7 research outputs found
Extraction and purification of the lectin found in the tubers of Eranthis hyemalis (winter aconite): DOI: 10.5584/jiomics.v1i2.72
No full text
Lectin are proteins which play an important role in the defence mechanisms of plants against the attack of microorganisms and insects: this role has provoked particular interest in the fields of biotechnology and agriculture. This paper describes the extraction and purification of the lectin found in tubers of the winter aconite (Eranthis hyemalis), with the aim of improving and modernising the existing extraction protocol. The Eranthis hyemalis lectin (EHL) is a member of the type-2 Ribosome Inactivating Proteins (RIP) family, proteins which have the ability to inhibit in vitro protein synthesis. RIPs have been linked to plant defence by their antiviral, antifungal and insecticidal properties, and some have been found to be potent inhibitors of the Human Immunodeficiency Virus-1 (HIV-1) virus. EHL was purified using affinity column chromatography and ammonium sulphate precipitation; thiourea was used as antioxidant in order to prevent EHL denaturing during the extraction process. The presence of EHL in the extract was verified using a blood agglutination test with rabbit erythrocytes. Sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) analysis was employed to determine the lectin size; EHL was found to be formed of two chains with molecular weights of approximately 31 kDa; the size of the whole protein was estimated as approximately 60 kDa. The concentration of the EHL in the post-column eluent, determined using the Bradford Assay, was 380.1 μg.cm-3. This improved extraction protocol is the first step which will enable future research on the potential use of EHL in crop protection, by studying its insecticidal, fungicidal and bactericidal properties
Development of a reagentless biosensor for inorganic phosphate, applicable over a wide concentration range
No full textA fluorescent reagentless biosensor for inorganic phosphate (Pi), based on the E. coli PstS phosphate binding protein, was redesigned to allow measurements of higher Pi concentrations and at low, substoichiometric concentrations of biosensor. This was achieved by weakening Pi binding of the previous biosensor, and different approaches are described that could enable this change in properties. The readout, providing response to the Pi concentration, is delivered by tetramethylrhodamine fluorescence. In addition to two cysteine mutations for rhodamine labeling at positions 17 and 197, the final variant had an I76G mutation in the hinge region between the two lobes that make up the protein. Upon Pi binding, the lobes rotate on this hinge and the mutation on the hinge lowers affinity ∼200-fold, with a dissociation constant now in the tens to hundreds micromolar range, depending on solution conditions. The signal change on Pi binding was up to 9-fold, depending on pH. The suitability of the biosensor for steady-state ATPase assays was demonstrated with low biosensor usage and its advantage in ability to cope with Pi contamination
Constraining the wind launching region in Herbig Ae stars: AMBER/VLTI spectroscopy of HD 104237
No full textThis is the author accepted manuscript. The final version is available from EDP Sciences via the DOI in this record.Aims. We investigate the origin of the Brγ emission of the Herbig Ae star HD 104237 on Astronomical Unit (AU) scales.
Methods. Using AMBER/VLTI at a spectral resolution R = 1500 we spatially resolve the emission in both the Brγ line and the adjacent continuum.
Results. The visibility does not vary between the continuum and the Brγ line, even though the line is strongly detected in the spectrum, with a peak
intensity 35% above the continuum. This demonstrates that the line and continuum emission have similar size scales. We assume that the K-band
continuum excess originates in a “puffed-up” inner rim of the circumstellar disk, and discuss the likely origin of Brγ.
Conclusions. We conclude that this emission most likely arises from a compact disk wind, launched from a region 0.2–0.5 AU from the star, with
a spatial extent similar to that of the near infrared continuum emission region, i.e., very close to the inner rim location.This work has been partly supported by the
MIUR COFIN grant 2003/027003-001 and 025227/2004 to the INAFOsservatorio
Astrofisico di Arcetri. This project has benefited from
funding from the French Centre National de la Recherche Scientifique
(CNRS) through the Institut National des Sciences de l’Univers
(INSU) and its Programmes Nationaux (ASHRA, PNPS). The authors
from the French laboratories would like to thank the successive
directors of the INSU/CNRS directors. C. Gil work was supported
in part by the Fundac¸˜ao para a Ciˆencia e a Tecnologia through
project POCTI/CTE-AST/55691/2004 from POCTI,with funds from
the European program FEDER
An asymmetry detected in the disk of κ Canis Majoris with AMBER/VLTI
No full textThis is the author accepted manuscript. The final version is available from the publisher via the DOI in this record.Variant title for accepted version: An asymmetry detected in the disk of κ CMa⋆ with the VLTI/AMBERAims. We study the geometry and kinematics of the circumstellar environment of the Be star κ CMa in the Brγ emission line and its nearby continuum.
