The First Post-Kepler Brightness Dips of KIC 8462852

We present a photometric detection of the first brightness dips of the unique variable star KIC 8462852 since the end of the Kepler space mission in 2013 May. Our regular photometric surveillance started in October 2015, and a sequence of dipping began in 2017 May continuing on through the end of 2017, when the star was no longer visible from Earth. We distinguish four main 1-2.5% dips, named "Elsie," "Celeste," "Skara Brae," and "Angkor", which persist on timescales from several days to weeks. Our main results so far are: (i) there are no apparent changes of the stellar spectrum or polarization during the dips; (ii) the multiband photometry of the dips shows differential reddening favoring non-grey extinction. Therefore, our data are inconsistent with dip models that invoke optically thick material, but rather they are in-line with predictions for an occulter consisting primarily of ordinary dust, where much of the material must be optically thin with a size scale <<1um, and may also be consistent with models invoking variations intrinsic to the stellar photosphere. Notably, our data do not place constraints on the color of the longer-term "secular" dimming, which may be caused by independent processes, or probe different regimes of a single process

Role of Fe and plant haemoglobins and Fe-superoxide dismutase on the production of nitrogen reactive species

Póster presentado en la XVIth International Conference on Dioxygen Binding and Sensing Proteins (O2BIP), celebrada en Hof van Leire (Bélgica) del 22 al 26 de agosto de 2010.Peer Reviewe

Conjugation of active iron superoxide dismutase to nanopatterned surfaces

Superoxide dismutase enzymes (SODs) are an essential part of the first line of cellular defense system against free radicals species. They catalyze the dismutation of superoxide radicals into oxygen and hydrogen peroxide. Although several studies have examined the attachment of superoxide dismutases to nanoparticles and nanostructures, never has been used a member of the Fe/MnSOD family. In this study, the behavior of plant origin FeSOD enzyme on three different nanopatterned surfaces was investigated as a function of covalent and electrostatic binding. Fluorescence microscopy was used to demonstrate that the protein is attached only to the gold layer. We also examined the activity of SOD by a colorimetric assay, and we have shown that the enzyme remains active after attachment to the three different surfaces under both kind of binding (electrostatic and covalent). This methodology could be useful for those who want to functionalize nanostructures with a SOD enzyme and test the activity. This process could be of great interest for the development of peroxynitrite and superoxide biosensors. © 2011 IEEE.Peer Reviewe

Direct Electrochemistry and Environmental Sensing of Rice Hemoglobin Immobilized at Graphite Electrodes

Non-symbiotic hemoglobin from rice (Oryza sativa L.), OsHb-1, with its rather hexacoordinated than pentacoordinated heme and high affinity for oxygen, may have a particular role in O2 and environmental sensing. Here, the 21 kDa monomeric OsHb-1 was electrochemically studied at graphite electrodes and further probed in analysis of environmental species such as hydrogen peroxide, cyanide, and superoxide. Redox potential of the OsHb-1 heme iron was found to be -136 mV vs. SCE, at pH 6.5, while the rate constant ks for the heterogeneous electron transfer (ET) between graphite and OsHb-1 immobilised in the Nafion membrane at the carbon nanotubes-modified electrodes was below 0.2 s-1. Despite sluggish ET, OsHb-1 efficiently, with current densities exceeding 2 mA cm-2 at ¿0.3 V, electrocatalyzed reduction of O2 starting from the potentials of OsHb-1¿s heme. The bioelectrocatalytic reduction of O2 was inhibited by CN- thus enabling its sensitive, 100 pM analysis. Peroxidase-like activity of OsHb-1 and the reaction of superoxide anion with the heme iron of OsHb-1, in de-oxygenated solutions, were studied and analysed in terms of OsHb-1 reactivity. The results obtained indicate OsHb-1 is a sensitive tool for environmental biosensing and toxicity screeningThe work was supported by the Danish Council for Independent Research, Natural Sciences (FNU), Project Number 11-107176, and by the Spanish Ministry of Economy and Competitiveness (Grant No. AGL2010-16167).Peer Reviewe

Evaluation of the anti-nitrative effect of plant antioxidants using a cowpea Fe-superoxide dismutase as a target

