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3-Dimensional Structure Of A Hemichrome Hemoglobin From Caudina arenicola
(1995-09) Mitchell, David T.; Ernst, Stephen R.; Wu, Wei-Xin; Hackert, Marvin L.; Mitchell, David T.; Ernst, Stephen R.; Wu, Wei-Xin; Hackert, Marvin L.
The structure of a monomeric hemichrome form of an invertebrate hemoglobin, Hb-C chain, from Caudina arenicola has been refined to an R value of 0.16 using the data from 5.0 to 2.5 Angstrom resolution (R = 0.21 from 10.0 to 2.5 Angstrom resolution). Hb-C crystallizes in space group P2(1) with cell constants a=45.74, b=45.23 and c=40.92 Angstrom and beta=104.4 degrees with two monomers packed in the unit cell (V-m = 2.34 Angstrom(3) Da(-1)). The phases were determined by the multiple isomorphous replacement method with Hg2+ the major derivative. The structure consists of 157 amino acids with N- and C-terminal regions and eight a-helices forming a heme pocket. The unique feature of this structure is the hemichrome form with the proximal and distal histidines coordinated to the heme Fe atom, which is nearly in the plane of the porphyrin ring. A total of 111 solvent molecules were added to the structure using difference density peaks of at least 3 sigma over background. Interestingly, all the heme groups present in the crystal are nearly coplanar.
The California Planet Survey. I. Four New Giant Exoplanets
(2010-10) Howard, Andrew W.; Johnson, John A.; Marcy, Geoffrey W.; Fischer, Debra A.; Wright, Jason T.; Bernat, David; Henry, Gregory W.; Peek, Kathryn M. G.; Isaacson, Howard; Apps, Kevin; Endl, Michael; Cochran, William D.; Valenti, Jeff A.; Anderson, Jay; Piskunov, Nikolai E.; Endl, Michael; Cochran, William D.
We present precise Doppler measurements of four stars obtained during the past decade at Keck Observatory by the California Planet Survey (CPS). These stars, namely, HD 34445, HD 126614, HD 13931, and Gl 179, all show evidence for a single planet in Keplerian motion. We also present Doppler measurements from the Hobby-Eberly Telescope (HET) for two of the stars, HD 34445 and Gl 179, that confirm the Keck detections and significantly refine the orbital parameters. These planets add to the statistical properties of giant planets orbiting near or beyond the ice line, and merit follow-up by astrometry, imaging, and space-borne spectroscopy. Their orbital parameters span wide ranges of planetary minimum mass (M sin i = 0.38-1.9 M(Jup)), orbital period (P = 2.87-11.5 yr), semimajor axis (a = 2.1-5.2 AU), and eccentricity (e = 0.02-0.41). HD 34445 b (P = 2.87 yr, M sin i = 0.79 MJup, e = 0.27) is a massive planet orbiting an old, G-type star. We announce a planet, HD 126614 Ab, and an M dwarf, HD 126614 B, orbiting the metal-rich star HD 126614 (which we now refer to as HD 126614 A). The planet, HD 126614 Ab, has minimum mass M sin i = 0.38 MJup and orbits the stellar primary with period P = 3.41 yr and orbital separation a = 2.3 AU. The faint M dwarf companion, HD 126614 B, is separated from the stellar primary by 489 mas (33 AU) and was discovered with direct observations using adaptive optics and the PHARO camera at Palomar Observatory. The stellar primary in this new system, HD 126614 A, has the highest measured metallicity ([ Fe/ H] = + 0.56) of any known planet-bearing star. HD 13931 b (P = 11.5 yr, M sin i = 1.88 MJup, e = 0.02) is a Jupiter analog orbiting a near solar twin. Gl 179 b (P = 6.3 yr, M sin i = 0.82 M(Jup), e = 0.21) is a massive planet orbiting a faint M dwarf. The high metallicity of Gl 179 is consistent with the planet-metallicity correlation among M dwarfs, as documented recently by Johnson & Apps.
