Electrocatalytic oxidation of ethanol and ethylene glycol on cubic, octahedral and rhombic dodecahedral palladium nanocrystals

Cubic, octahedral and rhombic dodecahedral Pd nanocrystals were synthesized and examined as nanocatalysts for electro-oxidation of ethanol and ethylene glycol. Combined electrochemical measurements and density functional theory calculations reveal that nanofacet-dependent affinity and reactivity of OHads and COads are closely linked to the C2 alcohol oxidation activities, with the highest reactivity found on the Pd nanocubes bounded by {100} facets

PKA Controls Calcium Influx into Motor Neurons during a Rhythmic Behavior

<div><p>Cyclic adenosine monophosphate (cAMP) has been implicated in the execution of diverse rhythmic behaviors, but how cAMP functions in neurons to generate behavioral outputs remains unclear. During the defecation motor program in <i>C. elegans</i>, a peptide released from the pacemaker (the intestine) rhythmically excites the GABAergic neurons that control enteric muscle contractions by activating a G protein-coupled receptor (GPCR) signaling pathway that is dependent on cAMP. Here, we show that the <i>C. elegans</i> PKA catalytic subunit, KIN-1, is the sole cAMP target in this pathway and that PKA is essential for enteric muscle contractions. Genetic analysis using cell-specific expression of dominant negative or constitutively active PKA transgenes reveals that knockdown of PKA activity in the GABAergic neurons blocks enteric muscle contractions, whereas constitutive PKA activation restores enteric muscle contractions to mutants defective in the peptidergic signaling pathway. Using real-time, in vivo calcium imaging, we find that PKA activity in the GABAergic neurons is essential for the generation of synaptic calcium transients that drive GABA release. In addition, constitutively active PKA increases the duration of calcium transients and causes ectopic calcium transients that can trigger out-of-phase enteric muscle contractions. Finally, we show that the voltage-gated calcium channels UNC-2 and EGL-19, but not CCA-1 function downstream of PKA to promote enteric muscle contractions and rhythmic calcium influx in the GABAergic neurons. Thus, our results suggest that PKA activates neurons during a rhythmic behavior by promoting presynaptic calcium influx through specific voltage-gated calcium channels.</p></div

Constitutively active PKA in GABAergic neurons partially bypasses the requirement of AEX-2/GPCR.

<p>(A) Diagram showing the construction of the constitutively active PKA (PKA[CA]). “R” and “C” indicate the PKA regulatory and catalytic subunit, respectively. The two asterisks (*) represent the two mutations (H96Q, W205R) in the PKA catalytic subunit KIN-1a, which presumably disrupt its association with the regulatory subunit but do not affect its enzymatic activity. (B) Quantification of the Exp step of young adults with the indicated genotypes. PKA[CA] denotes PKA constitutively active transgenic worms (<i>vjIs102</i> and <i>vjIs103</i>) expressing the mutated catalytic subunit <i>kin-1a</i>(H96Q, W205R) in the GABAergic neurons using the <i>unc-47</i> full length promoter. <i>vjIs103</i> and <i>vjIs77</i> were used for the PKA[CA];PKA[DN] strain. (C) Representative ethograms of ten consecutive defecation cycles of young adult worms with the indicated genotypes. Each dot represents 1 s. “p” stands for the pBoc step and “x” indicates the Exp step. Ectopic Exp steps are indicated by “<u>x</u>”. Means and standard errors are shown. Asterisks indicate significant differences between indicated groups: ** P<0.01, *** P<0.005 in Student's t-test.</p

Other non voltage-gated calcium channels are required from calcium influx in the GABAergic neurons.

