Los polímeros tipo elastina y su utilización como tags para la purificación de proteínas

Actualmente, una de las técnicas más ampliamente utilizadas en la purificación de proteínas recombinantes es la cromatografía de afinidad. Sin embargo, esta técnica es costosa, requiere de equipo especializado y es difícil de escalar. Por tanto, es deseable el desarrollo de métodos más económicos y técnicamente más sencillos. Uno de estos métodos está basado en aprovechar las características termosensibles y el comportamiento inteligente de los polímeros tipo elastina (ELP) para purificar una proteína de interés. El bajo coste que esta metodología requiere permitiría disminuir el precio de diversas proteínas de interés biomédico en el mercado, con las consiguientes repercusiones que ello conlleva a la hora de su aplicación en clínica. Por tanto, el presente artículo pretende indagar en la utilización de los ELP como tags para la purificación proteica, gracias al diseño y la producción de construcciones de fusión compuestas por la proteína diana de interés unida al tag elastomérico. Además se resaltarán otros efectos colaterales positivos que la presencia del ELP puede aportar a la proteína quimérica.Currently, chromatography is one of the most commonly used techniques to achieve protein purification. Nevertheless, such technique requires specialized equipment and is difficult to scale-up. Therefore, the development of new, simpler and broadly applicable purification methods to circumvent these problems is desirable. One such approach takes advantages of the thermo-sensitive and smart behavior of the elastin like polymers (ELP) to purify the target protein. The low-cost of carrying out such methodology may permit us to decrease the price of diverse biomedical useful proteins, with the consistent impact that such fact entails when applying in clinic. Therefore, the aim of this article is to clarify some aspects related to the use of the ELP as protein purification tags. For such use, it is necessary to design and produce fusion constructs between the target protein and the elastomeric tag. Moreover, apart from protein purification, further effects of the presence of the ELP in the fusion construct would be described.Peer ReviewedAward-winnin

Estudio de poblaciones de maíz y de fríjol en el sistema maíz x fríjol voluble para clima medio conservando constantes las distancias de siembra.

El objetivo del estudio fué determinar las poblaciones más adecuadas de maíz y fríjol en el sistema maíz-fríjol voluble en asociación. El diseño estadístico utilizado fue un factorial 3 x 3 en bloques al azar con 9 tratamientos. Se hizo además un análisis de presupuestos parciales para determinar el ingreso por tratamiento. Se observó que el incremento en la población de una de las especies aumenta su producción en detrimento de la otra. Se concluyó que es económico para el agricultor convertir el monocultivo de maíz en asocio maíz x fríjol voluble, además del efecto benéfico de la leguminosaFríjol-Phaseolus vulgarisMaíz-Zea may

Obtención de un polímero de tipo Elastina modificado con secuencias Bioactivas y Biodegradables, para su aplicación en ingeniería

La matriz extracelular es uno de los principales elementos reguladores de la actividad celular. Los diferentes módulos de las macromoléculas que la componen son capaces de desencadenar señales que activan diferentes rutas intracelulares que organizan las funciones vitales de las células. La ingeniería de tejidos se dedica a desarrollar sistemas capaces de imitar, temporalmente, el comportamiento de la matriz extracelular con objeto de promover la regeneración o el reemplazo de tejidos y órganos dañados, actuando como un soporte atractivo para las células que deben adherirse y crecer sobre ella, hasta reemplazarla por tejido sano. En este trabajo se describe el proceso de diseño y producción de un polímero de tipo elastina que se ha funcionalizado con secuencias bioactivas que añaden actividades específicas al andamio o soporte celular que constituye la elastina. Así,algunos dominios elastoméricos se modificaron con el aminoácido lisina para poder entrecruzar las moléculas de polímero y conseguir matrices. También se incluyó la secuencia REDV, presente el dominio CS5 de la fibronectina humana, como motivo de adhesión celular. Por último, el polímero se funcionalizó con secuencias diana de enzimas proteolíticas para mejorar su bioprocesabilidad.Extracellular matrix (ECM) is a major component for the regulation of cell activity. The different modules of the proteins which constitute the extracellular matrix macromolecules represent for the cells which enter in contact with them, new signals capable of activating several intracellular signaling pathways, resulting in the modulation of numerous cell functions. Tissue engineering tries to develop new materials based on these components as scaffolds for cells to promote their adhesion and growth. In this work, genetic engineering techniques were used to design and biosynthesize an extracellular matrix analogue based in the elastin component. The structural base of our scaffold is an elastin –derived sequence which confers an adequate mechanical behavior. In addition, several domains were included, for adding new bioactivities to this elastin-like polymer (ELP). Some of these elastic domains were modified to contain lysine for cross linking purposes. The polymer also contained periodically spaced fibronectin CS5 domain enclosing the well known cell attachment sequence REDV. Finally, the polymer had target sequences for proteolitic action.Peer ReviewedAward-winnin

Plan de comunicaciones para la campaña de prevención contra la sigatoka negra del plátano y banano en Urabá.