Copper(I) and Nickel(II) Complexes with 1:1 Vs. 1:2 Coordination of Ferrocenyl Hydrazone Ligands: Do the Geometry and Composition of Complexes Affect DNA Binding/Cleavage, Protein Binding, Antioxidant and Cytotoxic Activities?
(2012-02) Krishnamoorthy, Paramasivam; Sathyadevi, Palanisamy; Butorac, Rachel R.; Cowley, Alan H.; Bhuvanesh, Nattamai S. P.; Dharmaraj, Nallasamy; Butorac, Rachel R.; Cowley, Alan H.
A new series of geometrically different complexes containing ferrocenyl hydrazone ligands were synthesised by reacting suitable precursor complex [MCl2(PPh3)(2)] with the ligands HL1 or HL2 (where M = Cu(II) or Ni(II); HL1 = [Cp2Fe(CH=N-NH -CO-C6H5)] (1) and HL2 = [Cp2Fe(CH=N-NH-CO-C5H4N)]) (2). The new complexes of the composition [Cu(L-1)(PPh3)(2)], (3) [Cu(L-2)(PPh3)(2)] (4), [Ni(L-1)(2)] (5) and [Ni(L-2)(2)] (6) were characterised by various spectral studies. Among them, complexes 3 and 5 characterised by single crystal X-ray diffraction showed a distorted tetrahedral structure for the former with 1 : 1 metal-ligand stoichiometry, but a distorted square planar geometry with 1 : 2 metal-ligand stoichiometry in the case of the latter. Systematic biological investigations like DNA binding, DNA cleavage, protein binding, free radical scavenging and cytotoxicity activities were carried out using all the synthesised compounds and the results obtained were explained on the basis of structure-activity relationships. The binding constant (K-b) values of the synthesised compounds are found to be in the order of magnitude 10(3)-10(5) M-1 and also they exhibit significant cleavage of supercoiled (SC) pUC19 DNA in the presence of H2O2 as co-oxidant. The conformational changes of bovine serum albumin (BSA) upon binding with the above complexes were also studied. In addition, concentration dependent free radical scavenging potential of all the synthesised compounds (1-6) was also carried out under in vitro conditions. Assays on the cytotoxicity of the above complexes against HeLa and A431 tumor cells and NIH 3T3 normal cells were also carried out.
The Eighth Data Release of the Sloan DIGITal Sky Survey: First Data from SDSS-III
(2011-04) Aihara, Hiroaki; Allende Prieto, Carlos; An, Deokkeun; Anderson, Scott F.; Aubourg, Eric; Balbinot, Eduardo; Beers, Timothy C.; Berlind, Andreas A.; Bickerton, Steven J.; Bizyaev, Dmitry; Blanton, Michael R.; Bochanski, John J.; Bolton, Adam S.; Bovy, Jo; Brandt, W. N.; Brinkmann, J.; Brown, Peter J.; Brownstein, Joel R.; Busca, Nicolas G.; Campbell, Heather; Carr, Michael A.; Chen, Yanmei; Chiappini, Cristina; Comparat, Johan; Connolly, Natalia; Cortes, Marina; Croft, Rupert A. C.; Cuesta, Antonio J.; da Costa, Luiz N.; Davenport, James R. A.; Dawson, Kyle; Dhital, Saurav; Ealet, Anne; Ebelke, Garrett L.; Edmondson, Edward M.; Eisenstein, Daniel J.; Escoffier, Stephanie; Esposito, Massimiliano; Evans, Michael L.; Fan, Xiaohui; Femenia Castella, Bruno; Font-Ribera, Andreu; Frinchaboy, Peter M.; Ge, Jian; Gillespie, Bruce A.; Gilmore, G.; Gonzalez Hernandez, Jonay I.; Gott, J. Richard; Gould, Andrew; Grebel, Eva K.; Gunn, James E.; Hamilton, Jean-Christophe; Harding, Paul; Harris, David W.; Hawley, Suzanne L.; Hearty, Frederick R.; Ho, Shirley; Hogg, David W.; Holtzman, Jon A.; Honscheid, Klaus; Inada, Naohisa; Ivans, Inese I.; Jiang, Linhua; Johnson, Jennifer A.; Jordan, Cathy; Jordan, Wendell P.; Kazin, Eyal