Methods. We use the VLTI/AMBER instrument operating in the K band which provides a spatial resolution of about 6 mas with a spectral resolution of 1500 to study the kinematics within the disk and to infer its rotation law. In order to obtain more kinematical constraints we also use an high spectral resolution Paβ line profile obtain in December 2005 at the Observatorio do Pico do Dios, Brazil and we compile V/R line profile variations and spectral energy distribution data points from the literature.
Results. Using differential visibilities and differential phases across the Brγ line we detect an asymmetry in the disk. Moreover, we found that κ CMa seems difficult to fit within the classical scenario for Be stars, illustrated recently by α Arae observations, i.e. a fast rotating B star close to its breakup velocity surrounded by a Keplerian circumstellar disk with an enhanced polar wind. Finally we discuss the possibility for κ CMa to be a critical rotator with a Keplerian rotating disk and try to see if the detected asymmetry can be interpreted within the ”one-armed” viscous disk framework.The AMBER project has benefited from funding from the
French Centre National de la Recherche Scientifique (CNRS) through
the Institut National des Sciences de l’Univers (INSU) and its
Programmes Nationaux (ASHRA, PNPS). The authors from the
French laboratories would like to thank the successive directors of the
INSU/CNRS directors. The authors from the the Arcetri Observatory
acknowledge partial support from MIUR grants and from INAF
grants. C. Gil work was supported in part by the Fundac¸˜ao para a
Ciˆencia e a Tecnologia through project POCTI/CTE-AST/55691/2004
from POCTI, with funds from the European program FEDE
Interferometric data reduction with AMBER/VLTI. Principle, estimators, and illustration
No full textThis is the author accepted manuscript. The final version is available from EDP Sciences via the DOI in this record.Aims. In this paper, we present an innovative data reduction method for single-mode interferometry. It has been specifically developed for the
AMBER instrument, the three-beam combiner of the Very Large Telescope Interferometer, but it can be derived for any single-mode interferometer.
Methods. The algorithm is based on a direct modelling of the fringes in the detector plane. As such, it requires a preliminary calibration of the
instrument in order to obtain the calibration matrix that builds the linear relationship between the interferogram and the interferometric observable,
which is the complex visibility. Once the calibration procedure has been performed, the signal processing appears to be a classical least-square
determination of a linear inverse problem. From the estimated complex visibility, we derive the squared visibility, the closure phase, and the
spectral differential phase.
Results. The data reduction procedures have been gathered into the so-called amdlib software, now available for the community, and are presented
in this paper. Furthermore, each step in this original algorithm is illustrated and discussed from various on-sky observations conducted with the
VLTI, with a focus on the control of the data quality and the effective execution of the data reduction procedures. We point out the present limited
performances of the instrument due to VLTI instrumental vibrations which are difficult to calibrate.The AMBER project4 was founded by the French Centre
National de la Recherche Scientifique (CNRS), the Max Planck Institute für
Radioastronomie (MPIfR) in Bonn, the Osservatorio Astrofisico di Arcetri
(OAA) in Firenze, the French Region “Provence Alpes Côte D’Azur” and
the European Southern Observatory (ESO). The CNRS funding has been
made through the Institut National des Sciences de l’Univers (INSU) and its
Programmes Nationaux (ASHRA, PNPS, PNP).
The OAA co-authors acknowledge partial support from MIUR grants to the
Arcetri Observatory: A LBT interferometric arm, and analysis of VLTI interferometric
data and From Stars to Planets: accretion, disk evolution and
planet formation and from INAF grants to the Arcetri Observatory Stellar and
Extragalactic Astrophysics with Optical Interferometry. C. Gil work was supported
in part by the Fundação para a Ciência e a Tecnologia through project
POCTI/CTE-AST/55691/2004 from POCTI, with funds from the European program
FEDER
