270 research outputs found
Chemical abundances of stars with brown-dwarf companions
It is well-known that stars with giant planets are on average more metal-rich
than stars without giant planets, whereas stars with detected low-mass planets
do not need to be metal-rich. With the aim of studying the weak boundary that
separates giant planets and brown dwarfs (BDs) and their formation mechanism,
we analyze the spectra of a sample of stars with already confirmed BD
companions both by radial velocity and astrometry. We employ standard and
automatic tools to perform an EW-based analysis and to derive chemical
abundances from CORALIE spectra of stars with BD companions. We compare these
abundances with those of stars without detected planets and with low-mass and
giant-mass planets. We find that stars with BDs do not have metallicities and
chemical abundances similar to those of giant-planet hosts but they resemble
the composition of stars with low-mass planets. The distribution of mean
abundances of -elements and iron peak elements of stars with BDs
exhibit a peak at about solar abundance whereas for stars with low-mass and
high-mass planets the [X/H] and [X/H] peak abundances
remain at ~dex and ~dex, respectively. We display these
element abundances for stars with low-mass and high-mass planets, and BDs
versus the minimum mass, , of the most-massive substellar companion
in each system, and we find a maximum in -element as well as Fe-peak
abundances at jupiter masses. We discuss the
implication of these results in the context of the formation scenario of BDs in
comparison with that of giant planets.Comment: Accepted for publication in Astronomy & Astrophysic
Protein Tyrosine Nitration during Development and Abiotic Stress Response in Plants
In recent years, the study of nitric oxide (NO) in plant systems has attracted the attention of many researchers. A growing number of investigations have shown the significance of NO as a signal molecule or as a molecule involved in the response against (a)biotic processes. NO can be responsible of the post-translational modifications (NO-PTM) of target proteins by mechanisms such as the nitration of tyrosine residues. The study of protein tyrosine nitration during development and under biotic and adverse environmental conditions has increased in the last decade; nevertheless, there is also an endogenous nitration which seems to have regulatory functions. Moreover, the advance in proteome techniques has enabled the identification of new nitrated proteins, showing the high variability among plant organs, development stage and species. Finally, it may be important to discern between a widespread protein nitration because of greater RNS content, and the specific nitration of key targets which could affect cell-signaling processes. In view of the above point, we present a mini-review that offers an update about the endogenous protein tyrosine nitration, during plant development and under several abiotic stress conditions.This study was supported by an ERDF grant co-financed by the Ministry of Economy and Competitiveness (project BIO2015-66390-P) and Junta de Andalucía (groups BIO286 and BIO192). Research in FJC laboratory is supported by an ERDF grant co-financed by the Ministry of Economy and Competitiveness (AGL2015-65104-P).Peer reviewedPeer Reviewe
Paleomagnetic and paleoenvironmental implications of magnetofossil occurrences in late Miocene marine sediments from the Guadalquivir Basin, SW Spain.
Although recent studies have revealed more widespread occurrences of magnetofossils in pre-Quaternary sediments than have been previously reported, their significance for paleomagnetic and paleoenvironmental studies is not fully understood. We present a paleo- and rock-magnetic study of late Miocene marine sediments recovered from the Guadalquivir Basin (SW Spain). Well-defined paleomagnetic directions provide a robust magnetostratigraphic chronology for the two studied sediment cores. Rock magnetic results indicate the dominance of intact magnetosome chains throughout the studied sediments. These results provide a link between the highest-quality paleomagnetic directions and higher magnetofossil abundances. We interpret that bacterial magnetite formed in the surface sediment mixed layer and that these magnetic particles gave rise to a paleomagnetic signal in the same way as detrital grains. They, therefore, carry a magnetization that is essentially identical to a post-depositional remanent magnetization, which we term a bio-depositional remanent magnetization. Some studied polarity reversals record paleomagnetic directions with an apparent 60-70 kyr recording delay. Magnetofossils