A.; Kirkby, David; Klaene, Mark A.; Knapp, G. R.; Kneib, Jean-Paul; Kochanek, C. S.; Koesterke, Lars; Kollmeier, Juna A.; Kron, Richard G.; Lampeitl, Hubert; Lang, Dustin; Le Goff, Jean-Marc; Lee, Young Sun; Lin, Yen-Ting; Long, Daniel C.; Loomis, Craig P.; Lucatello, Sara; Lundgren, Britt; Lupton, Robert H.; Ma, Zhibo; MacDonald, Nicholas; Mahadevan, Suvrath; Maia, Marcio A. G.; Makler, Martin; Malanushenko, Elena; Malanushenko, Viktor; Mandelbaum, Rachel; Maraston, Claudia; Margala, Daniel; Masters, Karen L.; McBride, Cameron K.; McGehee, Peregrine M.; McGreer, Ian D.; Menard, Brice; Miralda-Escude, Jordi; Morrison, Heather L.; Mullally, F.; Muna, Demitri; Munn, Jeffrey A.; Murayama, Hitoshi; Myers, Adam D.; Naugle, Tracy; Neto, Angelo Fausti; Duy Cuong, Nguyen; Nichol, Robert C.; O'Connell, Robert W.; Ogando, Ricardo L. C.; Olmstead, Matthew D.; Oravetz, Daniel J.; Padmanabhan, Nikhil; Palanque-Delabrouille, Nathalie; Pan, Kaike; Pandey, Parul; Paris, Isabelle; Percival, Will J.; Petitjean, Patrick; Pfaffenberger, Robert; Pforr, Janine; Phleps, Stefanie; Pichon, Christophe; Pieri, Matthew M.; Prada, Francisco; Price-Whelan, Adrian M.; Raddick, M. Jordan; Ramos, Beatriz H. F.; Reyle, Celine; Rich, James; Richards, Gordon T.; Rix, Hans-Walter; Robin, Annie C.; Rocha-Pinto, Helio J.; Rockosi, Constance M.; Roe, Natalie A.; Rollinde, Emmanuel; Ross, Ashley J.; Ross, Nicholas P.; Rossetto, Bruno M.; Sanchez, Ariel G.; Sayres, Conor; Schlegel, David J.; Schlesinger, Katharine J.; Schmidt, Sarah J.; Schneider, Donald P.; Sheldon, Erin; Shu, Yiping; Simmerer, Jennifer; Simmons, Audrey E.; Sivarani, Thirupathi; Snedden, Stephanie A.; Sobeck, Jennifer S.; Steinmetz, Matthias; Strauss, Michael A.; Szalay, Alexander S.; Tanaka, Masayuki; Thakar, Aniruddha R.; Thomas, Daniel; Tinker, Jeremy L.; Tofflemire, Benjamin M.; Tojeiro, Rita; Tremonti, Christy A.; Vandenberg, Jan; Magana, M. Vargas; Verde, Licia; Vogt, Nicole P.; Wake, David A.; Wang, Ji; Weaver, Benjamin A.; Weinberg, David H.; White, Martin; White, Simon D. M.; Yanny, Brian; Yasuda, Naoki; Yeche, Christophe; Zehavi, Idit; Koesterke, Lars
The Sloan Digital Sky Survey (SDSS) started a new phase in 2008 August, with new instrumentation and new surveys focused on Galactic structure and chemical evolution, measurements of the baryon oscillation feature in the clustering of galaxies and the quasar Ly alpha forest, and a radial velocity search for planets around similar to 8000 stars. This paper describes the first data release of SDSS-III (and the eighth counting from the beginning of the SDSS). The release includes five-band imaging of roughly 5200 deg(2) in the southern Galactic cap, bringing the total footprint of the SDSS imaging to 14,555 deg(2), or over a third of the Celestial Sphere. All the imaging data have been reprocessed with an improved sky-subtraction algorithm and a final, self-consistent photometric recalibration and flat-field determination. This release also includes all data from the second phase of the Sloan Extension for Galactic Understanding and Exploration (SEGUE-2), consisting of spectroscopy of approximately 118,000 stars at both high and low Galactic latitudes. All the more than half a million stellar spectra obtained with the SDSS spectrograph have been reprocessed through an improved stellar parameter pipeline, which has better determination of metallicity for high-metallicity stars.
