Extraction of Two-Dimensional Aluminum Alloys from Decagonal Quasicrystals.

Atomically thin metallic alloys are receiving increased attention due to their prospective applications as interconnects/contacts in two-dimensional (2D) circuits, sensors, and catalysts, among others. In this work, we demonstrate an easily scalable technique for the synthesis of 2D metallic alloys from their 3D quasicrystalline precursors. We have used aluminum (Al)-based single-phase decagonal quasicrystal Al66Co17Cu17 alloy to extract the corresponding 2D alloy structure. The 2D layered Al alloy possesses 2-fold decagonal quasicrystalline symmetry and consists of two- or three-layer-thick sheets with a lateral dimension of microns. These 2D metallic layers were combined with the atomic layers of tungsten disulfide to form the stacked heterostructures, which is demonstrated to be a stable and efficient catalyst for hydrogen evolution reaction.

Quasicrystal as a Catalyst for the Synthesis of Carbon Nanotubes.

The present report describes the catalytic activity of mechanically activated nano quasicrystalline Al65Cu20Fe15 and related nano crystalline Al50Cu28Fe22 for the synthesis of carbon nanotubes (CNTs). CNTs are synthesized by catalytic decomposition of ethanol through nano quasicrystalline Al65Cu20Fe15 and related crystalline Al50Cu28Fe22 alloys as a catalyst. The synthesized multi-walled CNTs exhibits tube diameter ranging from 5 to 25 nm. The synthesized CNTs are characterized by scanning and transmission electron microscopy. It is found that Al65Cu20Fe15 nanoquasicystal shows better catalytic behaviour as compared to nano-crystalline Al50Cu28Fe22 alloys for decomposition of ethanol during the synthesis of multi-walled CNTs.

Scaffold attachment factor B1 regulates the androgen receptor in concert with the growth inhibitory kinase MST1 and the methyltransferase EZH2.

The androgen receptor (AR) is a transcription factor that employs many diverse interactions with coregulatory proteins in normal physiology and in prostate cancer (PCa). The AR mediates cellular responses in association with chromatin complexes and kinase cascades. Here we report that the nuclear matrix protein, scaffold attachment factor B1 (SAFB1), regulates AR activity and AR levels in a manner that suggests its involvement in PCa. SAFB1 mRNA expression was lower in PCa in comparison with normal prostate tissue in a majority of publicly available RNA expression data sets. SAFB1 protein levels were also reduced with disease progression in a cohort of human PCa that included metastatic tumors. SAFB1 bound to AR and was phosphorylated by the MST1 (Hippo homolog) serine-threonine kinase, previously shown to be an AR repressor, and MST1 localization to AR-dependent promoters was inhibited by SAFB1 depletion. Knockdown of SAFB1 in androgen-dependent LNCaP PCa cells increased AR and prostate-specific antigen (PSA) levels, stimulated growth of cultured cells and subcutaneous xenografts and promoted a more aggressive phenotype, consistent with a repressive AR regulatory function. SAFB1 formed a complex with the histone methyltransferase EZH2 at AR-interacting chromatin sites in association with other polycomb repressive complex 2 (PRC2) proteins. We conclude that SAFB1 acts as a novel AR co-regulator at gene loci where signals from the MST1/Hippo and EZH2 pathways converge.

Formation of nano-quasicrystalline decagonal phase in the Al70Cu10Co5Ni15 system by high energy ball milling.

A nano decagonal quasicrystalline phase in the Al70Cu10Co5Ni15 alloy has been synthesized by mechanical alloying of a mixture of elemental powders followed by annealing. A high-energy ball milling of the elemental mixture of Al, Cu, Co and Ni leads to the formation of B2 type quaternary intermetallic alloys. The X-ray diffraction and transmission electron microscopy techniques have been employed for characterization of the samples. It was observed that the dissolution of the individual elements into an alloy led to the formation of a nano B2 phase. This phase was found to be quite stable against milling and no other crystalline or amorphous phases could be detected. Milled powder after annealing at 700 degrees C for 60 h was found to transform to nano-decagonal phase. Attempts have been made to understand the evolution of the complex intermetallic nano phases and their relative stability during milling.