in these cases are interpreted to carry a biogeochemical remanent magnetization that is locked in at greater depth in the sediment column. A sharp decrease in magnetofossil abundance toward the middle of the studied boreholes coincides broadly with a major rise in sediment accumulation rates near the onset of the Messinian salinity crisis (MSC), an event caused by interruption of the connection between the Mediterranean Sea and the Atlantic Ocean. This correlation appears to have resulted from dilution of magnetofossils by enhanced terrigenous inputs that were driven, in turn, by sedimentary changes triggered in the basin at the onset of the MSC. Our results highlight the importance of magnetofossils as carriers of high-quality paleomagnetic and paleoenvironmental signals even in dominantly terrigenous sediments
Dual regulation of cytosolic ascorbate peroxidase (APX) by tyrosine nitration and S-nitrosylation
JBM acknowledges a PhD fellowship (F.P.U.) from the Ministry of Science and Innovation. This work was supported by an ERDF-co-financed grant from the Ministry of Science and Innovation (BIO2009-12003-C02-01, BIO2009-12003-C02-02, and BIO2012-33904) and Junta de Andalucia (group BIO286 and BIO192), Spain. LC/MS/MS analyses were carried out at the Laboratorio de Proteomica LP-CSIC/UAB, a member of the ProteoRed network. Technical and human support provided by CICT of Universidad de Jaen (UJA, MINECO, Junta de Andalucia, FEDER) is gratefully acknowledged. We acknowledge Mr Carmelo Ruiz-Torres for his excellent technical support.Post-translational modifications (PTMs) mediated by nitric oxide (NO)-derived molecules have become a new area
of research, as they can modulate the function of target proteins. Proteomic data have shown that ascorbate peroxidase (APX) is one of the potential targets of PTMs mediated by NO-derived molecules. Using recombinant pea cytosolic APX, the impact of peroxynitrite (ONOO–) and S-nitrosoglutathione (GSNO), which are known to mediate protein
nitration and S-nitrosylation processes, respectively, was analysed. While peroxynitrite inhibits APX activity, GSNO
enhances its enzymatic activity. Mass spectrometric analysis of the nitrated APX enabled the determination that Tyr5
and Tyr235 were exclusively nitrated to 3-nitrotyrosine by peroxynitrite. Residue Cys32 was identified by the biotin
switch method as S-nitrosylated. The location of these residues on the structure of pea APX reveals that Tyr235 is
found at the bottom of the pocket where the haem group is enclosed, whereas Cys32 is at the ascorbate binding site.
Pea plants grown under saline (150mM NaCl) stress showed an enhancement of both APX activity and S-nitrosylated
APX, as well as an increase of H2O2, NO, and S-nitrosothiol (SNO) content that can justify the induction of the APX
activity. The results provide new insight into the molecular mechanism of the regulation of APX which can be both
inactivated by irreversible nitration and activated by reversible S-nitrosylation.Spanish GovernmentERDF from the Ministry of Science and Innovation
BIO2009-12003-C02-01
BIO2009-12003-C02-02
BIO2012-33904Junta de Andalucia
BIO286
BIO192CICT of Universidad de Jaen (UJA, MINECO, Junta de Andalucia, FEDER
Nitro-fatty acids in plant signaling: Nitro-linolenic acid induces the molecular chaperone network in Arabidopsis
Nitro-fatty acids (NO-FAs) are the product of the reaction between reactive nitrogen species derived of nitric oxide (NO) and unsaturated fatty acids. In animal systems, NO-FAs are considered novel signaling mediators of cell function based on a proven antiinflammatory response. Nevertheless, the interaction of NO with fatty acids in plant systems has scarcely been studied. Here, we examine the endogenous occurrence of nitro-linolenic acid (NO-Ln) in Arabidopsis and the modulation of NO-Ln levels throughout this plant’s development by mass spectrometry. The observed levels of this NO-FA at picomolar concentrations suggested its role as a signaling effector of cell function. In fact, a transcriptomic analysis by RNA-seq technology established a clear signaling role for this molecule, demonstrating that NO-Ln was involved in plant defense response against different abiotic-stress conditions, mainly by inducing heat shock proteins and supporting a conserved mechanism of action in both animal and plant defense processes. Bioinformatics analysis revealed that NO-Ln was also involved in the response to oxidative stress conditions, mainly depicted by HO, reactive oxygen species, and oxygen-containing compound responses, with a high induction of ascorbate peroxidase expression. Closely related to these results, NO-Ln levels significantly rose under several abiotic-stress conditions such as wounding or exposure to salinity, cadmium, and low temperature, thus validating the outcomes found by RNA-seq technology. Jointly, to our knowledge, these are the first results showing the endogenous presence of NO-Ln in Arabidopsis (Arabidopsis thaliana) and supporting the strong signaling role of these molecules in the defense mechanism against different abiotic-stress situations.C.M.