Uptake, translocation and transformation of arsenate and arsenite in sunflower (Helianthus annuus):formation of arsenic-phytochelatin complexes during exposure to high arsenic concentrations

The aim of the study was to determine the time-dependent formation of arsenic-phytochelatin (As-PC) complexes in the roots, stems and leaves of an arsenic-nontolerant plant (Helianthus annuus) during exposure to 66 mol l(-1) arsenite (As(III)) or arsenate (As(V)). We used our previously developed method of simultaneous element-specific (inductively coupled plasma mass spectrometry, ICP-MS) and molecular-specific (electrospray-ionization mass spectrometry, ES-MS) detection systems interfaced with a suitable chromatographic column and eluent conditions, which enabled us to identify and quantify As-PC complexes directly. Roots of As-exposed H. annuus contained up to 14 different arsenic species, including the complex of arsenite with two (gamma-Glu-Cys)(2)-Gly molecules [As((III))-(PC(2))(2)], the newly identified monomethylarsonic phytochelatin-2 or (gamma-Glu-Cys)(2)-Gly CH(3)As (MA((III))-PC(2)) and at least eight not yet identified species. The complex of arsenite with (gamma-Glu-Cys)(3)-Gly (As((III))-PC(3)) and the complex of arsenite with glutathione (GSH) and (gamma-Glu-Cys)(2)-Gly (GS-As((III))-PC(2)) were present in all samples (roots, stems and leaves) taken from plants exposed to As. The GS-As((III))-PC(2) complex was the dominant complex after 1 h of exposure. As((III))-PC(3) became the predominant As-PC complex after 3 h, binding up to 40% of the As present in the exposed plants. No As-PC complexes were found in sap (mainly xylem sap from the root system), in contrast to roots, stems and leaves, which is unequivocal evidence that As-PC complexes are not involved in the translocation of As from root to leaves of H. annuus.

Conformational Change of Mitochondrial Complex I Increases ROS Sensitivity During Ischemia

Aims: Myocardial ischemia/reperfusion (I/R) is associated with mitochondrial dysfunction and subsequent cardiomyocyte death. The generation of excessive quantities of reactive oxygen species (ROS) and resultant damage to mitochondrial enzymes is considered an important mechanism underlying reperfusion injury. Mitochondrial complex I can exist in two interconvertible states: active (A) and deactive or dormant (D). We have studied the active/deactive (A/D) equilibrium in several tissues under ischemic conditions in vivo and investigated the sensitivity of both forms of the heart enzyme to ROS.

Results: We found that in the heart, t½ of complex I deactivation during ischemia was 10?min, and that reperfusion resulted in the return of A/D equilibrium to its initial level. The rate of superoxide generation by complex I was higher in ischemic samples where content of the D-form was higher. Only the D-form was susceptible to inhibition by H2O2 or superoxide, whereas turnover-dependent activation of the enzyme resulted in formation of the A-form, which was much less sensitive to ROS. The mitochondrial-encoded subunit ND3, most likely responsible for the sensitivity of the D-form to ROS, was identified by redox difference gel electrophoresis.

Innovation: A combined in vivo and biochemical approach suggests that sensitivity of the mitochondrial system to ROS during myocardial I/R can be significantly affected by the conformational state of complex I, which may therefore represent a new therapeutic target in this setting.

Conclusion: The presented data suggest that transition of complex I into the D-form in the absence of oxygen may represent a key event in promoting cardiac injury during I/R.

Splicing of HDAC7 modulates the SRF-myocardin complex during stem-cell differentiation towards smooth muscle cells

Histone deacetylases (HDACs) have a central role in the regulation of gene expression. Here we investigated whether HDAC7 has an impact on embryonic stem (ES) cell differentiation into smooth muscle cells (SMCs). ES cells were seeded on collagen-IV-coated flasks and cultured in the absence of leukemia inhibitory factor in differentiation medium to induce SMC differentiation. Western blots and double-immunofluorescence staining demonstrated that HDAC7 has a parallel expression pattern with SMC marker genes. In ex vivo culture of embryonic cells from SM22-LacZ transgenic mice, overexpression of HDAC7 significantly increased beta-galactosidase-positive cell numbers and enzyme activity, indicating its crucial role in SMC differentiation during embryonic development. We found that HDAC7 undergoes alternative splicing during ES cell differentiation. Platelet-derived growth factor enhanced ES cell differentiation into SMCs through upregulation of HDAC7 splicing. Further experiments revealed that HDAC7 splicing induced SMC differentiation through modulation of the SRF-myocardin complex. These findings suggest that HDAC7 splicing is important for SMC differentiation and vessel formation in embryonic development.

