Reticular synthesis and the design of new materials

The long-standing challenge of designing and constructing new crystalline solid-state materials from molecular building blocks is just beginning to be addressed with success. A conceptual approach that requires the use of secondary building units to direct the assembly of ordered frameworks epitomizes this process: we call this approach reticular synthesis. This chemistry has yielded materials designed to have predetermined structures, compositions and properties. In particular, highly porous frameworks held together by strong metal-oxygen-carbon bonds and with exceptionally large surface area and capacity for gas storage have been prepared and their pore metrics systematically varied and functionalized.     

REE geochemistry of suspended sediments from the rivers around the Yellow Sea and provenance indicators

Rare earth element (REE) compositions of the suspended sediments from the rivers around the Yellow Sea were different in that Korean river sediments (Han, Keum and Yeongsan Rivers) yield stronger fractionations than Chinese river sediments (Changjiang, Huanghe and Yalujiang), shown by obvious enrichments of LREE (light rare earth element) relative to UCC (upper continental crust).Variations of source rock compositions in the drainage basins are responsible for the differences of REE compositions between the river sediments. REE fractionation parameters including (La/Yb)ucc and (Gd/Yb)ucc as well as the ratios of La/Sc and Th/Sc can be treated as proper proxies for identifying the Chinese river sediments from those Korean river matters, and furthermore, for studying the provenances and paleoenvironmental changes of the marginal seas of China.     

A class of compact dwarf galaxies from disruptive processes in galaxy clusters

Dwarf galaxies have attracted increased attention in recent years, because of their susceptibility to galaxy transformation processes within rich galaxy clusters. Direct evidence for these processes, however, has been difficult to obtain, with a small number of diffuse light trails and intra-cluster stars being the only signs of galaxy disruption. Furthermore, our current knowledge of dwarf galaxy populations may be very incomplete, because traditional galaxy surveys are insensitive to extremely diffuse or compact galaxies. Aware of these concerns, we recently undertook an all-object survey of the Fornax galaxy cluster. This revealed a new population of compact members, overlooked in previous conventional surveys. Here we demonstrate that these 'ultra-compact' dwarf galaxies are structurally and dynamically distinct from both globular star clusters and known types of dwarf galaxy, and thus represent a new class of dwarf galaxy. Our data are consistent with the interpretation that these are the remnant nuclei of disrupted dwarf galaxies, making them an easily observed tracer of galaxy disruption.     

The voltage dependence of NADPH oxidase reveals why phagocytes need proton channels

The enzyme NADPH oxidase in phagocytes is important in the body's defence against microbes: it produces superoxide anions (O2-, precursors to bactericidal reactive oxygen species). Electrons move from intracellular NADPH, across a chain comprising FAD (flavin adenine dinucleotide) and two haems, to reduce extracellular O2 to O2-. NADPH oxidase is electrogenic, generating electron current (I(e)) that is measurable under voltage-clamp conditions. Here we report the complete current-voltage relationship of NADPH oxidase, the first such measurement of a plasma membrane electron transporter. We find that I(e) is voltage-independent from -100 mV to >0 mV, but is steeply inhibited by further depolarization, and is abolished at about +190 mV. It was proposed that H+ efflux mediated by voltage-gated proton channels compensates I(e), because Zn2+ and Cd2+ inhibit both H+ currents and O2- production. Here we show that COS-7 cells transfected with four NADPH oxidase components, but lacking H+ channels, produce O2- in the presence of Zn2+ concentrations that inhibit O2- production in neutrophils and eosinophils. Zn2+ does not inhibit NADPH oxidase directly, but through effects on H+ channels. H+ channels optimize NADPH oxidase function by preventing membrane depolarization to inhibitory voltages.     

Experimental demonstration of a robust,high-fidelity geometric two ion-qubit phase gate

Universal logic gates for two quantum bits (qubits) form an essential ingredient of quantum computation. Dynamical gates have been proposed in the context of trapped ions; however, geometric phase gates (which change only the phase of the physical qubits) offer potential practical advantages because they have higher intrinsic resistance to certain small errors and might enable faster gate implementation. Here we demonstrate a universal geometric pi-phase gate between two beryllium ion-qubits, based on coherent displacements induced by an optical dipole force. The displacements depend on the internal atomic states; the motional state of the ions is unimportant provided that they remain in the regime in which the force can be considered constant over the extent of each ion's wave packet. By combining the gate with single-qubit rotations, we have prepared ions in an entangled Bell state with 97% fidelity-about six times better than in a previous experiment demonstrating a universal gate between two ion-qubits. The particular properties of the gate make it attractive for a multiplexed trap architecture that would enable scaling to large numbers of ion-qubits.     

Nitric oxide can inhibit apoptosis or switch it into necrosis

Nitric oxide (NO) and its related molecules are important messengers that play central roles in pathophysiology. Redox modulation of thiol groups on protein cysteine residues by S-nitrosylation can modulate protein function. NO has emerged as a potent regulator of apoptosis in many cell types, either preventing cell death or driving an apoptotic response into a necrotic one. NO protects neuroblastoma cells from retinoid- and cisplatin-induced apoptosis, without significantly increasing necrotic cell damage. Nitrosylation of thiol groups of several critical factors may be important for cell survival. Indeed, S-nitrosylation of the active-site cysteine residue of apoptotic molecules, such as caspases and tissue transglutaminase, results in the inhibition of their catalytic activities and has important implications for the regulation of apoptosis by NO. On the other hand, NO is able to shift the anti-CD95- and ceramide-triggered apoptotic response of Jurkat T cells into necrotic cell death. In these apoptotic models, NO is therefore unable to solely inhibit cell death, indicating that it may act below the point of no return elicited by CD95-ligation and ceramide stimulation.     

The structure and function of initiation factors in eukaryotic protein synthesis

Protein synthesis is one of the most complex cellular processes, involving numerous translation components that interact in multiple sequential steps. The most complex stage in protein synthesis is the initiation process. It involves initiation factor-mediated assembly of a 40S ribosomal subunit and initiator tRNA into a 48S initiation complex at the initiation codon of an mRNA and subsequent joining of a 60S ribosomal subunit to form a translationally active 80S ribosome. The basal set of factors required for translation initiation has been determined, and biochemical, genetic, and structural studies are now beginning to reveal details of their individual functions in this process. The mechanism of translation initiation has also been found to be influenced significantly by structural properties of the 5' and 3' termini of individual mRNAs. This review describes some of the major developments in elucidating molecular details of the mechanism of initiation that have occurred over the last decade.