bluuebunny/crossref_metadata_2025 huggingface dataset:
TLP18.3, a novel thylakoid lumen protein regulating photosystem II repair cycle
Authors: Sirpiö Sari , Allahverdiyeva Yagut , Suorsa Marjaana , Paakkarinen Virpi , Vainonen Julia , Battchikova Natalia , Aro Eva-Mari
Published: August 2007

A proteome analysis of Arabidopsis thaliana thylakoid-associated polysome nascent chain complexes was performed to find novel proteins involved in the biogenesis, maintenance and turnover of thylakoid protein complexes, in particular the PSII (photosystem II) complex, which exhibits a high turnover rate. Four unknown proteins were identified, of which TLP18.3 (thylakoid lumen protein of 18.3 kDa) was selected for further analysis. The Arabidopsis mutants (SALK_109618 and GABI-Kat 459D12) lacking the TLP18.3 protein showed higher susceptibility of PSII to photoinhibition. The increased susceptibility of ΔTLP18.3 plants to high light probably originates from an inefficient reassembly of PSII monomers into dimers in the grana stacks, as well as from an impaired turnover of the D1 protein in stroma exposed thylakoids. Such dual function of the TLP18.3 protein is in accordance with its even distribution between the grana and stroma thylakoids. Notably, the lack of the TLP18.3 protein does not lead to a severe collapse of the PSII complexes, suggesting a redundancy of proteins assisting these particular repair steps to assure functional PSII. The ΔTLP18.3 plants showed no clear visual phenotype under standard growth conditions, but when challenged by fluctuating light during growth, the retarded growth of ΔTLP18.3 plants was evident.
Regulation of type V adenylate cyclase by Ric8a, a guanine nucleotide exchange factor
Authors: Wang Shyi-Chyi , Lai Hsing-Lin , Chiu Yi-Ting , Ou Ren , Huang Chuen-Lin , Chern Yijuang
Published: August 2007

In the present study, we demonstrate that AC5 (type V adenylate cyclase) interacts with Ric8a through directly interacting at its N-terminus. Ric8a was shown to be a GEF (guanine nucleotide exchange factor) for several α subunits of heterotrimeric GTP binding proteins (Gα proteins) in vitro. Selective Gα targets of Ric8a have not yet been revealed in vivo. An interaction between AC5 and Ric8a was verified by pull-down assays, co-immunoprecipitation analyses, and co-localization in the brain. Expression of Ric8a selectively suppressed AC5 activity. Treating cells with pertussis toxin or expressing a dominant negative Gαi mutant abolished the suppressive effect of Ric8a, suggesting that interaction between the N-terminus of AC5 and a GEF (Ric8a) provides a novel pathway to fine-tune AC5 activity via a Gαi-mediated pathway.
Na+/Ca2+ exchangers: three mammalian gene families control Ca2+ transport
Authors: Lytton Jonathan
Published: August 2007

Mammalian Na+/Ca2+ exchangers are members of three branches of a much larger family of transport proteins [the CaCA (Ca2+/cation antiporter) superfamily] whose main role is to provide control of Ca2+ flux across the plasma membranes or intracellular compartments. Since cytosolic levels of Ca2+ are much lower than those found extracellularly or in sequestered stores, the major function of Na+/Ca2+ exchangers is to extrude Ca2+ from the cytoplasm. The exchangers are, however, fully reversible and thus, under special conditions of subcellular localization and compartmentalized ion gradients, Na+/Ca2+ exchangers may allow Ca2+ entry and may play more specialized roles in Ca2+ movement between compartments. The NCX (Na+/Ca2+ exchanger) [SLC (solute carrier) 8] branch of Na+/Ca2+ exchangers comprises three members: NCX1 has been most extensively studied, and is broadly expressed with particular abundance in heart, brain and kidney, NCX2 is expressed in brain, and NCX3 is expressed in brain and skeletal muscle. The NCX proteins subserve a variety of roles, depending upon the site of expression. These include cardiac excitation–contraction coupling, neuronal signalling and Ca2+ reabsorption in the kidney. The NCKX (Na2+/Ca2+–K+ exchanger) (SLC24) branch of Na+/Ca2+ exchangers transport K+ and Ca2+ in exchange for Na+, and comprises five members: NCKX1 is expressed in retinal rod photoreceptors, NCKX2 is expressed in cone photoreceptors and in neurons throughout the brain, NCKX3 and NCKX4 are abundant in brain, but have a broader tissue distribution, and NCKX5 is expressed in skin, retinal epithelium and brain. The NCKX proteins probably play a particularly prominent role in regulating Ca2+ flux in environments which experience wide and frequent fluctuations in Na+ concentration. Until recently, the range of functions that NCKX proteins play was generally underappreciated. This situation is now changing rapidly as evidence emerges for roles including photoreceptor adaptation, synaptic plasticity and skin pigmentation. The CCX (Ca2+/cation exchanger) branch has only one mammalian member, NCKX6 or NCLX (Na+/Ca2+–Li+ exchanger), whose physiological function remains unclear, despite a broad pattern of expression.
Electrical characterization and current transportation in metal∕Dy2O3∕Si structure
Authors: Chiu Fu-Chien
Published: August 2007