Banano- Musa acuminata - Musa paradisiacaPlátano-Musa sapientu

Expansion of different subpopulations of CD26 −/low T cells in allergic and non-allergic asthmatics

CD26 displays variable levels between effector (TH ≫ TH > TH > Treg) and naïve/memory (memory > naïve) CD4 T lymphocytes. Besides, IL-6/IL 6R is associated with TH -differentiation and asthma severity. Allergic/atopic asthma (AA) is dominated by TH responses, while TH immunity might either modulate the TH -dependent inflammation in AA or be an important mechanism boosting non-allergic asthma (NAA). Therefore, in this work we have compared the expression of CD26 and CD126 (IL-6Rα) in lymphocytes from different groups of donors: allergic (AA) and non-allergic (NAA) asthma, rhinitis, and healthy subjects. For this purpose, flow cytometry, haematological/biochemical, and in vitro proliferation assays were performed. Our results show a strong CD26-CD126 correlation and an over-representation of CD26 subsets with a highly-differentiated effector phenotype in AA (CD4 CD26 T cells) and NAA (CD4 CD26 γδ-T cells). In addition, we found that circulating levels of CD26 (sCD26) were reduced in both AA and NAA, while loss of CD126 expression on different leukocytes correlated with higher disease severity. Finally, selective inhibition of CD26-mRNA translation led to enhanced T cell proliferation in vitro. These findings support that CD26 down-modulation could play a role in facilitating the expansion of highly-differentiated effector T cell subsets in asthma

Evaluación del sistema de yuca (Manihot esculenta Crantz) intercalada con maíz (Zea maíz L.) y fríjol (Phaseolus vulgaris L.) en clima medio.

Se evaluó la producción del cultivo múltiple de yuca intercalada, con maíz, fríjol arbustivo y fríjol asociado al maíz, en un suelo aluvial franco arenoso, utilizando un diseño de bloques al azar con 10 tratamientos y 3 repeticiones, en la Estación Experimental Tulio Ospina. Esta evaluación mostró que la producción de 30.6 t/ha del cultivo solo de la yuca no disminuyó cuando se le intercalaron, por ha 21000 plantas de maíz, 70000 de fríjol arbustivo y 14000 de fríjol voluble. De los 6 sistemas de cultivo múltiple estudiado, 4 aumentaron la producción en 17.1 por ciento en promedio y 2 la redujeron en 4 por ciento con relación a la yuca cultivada sola. El maíz solo, rindió 3485 kg/ha y disminuyó significativamente los rendimientos en 21.3 y 49.9 por ciento cuando se le adicionó 1 o 2 especies. El fríjol arbustivo sólo rindió 1125 kg/ha, pero cuando se asoció con los otros cultivos, tuvo una reducción de 17.4 y 44.0 por ciento de acuerdo al número de componentes que intervinieron en los sistemas. El fríjol liborino rindio 428 kg/ha en cultivo solo y al asociarlo con otras especies, redujo significativamente la producción entre 51.7 y 65.5 por ciento. Los índices económicos de ingreso neto, rentabilidad media al capital y el índice equivalente de la tierra, indican que los diferentes sistemas de cúltivo múltiple basados en la yuca superan en eficiencia a los cultivos solos o limpios de las tres especies estudiadasFríjol-Phaseolus vulgarisMaíz-Zea may

DNA synthesis determines the binding mode of the human mitochondrial single-stranded DNA-binding protein