Later Pleistocene evolution of the Exe valley: A chronstratigraphic model of terrace formation and its implications for Palaeolithic archaeology

This paper presents the ?rst systematic chronostratigraphic study of the river terraces of the Exe catchment in South West England and a new conceptual model for terrace formation in unglaciated basins with applicability to terrace staircase sequences elsewhere. The Exe catchment lay beyond the maximum extent of Pleistocene ice sheets and the drainage pattern evolved from the Tertiary to the Middle Pleistocene, by which time the major valley systems were in place and downcutting began to create a staircase of strath terraces. The higher terraces (8-6) typically exhibit altitudinal overlap or appear to be draped over the landscape, whilst the middle terraces show greater altitudinal separation and the lowest terraces are of a cut and ?ll form. The terrace deposits investigated in this study were deposited in cold phases of the glacial-interglacial Milankovitch climatic cycles with the lowest four being deposited in the Devensian Marine Isotope Stages (MIS) 4-2. A new cascade process-response model is proposed of basin terrace evolution in the Exe valley, which emphasises the role of lateral erosion in the creation of strath terraces and the reworking of inherited resistant lithological components down through the staircase. The resultant emergent valley topography and the reworking of artefacts along with gravel clasts, have important implications for the dating of hominin presence and the local landscapes they inhabited. Whilst the terrace chronology suggested here is still not as detailed as that for the Thames or the Solent System it does indicate a Middle Palaeolithic hominin presence in the region, probably prior to the late Wolstonian Complex or MIS 6. This supports existing data from cave sites in South West England.

Rapid formation of robust auditory memories: Insights from noise

Before a natural sound can be recognized, an auditory signature of its source must be learned through experience. Here we used random waveforms to probe the formation of new memories for arbitrary complex sounds. A behavioral measure was designed, based on the detection of repetitions embedded in noises up to 4 s long. Unbeknownst to listeners, some noise samples reoccurred randomly throughout an experimental block. Results showed that repeated exposure induced learning for otherwise totally unpredictable and meaningless sounds. The learning was unsupervised and resilient to interference from other task-relevant noises. When memories were formed, they emerged rapidly, performance became abruptly near-perfect, and multiple noises were remembered for several weeks. The acoustic transformations to which recall was tolerant suggest that the learned features were local in time. We propose that rapid sensory plasticity could explain how the auditory brain creates useful memories from the ever-changing, but sometimes repeating, acoustical world. © 2010 Elsevier Inc.

Decentralised formation control and stability analysis for cooperative multi-vehicle manoeuvre

Multi-vehicle cooperative formation control problem is an important and typical topic of research on multi-agent system. This paper presents a formation stability conjecture to conceive a new methodology for solving the decentralised multi-vehicle formation control problem. It employs the “extension-decomposition-aggregation” scheme to transform the complex multi-agent control problem into a group of sub-problems which is able to be solved conveniently. Based on this methodology, it is proved that if all the individual augmented subsystems can be stabilised by using any approach, the overall formation system is not only asymptotically but also exponentially stable in the sense of Lyapunov within a neighbourhood of the desired formation. Simulation study on 6-DOF aerial vehicles (Aerosonde UAVs) has been performed to verify the achieved formation stability result. The proposed multi-vehicle formation control strategy can be conveniently extended to other cooperative control problems of multi-agent systems.

Hybrid Polyoxovanadates: Anion-Influenced Formation of Nanoscopic Cages and Supramolecular Assemblies of Asymmetric Clusters

Organoarsonate-functionalized polyoxovanadates form upon the reduction of vanadates(V) in aqueous systems, whereby the underlying condensation reactions are influenced by the nature of the employed acid. In the presence of Cl− ions that derive from hydrochloric acid, a tetradecanuclear cage [VIV14O16(OH)8(O3AsC6H4-4-NH2)10]4– is obtained. When nitric acid is used, a condensed, decanuclear complex [V10O18(O3AsC6H4-4-NH2)7(DMF)2]5– forms. The latter organizes into a hexagonal packing arrangement in the solid state.