Metal-oxide-semiconductor capacitors incorporating Dy2O3 dielectric were fabricated and investigated. In this work, the electrical conduction mechanisms of 12nm Dy2O3 thin films as functions of temperature were studied. The dominant conduction mechanisms of the Al∕Dy2O3∕p-Si metal-dysprosium oxide-semiconductor capacitor are the space-charge-limited current from 350to525K and the Schottky emission from 300to325K in the accumulation mode. Three different regions were observed in the current-density–voltage (J-V) characteristics at 350K, namely, Ohm’s law region, trap-filled-limited region, and Child’s law region. The activation energy in Ohm’s law region calculated from the Arrhenius plots is about 0.2eV. This energy is attributed to shallow traps, distributed near the conduction band edge in the forbidden gap. The trap capture cross section is about 3.2×10−21cm2. The electronic mobility, trap density, dielectric relaxation time, and density of states in conduction band were obtained from the space-charge-limited conduction at 350K.
Magnetic collimation of fast electrons produced by ultraintense laser irradiation by structuring the target composition
Authors: Robinson A. P. L. , Sherlock M.
Published: August 2007

A scheme for collimating fast electrons in a specially engineered solid target is proposed. Unlike previous approaches, the collimation is achieved by generating an azimuthal magnetic field as opposed to a radial electric field. The target is engineered such that it consists of a fiber surrounded by material of a lower resistivity than that of the fiber. The fast electrons are collimated along the fiber. Hybrid Vlasov-Fokker-Planck simulations supported by analytic calculations show that this concept is viable.
Damping models in the truncated derivative nonlinear Schrödinger equation
Authors: Sanchez-Arriaga G. , Sanmartin J. R. , Elaskar S. A.
Published: August 2007

Four-dimensional flow in the phase space of three amplitudes of circularly polarized Alfven waves and one relative phase, resulting from a resonant three-wave truncation of the derivative nonlinear Schrödinger equation, has been analyzed; wave 1 is linearly unstable with growth rate Γ, and waves 2 and 3 are stable with damping γ2 and γ3, respectively. The dependence of gross dynamical features on the damping model (as characterized by the relation between damping and wave-vector ratios, γ2∕γ3, k2∕k3), and the polarization of the waves, is discussed; two damping models, Landau (γ∝k) and resistive (γ∝k2), are studied in depth. Very complex dynamics, such as multiple blue sky catastrophes and chaotic attractors arising from Feigenbaum sequences, and explosive bifurcations involving Intermittency-I chaos, are shown to be associated with the existence and loss of stability of certain fixed point P of the flow. Independently of the damping model, P may only exist for Γ<2(γ2+γ3)∕3, as against flow contraction just requiring Γ<γ2+γ3. In the case of right-hand (RH) polarization, point P may exist for all models other than Landau damping; for the resistive model, P may exist for RH polarization only if Γ<(γ2+γ3)∕2.
Growth modes of nanocrystalline Ni/Pt multilayers with deposition temperature
Authors: Karoutsos V. , Papasotiriou P. , Poulopoulos P. , Kapaklis V. , Politis C. , Angelakeris M. , Kehagias Th. , Flevaris N. K. , Papaioannou E. Th.
Published: August 2007

We compare the structure and growth modes of two series of nanocrystalline Ni/Pt multilayers deposited on glass, Si, and polyimide substrates by electron-beam evaporation at room temperature (40 °C) and at 200 °C. X-ray diffraction patterns are recorded in order of the quality of the layering to be examined. The morphology of the films is studied by atomic force microscopy. The roughness of the samples is found to depend on the substrate and the total thickness, following a power law. The crystal structure, the shape of the crystallites, and the layering of the samples were determined by transmission electron microscopy. Differences in the shape of the crystallites and the surface morphology between the two series of samples are observed and they are understood within the framework of structural zone models. Finally, it is demonstrated the large stability of the multilayer structure for a period of at least 12 years.
An analysis of the energy transfer and the locality of nonlinear interactions in turbulence
Authors: Domaradzki J. Andrzej , Carati Daniele
Published: August 2007

Using the results of direct numerical simulations of isotropic turbulence, we compute detailed energy exchanges between different scales of motion and investigate how they contribute to the global quantities such as the energy transfer, the spectral energy flux, and the subgrid-scale dissipation. The scales of motion are defined by decomposing velocity fields using sharp spectral and smooth, tangent hyperbolic filters. The analysis of detailed interactions reveals that individual nonlocal contributions are large but significant cancellations lead to the global quantities asymptotically dominated by the local interactions. Implications of these results for turbulence modeling are discussed.
Interaction of low-energy electrons with linear diphenylethynyl derivatives in the gas phase
Authors: Kukhta A. V. , Kukhta I. N. , Kazakov S. M. , Khristophorov O. V. , Neyra O. L.
Published: August 2007

The gas phase electron impact spectroscopy has been used to study the relative efficiency of excitation into singlet states and energies of singlet-triplet transitions for two electroactive organic materials, anthracene and biphenyl-containing diphenylethynyl derivatives. The probability of the lowest singlet-triplet transition in anthracene-containing molecule was found to be much higher than that in anthracene which is connected with triple bonds. No noticeable contribution of the triple bonds into singlet spectra of the studied molecules was observed. There are a number of intense transitions in the range higher than 10eV. The optical spectrum calculated using the density functional theory is in good agreement with experimental electron energy loss and optical absorption spectra.
Multiwell micromechanical cantilever array reader for biotechnology
Authors: Zhang R. , Best A. , Berger R. , Cherian S. , Lorenzoni S. , Macis E. , Raiteri R. , Cain R.
Published: August 2007