Nitric oxide cytotoxicity arises from its rapid conversion to peroxynitrite (ONOO(-)) in the presence of superoxide, provoking functional changes in proteins by nitration of tyrosine residues. The physiological significance of this post-translational modification is associated to tissue injury in animals, but has not been yet clarified in plants. The objective of this study was to establish new approaches that could help to understand ONOO(-) reactivity in plants. A recombinant Fe-superoxide dismutase from cowpea (Vigna unguiculata (L.) Walp.), rVuFeSOD, was the target of the ONOO(-)-generator SIN-1, and the anti-nitrative effect of plant antioxidants and haemoglobins was tested in vitro. Nitration on rVuFeSOD was evaluated immunochemically or as the loss of its enzymatic activity. This assay proved to be useful to test a variety of plant compounds for anti-nitrative capacity. Experimental data confirmed that rice (Oryza sativa L.) haemoglobin-1 (rOsHbI) and cowpea leghaemoglobin-2 exerted a protective function against ONOO(-) by diminishing nitration on rVuFeSOD. Both plant haemoglobins were nitrated by SIN-1. The chelator desferrioxamine suppressed nitration in rOsHbI, indicating that Fe plays a key role in the reaction. The removal of the haem moiety in rOsHbI importantly suppressed nitration, evidencing that this reaction may be self-catalyzed. Among small antioxidants, ascorbate remarkably decreased nitration in all tests. The phenolic compounds caffeic acid, gallic acid, pyrogallol, 4-hydroxybenzoic acid and the flavonoid gossypin also diminished tyrosine nitration and protected rVuFeSOD to different extents. It is concluded that small plant antioxidants, especially ascorbate, and haemoglobins may well play key roles in ONOO(-) homeostasis in vivo.E.U. was the recipient of a Ph.D. fellowship from the Public University of Navarre (UPNa). Financial support was provided by the MICINN/MINECO, Government of Spain (grant AGL2010-16167). A.C.A. and E.T. were supported by the project SABioD (Department of Innovation, Government of Navarra).Peer Reviewe

Expression of Bacillus thuringiensis Cry1Ia7 toxin in Pseudomonas fluorescens confers protection against UV radiation

Trabajo presentado en la 45th Annual Meeting of the Society for Invertebrate Pathology, celebrada en Buenos Aires del 5 al 9 de agosto de 2012.The Bacillus thuringiensis Cry1Ia7 insecticidal protein is toxic against several lepidopteran species, including the European grapevine moth Lobesia botrana (Lepidoptera: Tortricidae). Cry1Ia7 does not form part of the paraesporal crystal but is expressed and secreted during the vegetative phase.This,along with its rapid degradation upon exposure to solar ultraviolet radiation hinders its use as a biological insecticide.To address this problem, cry1Ia7 was cloned into a UV-resistant P. fluorescens strain. Cry1Ia7 was expressed and encapsulated in vegetative P. fluorescens cells following established protocols. The toxicity of Cry1Ia7 protein produced in P. fluorescenswas purified inanamylose affinity column usingamaltose binding protein (Pf-MBP-Cry1Ia7) and compared with that of Cry1Ia7 expressed and encapsulated in P.fluorescens(Pf-Cry1Ia7).Both proteins were active against L. botrana,and their mean lethal concentrations (LC50 values) were not statistically different (10.63and12.6/g/ml,respectively).The activity of free Pf-MBP- Cry1Ia7 protein was reduced 10-fold following exposure to a UV source; however, the LC50 of Pf-Cry1Ia7 encapsulated in P. fluorescens was not significantly affected by exposure to UV, due to the photoprotection offered by P. fluorescens encapsulation.This system of protein production can be used as a model for other Bacillus thuringiensis proteins that would benefit from improved protection against solar UV radiation.Peer Reviewe

Encapsulation of the Bacillus thuringiensis secretable toxins Vip3Aa and Cry1Ia in Pseudomonas fluorescens

Vip3A and Cry1I toxins are secreted during the vegetative growth of Bacillus thuringiensis. Vip3A toxins do not share homology to the crystal (Cry) proteins and are active against a different spectrum of lepidopteran species. Cry1I toxins share similarity with the Cry1 protein group but do not accumulate in the parasporal crystal. Since Vip3A and Cry1I toxins are released from the cell, they are excluded from biological formulates based on spores and crystals of B. thuringiensis. As an approach to obtain novel sprayable insecticides containing Vip3 or Cry1I toxins, Vip3Aa and Cry1Ia proteins were expressed in Pseudomonas fluorescens. This bacterium, non-pathogenic to animals or plants, can be used as a protectant agent in insecticide formulations after being subjected to a killing fixation process that strengthens the P. fluorescens cell wall. Vip3Aa and Cry1Ia expression into P. fluorescens and Escherichia coli was achieved by the cloning of the vip3Aa and the cry1Ia genes into the broad range expression vector pMEKm12. Both proteins remained encapsulated in the bacterial cells as shown by SDS-PAGE and Western Blot. The toxicity of Vip3Aa expressed in P. fluorescens against Spodoptera frugiperda (89ng/cm2 of diet) was similar to that of Vip3Aa microencapsulated in P. fluorescens (104ng/cm2 of diet). In bioassays with Lobesia botrana, the LC50 value of Cry1Ia purified from P. fluorescens (10.7μg/ml) was similar to that of Cry1Ia microencapsulated in P. fluorescens (12.6μg/ml) and that of Cry1Ia purified from E. coli (8.5μg/ml). These results support the suitability of P. fluorescens as a heterologous expression system for the development of novel insecticides based on the secretable Vip3Aa and Cry1Ia toxins from B. thuringiensis. © 2013 Elsevier Inc.This research was supported by the Generalitat Valenciana (APOSTD/2007/041 and GVPRE/2008/183) and the Spanish Ministry of Science and Technology (AGL2009-13340-CO2/AGR). We are grateful to Delia Muñoz for critically reading the manuscript.Peer Reviewe