Copper isotope evidence for sulfide fractionation and lower crustal foundering in making continental crust

The continental crust is strongly depleted in copper compared with its building blocks-primary arc magmas-and this depletion is intrinsically associated with continental crust formation. However, the process by which Cu removal occurs remains enigmatic. Here we show, using Cu isotopes, that subduction-zone processes and mantle melting produce limited fractionation of Cu isotopes in arc magmas, and, instead, the heterogeneous Cu isotopic compositions of lower crustal rocks, which negatively correlate with Cu contents, suggest segregation or accumulation of isotopically light sulfides during intracrustal differentiation of arc magmas. This is supported by the extremely light Cu isotopic compositions of lower crustal mafic cumulates and heavy Cu isotopic compositions of differentiated magmas in thick continental arcs. Intracrustal differentiation of mantle-derived magmas and subsequent foundering of sulfide-rich mafic cumulates preferentially removes isotopically light Cu, leaving a Cu-depleted and isotopically heavy continental crust.

Tapped-inductor bi-directional Cuk converter with high step-up/down conversion ratio and its optimum design

A bidirectional DC–DC converter is required for an energy storage system. High efficiency and a high step-up and step-down conversion ratio are the development trends. In this research, a series of bidirectional high-gain Cuk circuits was derived by combining tapped inductors and bidirectional Cuk. After analyzing and comparing the characteristics of each circuit, a bidirectional high-gain Cuk circuit with a tapped-inductor (reverse coupling) was proposed. The proposed converter has a simple structure and a high voltage gain in both the step-down (Buck) and step-up (Boost) operation modes. The voltage stress of S₂ was low. The voltage stress of S₁ was high, however, and this is a disadvantage of the proposed converter. The proposed circuit’s characteristics were thoroughly examined, including the voltage gain characteristics and the design of the main parameters. We established a power loss model of the new topology, and the tapped-inductor turn ratio was optimized for high efficiency. Finally, a 400 W experimental implementation of the converter was shown to achieve efficiencies of 93.5% and 92.4% in the step-up and step-down modes, respectively. These findings verified the validity of the proposed circuit’s theoretical analysis.

Influence of chitosan nanoparticle-mediated C-erbB-2 gene silencing on invasion and apoptosis of Hep-2 cells

We aimed to measure the invasion ability of Hep-2 laryngeal cancer cells after treatment with C-erbB-2-small interfering RNA (siRNA)-chitosan nanoparticles, and assess the applied value of chitosan nanoparticle-mediated C-erbB-2 interference in inhibiting laryngeal cancer invasion and metastasis. Nanoparticles of approximately 100 nm, comprising C-erbB-2 siRNA packaged with chitosan, were prepared and used to treat Hep-2 cells. Silencing of C-erbB-2 was detected by western blot and polymerase chain reaction. Cell invasion and apoptosis were estimated by transwell assay and flow cytometry, respectively. C-erbB-2-siRNA-chitosan nanoparticles significantly down-regulated C-erbB-2 expression in Hep-2 cells (P < 0.05), and cell invasion was noticeably decreased. Moreover, they significantly induced apoptosis of the Hep-2 cells (P < 0.05). Chitosan nanoparticle-mediated C-erbB-2 gene interference can inhibit the invasion of laryngeal cancer cells and induce their apoptosis.

Laser-ablation production of graphene oxide nanostructures: from ribbons to quantum dots

A new one-step method for the preparation of graphene oxide (GO) nanostructures has been developed by pulsed laser ablation in GO solution. The formation of different shapes of GO nanostructures, such as ribbons, nanoflakes (including nano-squares, nano-rectangles, nano-triangles, nano-hexagons, and nano-disks) and quantum dots, has been demonstrated by scanning electron microscopy and transmission electron microscopy. Photoreduction for the GO occurred during irradiation by the pulsed laser. The GO quantum dots exhibit a blue photoluminescence, originating from recombination of the localized carriers in the zigzag-edge states.

Phage display-selected sequences of the heavy-chain CDR3 loop of the anti-digoxin antibody 26-10 define a high affinity binding site for position 16-substituted analogs of digoxin

The heavy-chain CDR3 region of the high affinity (K(a) = 1.3 x 10(10) M(-)1) anti-digoxin monoclonal antibody 26-10 was modified previously to shift its specificity, by substitution of tryptophan 100 by arginine, toward binding analogs of digoxin containing substitutions at position 16. To further change specificity, two 5-mer libraries of the randomly mutagenized phage-displayed 26-10 HCDR3 region (positions 94-98) were panned against digoxin-bovine serum albumin (BSA) as well as against 16-acetylgitoxin-BSA. When a mutant Fab that binds 16-substituted analogs preferentially was used as a parent sequence, clones were obtained with affinities for digoxin increased 2-4-fold, by panning on digoxin-BSA yet retaining the specificity shift. Selection on 16-acetylgitoxin-BSA, however, resulted in nine clones that bound gitoxin (16-OH) up to 150-fold higher than the wild-type 26-10, due to a consensus mutation of Ser(H95) to Gly(H95). The residues at both position H95 (serine) and position H100 (tryptophan) contact hapten in the crystal structure of the Fab 26-10-digoxin complex. Thus, by mutating hapten contact residues, it is possible to reorder the combining site of a high affinity antibody, resulting in altered specificity, yet retain or substantially increase the relative affinity for the cross-reactive ligand.

