Synthesis of three-dimensionally ordered macroporous LaFeO3 perovskites and their performance for chemical-looping reforming of methane

Three-dimensionally ordered macroporous (3DOM) LaFeO3 perovskite-type oxides were synthesized using a polystyrene colloidal crystal templating method. The obtained 3DOM LaFeO3 was characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR). The reactivity of the perovskite-type oxides was evaluated using temperature-programmed reduction and multicyclic redox reactions by exposing them to an alternating methane and air atmosphere. The methane oxidation performance of the oxides was investigated in a fixed-bed reactor. The effect of the self-assembly method on the structure of the polystyrene template was also studied. A vertical deposition method yielded a more uniform and orderly polystyrene template than those obtained by centrifugation and evaporation techniques. The solvent and concentration of the precursor solution were the major factors to affect the prepared 3DOM perovskite. SEM analysis showed that samples synthesized with ethanol precursor solvent exhibited a better 3DOM structure than those produced with ethylene glycol, and that 1.0 mol/L may be an optimal precursor solution concentration. XRD and FTIR results suggested that the obtained 3DOM LaFeO3 was pure crystalline perovskite. Two kinds of oxygen species were found to exist on the 3DOM perovskites: surface adsorbed oxygen and bulk lattice oxygen. The surface oxygen contributed to the complete oxidization of methane to CO2 and H2O because of its higher reactivity, while the bulk lattice oxygen tended towards partial methane oxidation to H-2 and CO. The available oxygen in the 3DOM LaFeO3 was higher than that of the same mass of non-3DOM LaFeO3 during the partial oxidation of methane. Methane was partially oxidized into syngas with a H-2/CO ratio of around 2:1 in a wide time range of the reactions. The generated H-2/CO = 2 syngas was suitable for subsequent gas-to-liquids processes, such as Fischer-Tropsch and/or methanol synthesis. (c) 2013, Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by Elsevier B.V. All rights reserved

QKL injection ameliorates Alzheimer's disease-like pathology by regulating expression of RAGE

The onset of Alzheimer's disease is related to neuron damage caused by massive deposition of Aβ in the brain. Recent studies suggest that excessive Aβ in the brain mainly comes from peripheral blood, and BBB is the key to regulate Aβ in and out of the brain. In this study, we explored the pathogenesis of AD from the perspective of Aβ transport through the BBB and the effect of QKL injection in AD mice. The results showed that QKL could improve the cognitive dysfunction of AD mice, decrease the level of Aβ and Aβ transporter—RAGE, which was supported by the results of network pharmacology, molecular docking and molecular dynamics simulation. In conclusion, RAGE is a potential target for QKL's therapeutic effect on AD

Genetic Framework of Cyclin-Dependent Kinase Function in Arabidopsis

Summary Cyclin-dependent kinases (CDKs) are at the heart of eukaryotic cell-cycle control. The yeast Cdc2/CDC28 PSTAIRE kinase and its orthologs such as the mammalian Cdk1 have been found to be indispensable for cell-cycle progression in all eukaryotes investigated so far. CDKA;1 is the only PSTAIRE kinase in the flowering plant Arabidopsis and can rescue Cdc2/CDC28 mutants. Here, we show that cdka;1 null mutants are viable but display specific cell-cycle and developmental defects, e.g., in S phase entry and stem cell maintenance. We unravel that the crucial function of CDKA;1 is the control of the plant Retinoblastoma homolog RBR1 and that codepletion of RBR1 and CDKA;1 rescued most defects of cdka;1 mutants. Our work further revealed a basic cell-cycle control system relying on two plant-specific B1-type CDKs, and the triple cdk mutants displayed an early germline arrest. Taken together, our data indicate divergent functional differentiation of Cdc2-type kinases during eukaryote evolution

CC losses from areas delineated as mangrove forest in the initial survey.

<p>Each column represents a method of calculation from Equation <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0118880#pone.0118880.e001" target="_blank">1</a>–<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0118880#pone.0118880.e004" target="_blank">4</a>. The final two columns are the mid value of the four equations and the mean value of the four equations. Units are t of C.</p><p>CC losses from areas delineated as mangrove forest in the initial survey.</p

A General G1/S-Phase Cell-Cycle Control Module in the Flowering Plant <em>Arabidopsis thaliana</em>

