Identification and Partial Characterization of an L-Tyrosine Aminotransferase (TAT) from Arabidopsis thaliana

The aminotransferase gene family in the model plant Arabidopsis thaliana consists of 44 genes. Twenty six of these enzymes are classified as characterized meaning that the reaction(s) that the enzyme catalyzes are documented using experimental means. The remaining 18 enzymes are uncharacterized and are therefore deemed putative. Our laboratory is interested in elucidating the function(s) of the remaining putative aminotransferase enzymes. To this end, we have identified and partially characterized an aminotransferase (TAT) enzyme from Arabidopsis annotated by the locus tag At5g36160. The full-length cDNA was cloned and the purified recombinant enzyme was characterized using in vitro and in vivo experiments. In vitro analysis showed that the enzyme is capable of interconverting L-Tyrosine and 4-hydroxyphenylpyruvate, and L-Phenylalanine and phenylpyruvate. In vivo analysis by functional complementation showed that the gene was able to complement an E. coli with a background of aminotransferase mutations that confers auxotrophy for L-Tyrosine and L-Phenylalanine

Galaxy Distances in the Nearby Universe: Corrections For Peculiar Motions

By correcting the redshift--dependent distances for peculiar motions through a number of peculiar velocity field models, we recover the true distances of a wide, all-sky sample of nearby galaxies (~ 6400 galaxies with velocities cz<5500 km/s), which is complete up to the blue magnitude B=14 mag. Relying on catalogs of galaxy groups, we treat ~2700 objects as members of galaxy groups and the remaining objects as field galaxies. We model the peculiar velocity field using: i) a cluster dipole reconstruction scheme; ii) a multi--attractor model fitted to the Mark II and Mark III catalogs of galaxy peculiar velocities. According to Mark III data the Great Attractor has a smaller influence on local dynamics than previously believed, whereas the Perseus-Pisces and Shapley superclusters acquire a specific dynamical role. Remarkably, the Shapley structure, which is found to account for nearly half the peculiar motion of the Local Group, is placed by Mark III data closer to the zone of avoidance with respect to its optical position. Our multi--attractor model based on Mark III data favors a cosmological density parameter Omega ~ 0.5 (irrespective of a biasing factor of order unity). Differences among distance estimates are less pronounced in the ~ 2000 - 4000 km/s distance range than at larger or smaller distances. In the last regions these differences have a serious impact on the 3D maps of the galaxy distribution and on the local galaxy density --- on small scales.Comment: 24 pages including (9 eps figures and 7 tables). Figures 1,2,3,4 are available only upon request. Accepted by Ap

The X-ray Cluster Dipole

We estimate the dipole of the whole sky X-ray flux-limited sample of Abell/ACO clusters (XBACs) and compare it to the optical Abell/ACO cluster dipole. The X-ray cluster dipole is well aligned ($\le 25^{\circ}$) with the CMB dipole, while it follows closely the radial profile of its optical cluster counterpart although its amplitude is $\sim 10 - 30$ per cent lower. In view of the fact that the the XBACs sample is not affected by the volume incompleteness and the projection effects that are known to exist at some level in the optical parent Abell/ACO cluster catalogue, our present results confirm the previous optical cluster dipole analysis that there are significant contributions to the Local Group motion from large distances ($\sim 160h^{-1}$Mpc). In order to assess the expected contribution to the X-ray cluster dipole from a purely X-ray selected sample we compare the dipoles of the XBACs and the Brightest Cluster Sample (Ebeling et al. 1997a) in their overlap region. The resulting dipoles are in mutual good aggreement with an indication that the XBACs sample slightly underestimates the full X-ray dipole (by $\le 5$ per cent) while the Virgo cluster contributes about 10 - 15 per cent to the overall X-ray cluster dipole. Using linear perturbation theory to relate the X-ray cluster dipole to the Local group peculiar velocity we estimate the density parameter to be $\beta_{c_{x}} \simeq 0.24 \pm 0.05$.Comment: 16 pages, latex, + 4 ps figures, submitted to Ap

Dye staining and excavation of a lateral preferential flow network

International audiencePreferential flow features have been found to be important for runoff generation, solute transport, and slope stability in many areas around the world. Although many studies have identified the particular characteristics of individual features and measured the runoff generation and solute transport within hillslopes, no studies have determined how individual features are hydraulically connected at a hillslope scale. In this study, we used dye staining and excavation to determine the morphology and spatial pattern of a preferential flow network over a large scale (30 m). We explore the feasibility of extending small-scale dye staining techniques to the hillslope scale. We determine the lateral preferential flow features that are active during the steady state flow conditions and their interaction with the surrounding soil matrix. We also calculate the velocities of the flow through each cross-section of the hillslope and compare them to hillslope scale applied tracer measurements. Finally, we investigate the relationship between the contributing area and the characteristics of the preferential features. The experiment revealed that larger contributing areas coincided with highly developed and hydraulically connected preferential features that had flow with little interaction with the surrounding soil matrix. We found evidence of subsurface erosion and deposition of soil and organic material laterally and vertically within the soil. These results are important because they add to the understanding of the runoff generation, solute transport, and slope stability of these types of hillslopes