Synthesis of nanocrystalline (Co, Ni)Al2O4 spinel powder by mechanical milling of quasicrystalline materials.

In the present study, attempts have been made to synthesize the nano-crystalline (Co, Ni)Al2O4 spinel powders by ball milling and subsequent annealing. An alloy of Al70Co15Ni15, exhibiting the formation of a complex intermetallic compound known as decagonal quasicrystal is selected as the starting material for mechanical milling. It is interesting to note that this alloy is close to the stoichiometry of aluminum and transition metal atoms required to form the aluminate spinel. The milling was carried out in an attritor mill at 400 rpm for 40 hours with ball to powder ratio of 20 : 1 in hexane medium. Subsequent to this annealing was performed in an air ambience for 10, 20, and 40 h at 600 degrees C in side the furnace in order to oxidize the decagonal phase and finally to form the spinel structure. The X-ray diffraction (XRD) and transmission electron microscopy (TEM) confirmed the formation of nano-sized decagonal phase after milling and then (Co, Ni)Al2O4 spinel type phase after annealing. The XRD studies reveal the lattice parameter to be 8.075 angstroms and the lattice strain as 0.6%. The XRD and TEM explorations of spinel phase indicate the average grain size to be approximately 40 nm.

A symmetrical indexing scheme for decagonal quasicrystals analogous to Miller-Bravais indexing of hexagonal crystals.

The problems of redundancy and superfluous indices in indexing the planes and axes in a decagonal quasicrystal are considered, using a scheme of five coplanar vectors in the quasiperiodic plane and one perpendicular vector. Of all the indexing schemes in use, this scheme offers the maximum advantage. An analogy is drawn to the hexagonal system using Miller-Bravais indices. Based on this, a symmetry-based indexing system for decagonal phases is devised that follows a simplified approximate zone law analogous to the exact zone law for the hexagonal case. The indices based on this scheme will be designated as ;Frank indices'. High-symmetry electron diffraction zone-axis patterns as well as powder X-ray diffraction patterns are indexed using Frank indices and compared with those of other indexing schemes.

Histone deacetylation is directly involved in desilencing the expression of the catalytic subunit of telomerase in normal lung fibroblast.

The regulation of telomerase expression in normal cells is poorly understood. Moreover, the molecular mechanism underlying tumor-specific expression of telomerase remains unclear. We investigated the link between histone deacetylation and telomerase activity in normal lung and lung tumor cells. Four non-small-cell lung cancer (NSCLC) lines and one normal lung fibroblast line were tested for telomerase activity with or without Trichostatin A(TSA). The telomerase activity and the expression of telomerase associated components were determined by TRAP assay, RT-PCR analysis and Western blot analysis. All 4 NSCLC cell lines exposed to 1 microM TSA for 24 h had no change in telomerase activity or hTERT mRNA level. Telomerase activity was very low in normal lung fibroblasts (mrc-9) until exposed to 1 microM TSA for 24 h, at which time telomerase activity was readily detectable, with concomitant upregulation of hTERT mRNA (10-fold). The level of other telomerase associated components (hTER and TP1) were unaltered. Furthermore, 1 microM TSA exposure for 24 h did not alter the level of c-Myc or p21 mRNA. Immunodetection reveled that hTERT protein expression increased (approximately 6 fold) compared to c-Myc, p21, or gelsolin. The effect of TSA on hTERT expression is independent of DNA methylation as judged by 5-azacytidine (5aza) treatment. TSA effect on mrc-9 cells is unaltered even in the presence of 200 microg/ml cyclohexamide, suggesting a direct inhibition of histone deacetylation. Collectively, our study indicates that inhibition of histone deacetylation selectively regulates the transcriptional derepression of telomerase catalytic subunit in normal lung fibroblast cells compared to lung tumor cells.

Least path criterion (LPC) for unique indexing in a two-dimensional decagonal quasilattice.