<div><p>The decision to replicate its DNA is of crucial importance for every cell and, in many organisms, is decisive for the progression through the entire cell cycle. A comparison of animals versus yeast has shown that, although most of the involved cell-cycle regulators are divergent in both clades, they fulfill a similar role and the overall network topology of G1/S regulation is highly conserved. Using germline development as a model system, we identified a regulatory cascade controlling entry into S phase in the flowering plant <em>Arabidopsis thaliana</em>, which, as a member of the <em>Plantae</em> supergroup, is phylogenetically only distantly related to <em>Opisthokonts</em> such as yeast and animals. This module comprises the <em>Arabidopsis</em> homologs of the animal transcription factor E2F, the plant homolog of the animal transcriptional repressor Retinoblastoma (Rb)-related 1 (RBR1), the plant-specific F-box protein F-BOX-LIKE 17 (FBL17), the plant specific cyclin-dependent kinase (CDK) inhibitors KRPs, as well as CDKA;1, the plant homolog of the yeast and animal Cdc2⁺/Cdk1 kinases. Our data show that the principle of a double negative wiring of Rb proteins is highly conserved, likely representing a universal mechanism in eukaryotic cell-cycle control. However, this negative feedback of Rb proteins is differently implemented in plants as it is brought about through a quadruple negative regulation centered around the F-box protein FBL17 that mediates the degradation of CDK inhibitors but is itself directly repressed by Rb. Biomathematical simulations and subsequent experimental confirmation of computational predictions revealed that this regulatory circuit can give rise to hysteresis highlighting the here identified dosage sensitivity of CDK inhibitors in this network.</p> </div

Pollen phenotypes of mutants for components of the G1/S phase control module.

<p>(A) Tricellular mature wild-type DAPI-stained pollen at anthesis (one vegetative cell enclosing two sperm cells). (B) DAPI-stained pollen at anthesis from heterozygous <i>cdka;1</i> mutant plants (similar to pollen from heterozygous <i>fbl17</i> mutants, data not shown) containing approximately 43% bicellular pollen (one vegetative cell and one sperm-cell-like cell) and 57% tricellular, wild-type-like pollen. (C) DAPI-stained pollen at anthesis from double heterozygous <i>cdka;1 fbl17</i> mutant plants carrying a hemizygous <i>Pro_CDKA;1:CDKA;1:YFP</i> rescue construct (similar to pollen from <i>e2fa^−/− fbl17^+/−</i> mutants, data not shown) and containing single-celled pollen grains (only one vegetative-like cell), in addition to bicellular (<i>cdka;1</i>/<i>fbl17</i>-like) and tricellular (wild-type-like) pollen. (D) Close-up of bicellular pollen as found in <i>cdka;1</i> or <i>fbl17</i> heterozygous plants. (E) Close-up of monocellular pollen grains as found in <i>cdka;1 fbl17</i> or <i>e2fa fbl17</i> double heterozygous mutants. (F) Quantification of DAPI-stained pollen. The DNA content of the single-celled pollen from <i>cdka;1^+/− fbl17^+/−</i> or <i>e2fa^−/− fbl17^+/−</i> double mutants reaches 1C, similarly to the vegetative nucleus in wild-type pollen and, thus, resides in a G1 phase.</p

General G1/S phase cell-cycle control module.

<p>(A) The transcription factor E2F activates the expression of <i>FBL17</i>, which is repressed by RBR1. FBL17 targets the CDKA;1 inhibitors KRP1, KRP3, KRP4, KRP6 and KRP7 for proteasome-dependent degradation, enabling the germ cell to progress through S phase. Phosphorylation of RBR by the CDKA;1-cyclin complex will relieve the inhibition of the S-phase genes and allows transcription of the <i>FBL17</i> gene. Promoters and genes are depicted in light sand color; proteins in dark sand; transcription is indicated by a grey arrow; negative regulation, i.e. at the transcriptional or protein level, is shown by rust-colored lines with a blunt end; positive regulation by a green line with a green arrowhead. Receiving input is placed above and executing output under the respective gene/protein. (B) The model presented in A gives rise to a bistable switch controlling the G1-to-S transition in the plant cell cycle. KRPs inhibit the CDKA;1-cyclin complexes, which in turn downregulate the levels of KRPs by phosphorylating and inhibiting RBR1, thereby activating E2F-dependent FBL17 synthesis leading to the degradation of KRPs. The antagonistic interaction between CDKA;1 and KRP is illustrated by the two curves (red and green for KRP and for CDKA;1, respectively) along which the rates of synthesis and degradation of KRPs and the CDKA;1-cyclin complexes are exactly balanced. The KRP balance curve has an inverse S-shape with high and low levels, depending on the CDKA;1-cyclin values. The dashed branch of the balance curve represents unstable steady states. At low CDKA;1-cyclin levels, only one steady state exists with high KRP levels and low CDKA;1 activity. At intermediate CDKA;1 levels, the system is bistable with three steady states. At high CDKA;1-cyclin values, the steady-state level of KRP is low and the CDKA;1-cyclin complexes are fully active. The transition from high to low KRP values corresponds to the G1-to-S transition. (C) Quantitative expression analyses of <i>CDKA;1</i> and <i>FBL17</i> in wild type and heterozygous <i>cdka;1</i> mutants. The mean plus standard deviation of the normalized relative quantities (NRQ) of three biological replicates are shown. The stars indicate statistically significant differences based on a t-test of log-transformed data with a p<0.05. As expected, the expression of <i>CDKA;1</i> drops by approximately 50% in the mutant. In addition, <i>FBL17</i> expression declines, consistent with a prediction of the model presented in A and B.</p