<p>(A) and (B) Quantification of the Exp step of young adult worms with the indicated genotype types. (C) Classification of different patterns of pBoc, fluorescent spikes in DVB and Exp in worms with the indicated genotypes. <i>unc-2</i>: 40 cycles in 21 animals, <i>egl-19; unc-2</i>: 19 cycles in 11 animals, <i>PKA[CA]; egl-19; unc-2</i>: 24 cycles in 12 animals, PKA[CA]: 23 cycles in 12 animals. (D) and (E) Quantification of the duration and amplitude of regular DVB calcium spikes in worms with indicated genotypes. PKA[CA] represents transgenic worms with constitutively active PKA specifically expressed in GABAergic neurons (<i>vjIs103</i> in (B) and <i>vjIs102</i> in (C, D)). Note that in (C), (D) and (E), <i>unc-2</i> and PKA[CA] strains, but not the <i>egl-19; unc-2</i> and the PKA[CA]; <i>egl-19; unc-2</i> strains contain the <i>unc-13(s69)</i> mutation for immobilization, as <i>egl-19;unc-2</i> alone were almost completely paralyzed. <i>vjIs58</i>, the transgenic strain with GCaMP3 expressed in the DVB neuron, was used for the <i>unc-2</i> strain; while <i>vjIs64</i> was used for calcium imaging in other genotypes. Means and standard errors are shown. Asterisks indicate significant difference between indicated group and significant difference from wild type in (A), PKA[CA] in (B) and <i>egl-19; unc-2 mutants</i> in (D) and (E): * p<0.05; ***P<0.005 in Student's t-test. “n.s.” indicates no significant difference between indicated groups.</p

PKA is necessary for calcium influx in DVB neurons.

<p>(A) Expression of the genetically-encoded calcium indicator, GCaMP3 in DVB neurons (<i>vjIs58</i>). Top: diagram of the DVB neuron in the tail region. Synapse means the neuromuscular junction where the DVB neuron innervates enteric muscles. Middle and Bottom: two snapshots from a real-time imaging video of wild type animals showing an increase in fluorescence in synaptic region of DVB neurons, as indicated by the white arrow, right before the Exp step. (B) A representative trace of the GCaMP3 fluorescence in the synaptic region of DVB neurons in wild type animals showing DVB neurons are rhythmically activated during three consecutive defecation cycles. Note that the cycle length is longer than 50 seconds, likely due to <i>unc-13(s69)</i> mutation, which was used to immobilize the worms for calcium imaging (See <a href="http://www.plosgenetics.org/article/info:doi/10.1371/journal.pgen.1003831#s4" target="_blank">Materials and Methods</a> for details). (C) Representative traces of the GCaMP3 fluorescence in the synaptic region of DVB neurons in worms with the indicated genotypes. The observed pBoc step and Exp step are indicated by arrows and arrowheads, respectively. (D) Classification of the different patterns of pBoc, fluorescent spikes in DVB and Exp in worms with the indicated genotypes. <i>vjIs76</i> was used for the PKA[DN] strain. In (D), wild type: 23 cycles in 11 animals; <i>unc-25</i>: 44 cycles in 11 animals; <i>aex-2</i>: 44 cycles in 11 animals; PKA[DN]: 30 cycles in 12 animals.</p

PKA functions in GABAergic neurons to regulate the Exp step.

<p>(A) Diagram showing the construction of dominant negative PKA (PKA[DN]). “R” and “C” indicate the PKA regulatory and catalytic subunit, respectively. “x” represents the substitution (G310D) in the site B of the regulatory subunit KIN-2a, which presumably blocks cAMP binding and prevents its dissociation with PKA catalytic subunit. (B) and (C) Quantification of the Exp step of young adults with the indicated genotypes. PKA[DN] denotes PKA dominant negative transgenic worms (<i>vjIs76</i> and <i>vjIs77</i>) in which the mutated regulatory subunit <i>kin-2a</i>(G310D) was expressed specifically in GABAergic neurons using <i>unc-47</i> full length promoter. <i>gsa-1(gf)</i> is a gain-of-function allele (<i>ce81)</i> of <i>gsa-1</i>/Gαs. (D) Representative ethograms of ten consecutive defecation cycles of young adult worms with the indicated genotypes. <i>vjIs77</i> is used for PKA[DN] in (D). Each dot represents 1 s. “p” stands for the pBoc step and “x” indicates the Exp step. aBoc is omitted. Means and standard errors are shown. Asterisks (***) indicate significant difference from wild type in (B) and <i>gas-1(gf)/Gas</i> in (C): p<0.005 in Student's t-test. “n.s.” indicates no significant difference between indicated groups.</p

Constitutively active PKA causes ectopic calcium spikes in DVB neurons and increases calcium spike duration.