We use a multiwell micromechanical cantilever sensor (MCS) device to measure surface stress changes induced by specific adsorption of molecules. A multiplexed assay format facilitates the monitoring of the bending of 16 MCSs in parallel. The 16 MCSs are grouped within four separate wells. Each well can be addressed independently by different analyte liquids. This enables functionalization of MCS separately by flowing different solutions through each well. In addition, each well contains a fixed reference mirror which allows measuring the absolute bending of MCS. In addition, the mirror can be used to follow refractive index changes upon mixing of different solutions. The effect of the flow rate on the MCS bending change was found to be dependent on the absolute bending value of MCS. Experiments and finite element simulations of solution exchange in wells were performed. Both revealed that one solution can be exchanged by another one after 200μl volume has flown through. Using this device, the adsorption of thiolated DNA molecules and 6-mercapto-1-hexanol on gold surfaces was performed to test the nanomechanical response of MCS.
Dynamic force spectroscopy using cantilever higher flexural modes
Authors: Sugimoto Yoshiaki , Innami Seiji , Abe Masayuki , Custance Óscar , Morita Seizo
Published: August 2007

By means of force spectroscopy measurements performed with the cantilever first and second flexural modes under the frequency modulation detection method, the authors corroborate the validity of the relation between tip-surface interaction force and frequency shift for force spectroscopy acquisition using higher cantilever eigenmodes. They estimate a cantilever effective stiffness for the second eigenmode 73 times larger than the static stiffness. This large effective stiffness enables them to perform force spectroscopy with a cantilever oscillation amplitude (A0) as small as 3.6Å. The authors provide experimental evidence that, at such small A0 values, normalized frequency shift curves deviate from a A03∕2 scaling and the signal-to-noise ratio is considerably enhanced.
Small molecule based and solution processed highly efficient red electrophosphorescent organic light emitting devices
Authors: Kim Heekyung , Byun Younghun , Das Rupasree Ragini , Choi Byoung-Ki , Ahn Pil-Soo
Published: August 2007

The authors report the very high luminous efficiency in solution processed red electrophosphorescent organic light emitting devices using small molecular host and guest materials. The maximum luminous efficiency reached 12.7cd∕A, corresponding to external quantum efficiency of 15.1%, with its emission peak wavelength of 620nm and the Commission Internationale de l’Eclairage coordinates of (0.65, 0.33). Along with these excellent performances of the solution processed device, which were comparable to those of the vacuum deposited counterpart device with similar structure and materials, the comparative study on both devices suggests the merits of the solution process adopting robust small molecular materials only.
Organic light-emitting diodes with structured cathode
Authors: Liu Deang , Fina Michael , Chen Zhaoyang , Chen Xiaobo , Liu Gao , Johnson Steven , Mao Samuel S.
Published: August 2007

Organic light-emitting diode (OLED) devices were fabricated with a structured polymer-cathode interface. The devices have a layered structure indium tin oxide/poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate)/poly(2-methoxy-5-[(2′-ethylhexyl)oxy]-p-phenylenevinylene)/Al. The light-emitting polymer layers were patterned via a stamp imprinting process, followed by vapor deposition of the cathode. Devices employing the structured cathode showed improved electron injection and increased brightness when compared to conventional flat cathode devices. Electrostatic modeling of the structured cathode geometry revealed localized increase in electric field leading to enhanced electron tunneling through the polymer-cathode interface. Thus, improved OLED performance was demonstrated from cathode microstructuring.
Micro thermoindicators and optical-electronic temperature control for microfluidic applications
Authors: Liu Liyu , Peng Suili , Wen Weijia , Sheng Ping
Published: August 2007

The authors report the design and implementation of sensing and control of local temperature in polydimethylsiloxane microfluidic reaction chip, based on the fabrication of a microtemperature sensor with thermochromic color bars and the associated optical and electronic feedback controls. The thermochromic color bar demonstrates easy and accurate local temperature monitoring. In combination with a microheater, this contactless microchip temperature control approach may have wide application potentials in microchemical and microbiological analyses.
Low temperature transfer and formation of carbon nanotube arrays by imprinted conductive adhesive
Authors: Wang Teng , Carlberg Björn , Jönsson Martin , Jeong Goo-Hwan , Campbell Eleanor E. B. , Liu Johan
Published: August 2007

This letter demonstrates the transfer and formation of aligned carbon nanotube (CNT) arrays at low temperature by imprinted conductive adhesive. A thermoplastic isotropic conductive adhesive is patterned by an imprint and heat transfer process. The CNTs grown by thermal chemical vapor deposition are then transferred to another substrate by the conductive adhesive, forming predefined patterns. The current-voltage response of the transferred CNT bundles verifies that good electrical connection has been established. This process can enable the integration of CNTs into various temperature-sensitive processeses and materials.
Axial and radial growth of Ni-induced GaN nanowires
Authors: Geelhaar L. , Chèze C. , Weber W. M. , Averbeck R. , Riechert H. , Kehagias Th. , Komninou Ph. , Dimitrakopulos G. P. , Karakostas Th.
Published: August 2007

GaN nanowires (NWs) were grown on sapphire by molecular beam epitaxy. NWs form only in the presence of Ni seed particles and only under N-rich conditions. Their length increases linearly with growth time up to about 7.5μm while their diameter remains almost constant. In contrast, a switch to Ga-rich conditions after NW formation results in radial growth, i.e., the NW diameter increases while lengthening is negligible. These results corroborate the fact that the growth of III-V NWs is governed by the accumulation of group-III atoms in the seeds, while group-V species are not preferentially incorporated at the seeds.
Application of accelerators for the research and development of scintillators
Authors: Shibuya Kengo , Koshimizu Masanori , Asai Keisuke , Muroya Yusa , Katsumura Yosuke , Inadama Naoko , Yoshida Eiji , Nishikido Fumihiko , Yamaya Taiga , Murayama Hideo
Published: August 2007