[EN] Single-stranded DNA-binding proteins (SSBs) play a key role in genome maintenance, binding and organizing single-stranded DNA (ssDNA) intermediates. Multimeric SSBs, such as the human mitochondrial SSB (HmtSSB), present multiple sites to interact with ssDNA, which has been shown in vitro to enable them to bind a variable number of single-stranded nucleotides depending on the salt and protein concentration. It has long been suggested that different binding modes might be used selectively for different functions. To study this possibility, we used optical tweezers to determine and compare the structure and energetics of long, individual HmtSSB¿DNA complexes assembled on preformed ssDNA and on ssDNA generated gradually during `in situ¿ DNA synthesis. We show that HmtSSB binds to preformed ss-DNA in two major modes, depending on salt and protein concentration. However, when protein binding was coupled to strand-displacement DNA synthesis, only one of the two binding modes was observed under all experimental conditions. Our results reveal a key role for the gradual generation of ssDNA in modulating the binding mode of a multimeric SSB protein and consequently, in generating the appropriate nucleoprotein structure for DNA synthetic reactions required for genome maintenance.We are grateful to Prof. M. Salas laboratory (CBMSO-CSIC) for generously providing the Phi29 DNA polymerase and to Juan P. García Villaluenga (UCM) for useful discussions. Spanish Ministry of Economy and Competitiveness [MAT2015-71806-R to J.R.A-G, FIS2010-17440, FIS2015-67765-R to F.J.C., BFU2012-31825, BFU2015-63714-R to B.I.]; Spanish Ministry of Education, Culture and Sport [FPU13/02934 to J.J., FPU13/02826 to E.B-H.]; National Institutes of Health [GM45925 to L.S.K.]; University of Tampere (to G.L.C.); Programa de Financiacion Universidad Complutense de Madrid-Santander Universidades [CT45/15-CT46/15 to F.C.]. Funding for open access charge: Spanish Ministry of Economy and Competitiveness [BFU2015-63714-R].Morin, J.; Cerrón, F.; Jarillo, J.; Beltran-Heredia, E.; Ciesielski, G.; Arias-Gonzalez, JR.; Kaguni, L.... (2017). DNA synthesis determines the binding mode of the human mitochondrial single-stranded DNA-binding protein. Nucleic Acids Research. 45(12):7237-7248. https://doi.org/10.1093/nar/gkx395S723772484512Shereda, R. D., Kozlov, A. G., Lohman, T. M., Cox, M. M., & Keck, J. L. (2008). 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Microsecond Dynamics of Protein–DNA Interactions: Direct Observation of the Wrapping/Unwrapping Kinetics of Single-stranded DNA around the E.coli SSB Tetramer. Journal of Molecular Biology, 359(1), 55-65. doi:10.1016/j.jmb.2006.02.070Lohman, T. M., & Ferrari, M. E. (1994). Escherichia Coli Single-Stranded DNA-Binding Protein: Multiple DNA-Binding Modes and Cooperativities. Annual Review of Biochemistry, 63(1), 527-570. doi:10.1146/annurev.bi.63.070194.002523Maier, D., Farr, C. L., Poeck, B., Alahari, A., Vogel, M., Fischer, S., … Schneuwly, S. (2001). Mitochondrial Single-stranded DNA-binding Protein Is Required for Mitochondrial DNA Replication and Development in Drosophila melanogaster. Molecular Biology of the Cell, 12(4), 821-830. doi:10.1091/mbc.12.4.821Ruhanen, H., Borrie, S., Szabadkai, G., Tyynismaa, H., Jones, A. W. E., Kang, D., … Yasukawa, T. (2010). 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(1999). Functional Interactions of Mitochondrial DNA Polymerase and Single-stranded DNA-binding Protein. Journal of Biological Chemistry, 274(21), 14779-14785. doi:10.1074/jbc.274.21.14779Korhonen, J. A., Gaspari, M., & Falkenberg, M. (2003). TWINKLE Has 5′ → 3′ DNA Helicase Activity and Is Specifically Stimulated by Mitochondrial Single-stranded DNA-binding Protein. Journal of Biological Chemistry, 278(49), 48627-48632. doi:10.1074/jbc.m306981200Miralles Fusté, J., Shi, Y., Wanrooij, S., Zhu, X., Jemt, E., Persson, Ö., … Falkenberg, M. (2014). In Vivo Occupancy of Mitochondrial Single-Stranded DNA Binding Protein Supports the Strand Displacement Mode of DNA Replication. PLoS Genetics, 10(12), e1004832. doi:10.1371/journal.pgen.1004832Oliveira, M. T., & Kaguni, L. S. (2011). Reduced Stimulation of Recombinant DNA Polymerase γ and Mitochondrial DNA (mtDNA) Helicase by Variants of Mitochondrial Single-stranded DNA-binding Protein (mtSSB) Correlates with Defects in mtDNA Replication in Animal Cells. Journal of Biological Chemistry, 286(47), 40649-40658. doi:10.1074/jbc.m111.289983Williams, A. J., & Kaguni, L. S. (1995). Stimulation ofDrosophilaMitochondrial DNA Polymerase by Single-stranded DNA-binding