment of immune privilege. CNS injury induces an acute inflammatory reaction, composed mainly of invading leukocytes and activated microglial cells/macrophages. The generation of this robust immune response requires binding of receptors such as CD14, a pattern recognition receptor of the immune system. CD14, a surface molecule of monocytic cells, is up-regulated after monocyte stimulation and is involved in cellular activation. To examine CD14 expression in human brain lesions we investigated sections of brains obtained at autopsy from 25 cases following closed traumatic brain injury (TBI) and 5 control brains by immunohistochemistry. Detection of CD14 in controls demonstrated constitutive expression by perivascular cells, but not in parenchymal microglial cells, equivalent to known expression pattern of ED2 in rats. Following TBI, numbers of CD14(+) cells in perivascular spaces and in the brain parenchyma increased in parallel within 1-2 days, both at the lesion and in adjacent perilesional areas. The number of CD14(+) cells in perivascular spaces and in the brain parenchyma reached maximum levels within 4-8 days and remained elevated until weeks after trauma. In contrast to activated parenchymal microglia/macrophages, resting parenchymal microglial cells lacked CD14. Thus, early CD14 expression constitutes an essential part of the acute inflammatory CNS response following trauma.

In vitro localization of TIGR/MYOC in trabecular meshwork extracellular matrix and binding to fibronectin.

PURPOSE: To determine whether trabecular meshwork-inducible glucocorticoid response/myocilin (TIGR/MYOC) protein associates with the extracellular matrix (ECM) of human trabecular meshwork (HTM) cells. METHODS: The extracellular localization of TIGR/MYOC was examined by immunofluorescence microscopy in HTM cultures treated with and without dexamethasone and ascorbate and in a transformed HTM cell line, TM-1, transiently transfected with TIGR/MYOC cDNA. Antibodies to TIGR/MYOC, fibronectin, laminin, type IV collagen, or thrombospondin were used to determine the extracellular localization of TIGR/MYOC. Solid phase binding assays using 125I-recombinant TIGR/MYOC and types I and IV collagens, fibronectin, and laminin were done to examine the association of TIGR/MYOC with these proteins and to identify a specific TIGR/MYOC binding site within fibronectin. The domains of fibronectin tested were the fibrin/collagen binding domain, the RGD domain, and the Heparin II (Hep II) domain. RESULTS: TIGR/MYOC colocalized with fibronectin, laminin, and type IV collagen, but not thrombospondin in both dexamethasone and dexamethasone/ascorbate-treated HTM cultures and in TM-1 cultures transfected with TIGR/MYOC cDNA. In solid phase binding assays, 125I-TIGR/MYOC bound fibronectin but not laminin or type IV collagen. Binding to fibronectin could be competed with excess TIGR/MYOC or fibronectin. Specific binding was found for the Hep II domain of fibronectin. CONCLUSIONS: TIGR/MYOC can associate with components of the ECM via interactions with the Hep II domain of fibronectin. The interactions with the Hep II domain of fibronectin could alter cell-matrix interactions in the TM and provides an interesting lead to explore the role(s) of TIGR/MYOC in both steroid-induced and primary open angle glaucoma.