ND3, ND1 and 39 kDa subunits are more exposed in the de-active form of bovine mitochondrial complex I

An intriguing feature of mitochondrial complex I from several species is the so-called A/D transition, whereby the idle enzyme spontaneously converts from the active (A) form to the de-active (D) form. The A/D transition plays an important role in tissue response to the lack of oxygen and hypoxic deactivation of the enzyme is one of the key regulatory events that occur in mitochondria during ischaemia. We demonstrate for the first time that the A/D conformational change of complex I does not affect the macromolecular organisation of supercomplexes in vitro as revealed by two types of native electrophoresis. Cysteine 39 of the mitochondrially-encoded ND3 subunit is known to become exposed upon de-activation. Here we show that even if complex I is a constituent of the I + III + IV (S) supercomplex, cysteine 39 is accessible for chemical modification in only the D-form. Using lysine-specific fluorescent labelling and a DIGE-like approach we further identified two new subunits involved in structural rearrangements during the A/D transition: ND1 (MT-ND1) and 39 kDa (NDUFA9). These results clearly show that structural rearrangements during de-activation of complex I include several subunits located at the junction between hydrophilic and hydrophobic domains, in the region of the quinone binding site. De-activation of mitochondrial complex I results in concerted structural rearrangement of membrane subunits which leads to the disruption of the sealed quinone chamber required for catalytic turnover.

Complex organic molecules in protoplanetary disks

Context. Protoplanetary disks are vital objects in star and planet formation, possessing all the material, gas and dust, which may form a planetary system orbiting the new star. Small, simple molecules have traditionally been detected in protoplanetary disks; however, in the ALMA era, we expect the molecular inventory of protoplanetary disks to significantly increase.

Aims. We investigate the synthesis of complex organic molecules (COMs) in protoplanetary disks to put constraints on the achievable chemical complexity and to predict species and transitions which may be observable with ALMA.

Methods. We have coupled a 2D steady-state physical model of a protoplanetary disk around a typical T Tauri star with a large gas-grain chemical network including COMs. We compare the resulting column densities with those derived from observations and perform ray-tracing calculations to predict line spectra. We compare the synthesised line intensities with current observations and determine those COMs which may be observable in nearby objects. We also compare the predicted grain-surface abundances with those derived from cometary comae observations.

Results. We find COMs are efficiently formed in the disk midplane via grain-surface chemical reactions, reaching peak grain-surface fractional abundances similar to 10(-6)-10(-4) that of the H nuclei number density. COMs formed on grain surfaces are returned to the gas phase via non-thermal desorption; however, gas-phase species reach lower fractional abundances than their grain-surface equivalents, similar to 10(-12)-10(-7). Including the irradiation of grain mantle material helps build further complexity in the ice through the replenishment of grain-surface radicals which take part in further grain-surface reactions. There is reasonable agreement with several line transitions of H2CO observed towards T Tauri star-disk systems. There is poor agreement with HC3(N) lines observed towards LkCa 15 and GO Tau and we discuss possible explanations for these discrepancies. The synthesised line intensities for CH3OH are consistent with upper limits determined towards all sources. Our models suggest CH3OH should be readily observable in nearby protoplanetary disks with ALMA; however, detection of more complex species may prove challenging, even with ALMA "Full Science" capabilities. Our grain-surface abundances are consistent with those derived from cometary comae observations providing additional evidence for the hypothesis that comets (and other planetesimals) formed via the coagulation of icy grains in the Sun's natal disk.

Complex organic molecules along the accretion flow in isolated and externally irradiated protoplanetary disks

(Abridged) The birth environment of the Sun will have influenced the conditions in the pre-solar nebula, including the attainable chemical complexity, important for prebiotic chemistry. The formation and distribution of complex organic molecules (COMs) in a disk around a T Tauri star is investigated for two scenarios: (i) an isolated disk, and (ii) a disk irradiated externally by a nearby massive star. The chemistry is calculated along the accretion flow from the outer disk inwards using a comprehensive network. Two simulations are performed, one beginning with complex ices and one with simple ices only. For the isolated disk, COMs are transported without major alteration into the inner disk where they thermally desorb into the gas reaching an abundance representative of the initial assumed ice abundance. For simple ices, COMs efficiently form on grain surfaces under the conditions in the outer disk. Gas-phase COMs are released into the molecular layer via photodesorption. For the irradiated disk, complex ices are also transported inwards; however, they undergo thermal processing caused by the warmer conditions in the irradiated disk which tends to reduce their abundance along the accretion flow. For simple ices, grain-surface chemistry cannot synthesise COMs in the outer disk because the necessary grain-surface radicals, which tend to be particularly volatile, are not sufficiently abundant on the grain surfaces. Gas-phase COMs are formed in the inner region of the irradiated disk via gas-phase chemistry induced by the desorption of strongly bound molecules such as methanol; hence, the abundances are not representative of the initial molecular abundances injected into the outer disk. These results suggest that the composition of comets formed in isolated disks may differ from those formed in externally irradiated disks with the latter composed of more simple ices.