-P. thanks the University of Jaén for funding the Ph.D. fellowship. LC-MS/MS analyses were carried out at the Technical Services Department of the University of Granada, Spain. ACSCs were kindly provided by Dr. Juan Bautista Arellano from the Institute of Natural Resources and Agrobiology (IRNASA-CSIC, Salamanca, Spain).Peer Reviewe
Magnetobiochronology of lower Pliocene marine sediments from the lower Guadalquivir Basin: insights into the tectonic evolution of the Strait of Gibraltar area
The Gibraltar Arc is a complex tectonic region, and several competing models have been proposed to explain its evolution. We studied the sedimentary fill of the Guadalquivir Basin to identify tectonic processes that were occurring when the reopening of the Strait of Gibraltar led to the reestablishment of Mediterranean outflow. We present a chronostratigraphic framework for the Lower Pliocene sediments from the lower Guadalquivir Basin (SW Spain). The updated chronology is based on magnetobiostratigraphic data from several boreholes. Our results show that the studied interval in the La Matilla core is in the early Pliocene section, providing better constraints on the sedimentary evolution of the basin during that period. Migrating depositional facies led to a younger onset of sandy deposition basinward. At the northwestern passive margin, a 0.7 m.y. period of sedimentary bypass related to a sharp decrease in sedimentation rates and lower sea levels resulted from the tectonic uplift of the forebulge. In contrast, high sedimentation rates with continuous deep-marine sedimentation are recorded at the basin center due to continuous tectonic subsidence and west-southwestward progradation of axial depositional systems. The marginal forebulge uplift, continuous tectonic basinal subsidence, and southward progradation of clinoforms in the early Pliocene can be explained by the pull of a lithospheric slab beneath the Gibraltar Arc as the Strait of Gibraltar opened. These findings are, to our knowledge, the first reported sedimentary expression of slab pull beneath the Betics related to the opening of the Strait of Gibraltar after the Messinian salinity crisis
Differential molecular response of monodehydroascorbate reductase and glutathione reductase by nitration and S-nitrosylation
The ascorbate–glutathione cycle is a metabolic pathway that detoxifies hydrogen peroxide and involves enzymatic
and non-enzymatic antioxidants. Proteomic studies have shown that some enzymes in this cycle such as ascorbate
peroxidase (APX), monodehydroascorbate reductase (MDAR), and glutathione reductase (GR) are potential targets
for post-translational modifications (PMTs) mediated by nitric oxide-derived molecules. Using purified recombinant
pea peroxisomal MDAR and cytosolic and chloroplastic GR enzymes produced in Escherichia coli, the effects of peroxynitrite
(ONOO–) and S-nitrosoglutathione (GSNO) which are known to mediate protein nitration and S-nitrosylation
processes, respectively, were analysed. Although ONOO– and GSNO inhibit peroxisomal MDAR activity, chloroplastic
and cytosolic GR were not affected by these molecules. Mass spectrometric analysis of the nitrated MDAR revealed
that Tyr213, Try292, and Tyr345 were exclusively nitrated to 3-nitrotyrosine by ONOO–. The location of these residues in
the structure of pea peroxisomal MDAR reveals that Tyr345 is found at 3.3 Å of His313 which is involved in the NADPbinding
site. Site-directed mutagenesis confirmed Tyr345 as the primary site of nitration responsible for the inhibition
of MDAR activity by ONOO–. These results provide new insights into the molecular regulation of MDAR which is deactivated
by nitration and S-nitrosylation. However, GR was not affected by ONOO– or GSNO, suggesting the existence
of a mechanism to conserve redox status by maintaining the level of reduced GSH. Under a nitro-oxidative stress
induced by salinity (150 mM NaCl), MDAR expression (mRNA, protein, and enzyme activity levels) was increased,
probably to compensate the inhibitory effects of S-nitrosylation and nitration on the enzyme. The present data show
the modulation of the antioxidative response of key enzymes in the ascorbate–glutathione cycle by nitric oxide (NO)-