Protein. Journal of Biological Chemistry, 270(2), 860-865. doi:10.1074/jbc.270.2.860Bogenhagen, D. F., Wang, Y., Shen, E. L., & Kobayashi, R. (2003). Protein Components of Mitochondrial DNA Nucleoids in Higher Eukaryotes. Molecular & Cellular Proteomics, 2(11), 1205-1216. doi:10.1074/mcp.m300035-mcp200BARAT-GUERIDE, M., DUFRESNE, C., & RICKWOOD, D. (1989). Effect of DNA conformation on the transcription of mitochondrial DNA. European Journal of Biochemistry, 183(2), 297-302. doi:10.1111/j.1432-1033.1989.tb14928.xYang, C., Curth, U., Urbanke, C., & Kang, C. (1997). Crystal structure of human mitochondrial single-stranded DNA binding protein at 2.4 Å resolution. Nature Structural Biology, 4(2), 153-157. doi:10.1038/nsb0297-153Raghunathan, S., Ricard, C. S., Lohman, T. M., & Waksman, G. (1997). Crystal structure of the homo-tetrameric DNA binding domain of Escherichia coli single-stranded DNA-binding protein determined by multiwavelength x-ray diffraction on the selenomethionyl protein at 2.9-A resolution. Proceedings of the National Academy of Sciences, 94(13), 6652-6657. doi:10.1073/pnas.94.13.6652CURTH, U., URBANKE, C., GREIPEL, J., GERBERDING, H., TIRANTI, V., & ZEVIANI, M. (1994). Single-stranded-DNA-binding proteins from human mitochondria and Escherichia coli have analogous physicochemical properties. European Journal of Biochemistry, 221(1), 435-443. doi:10.1111/j.1432-1033.1994.tb18756.xOverman, L. B., & Lohman, T. M. (1994). Linkage of pH, Anion and Cation Effects in Protein-Nucleic Acid Equilibria. Journal of Molecular Biology, 236(1), 165-178. doi:10.1006/jmbi.1994.1126Bhattacharyya, B., George, N. P., Thurmes, T. M., Zhou, R., Jani, N., Wessel, S. R., … Keck, J. L. (2013). Structural mechanisms of PriA-mediated DNA replication restart. Proceedings of the National Academy of Sciences, 111(4), 1373-1378. doi:10.1073/pnas.1318001111Carlini, L. E., Porter, R. D., Curth, U., & Urbanke, C. (1993). Viability and preliminary in vivo characterization of site directed mutants of Escherichia coli single-stranded DNA-binding protein. Molecular Microbiology, 10(5), 1067-1075. doi:10.1111/j.1365-2958.1993.tb00977.xGriffith, J. D., Harris, L. D., & Register, J. (1984). Visualization of SSB-ssDNA Complexes Active in the Assembly of Stable RecA-DNA Filaments. Cold Spring Harbor Symposia on Quantitative Biology, 49(0), 553-559. doi:10.1101/sqb.1984.049.01.062Morrical, S. W., & Cox, M. M. (1990). Stabilization of recA protein-ssDNA complexes by the single-stranded DNA binding protein of Escherichia coli. Biochemistry, 29(3), 837-843. doi:10.1021/bi00455a034Muniyappa, K., Williams, K., Chase, J. W., & Radding, C. M. (1990). Active nucleoprotein filaments of single-stranded binding protein and recA protein on single-stranded DNA have a regular repeating structure. Nucleic Acids Research, 18(13), 3967-3973. doi:10.1093/nar/18.13.3967Wessel, S. R., Marceau, A. H., Massoni, S. C., Zhou, R., Ha, T., Sandler, S. J., & Keck, J. L. (2013). PriC-mediated DNA Replication Restart Requires PriC Complex Formation with the Single-stranded DNA-binding Protein. Journal of Biological Chemistry, 288(24), 17569-17578. doi:10.1074/jbc.m113.478156Bell, J. C., Liu, B., & Kowalczykowski, S. C. (2015). Imaging and energetics of single SSB-ssDNA molecules reveal intramolecular condensation and insight into RecOR function. eLife, 4. doi:10.7554/elife.08646Suksombat, S., Khafizov, R., Kozlov, A. G., Lohman, T. M., & Chemla, Y. R. (2015). Structural dynamics of E. coli single-stranded DNA binding protein reveal DNA wrapping and unwrapping pathways. eLife, 4. doi:10.7554/elife.08193Zhou, R., Kozlov, A. G., Roy, R., Zhang, J., Korolev, S., Lohman, T. M., & Ha, T. (2011). SSB Functions as a Sliding Platform that Migrates on DNA via Reptation. Cell, 146(2), 222-232. doi:10.1016/j.cell.2011.06.036Pant, K., Karpel, R. L., Rouzina, I., & Williams, M. C. (2004). Mechanical Measurement of Single-molecule Binding Rates: Kinetics of DNA Helix-destabilization by T4 Gene 32 Protein. Journal of Molecular Biology, 336(4), 851-870. doi:10.1016/j.jmb.2003.12.025Pant, K., Karpel, R. L., Rouzina, I., & Williams, M. C. (2005). Salt Dependent Binding of T4 Gene 32 Protein to Single and Double-stranded DNA: Single Molecule Force Spectroscopy Measurements. Journal of Molecular Biology, 349(2), 317-330. doi:10.1016/j.jmb.2005.03.065Robberson, D. L., & Clayton, D. A. (1972). Replication of Mitochondrial DNA in Mouse L Cells and Their Thymidine Kinase- Derivatives: Displacement Replication on a Covalently-Closed Circular Template. Proceedings of the National Academy of Sciences, 69(12), 