High-Velocity Line Forming Regions In The Type Ia Supernova 2009ig
(2013-11) Marion, G. H.; Vinko, Jozsef; Wheeler, J. Craig; Foley, Ryan J.; Hsiao, Eric Y.; Brown, Peter J.; Challis, Peter; Filippenko, Alexei V.; Garnavich, Peter; Kirshner, Robert P.; Landsman, Wayne B.; Parrent, Jerod T.; Pritchard, Tyler A.; Roming, Peter W. A.; Silverman, Jeffrey M.; Wang, Xiaofeng; Marion, G. H.; Vinko, Jozsef; Wheeler, J. Craig; Silverman, Jeffrey M.
We report measurements and analysis of high-velocity (HVF) (>20,000 km s(-1)) and photospheric absorption features in a series of spectra of the Type Ia supernova (SN) 2009ig obtained between -14 days and +13 days with respect to the time of maximum B-band luminosity (B-max). We identify lines of Si II, Si III, S II, Ca II, and Fe II that produce both HVF and photospheric-velocity (PVF) absorption features. SN 2009ig is unusual for the large number of lines with detectable HVF in the spectra, but the light-curve parameters correspond to a slightly overluminous but unexceptional SN Ia (M-B = -19.46 mag and Delta m(15)(B) = 0.90 mag). Similarly, the Si II lambda 6355 velocity at the time of B-max is greater than "normal" for an SN Ia, but it is not extreme (upsilon(Si) = 13,400 km s(-1)). The -14 days and -13 days spectra clearly resolve HVF from Si II lambda 6355 as separate absorptions from a detached line forming region. At these very early phases, detached HVF are prevalent in all lines. From -12 days to -6 days, HVF and PVF are detected simultaneously, and the two line forming regions maintain a constant separation of about 8000 km s(-1). After -6 days all absorption features are PVF. The observations of SN 2009ig provide a complete picture of the transition from HVF to PVF. Most SNe Ia show evidence for HVF from multiple lines in spectra obtained before -10 days, and we compare the spectra of SN 2009ig to observations of other SNe. We show that each of the unusual line profiles for Si II lambda 6355 found in early-time spectra of SNe Ia correlate to a specific phase in a common development sequence from HVF to PVF.
Identifying Structural Variation in Haploid Microbial Genomes from Short-Read Resequencing Data Using Breseq
(2014-11) Barrick, Jeffrey E.; Colburn, Geoffrey; Deatherage, Daniel E.; Traverse, Charles C.; Strand, Matthew D.; Borges, Jordan J.; Knoester, David B.; Reba, Aaron; Meyer, Austin G.; Barrick, Jeffrey E.; Colburn, Geoffrey; Deatherage, Daniel E.; Traverse, Charles C.; Strand, Matthew D.; Borges, Jordan J.; Reba, Aaron; Meyer, Austin G.
Mutations that alter chromosomal structure play critical roles in evolution and disease, including in the origin of new lifestyles and pathogenic traits in microbes. Large-scale rearrangements in genomes are often mediated by recombination events involving new or existing copies of mobile genetic elements, recently duplicated genes, or other repetitive sequences. Most current software programs for predicting structural variation from short-read DNA resequencing data are intended primarily for use on human genomes. They typically disregard information in reads mapping to repeat sequences, and significant post-processing and manual examination of their output is often required to rule out false-positive predictions and precisely describe mutational events. Results: We have implemented an algorithm for identifying structural variation from DNA resequencing data as part of the breseq computational pipeline for predicting mutations in haploid microbial genomes. Our method evaluates the support for new sequence junctions present in a clonal sample from split-read alignments to a reference genome, including matches to repeat sequences. Then, it uses a statistical model of read coverage evenness to accept or reject these predictions. Finally, breseq combines predictions of new junctions and deleted chromosomal regions to output biologically relevant descriptions of mutations and their effects on genes. We demonstrate the performance of breseq on simulated Escherichia coli genomes with deletions generating unique breakpoint sequences, new insertions of mobile genetic elements, and deletions mediated by mobile elements. Then, we reanalyze data from an E. coli K-12 mutation accumulation evolution experiment in which structural variation was not previously identified. Transposon insertions and large-scale chromosomal changes detected by breseq account for similar to 25% of spontaneous mutations in this strain. In all cases, we find that breseq is able to reliably predict structural variation with modest read-depth coverage of the reference genome (>40-fold). Conclusions: Using breseq to predict structural variation should be useful for studies of microbial epidemiology, experimental evolution, synthetic biology, and genetics when a reference genome for a closely related strain is available. In these cases, breseq can discover mutations that may be responsible for important or unintended changes in genomes that might otherwise go undetected.
