6,637 research outputs found
TACC3-ch-TOG track the growing tips of microtubules independently of clathrin and Aurora-A phosphorylation
No full textThe interaction between TACC3 (transforming acidic coiled coil protein 3) and the microtubule polymerase ch-TOG (colonic, hepatic tumor overexpressed gene) is evolutionarily conserved. Loading of TACC3–ch-TOG onto spindle microtubules requires the phosphorylation of TACC3 by Aurora-A kinase and the subsequent interaction of TACC3 with clathrin to form a microtubule binding surface. Whether there is a pool of TACC3–ch-TOG that is independent of clathrin in human cells, and what is the function of this pool, are open questions. Here, we report that TACC3 is recruited to the plus-ends of microtubules by its association with ch-TOG and that this pool is independent of phosphorylation and binding to clathrin. The plus-end binding of TACC3–ch-TOG persists in interphase and we propose that one cellular function of TACC3–ch-TOG is to modulate cell migration. We also describe the distinct subcellular pools of TACC3, ch-TOG and clathrin. TACC3 is often described as a centrosomal protein, but we show that there is no significant population of TACC3 at centrosomes. The delineation of distinct protein pools reveals a simplified view of how these proteins are organized and controlled by post-translational modification
Life at the end of worlds : modelling the biosignatures of microbial life in diverse environments at the end of the habitable lifetimes of Earth-like planets
No full textThis thesis investigates how increased global mean temperatures on Earth, induced by the increase in the luminosity of the Sun as it ages, change the types of habitable environments on the planet at local scales over the next 3 Gyr. Rising temperatures enhance silicate weathering rates, reducing atmospheric CO₂ levels to below the threshold for photosynthesis, while simultaneously pushing environments past the temperature tolerances of plant and animal species. This leads to the end of all plant life and animal life (due to reduced food, O₂ and H₂O availability, as well as higher temperatures) within the next 1 Gyr. The reduction in the extent of the remaining microbial biosphere due to increasing temperatures and rapid ocean evaporation is then modelled, incorporating orbital parameter changes until all known types of life become extinct; a maximum of 2.8 Gyr from the present. The biosignatures associated with these changes are determined and the analysis extended to Earth-like extrasolar planets nearing the end of their habitable lifetimes. In particular, the stages in the main sequence evolutions of Sun-like stars within 10 pc are evaluated and used to extrapolate the stage that an Earth-analogue planet would be at in its habitable evolution, to determine the best candidate systems for a far-future Earth-analogue biosphere, highlighting the Beta Canum Venaticorum system as a good target.
One of the most promising biosignatures for a microbial biosphere on the far-future Earth (and similar planets) may be CH₄, which could reach levels in the atmosphere that make it more readily detectable than it is for a present-day Earth-like atmosphere. Determining these biosignatures will help expand the search for life to the wider range of environments that will be found as the habitable exoplanet inventory grows and planets are found at different stages in their habitable evolution
Effects of a simulated Martian UV flux on the cyanobacterium, Chroococcidiopsis sp. 029
No full textDried monolayers of Chroococcidiopsis sp. 029, a desiccation-tolerant, endolithic cyanobacterium, were exposed to a simulated martian-surface UV and visible light flux, which may also approximate to the worst-case scenario for the Archean Earth. After 5 min, there was a 99% loss of cell viability, and there were no survivors after 30 min. However, this survival was approximately 10 times higher than that previously reported for Bacillus subtilis. We show that under 1 mm of rock, Chroococcidiopsis sp. could survive (and potentially grow) under the high martian UV flux if water and nutrient requirements for growth were met. In isolated cells, phycobilisomes and esterases remained intact hours after viability was lost. Esterase activity was reduced by 99% after a 1-h exposure, while 99% loss of autofluorescence required a 4-h exposure. However, cell morphology was not changed, and DNA was still detectable by 4',6-diamidino-2-phenylindole staining after an 8-h exposure (equivalent to approximately 1 day on Mars at the equator). Under 1 mm of simulant martian soil or gneiss, the effect of UV radiation could not be detected on esterase activity or autofluorescence after 4 h. These results show that under the intense martian UV flux the morphological signatures of life can persist even after viability, enzymatic activity, and pigmentation have been destroyed. Finally, the global dispersal of viable, isolated cells of even this desiccation-tolerant, ionizing-radiation-resistant microorganism on Mars is unlikely as they are killed quickly by unattenuated UV radiation when in a desiccated state. These findings have implications for the survival of diverse microbial contaminants dispersed during the course of human exploratory class missions on the surface of Mars
Les diminutifs basques avec ch
No full textSe presentan formaciones similares a los diminutivos vascos con "ch" en España y América latina. Se dan ejemplosThe author introduces similar formations to the Basque diminutive "ch" in Spain and Latin America. Examples are provide