3810-3814. doi:10.1073/pnas.69.12.3810Ciesielski, G. L., Bermek, O., Rosado-Ruiz, F. A., Hovde, S. L., Neitzke, O. J., Griffith, J. D., & Kaguni, L. S. (2015). Mitochondrial Single-stranded DNA-binding Proteins Stimulate the Activity of DNA Polymerase γ by Organization of the Template DNA. Journal of Biological Chemistry, 290(48), 28697-28707. doi:10.1074/jbc.m115.673707Lázaro, J. M., Blanco, L., & Salas, M. (1995). [5] Purification of bacteriophage φ29 DNA polymerase. DNA Replication, 42-49. doi:10.1016/0076-6879(95)62007-9Ibarra, B., Chemla, Y. R., Plyasunov, S., Smith, S. B., Lázaro, J. M., Salas, M., & Bustamante, C. (2009). Proofreading dynamics of a processive DNA polymerase. The EMBO Journal, 28(18), 2794-2802. doi:10.1038/emboj.2009.219Morin, J. A., Cao, F. J., Lazaro, J. M., Arias-Gonzalez, J. R., Valpuesta, J. M., Carrascosa, J. L., … Ibarra, B. (2012). Active DNA unwinding dynamics during processive DNA replication. Proceedings of the National Academy of Sciences, 109(21), 8115-8120. doi:10.1073/pnas.1204759109Smith, S. B., Cui, Y., & Bustamante, C. (2003). [7] Optical-trap force transducer that operates by direct measurement of light momentum. Biophotonics, Part B, 134-162. doi:10.1016/s0076-6879(03)61009-8Bosco, A., Camunas-Soler, J., & Ritort, F. (2013). Elastic properties and secondary structure formation of single-stranded DNA at monovalent and divalent salt conditions. Nucleic Acids Research, 42(3), 2064-2074. doi:10.1093/nar/gkt1089Smith, S., Finzi, L., & Bustamante, C. (1992). Direct mechanical measurements of the elasticity of single DNA molecules by using magnetic beads. Science, 258(5085), 1122-1126. doi:10.1126/science.1439819Longley, M. J., Smith, L. A., & Copeland, W. C. (2009). Preparation of Human Mitochondrial Single-Stranded DNA-Binding Protein. Mitochondrial DNA, 73-85. doi:10.1007/978-1-59745-521-3_5Li, K., & Williams, R. S. (1997). Tetramerization and Single-stranded DNA Binding Properties of Native and Mutated Forms of Murine Mitochondrial Single-stranded DNA-binding Proteins. Journal of Biological Chemistry, 272(13), 8686-8694. doi:10.1074/jbc.272.13.8686Jarillo, J., Morín, J. A., Beltrán-Heredia, E., Villaluenga, J. P. G., Ibarra, B., & Cao, F. J. (2017). Mechanics, thermodynamics, and kinetics of ligand binding to biopolymers. PLOS ONE, 12(4), e0174830. doi:10.1371/journal.pone.0174830Bujalowski, W., & Lohman, T. M. (1986). Escherichia coli single-strand binding protein forms multiple, distinct complexes with single-stranded DNA. Biochemistry, 25(24), 7799-7802. doi:10.1021/bi00372a003Thömmes, P., Farr, C. L., Marton, R. F., Kaguni, L. S., & Cotterill, S. (1995). Mitochondrial Single-stranded DNA-binding Protein fromDrosophilaEmbryos. Journal of Biological Chemistry, 270(36), 21137-21143. doi:10.1074/jbc.270.36.21137Rodriguez, I., Lazaro, J. M., Blanco, L., Kamtekar, S., Berman, A. J., Wang, J., … de Vega, M. (2005). A specific subdomain in  29 DNA polymerase confers both processivity and strand-displacement capacity. Proceedings of the National Academy of Sciences, 102(18), 6407-6412. doi:10.1073/pnas.0500597102Kamtekar, S., Berman, A. J., Wang, J., Lázaro, J. M., de Vega, M., Blanco, L., … Steitz, T. A. (2004). Insights into Strand Displacement and Processivity from the Crystal Structure of the Protein-Primed DNA Polymerase of Bacteriophage φ29. Molecular Cell, 16(4), 609-618. doi:10.1016/j.molcel.2004.10.019Chrysogelos, S., & Griffith, J. (1982). Escherichia coli single-strand binding protein organizes single-stranded DNA in nucleosome-like units. Proceedings of the National Academy of Sciences, 79(19), 5803-5807. doi:10.1073/pnas.79.19.5803Hamon, L., Pastre, D., Dupaigne, P., Breton, C. L., Cam, E. L., & Pietrement, O. (2007). High-resolution AFM imaging of single-stranded DNA-binding (SSB) protein--DNA complexes. Nucleic Acids Research, 35(8), e58-e58. doi:10.1093/nar/gkm147Takamatsu, C., Umeda, S., Ohsato, T., Ohno, T., Abe, Y., Fukuoh, A., … Kang, D. (2002). Regulation of mitochondrial D‐loops by transcription factor A and single‐stranded DNA‐binding protein. EMBO reports, 3(5), 451-456. doi:10.1093/embo-reports/kvf099Wang, Y., & Bogenhagen, D. F. (2006). Human Mitochondrial DNA Nucleoids Are Linked to Protein Folding Machinery and Metabolic Enzymes at the Mitochondrial Inner Membrane. Journal of Biological Chemistry, 281(35), 25791-25802. doi:10.1074/jbc.m604501200Brown, T. A. (2005). Replication of mitochondrial DNA occurs by strand displacement with alternative light-strand origins, not via a strand-coupled mechanism. Genes & Development, 19(20), 2466-2476. doi:10.1101/gad.135210