We introduce experimental systems which use accelerators to evaluate scintillation properties such as scintillation intensity, wavelength, and lifetime. A single crystal of good optical quality is often unavailable during early stages in the research and development (R&D) of new scintillator materials. Because of their beams’ high excitation power and/or low penetration depth, accelerators facilitate estimation of the properties of early samples which may only be available as powders, thin films, and very small crystals. We constructed a scintillation spectrum measurement system that uses a Van de Graaff accelerator and an optical multichannel analyzer to estimate the relative scintillation intensity. In addition, we constructed a scintillation time profile measurement system that uses an electron linear accelerator and a femtosecond streak camera or a microchannel plate photomultiplier tube followed by a digital oscilloscope to determine the scintillation lifetimes. The time resolution is approximately 10ps. The scintillation spectra or time profiles can be obtained in a significantly shorter acquisition time in comparison with that required by conventional measuring systems. The advantages of the systems described in this study can significantly promote the R&D of novel scintillator materials.
Growth mode transition to pyramid from layer by layer of heteroepitaxial PbTiO3 islands on a (001) vicinal SrTiO3 substrate fabricated by hydrothermal epitaxy
Authors: Jeon J. H. , Choi S. K.
Published: August 2007

The authors observed the surface morphology transition from the atomically flat two dimensional layer-by-layer mode to the three dimensional pyramidal mode of heteroepitaxial PbTiO3 (PTO) islands synthesized by hydrothermal epitaxy by scanning electron microscopy and atomic force microscopy. Two types of (001) Nb–SrTiO3 (NSTO) with the same step height, ∼0.25 and ∼1μm terrace widths, were used for substrates. They found the critical island thickness at which the growth mode of PTO island was converted and its relation to the terrace width of the substrate. It is suggested that the relaxation of the misfit strain, which originates from out-of-plane lattice mismatch between the PTO island unit cell and the NSTO substrate step or somewhere interior of the film, has an effect on the PTO island growth mode transition.
Electrical coherent control of nuclear spins in a breakdown regime of quantum Hall effect
Authors: Takahashi H. , Kawamura M. , Masubuchi S. , Hamaya K. , Machida T. , Hashimoto Y. , Katsumoto S.
Published: August 2007

Using a conventional Hall-bar geometry with a micrometal strip on top of the surface, the authors demonstrate an electrical coherent control of nuclear spins in an AlGaAs∕GaAs semiconductor heterostructure. A breakdown of integer quantum Hall (QH) effect is utilized to dynamically polarize nuclear spins. By applying a pulse rf magnetic field with the metal strip, the quantum state of the nuclear spins shows Rabi oscillations, which is detected by measuring longitudinal voltage of the QH conductor.
Tuning the domain wall orientation in thin magnetic strips using induced anisotropy
Authors: Cherifi S. , Hertel R. , Locatelli A. , Watanabe Y. , Potdevin G. , Ballestrazzi A. , Balboni M. , Heun S.
Published: August 2007

The authors report on a method to tune the orientation of in-plane magnetic domains and domain walls in thin ferromagnetic strips by manipulating the magnetic anisotropy of the system. Uniaxial in-plane anisotropy is induced in a controlled way by oblique evaporation of magnetic thin strips. A direct correlation between the magnetization direction and the domain wall orientation is found experimentally and confirmed by micromagnetic simulations. The domain walls in the strips are always oriented along the oblique evaporation-induced easy axis, irrespective of the shape anisotropy. The controlled manipulation of domain wall orientations could provide promising possibilities for recently proposed devices based on domain wall propagation.
Model for cage formation in colloidal suspension of laponite
Authors: Joshi Yogesh M.
Published: August 2007

In this paper we investigate glass transition in aqueous suspension of synthetic hectorite clay, laponite. We believe that upon dispersing laponite clay in water, the system comprises of clusters (agglomerates) of laponite dispersed in the same. Subsequent osmotic swelling of these clusters leads to an increase in their volume fraction. We propose that this phenomenon is responsible for slowing down of the overall dynamics of the system. As clusters fill up the space, the system undergoes glass transition. Along with the mode coupling theory, the proposed mechanism rightly captures various characteristic features of the system in the ergodic regime as it approaches glass transition.
The effect of elevated CO2, soil and atmospheric water deficit and seasonal phenology on leaf and ecosystem isoprene emission
Authors: Pegoraro Emiliano , Potosnak Mark J. , Monson Russell K. , Rey Ana , Barron-Gafford Greg , Osmond C. Barry
Published: August 2007

Two cottonwood plantations were grown at different CO2 concentrations at the Biosphere 2 Laboratory in Arizona to investigate the response of isoprene emission to elevated [CO2] and its interaction with water deficits. We focused on responses due to seasonal variation and variation in the mean climate from one year to the next. In fall and in spring, isoprene emission rate showed a similar inhibition by elevated [CO2], despite an 8–10°C seasonal difference in mean air temperature. The overall response of isoprene emission to drought was also similar for observations conducted during the spring or fall, and during the fall of two different years with an approximate 5°C difference in mean air temperature. In general, leaf-level isoprene emission rates, measured at constant temperature and photon-flux density, decreased slightly, or remained constant during drought, whereas ecosystem-level isoprene emission rates increased. The uncoupling of ecosystem- and leaf-scale responses is not due to differential dependence on leaf area index (LAI) as LAI increased only slightly, or decreased, during the drought treatments at the same time that ecosystem isoprene emission rate increased greatly. Nor does the difference in isoprene emission rate between leaves and ecosystems appear to be due solely to increases in canopy surface temperature during the drought, though some increase in temperature was observed. It is possible that still further factors, such as increased penetration of PPFD into the canopy as a result of changes in leaf angle, reduced sink strength of the soil for atmospheric isoprene, and decreases in the mean Ci of leaves, combined with the small increases in canopy surface temperature, increased the ecosystem isoprene emission rate. Whatever the causes of the differences in the leaf and ecosystem responses, we conclude that the overall shape of the leaf and ecosystem responses to drought was constant irrespective of season or year.
Photoinhibition and D1 protein degradation in mesophyll and agranal bundle sheath thylakoids of maize
Authors: Pokorska Berenika , Romanowska Elzbieta
Published: August 2007