One-pot two-step mechanochemical synthesis: ligand and complex preparation without isolating intermediates

Although the use of ball milling to induce reactions between solids (mechanochemical synthesis) can provide lower-waste routes to chemical products by avoiding solvent during the reaction, there are further potential advantages in using one-pot multistep syntheses to avoid the use of bulk solvents for the purification of intermediates. We report here two-step syntheses involving formation of salen-type ligands from diamines and hydroxyaldehydes followed directly by reactions with metal salts to provide the corresponding metal complexes. Five salen-type ligands 2,2'-[1,2-ethanediylbis[(E)-nitrilomethylidyne]] bisphenol, ` salenH2', 1; 2,2'-[(+/-)-1,2-cyclohexanediylbis-[(E)-nitrilomethylidyne]] bis-phenol, 2; 2,2'-[1,2-phenylenebis( nitrilomethylidyne)]-bis-phenol, ` salphenH2' 3; 2-[[(2-aminophenyl) imino] methyl]-phenol, 4; 2,2'-[(+/-)-1,2-cyclohexanediylbis[(E)-nitrilomethylidyne]]-bis[4,6-bis(1,1-dimethylethyl)]-phenol, ` Jacobsen ligand', 5) were found to form readily in a shaker-type ball mill at 0.5 to 3 g scale from their corresponding diamine and aldehyde precursors. Although in some cases both starting materials were liquids, ball milling was still necessary to drive those reactions to completion because precipitation of the product and or intermediates rapidly gave in thick pastes which could not be stirred conventionally. The only ligand which required the addition of solvent was the Jacobsen ligand 5 which required 1.75 mol equivalents of methanol to go to completion. Ligands 1-5 were thus obtained directly in 30-60 minutes in their hydrated forms, due to the presence of water by-product, as free-flowing yellow powders which could be dried by heating to give analytically pure products. The one-armed salphen ligand 4 could also be obtained selectively by changing the reaction stoichiometry to 1 : 1. SalenH(2) 1 was explored for the onepot two-step synthesis of metal complexes. In particular, after in situ formation of the ligand by ball milling, metal salts (ZnO, Ni(OAc)2 center dot 4H(2)O or Cu(OAc)(2)center dot H2O) were added directly to the jar and milling continued for a further 30 minutes. Small amounts of methanol (0.4-1.1 mol equivalents) were needed for these reactions to run to completion. The corresponding metal complexes [M(salen)] (M = Zn, 6; Ni, 7; or Cu, 8) were thus obtained quantitatively after 30 minutes in hydrated form, and could be heated briefly to give analytically pure dehydrated products. The all-at-once ` tandem' synthesis of [Zn(salen)] 6 was also explored by milling ZnO, ethylene diamine and salicylaldehyde together in the appropriate mole ratio for 60 minutes. This approach also gave the target complex selectively with no solvent needing to be added. Overall, these syntheses were found to be highly efficient in terms of time and the in avoidance of bulk solvent both during the reaction and for the isolation of intermediates. The work demonstrates the applicability of mechanochemical synthesis to one-pot multi-step strategies.