Letter to Unknown from H.R. Aldrich on 1940-12-27
(1940-12-27) Aldrich, H.R.
A Long-Period Massive Planet Around HD 106515A
(2012-10) Desidera, S.; Gratton, R.; Carolo, E.; Fiorenzano, A. F. M.; Endl, M.; Mesa, D.; Cecconi, M.; Claudi, R.; Cosentino, R.; Scuderi, S.; Sozzetti, A.; Zurlo, A.; Endl, M.
We have performed radial velocity (RV) monitoring of the components of the binary system HD 106515 over almost 11 years using the high-resolution spectrograph SARG at Telescopio Nazionale Galileo (TNG). The primary shows long-period radial velocity variations that indicate the presence of a low-mass companion whose projected mass is in the planetary regime (msin i = 9.33 M-J). The 9.8 year orbit is quite eccentric (e = 0.57), as is typical for massive giant planets. Our results confirm the previously made preliminary announcement of the planet by Mayor et al. (2011, A&A, submitted [arXiv:1109.2497]). The secondary instead does not show significant RV variations. The two components do not differ significantly in chemical composition, as was also found for other pairs of which one component hosts giant planets. Adaptive optics images obtained with TNG/AdOpt do not reveal additional stellar companions. From the analysis of the relative astrometry of the components of the wide pair we compute an upper limit on the mass of the newly detected companion of about 0.25 M-circle dot. State-of-the-art or near-future instrumentation can provide true mass determination, thanks to the availability of the wide companion HD106515B as reference. Therefore, HD 106515Ab will allow a deeper insight into the transition region between planets and brown dwarfs.
Temperature Dependence Of Brillouin Light Scattering Spectra Of Acoustic Phonons In Silicon
(2015-02) Olsson, Kevin S.; Klimovich, Nikita; An, Kyongmo; Sullivan, Sean; Weathers, Annie; Shi, Li; Li, Xiaoqin; Olsson, Kevin S.; Klimovich, Nikita; An, Kyongmo; Sullivan, Sean; Weathers, Annie; Shi, Li; Li, Xiaoqin
Electrons, optical phonons, and acoustic phonons are often driven out of local equilibrium in electronic devices or during laser-material interaction processes. The need for a better understanding of such non-equilibrium transport processes has motivated the development of Raman spectroscopy as a local temperature sensor of optical phonons and intermediate frequency acoustic phonons, whereas Brillouin light scattering (BLS) has recently been explored as a temperature sensor of low-frequency acoustic phonons. Here, we report the measured BLS spectra of silicon at different temperatures. The origins of the observed temperature dependence of the BLS peak position, linewidth, and intensity are examined in order to evaluate their potential use as temperature sensors for acoustic phonons. (C) 2015 AIP Publishing LLC.
The Twofold Debris Disk Around HD113766 A Warm And Cold Dust As Seen With VLTI/MIDI And Herschel/PACS
(2013-03) Olofsson, J.; Henning, T.; Nielbock, M.; Augereau, J. C.; Juhasz, A.; Oliveira, I.; Absil, O.; Tamanai, A.; Oliveira, I.