Susceptibility of photosystem II complex (PSII) to photoinhibition and degradation of D1 protein has been described in the chloroplasts of C3 plants but so far, the PSII turnover has not been characterised in any C4 plant, which contains two types of chloroplasts differing biochemically and structurally. In maize (Zea mays L. Oleńka), chloroplasts located in mesophyll (M) develop grana, while bundle sheath (BS) chloroplasts are agranal. In this paper, we report the D1 protein phosphorylation, damage and proteolysis in mesophyll as well as in agranal bundle sheath thylakoids of maize plants. Photoinhibitory treatment (1800 μmol photons m–2 s–1) of isolated thylakoids led to donor side inhibition of PSII electron transport and then to damage of reaction centre in both M and BS thylakoids. Rate of D1 degradation rate was faster in BS than in M thylakoids, and the addition of ATP to incubation medium delayed D1 degradation in both types of thylakoids. Furthermore, we demonstrated that the proteases belonging to FtsH and Deg families were present but their amounts significantly differed in M and BS thylakoids. Protease inhibitor studies revealed that serine- and metallo-proteases were involved in degradation of D1 protein. Apparent existence of D1 degradation cycle and the presence of proteolytic enzymes responsible for this process in BS thylakoids confirm that PSII plays an important role in agranal membranes, and when damaged, D1 can be rapidly degraded to enable PSII repair and restoration in these membranes.
Overexpression of sedoheptulose-1,7-bisphosphatase enhances photosynthesis and growth under salt stress in transgenic rice plants
Authors: Feng Lingling , Han Yujun , Liu Gai , An Baoguang , Yang Jing , Yang Guohua , Li Yangsheng , Zhu Yingguo
Published: August 2007

Activity of the Calvin cycle enzyme sedoheptulose-1,7-bisphosphatase (SBPase; EC3.1.3.37) was increased in the transgenic rice cultivar zhonghua11 (Oryza sativa L. ssp. japonica) by overexpressing OsSbp cDNA from the rice cultivar 9311 (Oryza sativa ssp. indica). This genetic engineering enabled the transgenic plants to accumulate SBPase in chloroplasts and resulted in enhanced tolerance of transgenic rice plants to salt stress at the young seedlings stage. Moreover, CO2 assimilation in transgenic rice plants was significantly more tolerant to salt stress than in wild-type plants. The analysis of chlorophyll fluorescence and the activity of SBPase indicated that the enhancement of photosynthesis in salt stress was not related to the function of PSII but to the activity of SBPase. Western-blot analysis showed that salt stress led to the association of SBPase with the thylakoid membranes from the stroma fractions. However, this association was much more prominent in wild-type plants than in transgenic plants. Results suggested that under salt stress, SBPase maintained the activation of ribulose-1,5-bisphosphate carboxylase-oxygenase by providing more regeneration of the acceptor molecule ribulose-1,5-bisphosphate in the soluble stroma and by preventing the sequestration of Rubisco activase to the thylakoid membrane from the soluble stroma, and, thus, enhanced the tolerance of photosynthesis to salt stress. Results suggested that overexpression of SBPase was an effective method for enhanncing salt tolerance in rice.
Molecular evidence of Late Archean archaea and the presence of a subsurface hydrothermal biosphere
Authors: Ventura Gregory T. , Kenig Fabien , Reddy Christopher M. , Schieber Juergen , Frysinger Glenn S. , Nelson Robert K. , Dinel Etienne , Gaines Richard B. , Schaeffer Philippe
Published: August 2007

Highly cracked and isomerized archaeal lipids and bacterial lipids, structurally changed by thermal stress, are present in solvent extracts of 2,707- to 2,685-million-year-old (Ma) metasedimentary rocks from Timmins, ON, Canada. These lipids appear in conventional gas chromatograms as unresolved complex mixtures and include cyclic and acyclic biphytanes, C
36
–C
39
derivatives of the biphytanes, and C
31
–C
35
extended hopanes. Biphytane and extended hopanes are also found in high-pressure catalytic hydrogenation products released from solvent-extracted sediments, indicating that archaea and bacteria were present in Late Archean sedimentary environments. Postdepositional, hydrothermal gold mineralization and graphite precipitation occurred before metamorphism (≈2,665 Ma). Late Archean metamorphism significantly reduced the kerogen's adsorptive capacity and severely restricted sediment porosity, limiting the potential for post-Archean additions of organic matter to the samples. Argillites exposed to hydrothermal gold mineralization have disproportionately high concentrations of extractable archaeal and bacterial lipids relative to what is releasable from their respective high-pressure catalytic hydrogenation product and what is observed for argillites deposited away from these hydrothermal settings. The addition of these lipids to the sediments likely results from a Late Archean subsurface hydrothermal biosphere of archaea and bacteria.
Inhibition of the leucine-rich repeat protein LINGO-1 enhances survival, structure, and function of dopaminergic neurons in Parkinson's disease models
Authors: Inoue Haruhisa , Lin Ling , Lee Xinhua , Shao Zhaohui , Mendes Shannon , Snodgrass-Belt Pamela , Sweigard Harry , Engber Tom , Pepinsky Blake , Yang Lichuan , Beal M. Flint , Mi Sha , Isacson Ole
Published: August 2007