Stress tolerance and virulence of insect-pathogenic fungi are determined by environmental conditions during conidial formation

The virulence to insects and tolerance to heat and UV-B radiation of conidia of entomopathogenic fungi are greatly influenced by physical, chemical, and nutritional conditions during mycelial growth. This is evidenced, for example, by the stress phenotypes of Metarhizium robertsii produced on various substrates. Conidia from minimal medium (Czapek's medium without sucrose), complex medium, and insect (Lepidoptera and Coleoptera) cadavers had high, moderate, and poor tolerance to UV-B radiation, respectively. Furthermore, conidia from minimal medium germinated faster and had increased heat tolerance and were more virulent to insects than those from complex medium. Low water-activity or alkaline culture conditions also resulted in production of conidia with high tolerance to heat or UV-B radiation. Conidia produced on complex media exhibited lower stress tolerance, whereas those from complex media supplemented with NaCl or KCl (to reduce water activity) were more tolerant to heat and UV-B than those from the unmodified complex medium. Osmotic and nutritive stresses resulted in production of conidia with a robust stress phenotype, but also were associated with low conidial yield. Physical conditions such as growth under illumination, hypoxic conditions, and heat shock before conidial production also induced both higher UV-B and heat tolerance; but conidial production was not decreased. In conclusion, physical and chemical parameters, as well as nutrition source, can induce great variability in conidial tolerance to stress for entomopathogenic fungi. Implications are discussed in relation to the ecology of entomopathogenic fungi in the field, and to their use for biological control. This review will cover recent technologies on improving stress tolerance of entomopathogenic fungi for biological control of insects.

Direct oxidation of amines to nitriles in the presence of ruthenium-terpyridyl complex immobilized on ILs/SILP

The immobilization of a ruthenium complex (Ru2Cl4(az-tpy)2) within a range of supported ionic liquids ([C4C1im]Cl, [C4C1im][NTf2], [C6C1im]Cl, [C4C1pyrr]Br, [C4C1im]Br, [C4C1pyrr]Cl) dispersed silica (SILP) operates as an efficient heterogeneous catalyst in oxidation of long chain linear primary amines to corresponding nitriles. This reaction follows a “green” route using a cheap and easy to handles oxidant (oxygen or air). The conversion was found to be strongly influenced by the alkyl chain length of the amine substrate and the choice of oxidant. No condensation reaction was observed between the starting amines and the selectivity to nitrile is 100%. Moving from a composition of 20 atm N2/5 atm O2 to 5 atm N2/20 atm O2 led to enhancements in the conversion (n-alkylamines) and selectivity (benzonitrile) which have been correlated with an increase of the solubilized oxygen. This was further supported by using different inert gas (nitrogen, helium, argon)/oxygen mixtures indicating that the O2 solubility in the SILP system, has an important effect on conversions and TON in this reaction using SILP catalysts. Experiments performed in the presence of CO2 led to a different behaviour due to the formation of amine-CO2 adducts. The application of the Weisz–Prater criterion confirmed the absence of any diffusional constraints.

Polymer dissolution and blend formation in ionic liquids.

The ionic liqs. are for the dissoln. of various polymers and/or copolymers, the formation of resins and blends, and the reconstitution of polymer and/or copolymer solns., and the dissoln. and blending of functional additives and/or various polymers and/or copolymers. Thus, ≥1 ionic liq., which is a liq. salt complex that exists in the liq. phase between about -70 to 300°, is mixed with ≥2 differing polymeric materials to form a mixt., and adding a nonsolvent to the mixt. to remove the ionic liq. from the resin or blend. [on SciFinder(R)]

Solitary and repetitive binding motifs for the AP2 complex alpha-appendage in amphiphysin and other accessory proteins

Adaptor protein (AP) complexes bind to transmembrane proteins destined for internalization and to membrane lipids, so linking cargo to the accessory internalization machinery. This machinery interacts with the appendage domains of APs, which have platform and beta-sandwich subdomains, forming the binding surfaces for interacting proteins. Proteins that interact with the subdomains do so via short motifs, usually found in regions of low structural complexity of the interacting proteins. So far, up to four motifs have been identified that bind to and partially compete for at least two sites on each of the appendage domains of the AP2 complex. Motifs in individual accessory proteins, their sequential arrangement into motif domains, and partial competition for binding sites on the appendage domains coordinate the formation of endocytic complexes in a temporal and spatial manner. In this work, we examine the dominant interaction sequence in amphiphysin, a synapse-enriched accessory protein, which generates membrane curvature and recruits the scission protein dynamin to the necks of coated pits, for the platform subdomain of the alpha-appendage. The motif domain of amphiphysin1 contains one copy of each of a DX(F/W) and FXDXF motif. We find that the FXDXF motif is the main determinant for the high affinity interaction with the alpha-adaptin appendage. We describe the optimal sequence of the FXDXF motif using thermodynamic and structural data and show how sequence variation controls the affinities of these motifs for the alpha-appendage.