PTMs, thus indicating the close involvement of NO and reactive oxygen species metabolism in antioxidant defence
against nitro-oxidative stress situations in plants.Spanish GovernmentERDF - Ministry of Economy and Competitiveness
BIO2012-33904Junta de Andalucía
BIO286
BIO19
Sub-second infrared variability from the archetypal accreting neutron star 4U 1728−34
We report on the first simultaneous high-time resolution X-ray and infrared (IR) observations of a neutron star low mass X-ray binary in its hard state. We performed ≈ 2 h of simultaneous observations of 4U 1728−34 using HAWK-I@VLT, XMM– Newton, and NuSTAR. The source displayed significant X-ray and IR variability down to sub-second time-scales. By measuring the cross-correlation function between the IR and X-ray lightcurves, we discovered a significant correlation with an IR lead of ≈ 30–40 ms with respect to the X-rays. We analysed the X-ray energy dependence of the lag, finding a marginal increase towards higher energies. Given the sign of the lag, we interpret this as possible evidence of Comptonization from external seed photons. We discuss the origin of the IR seed photons in terms of cyclo-synchrotron radiation from an extended hot flow. Finally, we also observed the IR counterpart of a type-I X-ray burst, with a delay of ≈ 7.2 s. Although some additional effects may be at play, by assuming that this lag is due to light travel time between the central object and the companion star, we find that 4U 1728−34 must have an orbital period longer than 3 h and an inclination higher than 8◦
Scientific exploitation of PAZ products in coastal surveillance and monitoring tasks
Revista oficial de la Asociación Española de Teledetección[EN] PAZ mission appears due to the need of a Spanish SAR satellite able to provide radar image products for security and defense, civil and scientific users. INTA is responsible for the technical direction of the Ground Segment, as well as the development of the Calibration and Validation Centre and the scientific exploitation. The ‘Demonstrator of Maritime SAR Applications’ is proposed as an answer to detection tasks in maritime synthetic aperture radar imagery, which are not completely solved yet. DeMSAR has been developed in the framework of a contract between the Spanish National Institute for Aerospace Technology (INTA) and the University of Alcalá. It is intended to be used as a demonstrator of the capabilities of the airborne SAR prototypes of INTA as well as for PAZ, the Spanish SAR satellite. With two operation modes, an automatic ship detector and a toolboxes mode, DeMSAR offers the user a high flexibility in SAR data processing tasks such as speckle filtering, coastline detection, land mask estimation and ship detection and characterization.[ES] La misión PAZ surge ante la necesidad de un satélite SAR español que pueda proporcionar productos imagen radar para usuarios de seguridad y defensa, civiles y científicos. INTA es el responsable de la dirección técnica del Segmento Terreno, así como del desarrollo y operación del Centro de Calibración y Validación y de la Explotación Científica. Dentro de este ámbito de explotación, se desarrolla un demostrador de aplicaciones SAR marítimas (DeMSAR) como herramienta robusta capaz de llevar a cabo tareas de detección sobre la superficie marina, empleando las imágenes adquiridas por radares de apertura sintética. Se desarrolla bajo un marco de colaboración entre el INTA y la Universidad de Alcalá con el fin de convertirse en un demostrador de las capacidades de los sistemas aerotransportados de INTA y, en el futuro, para procesar los datos adquiridos por el sensor PAZ. Con capacidad de operar en modo automático de detección de barcos o mediante librerías de procesado SAR, DeMSAR ofrece una gran versatilidad al usuario en tareas de procesado tales como filtrado de ruido speckle, detección de líneas de costa, estimación de máscaras de tierra y detección y caracterización de barcos.Jarabo, M.; González, M.; De La Mata, D.; Martín De Nicolás, J.; Del Rey, N.; Bárcena, J.; Peláez, V. (2014). Explotación científica de productos PAZ en tareas de vigilancia y monitorización costera. Revista de Teledetección. (41):97-109. doi:10.4995/raet.2014.2287.SWORD9710941Comaniciu, D., & Meer, P. (2002). Mean shift: a robust approach toward feature space analysis. IEEE Transactions on Pattern Analysis and Machine Intelligence, 24(5), 603-619. doi:10.1109/34.1000236Duda, R. O. & Hart, P. E., 1973. Pattern classification and scene analysis. Wiley.Mallat, S., 2008. A wavelet tour of signal processing. 3rd Edition. Academic Press
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