The nervous system-specific leucine-rich repeat Ig-containing protein LINGO-1 is associated with the Nogo-66 receptor complex and is endowed with a canonical EGF receptor (EGFR)-like tyrosine phosphorylation site. Our studies indicate that LINGO-1 expression is elevated in the substantia nigra of Parkinson's disease (PD) patients compared with age-matched controls and in animal models of PD after neurotoxic lesions. LINGO-1 expression is present in midbrain dopaminergic (DA) neurons in the human and rodent brain. Therefore, the role of LINGO-1 in cell damage responses of DA neurons was examined
in vitro
and in experimental models of PD induced by either oxidative (6-hydroxydopamine) or mitochondrial (
N
-methyl-4-phenyl-1,2,3,6-tetrahydropyridine) toxicity. In LINGO-1 knockout mice, DA neuron survival was increased and behavioral abnormalities were reduced compared with WT. This neuroprotection was accompanied by increased Akt phosphorylation (
p
-Akt). Similar neuroprotective
in vivo
effects on midbrain DA neurons were obtained in WT mice by blocking LINGO-1 activity using LINGO-1-Fc protein. Neuroprotection and enhanced neurite growth were also demonstrated for midbrain DA neurons
in vitro
. LINGO-1 antagonists (LINGO-1-Fc, dominant negative LINGO-1, and anti-LINGO-1 antibody) improved DA neuron survival in response to MPP
+
in part by mechanisms that involve activation of the EGFR/Akt signaling pathway through a direct inhibition of LINGO-1's binding to EGFR. These results show that inhibitory agents of LINGO-1 activity can protect DA neurons against degeneration and indicate a role for the leucine-rich repeat protein LINGO-1 and related classes of proteins in the pathophysiological responses of midbrain DA neurons in PD.
Essential role for autophagy protein Atg7 in the maintenance of axonal homeostasis and the prevention of axonal degeneration
Authors: Komatsu Masaaki , Wang Qing Jun , Holstein Gay R. , Friedrich Victor L. , Iwata Jun-ichi , Kominami Eiki , Chait Brian T. , Tanaka Keiji , Yue Zhenyu
Published: August 2007

Autophagy is a regulated lysosomal degradation process that involves autophagosome formation and transport. Although recent evidence indicates that basal levels of autophagy protect against neurodegeneration, the exact mechanism whereby this occurs is not known. By using conditional knockout mutant mice, we report that neuronal autophagy is particularly important for the maintenance of local homeostasis of axon terminals and protection against axonal degeneration. We show that specific ablation of an essential autophagy gene,
Atg7
, in Purkinje cells initially causes cell-autonomous, progressive dystrophy (manifested by axonal swellings) and degeneration of the axon terminals. Consistent with suppression of autophagy, no autophagosomes are observed in these dystrophic swellings, which is in contrast to accumulation of autophagosomes in the axonal dystrophic swellings under pathological conditions. Axonal dystrophy of mutant Purkinje cells proceeds with little sign of dendritic or spine atrophy, indicating that axon terminals are much more vulnerable to autophagy impairment than dendrites. This early pathological event in the axons is followed by cell-autonomous Purkinje cell death and mouse behavioral deficits. Furthermore, ultrastructural analyses of mutant Purkinje cells reveal an accumulation of aberrant membrane structures in the axonal dystrophic swellings. Finally, we observe double-membrane vacuole-like structures in wild-type Purkinje cell axons, whereas these structures are abolished in mutant Purkinje cell axons. Thus, we conclude that the autophagy protein Atg7 is required for membrane trafficking and turnover in the axons. Our study implicates impairment of axonal autophagy as a possible mechanism for axonopathy associated with neurodegeneration.
A cyclic nucleotide-gated channel is essential for polarized tip growth of pollen
Authors: Frietsch Sabine , Wang Yong-Fei , Sladek Chris , Poulsen Lisbeth R. , Romanowsky Shawn M. , Schroeder Julian I. , Harper Jeffrey F.
Published: August 2007

Ion signals are critical to regulating polarized growth in many cell types, including pollen in plants and neurons in animals. Genetic evidence presented here indicates that pollen tube growth requires cyclic nucleotide-gated channel (CNGC) 18. CNGCs are nonspecific cation channels found in plants and animals and have well established functions in excitatory signal transduction events in animals. InArabidopsis, male sterility was observed for twocngc18null mutations.CNGC18is expressed primarily in pollen, as indicated from a promoter::GUS(β-glucuronidase) reporter analysis and expression profiling. The underlying cause of sterility was identified as a defect in pollen tube growth, resulting in tubes that were kinky, short, often thin, and unable to grow into the transmitting tract. Expression of a GFP-tagged CNGC18 in mutant pollen provided complementation and evidence for asymmetric localization of CNGC18 to the plasma membrane at the growing tip, starting at the time of pollen grain germination. Heterologous expression of CNGC18 inEscherichia coliresulted in a time- and concentration-dependent accumulation of more Ca2+. Thus, CNGC18 provides a mechanism to directly transduce a cyclic nucleotide (cNMP) signal into an ion flux that can produce a localized signal capable of regulating the pollen tip-growth machinery. These results identify a CNGC that is essential to an organism's life cycle and raise the possibility that CNGCs have a widespread role in regulating cell-growth dynamics in both plant and animals.
Gαi generates multiple Pins activation states to link cortical polarity and spindle orientation in
Drosophila
neuroblasts
Authors: Nipper Rick W. , Siller Karsten H. , Smith Nicholas R. , Doe Chris Q. , Prehoda Kenneth E.
Published: August 2007