Transition to parenthood after successful non-donor in vitro fertilisation: The effects of infertility and in vitro fertilisation on previously infertile couples' experiences of early parenthood

Recent social science research in the field of parenting following assisted conception has focused on the experiences of donor assisted conception and surrogacy. This paper draws from a study which explored the experiences of the transition to early parenthood in 16 heterosexual non-donor couples and includes a specific consideration of the experiences of men as they navigate this journey. We argue that these couples’ transition to early parenthood can be as complex and provisional as in other newer forms of family making as they struggle with an emerging identity as a parent after successful non-donor IVF following their experiences of infertility. Their family making is contingent upon their ability to work at integrating their experiences of infertility and IVF into their emerging identity as a parent. This struggle is prominent when they contemplate a further pregnancy. Considering a sibling causes them further uncertainty and anxiety because it reminds them of their infertile identify and the possibility of further IVF. We report novel findings about the experiences of this transition to parenthood: how couples’ identity as parents is shaped by the losses and grief of infertility and the anxiety of IVF. We argue that their struggle with an emerging parenthood identity challenges the normative, naturalised view of non-donor heterosexual IVF parenthood. Our work contributes to the work on identity in parenthood after IVF in an ongoing effort to understand how assisted technologies shape infertile parents’ lives. This paper reports a small study with a relatively homogenous sample recruited from one fertility clinic. Nevertheless as an exploratory study of an under researched topic, we discuss useful insights and ideas for further research with larger and more diverse samples

An Ultra-High-Resolution Survey of the Interstellar ^7Li-to-^6Li Isotope Ratio in the Solar Neighborhood

In an effort to probe the extent of variations in the interstellar ^7Li/^6Li ratio seen previously, ultra-high-resolution (R ~ 360,000), high signal-to-noise spectra of stars in the Perseus OB2 and Scorpius OB2 Associations were obtained. These measurements confirm our earlier findings of an interstellar ^7Li/^6Li ratio of about 2 toward o Per, the value predicted from models of Galactic cosmic ray spallation reactions. Observations of other nearby stars yield limits consistent with the isotopic ratio ~ 12 seen in carbonaceous chondrite meteorites. If this ratio originally represented the gas toward o Per, then to decrease the original isotope ratio to its current value an order of magnitude increase in the Li abundance is expected, but is not seen. The elemental K/Li ratio is not unusual, although Li and K are formed via different nucleosynthetic pathways. Several proposals to account for the low ^7Li/^6Li ratio were considered, but none seems satisfactory. Analysis of the Li and K abundances from our survey highlighted two sight lines where depletion effects are prevalent. There is evidence for enhanced depletion toward X Per, since both abundances are lower by a factor of 4 when compared to other sight lines. Moreover, a smaller Li/H abundance is observed toward 20 Aql, but the K/H abundance is normal, suggesting enhanced Li depletion (relative to K) in this direction. Our results suggest that the ^7Li/^6Li ratio has not changed significantly during the last 4.5 billion years and that a ratio ~ 12 represents most gas in the solar neighborhood. In addition, there appears to be a constant stellar contribution of ^7Li, indicating that one or two processes dominate its production in the Galaxy.Comment: 54 pages, accepted for publication in the Astrophysical Journa

The Radiated Energy Budget of Chromospheric Plasma in a Major Solar Flare Deduced From Multi-Wavelength Observations

This paper presents measurements of the energy radiated by the lower solar atmosphere, at optical, UV, and EUV wavelengths, during an X-class solar flare (SOL2011-02-15T01:56) in response to an injection of energy assumed to be in the form of nonthermal electrons. Hard X-ray observations from RHESSI were used to track the evolution of the parameters of the nonthermal electron distribution to reveal the total power contained in flare accelerated electrons. By integrating over the duration of the impulsive phase, the total energy contained in the nonthermal electrons was found to be $>2\times10^{31}$ erg. The response of the lower solar atmosphere was measured in the free-bound EUV continua of H I (Lyman), He I, and He II, plus the emission lines of He II at 304\AA\ and H I (Ly$\alpha$) at 1216\AA\ by SDO/EVE, the UV continua at 1600\AA\ and 1700\AA\ by SDO/AIA, and the WL continuum at 4504\AA, 5550\AA, and 6684\AA, along with the Ca II H line at 3968\AA\ using Hinode/SOT. The summed energy detected by these instruments amounted to $\sim3\times10^{30}$ erg; about 15% of the total nonthermal energy. The Ly$\alpha$ line was found to dominate the measured radiative losses. Parameters of both the driving electron distribution and the resulting chromospheric response are presented in detail to encourage the numerical modelling of flare heating for this event, to determine the depth of the solar atmosphere at which these line and continuum processes originate, and the mechanism(s) responsible for their generation.Comment: 14 pages, 18 figures. Accepted for publication in Astrophysics Journa