13 research outputs found

    Legislative Documents

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    Also, variously referred to as: House bills; House documents; House legislative documents; legislative documents; General Court documents

    In Situ Spectroscopic and Computational Studies on a MnO<sub>2</sub>–CuO Catalyst for Use in Volatile Organic Compound Decomposition

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    In situ near-edge X-ray absorption fine structure (NEXAFS) spectroscopy and density functional theory calculations were conducted to demonstrate the decomposition mechanism of propylene glycol methyl ether acetate (PGMEA) on a MnO<sub>2</sub>–CuO catalyst. The catalytic activity of MnO<sub>2</sub>–CuO was higher than that of MnO<sub>2</sub> at low temperatures, although the pore properties of MnO<sub>2</sub> were similar to those of MnO<sub>2</sub>–CuO. In addition, whereas the chemical state of MnO<sub>2</sub> remained constant following PGMEA dosing at 150 °C, MnO<sub>2</sub>–CuO was reduced under identical conditions, as confirmed by in situ NEXAFS spectroscopy. These results indicate that the presence of Cu in the MnO<sub>2</sub>–CuO catalyst enables the release of oxygen at lower temperatures. More specifically, the released oxygen originated from the Mn–<u>O</u>–Cu moiety on the top layer of the MnO<sub>2</sub>–CuO structure, as confirmed by calculation of the oxygen release energies in various oxygen positions of MnO<sub>2</sub>–CuO. Furthermore, the spectral changes in the in situ NEXAFS spectrum of MnO<sub>2</sub>–CuO following the catalytic reaction at 150 °C corresponded well with those of the simulated NEXAFS spectrum following oxygen release from Mn–<u>O</u>–Cu. Finally, after the completion of the catalytic reaction, the quantities of lactone and ether functionalities in PGMEA decreased, whereas the formation of CC bonds was observed

    Mechanism of the pH-Induced Conformational Change in the Sensor Domain of the DraK Histidine Kinase via the E83, E105, and E107 Residues

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    <div><p>The DraR/DraK two-component system was found to be involved in the differential regulation of antibiotic biosynthesis in a medium-dependent manner; however, its function and signaling and sensing mechanisms remain unclear. Here, we describe the solution structure of the extracellular sensor domain of DraK and suggest a mechanism for the pH-dependent conformational change of the protein. The structure contains a mixed alpha-beta fold, adopting a fold similar to the ubiquitous sensor domain of histidine kinase. A biophysical study demonstrates that the E83, E105, and E107 residues have abnormally high pKa values and that they drive the pH-dependent conformational change for the extracellular sensor domain of DraK. We found that a triple mutant (E83L/E105L/E107A) is pH independent and mimics the low pH structure. An i<i>n vivo</i> study showed that DraK is essential for the recovery of the pH of <i>Streptomyces coelicolor</i> growth medium after acid shock. Our findings suggest that the DraR/DraK two-component system plays an important role in the pH regulation of <i>S. coelicolor</i> growth medium. This study provides a foundation for the regulation and the production of secondary metabolites in <i>Streptomyces</i>.</p></div

    pH profiles and cell phenotypes.

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    <p>(<b>A</b>) Time-dependent pH profiles of culture plates for wild type DraK (black), the Δ<i>draK</i> mutant (red), and the Δ<i>draR</i> mutant (blue) following pH shock. (<b>B</b>) Time-dependent cell phenotypes of <i>S. coelicolor</i> for wild type DraK, the Δ<i>draK</i> mutant, and the Δ<i>draR</i> mutant in pH shock culture (PSC).</p

    <sup>1</sup>H-<sup>15</sup>N HSQC spectra of the ESD mutants in 10 mM HEPES pH 7.5 and 100 mM NaCl.

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    <p>Each glutamate residue at positions 83, 105, or 107 is mutated to alanine, glutamine, or leucine. <sup>1</sup>H-<sup>15</sup>N HSQC spectrum of the wild type protein under the same conditions shown in the previous report <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0107168#pone.0107168-Yeo1" target="_blank">[23]</a>.</p

    pH-dependent fluorescence and near-UV CD spectra of the ESD.

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    <p>The signals were measured at pH 4.5 (solid line), 7.5 (dashed line), and 10.0 (dotted line). The excitation wavelength was 277 nm. (<b>A</b>) and (<b>B</b>) denote fluorescence and near-UV CD spectra, respectively.</p

    Solution structure of the ESD (E83Q) and sequence and secondary structure alignments with the sensor domain of CitA.

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    <p>(<b>A</b>) A solution structure of the ESD (E83Q) from the 20 lowest-energy structures is represented by the ribbon diagram. Α helices and β strands are colored red and yellow, respectively. (<b>B</b>) The structure of the ESD (yellow) and that of the CitA sensor domain (green) are superimposed. The magenta color indicates the absent structural elements in the ESD of DraK. (<b>C</b>) Sequence alignment and comparison of the secondary structure between the sensor domain of DraK and that of CitA. The red blocks denote regions of sequence identity across the two domains, and the blue boxes indicate partially conserved residues.</p
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