The least path criterion or least path length in the context of redundant basis vector systems is discussed and a mathematical proof is presented of the uniqueness of indices obtained by applying the least path criterion. Though the method has greater generality, this paper concentrates on the two-dimensional decagonal lattice. The order of redundancy is also discussed; this will help eventually to correlate with other redundant but desirable indexing sets.

Brain armadillo protein delta-catenin interacts with Abl tyrosine kinase and modulates cellular morphogenesis in response to growth factors.

delta-Catenin associates with adhesive junctions and facilitates cellular morphogenesis (Lu et al., 1999). Here we show that delta-catenin colocalizes with actin filaments and Abl tyrosine kinase in the growth cones of cultured hippocampal neurons. PC12 cells induced to express delta-catenin show accelerated neurite extension upon nerve growth factor (NGF) stimulation. STI571, an Abl family kinase inhibitor, further accentuates these stimulatory effects. delta-Catenin is a potent substrate for Abl in vitro using an immunocomplex assay and most of the Abl-induced tyrosine phosphorylation within cells is present in the N-terminus of delta-catenin. When delta-catenin-expressing epithelial cells are induced to scatter in response to hepatocyte growth factor (HGF), STI571 leads to the rapid redistribution of delta-catenin and changes in cellular morphology. We suggest that delta-catenin is a possible Abl substrate and acts downstream of Abl to orchestrate actin-based cellular morphogenesis.

Tyrosine phosphorylation of the proto-oncoprotein Raf-1 is regulated by Raf-1 itself and the phosphatase Cdc25A.

There is a growing body of evidence demonstrating that Raf-1 is phosphorylated on tyrosines upon stimulation of a variety of receptors. Although detection of Raf-1 tyrosine phosphorylation has remained elusive, genetic analyses have demonstrated it to be important for Raf-1 activation. Here we report new findings which indicate that Raf-1 tyrosine phosphorylation is regulated in vivo. In both a mammalian and baculovirus expression system, a kinase-inactive allele of Raf-1 was found to be tyrosine phosphorylated at levels much greater than that of wild-type Raf-1. The level of tyrosine phosphate on Raf-1 was markedly increased upon treatment with phosphatase inhibitors either before or after cell lysis. Cdc25A was found to dephosphorylate Raf-1 on tyrosines that resulted in a significant decrease in Raf-1 kinase activity. In NIH 3T3 cells, coexpression of wild-type Raf-1 and phosphatase-inactive Cdc25A led to a marked increase in Raf-1 tyrosine phosphorylation in response to platelet-derived growth factor. These data suggest that the tyrosine phosphorylation of Raf-1 is regulated not only by itself but also by Cdc25A.

The cytokine-activated tyrosine kinase JAK2 activates Raf-1 in a p21ras-dependent manner.

JAK2, a member of the Janus kinase superfamily was found to interact functionally with Raf-1, a central component of the ras/mitogen-activated protein kinase signal transduction pathway. Interferon-gamma and several other cytokines that are known to activate JAK2 kinase were also found to stimulate Raf-1 kinase activity toward MEK-1 in mammalian cells. In the baculovirus coexpression system, Raf-1 was activated by JAK2 in the presence of p21ras. Under these conditions, a ternary complex of p21ras, JAK2, and Raf-1 was observed. In contrast, in the absence of p21ras, coexpression of JAK2 and Raf-1 resulted in an overall decrease in the Raf-1 kinase activity. In addition, JAK2 phosphorylated Raf-1 at sites different from those phosphorylated by pp60v-src. In mammalian cells treated with either erythropoietin or interferon-gamma, a small fraction of Raf-1 coimmunoprecipitated with JAK2 in lysates of cells in which JAK2 was activated as judged by its state of tyrosine phosphorylation. Taken together, these data suggest that JAK2 and p21ras cooperate to activate Raf-1.

An array of insulin-activated, proline-directed serine/threonine protein kinases phosphorylate the p70 S6 kinase.