Context. Warm debris disks are a sub-sample of the large population of debris disks, and display excess emission in the mid-infrared. Around solar-type stars, very few objects (similar to 2% of all debris disks) show emission features in mid-IR spectroscopic observations that are attributed to small, warm silicate dust grains. The origin of this warm dust could be explained either by a recent catastrophic collision between several bodies or by transport from an outer belt similar to the Kuiper belt in the solar system. Aims. We present and analyze new far-IR Herschel/PACS photometric observations, supplemented by new and archival ground-based data in the mid-IR (VLTI/MIDI and VLT/VISIR), for one of these rare systems: the 10-16 Myr old debris disk around HD 113766 A. We improve an existing model to account for these new observations. Methods. We implemented the contribution of an outer planetesimal belt in the DEBRA code, and successfully used it to model the spectral energy distribution (SED) as well as complementary observations, notably MIDI data. We better constrain the spatial distribution of the dust and its composition. Results. We underline the limitations of SED modeling and the need for spatially resolved observations. We improve existing models and increase our understanding of the disk around HD 113766 A. We find that the system is best described by an inner disk located within the first AU, well constrained by the MIDI data, and an outer disk located between 9-13 AU. In the inner dust belt, our previous finding of Fe-rich crystalline olivine grains still holds. We do not observe time variability of the emission features over at least an eight-year time span in an environment subjected to strong radiation pressure. Conclusions. The time stability of the emission features indicates that mu m-sized dust grains are constantly replenished from the same reservoir, with a possible depletion of sub-mu m-sized grains. We suggest that the emission features may arise from multi-composition aggregates. We discuss possible scenarios concerning the origin of the warm dust observed around HD 113766 A. The compactness of the innermost regions as probed by the MIDI visibilities and the dust composition suggest that we are witnessing the results of (at least) one collision between partially differentiated bodies, in an environment possibly rendered unstable by terrestrial planetary formation.
The Twofold Debris Disk Around HD113766 A Warm And Cold Dust As Seen With VLTI/MIDI And Herschel/PACS
(2013-03) Olofsson, J.; Henning, T.; Nielbock, M.; Augereau, J. C.; Juhasz, A.; Oliveira, I.; Absil, O.; Tamanai, A.; Oliveira, I.
Context. Warm debris disks are a sub-sample of the large population of debris disks, and display excess emission in the mid-infrared. Around solar-type stars, very few objects (similar to 2% of all debris disks) show emission features in mid-IR spectroscopic observations that are attributed to small, warm silicate dust grains. The origin of this warm dust could be explained either by a recent catastrophic collision between several bodies or by transport from an outer belt similar to the Kuiper belt in the solar system. Aims. We present and analyze new far-IR Herschel/PACS photometric observations, supplemented by new and archival ground-based data in the mid-IR (VLTI/MIDI and VLT/VISIR), for one of these rare systems: the 10-16 Myr old debris disk around HD 113766 A. We improve an existing model to account for these new observations. Methods. We implemented the contribution of an outer planetesimal belt in the DEBRA code, and successfully used it to model the spectral energy distribution (SED) as well as complementary observations, notably MIDI data. We better constrain the spatial distribution of the dust and its composition. Results. We underline the limitations of SED modeling and the need for spatially resolved observations. We improve existing models and increase our understanding of the disk around HD 113766 A. We find that the system is best described by an inner disk located within the first AU, well constrained by the MIDI data, and an outer disk located between 9-13 AU. In the inner dust belt, our previous finding of Fe-rich crystalline olivine grains still holds. We do not observe time variability of the emission features over at least an eight-year time span in an environment subjected to strong radiation pressure. Conclusions. The time stability of the emission features indicates that mu m-sized dust grains are constantly replenished from the same reservoir, with a possible depletion of sub-mu m-sized grains. We suggest that the emission features may arise from multi-composition aggregates. We discuss possible scenarios concerning the origin of the warm dust observed around HD 113766 A. The compactness of the innermost regions as probed by the MIDI visibilities and the dust composition suggest that we are witnessing the results of (at least) one collision between partially differentiated bodies, in an environment possibly rendered unstable by terrestrial planetary formation.