<p>(A) A representative trace of the GCaMP3 fluorescence in the synaptic region of DVB neurons in transgenic worms expressing PKA[CA] (<i>vjIs102</i>) during two consecutive defecation cycles. An ectopic calcium spike in DVB neurons was observed, as indicated by the bracket. Note that the cycle length is longer than 50 seconds, likely due to <i>unc-13(s69)</i> mutation, which was used to immobilize the worms for calcium imaging (See <a href="http://www.plosgenetics.org/article/info:doi/10.1371/journal.pgen.1003831#s4" target="_blank">Materials and Methods</a> for details). (B) Representative traces of the GCaMP3 fluorescence in the synaptic region of DVB neurons in worms with the indicated genotypes. The observed pBoc step and Exp step are indicated by arrows and arrowheads, respectively. (C) Average frequency of ectopic calcium spikes in DVB neurons during a 250-second imaging period in wild type animals (0.0±0.00 events per 250 seconds, n = 10 animals) and <i>vjIs102</i> (2.4±0.69 events per 250 seconds, n = 11 animals). (D) and (E) the duration and amplitude of regular DVB calcium spikes and ectopic calcium spikes in wild type and PKA[CA] (<i>vjIs102</i>) animals. Means and standard errors are shown. Asterisks indicate significant differences from wild type: ** P<0.01, *** P<0.005 in Student's t-test. “n.s.” indicates no significant difference between indicated groups.</p

Chromosomal locations of <i>Populus Dof</i> genes.

<p>Forty-one <i>Dof</i> genes were mapped to 19 linkage groups (LG). A schematic view of chromosome reorganization caused by recent whole-genome duplication in <i>Populus</i> is shown. Segmental duplicated homologous blocks are indicated by the same color. The scale represents mega bases (Mb). The LG numbers are indicated above each bar.</p

Characterization of Dof Transcription Factors and Their Responses to Osmotic Stress in Poplar (<i>Populus trichocarpa</i>)

<div><p>The DNA-binding One Zinc Finger (<i>Dof</i>) genes are ubiquitous in many plant species and are especial transcription regulators that participate in plant growth, development and various procedures, including biotic and abiotic stress reactions. In this study, we identified 41 <i>PtrDof</i> members from <i>Populus trichocarpa</i> genomes and classified them into four groups. The conserved motifs and gene structures of some <i>PtrDof</i> genes belonging to the same subgroup were almost the same. The 41 <i>PtrDof</i> genes were dispersed on 18 of the 19 <i>Populus</i> chromosomes. Many key stress- or phytohormone-related <i>cis</i>-elements were discovered in the <i>PtrDof</i> gene promoter regions. Consequently, we undertook expression profiling of the <i>PtrDof</i> genes in leaves and roots in response to osmotic stress and abscisic acid. A total of seven genes (<i>PtrDof14</i>, <i>16</i>, <i>25</i>, <i>27</i>, <i>28</i>, <i>37</i> and <i>39</i>) in the <i>Populus Dof</i> gene family were consistently upregulated at point in all time in the leaves and roots under osmotic and abscisic acid (ABA) stress. We observed that 12 <i>PtrDof</i> genes could be targeted by 15 miRNAs. Moreover, we mapped the cleavage site in <i>PtrDof30</i> using the 5’RLM-RACE. The results showed that <i>PtrDofs</i> may have a role in resistance to abiotic stress in <i>Populus trichocarpa</i>.</p></div

Ultrafast Charge Transfer Enhancement in CdS–MoS₂ via a Linker Molecule

Hybrid systems, which take advantage of the low material dimensionality, have great potential for designing nanoscale devices. Quantum dots can be combined with two-dimensional (2D) monolayers to achieve success in photovoltaics and water splitting. In such colloidal systems, ligand molecules play an important role in stabilizing the nanostructures, but their role in heterostructure device performance is still poorly understood. In this study, time-dependent density functional theory is employed to explore how the cysteine ligand affects the charge transfer across the CdS–MoS2 heterostructure, at the ultrafast time scale. We show that the cysteine ligand enhances charge transfer, not only by coupling the CdS and MoS2 electronic states across the junction but also through enhanced electron–phonon coupling, where the carrier energy is quickly dissipated to high-frequency local vibrational modes arising from the lighter ligand atoms. This enhanced electron–phonon mechanism associated with the ligand is expected to be broadly applicable to most solution-based nanodevices