This study characterizes the insulin-activated serine/threonine protein kinases in H4 hepatoma cells active on a 37-residue synthetic peptide (called the SKAIPS peptide) corresponding to a putative autoinhibitory domain in the carboxyl-terminal tail of the p70 S6 kinase as well as on recombinant p70 S6 kinase. Three peaks of insulin-stimulated protein kinase active on both these substrates are identified as two (possibly three) isoforms of the 40-45-kDa erk/microtubule-associated protein (MAP)-2 kinase family and a 150-kDa form of cdc2. Although distinguishable in their substrate specificity, these protein kinases together with the p54 MAP-2 kinase share a major common specificity determinant reflected in the SKAIPS peptide: the requirement for a proline residue immediately carboxyl-terminal to the site of Ser/Thr phosphorylation. In addition, however, at least one peak of insulin-stimulated protein kinase active on recombinant p70, but not on the SKAIPS peptide, is present although not yet identified. MFP/cdc2 phosphorylates both rat liver p70 S6 kinase and recombinant p70 S6 kinase exclusively at a set of Ser/Thr residues within the putative autoinhibitory (SKAIPS peptide) domain. erk/MAP kinase does not phosphorylate rat liver p70 S6 kinase, but readily phosphorylates recombinant p70 S6 kinase at sites both within and in addition to those encompassed by the SKAIPS peptide sequences. Although the tryptic 32P-peptides bearing the cdc2 and erk/MAP kinase phosphorylation sites co-migrate with a subset of the sites phosphorylated in situ in insulin-stimulated cells, phosphorylation of the p70 S6 kinase by these proline-directed protein kinases in vitro does not reproducibly activate p70 S6 kinase activity. Thus, one or more erk/MAP kinases and cdc2 are likely to participate in the insulin-induced phosphorylation of the p70 S6 kinase. In addition to these kinases, however, phosphorylation of the p70 S6 kinase by other as yet unidentified protein kinases is necessary to recapitulate the multisite phosphorylation required for activation of the p70 S6 kinase.

Insulin-activated protein kinases phosphorylate a pseudosubstrate synthetic peptide inhibitor of the p70 S6 kinase.

p70 S6 kinase, a major insulin-mitogen-activated ribosomal S6 protein kinase in mammalian cells, is activated by phosphorylation of multiple Ser/Thr residues on the enzyme polypeptide. A synthetic peptide, corresponding to a 37-residue segment from the carboxyl-terminal tail of the kinase which resembles the sequence phosphorylated in S6, acts as a competitive inhibitor of p70 S6 kinase without itself being phosphorylated by the enzyme. This synthetic peptide is phosphorylated by an array of protein kinases which are rapidly activated by insulin. Thus, these sequences of p70 S6 kinase constitute a potential autoinhibitory pseudosubstrate site, whose phosphorylation is catalyzed by candidate upstream-activating protein kinases.

Characterization of a phosphomonoesterase from Brucella abortus.

Brucellae are facultative intracellular bacterial pathogens that reside primarily in cells of the reticuloendothelial system. The high-speed supernatant obtained after centrifuging a suspension of Brucella abortus that had been frozen-thawed and sonicated contained abundant phosphomonoesterase activity, determined by using 4-methylumbelliferylphosphate as the substrate; this enzyme was purified 2,900-fold (yield, 570%) by chromatography on DE-52 cellulose and hydroxylapatite columns and high-performance liquid chromatography-gel filtration. The native enzyme had a molecular mass of 120,000 daltons (+/- 10,000 daltons), as determined by gel filtration chromatography, and resolved into two bands (60,000 and 66,000 daltons) when subjected to polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate. The B. abortus phosphomonoesterase had the following properties: pH optimum, 6.0 to 6.5; isoelectric point, 3.0; substrate specificity, 5'-AMP greater than 3'-AMP greater than 3'-GMP greater than 5'-GDP greater than 5'-CDP greater than 5'-CTP greater than 5'-UPT greater than phosphotyrosine greater than phosphoserine greater than phosphothreonine. The Km for 5'-AMP was 0.37 mM. Phosphatidylinositol 4,5-bisphosphate and myo-inositol 1,3,4-trisphosphate were poor substrates for the B. abortus enzyme. The phosphomonoesterase did not inhibit superoxide anion production by human neutrophils stimulated with formyl-methionyl-leucyl-phenylalanine. The phosphomonoesterase may be one of the bacterial enzymes in the pathway leading to the production of adenine, which is secreted by B. abortus and blocks the activation of neutrophils.