Mature ovules and seed development in wild type and <i>cdka;1 fbl17</i> double mutant.

<p>(A–C) Wild-type embryo sac and seed development; (D–F) aberrant development in a class of <i>cdka;1 fbl17</i> mutant plants. (A) Wild type showing a typical cellular morphology (arrowheads pointing to the central cell nucleus and the egg cell nucleus from top to bottom, respectively). Aberrant morphologies in the <i>cdka;1^+/− fbl17^+/−</i> double mutant with one (D), or two (G) nuclei in the absence of a cellularized egg apparatus. (B) While the wild-type seed 3 days after pollination has a normal embryo and endosperm development, the double mutant seed development collapsed after pollination, with only one (E) or two (H) nuclei staying in the middle of the empty embryo sac. (C) Wild type showing normal seed development 6 days after pollination, while <i>cdka;1^+/− fbl17^+/−</i> double mutants show approximately 24% seed abortion (F) after pollination with the wild-type pollen.</p

Accumulation and localization of CDKA;1-YFP fusion protein during female and male gametophyte development.

<p>(A-A^VI) Expression of a <i>PRO_CDKA;1:CDKA;1-YFP</i> construct completely rescues <i>cdka;1</i> pollen resulting in wild-type-like pollen with one vegetative cell (arrowhead in A^V) and two sperm cells (triangle in A^V and A^VI, see also <a href="http://www.plosgenetics.org/article/info:doi/10.1371/journal.pgen.1002847#pgen-1002847-g001" target="_blank">Figure 1</a>). <i>CDKA;1</i> is expressed throughout male gametophyte development but becomes restricted at anthesis to the two sperm cells as revealed by YFP accumulation. (B-B^VI) A hemizygous <i>PRO_CDKA;1:CDKA;1-YFP^+/−</i> allele in homozygous mutant <i>cdka;1^−/−</i> plants mimics heterozygous <i>cdka;1^+/−</i> mutant plants that produce pollen of which half resembles wild-type pollen but half comprises one vegetative cell and only one instead of two sperm cells at anthesis (see <a href="http://www.plosgenetics.org/article/info:doi/10.1371/journal.pgen.1002847#pgen-1002847-g001" target="_blank">Figure 1</a>). Continuous observation of the CDK-YFP fusion protein during male gametophyte development showed that the CDKA;1 protein concentration gradually decreased in 50% of pollen (marked by an asterisk) and that around the bicellular stage, clearly one pollen population can be identified that shows no or very little YFP fluorescence; occasionally, residual CDKA;1-YFP protein could be detected in the single sperm pollen at anthesis (red arrowhead in B^VI). A and B, Microspore mother cell; A^I and B^I, tetrads; A^II and B^II, monocellular stage; A^III and B^III, early bicellular stage; A^IV and B^IV, late bicellular stage; A^V and B^V, tricellular stage; A^VI and B^VI, anthesis. (C) Cartoon summarizing the decrease in CDKA;1 concentration as seen in B-B^VI. At the bicellular stage, CDKA;1 levels in mutant pollen (dashed yellow line) drop below an assumed threshold (dashed red line) for executing mitosis. Consistent with the disappearance of the YFP fluorescence at this stage, <i>cdka;1</i> mutant pollen typically arrest before PMII. (D-D^VI) CDKA;1-YFP signal appears in all nuclei at all developmental stages of the developing embryo sac (MMC to FG7, arrowheads mark the nuclei in the embryo sac). At maturity, YFP fluorescence is only present in the gametic cells, the egg cell and the central cell (marked by a white triangle in D^VI). MMC, megaspore mother cell/microspore mother cell; MC, monocellular; BC, bicellular; TC, tricellular; FG, female gametophyte stage.</p