Drosophila
neuroblasts divide asymmetrically by aligning their mitotic spindle with cortical cell polarity to generate distinct sibling cell types. Neuroblasts asymmetrically localize Gαi, Pins, and Mud proteins; Pins/Gαi direct cortical polarity, whereas Mud is required for spindle orientation. It is currently unknown how Gαi–Pins–Mud binding is regulated to link cortical polarity with spindle orientation. Here, we show that Pins forms a “closed” state via intramolecular GoLoco–tetratricopeptide repeat (TPR) interactions, which regulate Mud binding. Biochemical, genetic, and live imaging experiments show that Gαi binds to the first of three Pins GoLoco motifs to recruit Pins to the apical cortex without “opening” Pins or recruiting Mud. However, Gαi and Mud bind cooperatively to the Pins GoLocos 2/3 and tetratricopeptide repeat domains, respectively, thereby restricting Pins–Mud interaction to the apical cortex and fixing spindle orientation. We conclude that Pins has multiple activity states that generate cortical polarity and link it with mitotic spindle orientation.
Role of VEGF in maintaining renal structure and function under normotensive and hypertensive conditions
Authors: Advani Andrew , Kelly Darren J. , Advani Suzanne L. , Cox Alison J. , Thai Kerri , Zhang Yuan , White Kathryn E. , Gow Renae M. , Marshall Sally M. , Steer Brent M. , Marsden Philip A. , Rakoczy P. Elizabeth , Gilbert Richard E.
Published: August 2007

Inhibiting the actions of VEGF is a new therapeutic paradigm in cancer management with antiangiogenic therapy also under intensive investigation in a range of nonmalignant diseases characterized by pathological angiogenesis. However, the effects of VEGF inhibition on organs that constitutively express it in adulthood, such as the kidney, are mostly unknown. Accordingly, we examined the effect of VEGF inhibition on renal structure and function under physiological conditions and in the setting of the common renal stressors: hypertension and activation of the renin–angiotensin system. When compared with normotensive Sprague–Dawley (SD) rats, glomerular VEGF mRNA was increased 2-fold in transgenic (mRen-2)27 rats that overexpress renin with spontaneously hypertensive rat (SHR) kidneys showing VEGF expression levels that were intermediate between them. Administration of either an orally active inhibitor of the type 2 VEGF receptor (VEGFR-2) tyrosine kinase or a VEGF neutralizing antibody to TGR(mRen-2)27 rats resulted in loss of glomerular endothelial cells and transformation to a malignant hypertensive phenotype with severe glomerulosclerosis. VEGFR-2 kinase inhibition treatment was well tolerated in SDs and SHRs; although even in these animals there was detectable endothelial cell loss and rise in albuminuria. Mild mesangial expansion was also noted in hypertensive SHR, but not in SD rats. These studies illustrate: (
i
) VEGF has a role in the maintenance of glomerular endothelial integrity under physiological circumstances, (
ii
) glomerular VEGF is increased in response to hypertension and activation of the renin–angiotensin system, and (
iii
) VEGF signaling plays a protective role in the setting of these renal stressors.
Lsh controls Hox gene silencing during development
Authors: Xi Sichuan , Zhu Heming , Xu Hong , Schmidtmann Anja , Geiman Theresa M. , Muegge Kathrin
Published: August 2007

Polycomb-mediated repression and DNA methylation are important epigenetic mechanisms of gene silencing. Recent evidence suggests a functional link between the polycomb repressive complex (PRC) and Dnmts in cancer cells. Here we provide evidence that Lsh, a regulator of DNA methylation, is also involved in normal control of PRC-mediated silencing during embryogenesis. We demonstrate that Lsh, a SNF2 homolog, can associate with some Hox genes and regulates Dnmt3b binding, DNA methylation, and silencing of Hox genes during development. Moreover, Lsh can associate with PRC1 components and influence PRC-mediated histone modifications. Thus Lsh is part of a physiological feedback loop that reinforces DNA methylation and silencing of PRC targets.
Arabidopsis
CYCD3 D-type cyclins link cell proliferation and endocycles and are rate-limiting for cytokinin responses
Authors: Dewitte Walter , Scofield Simon , Alcasabas Annette A. , Maughan Spencer C. , Menges Margit , Braun Nils , Collins Carl , Nieuwland Jeroen , Prinsen Els , Sundaresan Venkatesan , Murray James A. H.
Published: August 2007

Current understanding of the integration of cell division and expansion in the development of plant lateral organs such as leaves is limited. Cell number is established during a mitotic phase, and subsequent growth into a mature organ relies primarily on cell expansion accompanied by endocycles. Here we show that the three
Arabidopsis
cyclin D3 (
CYCD3
) genes are expressed in overlapping but distinct patterns in developing lateral organs and the shoot meristem. Triple loss-of-function mutants show that
CYCD3
function is essential neither for the mitotic cell cycle nor for morphogenesis. Rather, analysis of mutant and reciprocal overexpression phenotypes shows that
CYCD3
function contributes to the control of cell number in developing leaves by regulating the duration of the mitotic phase and timing of the transition to endocycles. Petals, which normally do not endoreduplicate, respond to loss of
CYCD3
function with larger cells that initiate endocycles. The phytohormone cytokinin regulates cell division in the shoot meristem and developing leaves and induces
CYCD3
expression. Loss of
CYCD3
impairs shoot meristem function and leads to reduced cytokinin responses, including the inability to initiate shoots on callus, without affecting endogenous cytokinin levels. We conclude that
CYCD3
activity is important for determining cell number in developing lateral organs and the relative contribution of the alternative processes of cell production and cell expansion to overall organ growth, as well as mediating cytokinin effects in apical growth and development.
Tracing electronic pathways in molecules by using inelastic tunneling spectroscopy
Authors: Troisi Alessandro , Beebe Jeremy M. , Picraux Laura B. , van Zee Roger D. , Stewart Duncan R. , Ratner Mark A. , Kushmerick James G.
Published: August 2007