Heparin binds to Leishmania donovani promastigotes and inhibits protein phosphorylation.

We show that promastigotes of Leishmania donovani, the causative agent of visceral leishmaniasis (kala-azar), possess heparin receptors on their surface. From a linear Scatchard plot of the binding data obtained using [3H]heparin and viable promastigotes, one derives a binding constant of 4.7 x 10(-7) M and an estimate of 860,000 receptors per parasite. The [3H]heparin bound to parasites could not be displaced by hyaluronic acid or by three other glycosaminoglycans (dermatan sulphate, chondroitin 4-sulphate and chondroitin 6-sulphate). It was demonstrated that exponential phase promastigotes growing in medium 199 supplemented with fetal bovine serum incorporate 35SO4 into a cell-associated macromolecule that has the properties of heparin proteoglycan. Heparin inhibits the activity of the cell-surface histone-protein kinase; incubation of viable promastigotes with [gamma-32P]ATP and MgCl2 (10 mM) in the absence and presence of heparin (0.01-0.5 mg/ml) for 10 min, followed by analysis by SDS/polyacrylamide-gel electrophoresis and autoradiography, revealed that the phosphorylation of 12 or 13 parasite proteins was inhibited by the glycosaminoglycan. These data suggest that heparin may play a role in the host-parasite relationship.

Legionella micdadei protein kinase catalyzes phosphorylation of tubulin and phosphatidylinositol.

Legionella micdadei, a pathogen which enters into host phagocyte phagolysosomal structures, contains at least two protein kinases. We have purified to homogeneity the predominant, nucleotide-independent protein kinase and examined its ability to catalyze the transfer of phosphate from ATP to acceptors in human neutrophils. The L. micdadei protein kinase catalyzed the phosphorylation of proteins of 11.5, 14, 19, 23, 28, 34, and 38 kilodaltons (kDa) present in a Triton X-100 extract of neutrophil membranes and of 11.5, 13.5, 25, and 38 kDa in the neutrophil cytosol. Tubulin was a good substrate for the L. micdadei protein kinase in vitro. The bacterial kinase also catalyzed the phosphorylation of phosphatidylinositol (PI) at about half the rate at which histones were phosphorylated; phosphatidylinositol-4-phosphate (PIP) was not phosphorylated by the kinase. The PI kinase activity of the L. micdadei enzyme was optimum at pH 7.0, and the divalent cation requirement was satisfied best by Mg2+ and Ca2+. The maximum rate of PI phosphorylation was obtained with 0.6 mM PI; in the presence of MgCl2 (10 mM), the Km for PI was 0.9 mM and the Km for ATP was 1.5 mM. The detergents octyl-beta-D-glucoside (10 to 20 mM) and Triton X-100 (0.5%) stimulated kinase activity twofold when PI was the phosphate acceptor; however, only octyl glucoside stimulated histone kinase activity. Various membrane phospholipids inhibited PI kinase activity. The most potent phospholipid inhibitor was the product of the PI kinase reaction, PIP, which at a 0.6 mM concentration inhibited both PI and tubulin phosphorylation by 80%. The inhibition of kinase activity by PIP when histone served as the acceptor was noncompetitive in character. The L. micdadei kinase also phosphorylated PI in intact. (3H)inositol-labeled neutrophils. The PI kinase and histone kinase activities of teh L. micdadei kinase copurified and cofucused (pI, 5.8) when subjected to isoelectric focusing, suggesting that the two enzymatic activities reside in a single protein.

Inhibition of neutrophil and natural killer cell function by human seminal fluid acid phosphatase.