The puzzle of HD 104994 (WR 46)

Intense coordinated spectroscopic and photometric monitoring of the suspected Wolf-Rayet binary WR 46 in 1999 reveals clear periodic variations, P = 0.329 ± 0.013 days, in the radial velocities of the emission lines of highest ionization potential, O VI and N V, found deepest in the Wolf-Rayet wind and thus least likely to be perturbed by a companion. These are accompanied by coherent variability in the profiles of lines with lower ionization/excitation potential and in the continuum flux. Most probably originating from orbital motion of the Wolf-Rayet component of the binary, this periodic radial velocity signal disappears from time to time, thus creating a puzzle yet to be solved. We show that the entangled patterns of the line profile variability are mainly governed by transitions between high and low states of the system's continuum flux.Facultad de Ciencias Astronómicas y Geofísica

The puzzle of HD 104994 (WR 46)

Intense coordinated spectroscopic and photometric monitoring of the suspected Wolf-Rayet binary WR 46 in 1999 reveals clear periodic variations, P = 0.329 ± 0.013 days, in the radial velocities of the emission lines of highest ionization potential, O VI and N V, found deepest in the Wolf-Rayet wind and thus least likely to be perturbed by a companion. These are accompanied by coherent variability in the profiles of lines with lower ionization/excitation potential and in the continuum flux. Most probably originating from orbital motion of the Wolf-Rayet component of the binary, this periodic radial velocity signal disappears from time to time, thus creating a puzzle yet to be solved. We show that the entangled patterns of the line profile variability are mainly governed by transitions between high and low states of the system's continuum flux.Facultad de Ciencias Astronómicas y Geofísica