80 research outputs found
Dark-ages reionization and galaxy formation simulation XI: Clustering and halo masses of high redshift galaxies
We investigate the clustering properties of Lyman-break galaxies (LBGs) at
- . Using the semi-analytical model {\scshape Meraxes} constructed
as part of the Dark-ages Reionization And Galaxy-formation Observables from
Numerical Simulation (DRAGONS) project, we predict the angular correlation
function (ACF) of LBGs at - . Overall, we find that the predicted
ACFs are in good agreement with recent measurements at and from observations consisting of the Hubble eXtreme Deep Field (XDF), the
Hubble Ultra-Deep Field (HUDF) and Cosmic Assembly Near-infrared Deep
Extragalactic Legacy Survey (CANDELS) field. We confirm the dependence of
clustering on luminosity, with more massive dark matter haloes hosting brighter
galaxies, remains valid at high redshift. The predicted galaxy bias at fixed
luminosity is found to increase with redshift, in agreement with observations.
We find that LBGs of magnitude at reside in dark matter haloes of mean mass -
, and this dark matter halo mass does not evolve
significantly during reionisation.Comment: 14 pages, 10 figures, published in MNRA
Research Progress on Natural Diterpenoids in Reversing Multidrug Resistance
Multidrug resistance (MDR) is one of the main impediments in successful chemotherapy in cancer treatment. Overexpression of ATP-binding cassette (ABC) transporter proteins is one of the most important mechanisms of MDR. Natural products have their unique advantages in reversing MDR, among which diterpenoids have attracted great attention of the researchers around the world. This review article summarizes and discusses the research progress on diterpenoids in reversing MDR
Glycoside-metabolizing oxidoreductase D3dgpA from human gut bacterium
The Gfo/Idh/MocA family enzyme DgpA was known to catalyze the regiospecific oxidation of puerarin to 3”-oxo-puerarin in the presence of 3-oxo-glucose. Here, we discovered that D3dgpA, dgpA cloned from the human gut bacterium Dorea sp. MRG-IFC3, catalyzed the regiospecific oxidation of various C-/O-glycosides, including puerarin, in the presence of methyl β-D-3-oxo-glucopyranoside. While C-glycosides were converted to 3”- and 2”-oxo-products by D3dgpA, O-glycosides resulted in the formation of aglycones and hexose enediolone from the 3”-oxo-products. From DFT calculations, it was found that isomerization of 3”-oxo-puerarin to 2”-oxo-puerarin required a small activation energy of 9.86 kcal/mol, and the O-glycosidic bond cleavage of 3”-oxo-products was also thermodynamically favored with a small activation energy of 3.49 kcal/mol. In addition, the reaction mechanism of D3dgpA was discussed in comparison to those of Gfo/Idh/MocA and GMC family enzymes. The robust reactivity of D3dgpA was proposed as a new general route for derivatization of glycosides
Structural and Functional Analysis of Phytotoxin Toxoflavin-Degrading Enzyme
Pathogenic bacteria synthesize and secrete toxic low molecular weight compounds as virulence factors. These microbial toxins play essential roles in the pathogenicity of bacteria in various hosts, and are emerging as targets for antivirulence strategies. Toxoflavin, a phytotoxin produced by Burkholderia glumae BGR1, has been known to be the key factor in rice grain rot and wilt in many field crops. Recently, toxoflavin-degrading enzyme (TxDE) was identified from Paenibacillus polymyxa JH2, thereby providing a possible antivirulence strategy for toxoflavin-mediated plant diseases. Here, we report the crystal structure of TxDE in the substrate-free form and in complex with toxoflavin, along with the results of a functional analysis. The overall structure of TxDE is similar to those of the vicinal oxygen chelate superfamily of metalloenzymes, despite the lack of apparent sequence identity. The active site is located at the end of the hydrophobic channel, 9 Å in length, and contains a Mn(II) ion interacting with one histidine residue, two glutamate residues, and three water molecules in an octahedral coordination. In the complex, toxoflavin binds in the hydrophobic active site, specifically the Mn(II)-coordination shell by replacing a ligating water molecule. A functional analysis indicated that TxDE catalyzes the degradation of toxoflavin in a manner dependent on oxygen, Mn(II), and the reducing agent dithiothreitol. These results provide the structural features of TxDE and the early events in catalysis
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