A Unique Star in the Outer Halo of the Milky Way
(2009-05) Lai, David K.; Rockosi, Constance M.; Bolte, Michael; Johnson, Jennifer A.; Beers, Timothy C.; Lee, Young Sun; Prieto, Carlos Allende; Yanny, Brian; Prieto, Carlos Allende
As part of a program to measure abundance ratios in stars beyond 15 kpc from the Galactic center, we have discovered a metal-poor star in the outer halo with a unique chemical signature. We originally identified it in the Sloan Extension for Galactic Understanding and Exploration survey as a distant metal-poor star. We obtained a follow-up spectrum using the Echelle Spectrometer and Imager at the Keck 2 telescope, and measure [Fe/H] = -3.17, [Mg/Fe]= -0.10, and [Ca/Fe] = +1.11. This is one of the largest over-abundances of Ca measured in any star to date; the extremely low value of [Mg/Ca] = -1.21 is entirely unique. To have found such an unusual star in our small sample of 27 targets suggests that there may be previously unobserved classes of stars yet to be found in situ in the Galactic halo.
A Vigorous Activity Cycle Mimicking A Planetary System In HD 200466
(2014-07) Carolo, E.; Desidera, S.; Gratton, R.; Fiorenzano, A. F. M.; Marzari, F.; Endl, M.; Mesa, D.; Barbieri, M.; Cecconi, M.; Claudi, R. U.; Cosentino, R.; Scuderi, S.; Endl, M.
Stellar activity can be a source of radial velocity (RV) noise and can reproduce periodic RV variations similar to those produced by an exoplanet. We present the vigorous activity cycle in the primary of the visual binary HD 200466, a system made of two almost identical solar-type stars with an apparent separation of 4.6 arcsec at a distance of 44 +/- 2 pc. High precision RV over more than a decade, adaptive optics (AO) images, and abundances have been obtained for both components. A linear trend in the RV is found for the secondary. We assumed that it is due to the binary orbit and once coupled with the astrometric data, it strongly constrains the orbital solution of the binary at high eccentricities (e similar to 0.85) and quite small periastron of similar to 21 AU. If this orbital motion is subtracted from the primary radial velocity curve, a highly significant (false alarm probability <0.1%) period of about 1300 d is obtained, suggesting in a first analysis the presence of a giant planet, but it turned out to be due to the stellar activity cycle. Since our spectra do not include the Ca II resonance lines, we measured a chromospheric activity indicator based on the H, line to study the correlation between activity cycles and long-term activity variations. While the bisector analysis of the line profile does not show a clear indication of activity, the correlation between the H, line indicator and the RV measurements identify the presence of a strong activity cycle.
X-Ray Structure Determination Of A Dimeric Hemoglobin From Caudina arenicola
(1995-09) Mitchell, David T.; Ernst, Stephen R.; Hackert, Marvin L.; Mitchell, David T.; Ernst, Stephen R.; Hackert, Marvin L.
The X-ray structure of a dimeric, cyanomet-liganded hemoglobin D-chain (Hb-D) from Caudina arenicola has been determined by the molecular-replacement method. The search model was a concatenated model of three hemoglobin structures superimposed on the backbone of monomeric, hemichrome hemoglobin C-chain (Hb-C) from the same organism. Hb-D crystallizes in space group P4(1)2(1)2 with cell constants a = b = 77.0 and c = 61.5 Angstrom with one subunit in the asymmetric unit. The dimer twofold axis corresponds to a crystallographic twofold along one of the body diagonals of the unit cell. Rotation and translation searches as well as model refinement were carried out in X-PLOR with the final model having an R value of 0.19 using the data from 5.0 to 2.9 Angstrom resolution (R = 0.26 for 10.0 to 2.9 Angstrom resolution). The homodimeric structure of Caudina Hb-D features close heme-heme contacts with an Fe-Fe distance of 19.0 Angstrom. The subunit-subunit interface involves both the E and F helices from each subunit with the E helices oriented antiparallel at 50 degrees with respect to one another, similar to the quaternary structure observed for the homodimeric hemoglobin from Scapharca inaequivalvis.