The major acid phosphatase of human seminal fluid was purified to homogeneity by chromatography on Sephadex G-150, and DEAE-Sephadex, and by isoelectric focusing (pI, 4.3). This purified preparation of seminal fluid acid phosphatase blocked superoxide anion production by neutrophils stimulated with fMet-Leu-Phe (fMLP) by 50%. The phosphatase also hydrolysed myo-inositol 1,4,5-trisphosphate (IP3) in vitro, an intracellular second messenger which releases Ca2+ from intracellular pools, at nearly one-third the rate at which the nonphysiologic substrate 4-methylumbelliferylphosphate (MUP) was cleaved. In contrast, two phosphoinositide lipids, namely phosphatidylinositol 4,5-bisphosphate and phosphatidylinositol 4-monophosphate, were poor phosphatase substrates. Following fMLP stimulation of [3H]inositol-labeled neutrophils, the quantity of IP3 produced by phosphatase-treated cells was reduced by 69%. These results indicate that the human seminal fluid acid phosphatase may compromise the neutrophil's microbicidal response to the organism by hydrolyzing a second messenger (IP3) which is directly involved in the regulation of intracellular Ca2+ concentrations. The seminal fluid phosphatase also inhibited by 85% the ability of murine natural killer (NK) cells to inactivate target cells.

Comparison of the protein kinase and acid phosphatase activities of five species of Leishmania.

Promastigotes from log phase and stationary phase cultures of Leishmania donovani, L. braziliensis panamensis, L. tropica, L. major, and L. mexicana amazonensis were analyzed for their content of protein kinase and acid phosphatase activities. Cell surface, histone-specific protein kinase activity was 1.3- to 2.8-fold higher in stationary phase cells of all species except for L. tropica in which the activities of stationary and log phase cells were equal; L. mexicana amazonensis had the highest histone-specific protein kinase activity and L. donovani the lowest. When viable, motile promastigotes of all five species were incubated for 10 min with [gamma-32P]ATP and Mg2+ (10 mM) in the absence of exogenous histone acceptor; about one dozen proteins were phosphorylated in each case. Both log phase and stationary phase promastigotes of all five species extensively phosphorylated a 50-kDa protein that had the mobility of tubulin. Incubation of pure calf brain tubulin with [gamma-32P]ATP and purified L. donovani protein kinase resulted in extensive phosphorylation of the former. Highly infective metacyclic forms (PNA-) of L. major, isolated from a stationary culture using the peanut agglutinin (PNA), contained eight times more histone-specific protein kinase activity than noninfective log phase cells (PNA+). The PNA- and PNA+ forms of L. major both phosphorylated a 50-kDa protein when incubated with [gamma-32P]ATP and magnesium or manganese ions (10 mM); the 50-kDa protein was precipitated by anti-tubulin rabbit antibodies. Extracts of all five species contained large amounts of acid phosphatase activity.(ABSTRACT TRUNCATED AT 250 WORDS)

Genetic analysis fo the mycobacillin biosynthetic pathway in Bacillus subtilis B3.

Twelve mycobacillin-negative (My-) mutants of Bacillus subtilis B3 were isolated from an auxotrophically tagged mycobacillin producer organism. In whole-cell fermentations of some of these My- mutants a penta- and a nonapeptide accumulated; these peptides were also obtained in a cell-free system in which a new tripeptide was also detected. The amino acid composition, N- and C-terminal residues and amino acid sequence of these peptides agreed with those of equivalent segments of the mycobacillin molecule. The mycobacillin-synthesizing enzyme can be divided into three fractions that catalyse different steps in biosynthesis, and the defective enzyme fractions in the various mutant strains were identified by reconstitution experiments in vitro. The defects were further pin-pointed in mutant enzyme fractions by an ATP in equilibrium Pi exchange reaction and also by cell-free synthesis involving the use of membrane-bound enzyme. The defects so identified indicated the formation of tri-, penta- and nonapeptides as intermediates in the mycobacillin biosynthetic pathway.