Using inelastic electron tunneling spectroscopy (IETS) to measure the vibronic structure of nonequilibrium molecular transport, aided by a quantitative interpretation scheme based on Green's function-density functional theory methods, we are able to characterize the actual pathways that the electrons traverse when moving through a molecule in a molecular transport junction. We show that the IETS observations directly index electron tunneling pathways along the given normal coordinates of the molecule. One can then interpret the maxima in the IETS spectrum in terms of the specific paths that the electrons follow as they traverse the molecular junction. Therefore, IETS measurements not only prove (by the appearance of molecular vibrational frequencies in the spectrum) that the tunneling charges, in fact, pass through the molecule, but also can be used to determine the transport pathways and how they change with the geometry and placement of molecules in junctions.
Inhibitors of metabolism rescue cell death in Huntington's disease models
Authors: Varma Hemant , Cheng Richard , Voisine Cindy , Hart Anne C. , Stockwell Brent R.
Published: August 2007

Huntington's disease (HD) is a fatal inherited neurodegenerative disorder. HD is caused by polyglutamine expansions in the huntingtin (htt) protein that result in neuronal loss and contribute to HD pathology. The mechanisms of neuronal loss in HD are elusive, and there is no therapy to alleviate HD. To find small molecules that slow neuronal loss in HD, we screened 1,040 biologically active molecules to identify suppressors of cell death in a neuronal cell culture model of HD. We found that inhibitors of mitochondrial function or glycolysis rescued cell death in this cell culture and inin vivoHD models. These inhibitors prevented cell death by activating prosurvival ERK and AKT signaling but without altering cellular ATP levels. ERK and AKT inhibition through the use of specific chemical inhibitors abrogated the rescue, whereas their activation through the use of growth factors rescued cell death, suggesting that this activation could explain the protective effect of metabolic inhibitors. Both ERK and AKT signaling are disrupted in HD, and activating these pathways is protective in several HD models. Our results reveal a mechanism for activating prosurvival signaling that could be exploited for treating HD and possibly other neurodegenerative disorders.
Enhanced subunit interactions with gemcitabine-5′-diphosphate inhibit ribonucleotide reductases
Authors: Wang Jun , Lohman Gregory J. S. , Stubbe JoAnne
Published: August 2007

Ribonucleotide reductases (RNRs) catalyze the conversion of nucleotides to deoxynucleotides in all organisms. The class I RNRs are composed of two subunits, α and β, with proposed quaternary structures of α2β2, α6β2, or α6β6, depending on the organism. The α subunits bind the nucleoside diphosphate substrates and the dNTP/ATP allosteric effectors that govern specificity and turnover. The β2 subunit houses the diferric Y
•
(1 radical per β2) cofactor that is required to initiate nucleotide reduction. 2′,2′-Difluoro-2′-deoxycytidine (F
2
C) is presently used clinically in a variety of cancer treatments and the 5′-diphosphorylated F
2
C (F
2
CDP) is a potent inhibitor of RNRs. The studies with [1′-
3
H]-F
2
CDP and [5-
3
H]-F
2
CDP have established that F
2
CDP is a substoichiometric mechanism based inhibitor (0.5 eq F
2
CDP/α) of both the
Escherichia coli
and the human RNRs in the presence of reductant. Inactivation is caused by covalent labeling of RNR by the sugar of F
2
CDP (0.5 eq/α) and is accompanied by release of 0.5 eq cytosine/α. Inactivation also results in loss of 40% of β2 activity. Studies using size exclusion chromatography reveal that in the
E. coli
RNR, an α2β2 tight complex is generated subsequent to enzyme inactivation by F
2
CDP, whereas in the human RNR, an α6β6 tight complex is generated. Isolation of these complexes establishes that the weak interactions of the subunits in the absence of nucleotides are substantially increased in the presence of F
2
CDP and ATP. This information and the proposed asymmetry between the interactions of αnβn provide an explanation for complete inactivation of RNR with substoichiometric amounts of F
2
CDP.
Is subcutaneous local anesthesia in shoulder magnetic resonance arthrography necessary?
Authors: Koivikko M. P. , Koskinen S. K.
Published: August 2007

Background: Magnetic resonance arthrography is a well-established diagnostic method in degenerative and traumatic disorders of the shoulder. Some radiologists prefer to apply a local anesthetic to the skin prior to performing the joint puncture. However, no information regarding the efficacy of local anesthetics exists.

Purpose: To assess patient discomfort in arthrography injection.

Material and Methods: A patient survey ( n = 74) utilizing a visual analog scale (VAS) measured the intensity of pain in arthrography injection by those receiving local anesthetics ( n = 36) versus those who did not ( n = 38).

Results: Mean VAS scores were 20.8 (median 10.5, SD 24.3) for those receiving local anesthetics versus 19.3 (median 13.0, SD 20.7) for those who did not ( P = 0.83, Mann-Whitney U test).

Conclusion: Routine use of local anesthesia of the skin in arthrography injection is unnecessary.