Genomic organization of the human leukocyte immunoglobulin-like receptors within the leukocyte receptor complex on chromosome 19q13.4

The leukocyte immunoglobulin (Ig)-like receptors (LIRs) comprise a family of cell surface receptors that couple to either activating or inhibitory signals depending on the nature of their transmembrane and cytoplasmic domains. We describe the organization and fine localization of the genes for LIR-1 and LIR-5, which are inhibitory receptors, and LIR-6, which is an activating receptor. The genomic organization of all three genes is highly conserved from the signal peptide through the membrane-proximal Ig domain but diverges thereafter depending on the inhibitory or activating nature of the gene product. The 3' untranslated region of the gene for LIR-6 contains a 37-base pair repeat not present in the LIR-1 or LIR-5 genes. 5' rapid amplification of cDNA ends defined the putative transcription initiation site of the LIR-5 gene, which is TATA-less. A nucleotide substitution in the LIR-5 gene led to loss of an intron present in the 5' untranslated region of the LIR-1 and LIR-6 genes. Differences in the genomic structure of these three LIR genes suggests possible mechanisms for their differential expression in cells of hematopoietic lineage. The three genes are in a region of Chromosome 19q13.4 that is immediately centromeric of the killer cell Ig-like receptor genes and are separated from one another by approximately 20 to 30 kb, suggesting that they arose by gene duplication from a common ancestor.

Discrimination between sialic acid-containing receptors and pseudoreceptors regulates polyomavirus spread in the mouse

Variations in the polyomavirus major capsid protein VP1 underlie important biological differences between highly pathogenic large-plaque and relatively nonpathogenic small-plaque strains. These polymorphisms constitute major determinants of virus spread in mice and also dictate previously recognized strain differences in sialyloligosaccharide binding. X-ray crystallographic studies have shown that these determinants affect binding to the sialic acids. Here we report results of further experiments designed to test the importance of specific contacts between VP1 and the carbohydrate moieties of the receptor. With minor exceptions, substitutions at positions predicted from crystallography to be important in binding the terminal alpha-2,3-linked sialic acid or the penultimate sugar (galactose) destroyed the ability of the virus to replicate in cell culture. Substitutions that prevented binding to a branched disialyloligosaccharide were found to result in viruses that were both viable in culture and tumorigenic in the mouse. Conversely, substitutions that allowed recognition and binding of the branched carbohydrate chain inhibited spread in the mouse, though the viruses remained viable in culture. Mice of five different inbred strains, all highly susceptible to large-plaque virus, showed resistance to the spread of polyomavirus strains bearing the VP1 type which binds the branched-chain receptor. We suggest that glycoproteins bearing the appropriate O-linked branched sialyloligosaccharide chains are effective pseudoreceptors in the host and that they block the spread of potentially tumorigenic or virulent virus strains.

Characterization of the murine mitochondrial glycerol-3-phosphate acyltransferase promoter

Glycerol-3-phosphate acyltransferase (GPAT) catalyzes the acylation of sn-glycerol 3-phosphate to form 1-acyl-sn-glycerol 3-phosphate, a committed step in triacylglycerol and phospholipid biosynthesis. We have previously reported the cDNA cloning and transcriptional regulation of the murine mitochondrial GPAT (mGPAT). We now report the cloning of the 5'-flanking region of the murine mitochondrial GPAT. The transcription start site was identified by primer extension and RNase protection assays. A TATA box-like motif (TTATTAT) was located between -34 and -29 and a reverse CCAAT box (ATTGG) was located between -78 and -74, relative to the transcription start site. To begin studying mechanisms underlying transcriptional regulation of the mGPAT gene, chimeric luciferase (LUC) plasmids containing serial deletions, from -1447 to -38, of the 5'-flanking region of the murine mGPAT gene were prepared and transfected into 3T3-L1 cells. The fusion construct -1447 GPAT.LUC showed high promoter activity and deletions to -1353, -747, -322, and -86 did not markedly change the promoter activity. With all constructs, luciferase activity was 2-fold higher when plasmids were transfected into 3T3-L1 adipocytes. However, deletion of sequences between -86 and -55 resulted in a 9-fold decrease in LUC activity in both preadipocytes and adipocytes. Deletion of sequences between -55 and -38 did not alter promoter activity. DNase I footprint analysis revealed a protected region between -95 and -65 which included the putative CTF/NF1 binding site. Electrophoretic mobility shift assays demonstrated a single protein-DNA complex formation. Oligonucleotides synthesized according to the CTF/NF1 consensus sequence or the adenovirus NF-1 site showed a different and more complex pattern of protein-DNA interaction and were not able to compete away the mGPAT promoter-protein complex, indicating that a distinct protein was bound to -86/-55, a region important for the basal promoter activity in 3T3-L1 cells. Luciferase activity was increased 2.8- and 8-fold when adipocytes stably transfected with -322 GPAT.LUC were treated with 5 and 25 mM glucose, respectively, in the presence of 10 nM insulin. These results indicate that carbohydrate-responsive sequences are located within -322 base pairs of the mGPAT promoter.