COUPLING OF THE C-H STRETCH TO LARGE-AMPLITUDE TORSION AND INVERSION MOTIONS: COMPARISON OF CHCH, CHOH AND CHNH
No full textAuthor Institution: Department of Polymer Science and Department of Chemistry, The University of Akron; Department of Chemistry, The University of Akron, OH 44325In each of the title molecules, torsional and inversion tunneling occurs between six equivalent minima. Coupling of these degrees of freedom to the CH stretch occurs via variation of the C-H stretching force constants as a function of the torsional () and inversion () angles. Maps of the couplings have been computed at the MP2/6-311++G(3df,2p) level. Both the single bond CH stretch force constants and the bilinear couplings between CH bonds are presented as a function of and . Although the torsional barriers differ by more than a factor of 20, the torsion-inversion-vibration coupling patterns are very similar for CHNH and CHCH. On the other hand, the torsion-inversion-vibration coupling in the charged species CHOH is much weaker
Reply to the Ch. Lagrange’s note
No full textThe author answers to a Ch. Lagrange’s note who refutes his theory on the diurnal nutation.L’auteur répond à une note de Ch. Lagrange qui réfute sa théorie sur la nutation diurne
NATURE OF TORSION-INVERSION COUPLING IN CHNH, CHOH AND CHCH
No full textAuthor Institution: Department of Chemistry, The University of Akron, OH; 44325-3601Two-dimensional torsion-inversion surfaces for methylamine, protonated methanol and ethyl radical were calculated and fit to a function containing a polynomial in the inversion angle() and trigonometric functions of the torsional angle(). Calculations were done at the B3LYP, MP2, and CCSD(T) levels with the 6-311++G(d,p) and 6-311++G(3df, 2p) basis sets and partial optimization. CHNH, CHOH and CHCH have G symmetry with 6-equivalent minima which are located by the various calculations at inversion angles 6.5 to 11; 42 to 45.5 and 52.5 to 55 degrees respectively on either side of planar. The three molecules have very different barriers to inversion ranging from no barrier for CHCH to 838 cm for CHOH to 1837 cm for CHNH. The dominant torsion-inversion coupling term in all cases has the form
Note about Mr. Ch. Lagrange’s recent communication
No full textThe author establishes a note about Mr. Ch. Lagrange’s communication on the Eulerian nutation period.L’auteur établit une note au sujet d’une communication de Ch. Lagrande sur la période de la nutation eulérienne
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Using δ¹³C-CH₄ and δD-CH₄ to constrain Arctic methane emissions
No full text© Author(s) 2016.We present a global methane modelling study assessing the sensitivity of Arctic atmospheric CH₄ mole fractions, δ¹³C-CH₄ and δD-CH₄ to uncertainties in Arctic methane sources. Model simulations include methane tracers tagged by source and isotopic composition and are compared with atmospheric data at four northern high-latitude measurement sites. We find the model's ability to capture the magnitude and phase of observed seasonal cycles of CH₄ mixing ratios, δ¹³C-CH₄ and δD-CH₄ at northern high latitudes is much improved using a later spring kick-off and autumn decline in northern high-latitude wetland emissions than predicted by most process models. Results from our model simulations indicate that recent predictions of large methane emissions from thawing submarine permafrost in the East Siberian Arctic Shelf region could only be reconciled with global-scale atmospheric observations by making large adjustments to high-latitude anthropogenic or wetland emission inventories
PROBING THE REACTION PATH OF CH + H CH CH + H AND ISOTOPOLOGUES
No full textZ. Jin, B. J. Braams, J. M. Bowman, J. Phys. Chem. A 110, 1569 (2006).A. B. McCoy, B. J. Braams, A. Brown, X. Huang., Z. Jin, J. M. Bowman, J. Phys. Chem. A 108, 4991 (2004).Author Institution: Department of Chemistry, The Ohio State University, Columbus; OH 43210Protonated methane has long been of interest to astrochemists due to its presumed importance as a reaction intermediate in the reaction involving CH + HD within the interstellar medium. Within the interstellar medium there is a nonstatistical H/D isotopic abundance observed for isotopologues of CH. While classical trajectory calculations have been performed dissociating CH and CHD into the fragments, CH + H, CHD + H and CH + HD{}, these calculations do not account for a large portion of the available energy being tied up in the zero point energy of the reactants and products. Earlier work in our group on CHD{} showed the deuterium atoms were localized to the CH group, rather than the H moiety. Classical calculations fail to account for this observed localization, instead showing full delocalization of D between both CH and H. With a quantum mechanical treatment, the energetics and wave functions will depend on which asymptotic channel is chosen, while in the classical treatment, these channels will be energetically equivalent. By performing Diffusion Monte Carlo simulations in Jacobi coordinates, we can constrain the distance between the CH and H subunits. Using this technique we have evaluated a one-dimensional reaction potential that includes the full anharmonic zero point energy in the remaining degrees of freedom and can determine how energetics of this reaction change upon partial deuteration of CH or H. We have also evaluated the probability amplitude associated with the wave functions that are obtained in the DMC simulations at various values of the reaction coordinate
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