1,143 research outputs found
Gemini spectra of 12000K white dwarf stars
We report signal-to-noise ratio SNR ~ 100 optical spectra for four DA white
dwarf stars acquired with the GMOS spectrograph of the 8m Gemini north
telescope. These stars have 18<g<19 and are around Teff ~ 12000 K, were the
hydrogen lines are close to maximum. Our purpose is to test if the effective
temperatures and surface gravities derived from the relatively low
signal-to-noise ratio ( ~ 21) optical spectra acquired by the Sloan
Digital Sky Survey through model atmosphere fitting are trustworthy. Our
spectra range from 3800A to 6000A, therefore including H beta to H9. The H8
line was only marginally present in the SDSS spectra, but is crucial to
determine the gravity. When we compare the values published by Kleinman et al.
(2004) and Eisenstein et al. (2006) with our line-profile (LPT) fits, the
average differences are: Delta Teff ~ 320 K, systematically lower in SDSS, and
Delta log g ~ 0.24 dex, systematically larger in SDSS. The correlation between
gravity and effective temperature can only be broken at wavelengths bluer than
3800 A. The uncertainties in Teff are 60% larger, and in log g larger by a
factor of 4, than the Kleinman et al. (2004) and Eisenstein et al. (2006)
internal uncertainties.Comment: 11 pages and 8 figure
Escherichia coli expression, refolding and characterization of human laforin
Laforin is a unique human dual-specificity phosphatase as it contains an amino terminal carbohydrate binding module (CBM). Laforin gene mutations lead to Lafora disease, a progressive myoclonus epilepsy with an early fatal issue. Previous attempts to produce recombinant laforin faced various difficulties, namely the appearance of protein inclusion bodies, the contamination with bacterial proteins and a high tendency of the protein to aggregate, despite the use of fusion tags to improve solubility and ease the purification process. In this work, we have expressed human laforin in Escherichia coli in the form of inclusion bodies devoid of any fusion tags. After a rapid dilution refolding step, the protein was purified by two chromatographic steps, yielding 5–7 mg of purified protein per liter of bacterial culture. The purified protein was shown to have the kinetic characteristics of a dual-specificity phosphatase, and a functional carbohydrate binding module.
With this protocol, we were able for the first time, to produce and purify laforin without fusion tags in the amounts traditionally needed for the crystallographic structural studies paving the way to the understanding of the molecular mechanisms of laforin activity and to the development of novel therapies for Lafora disease.Fundação para a Ciência e a Tecnologia (FCT) – Programa Operacional “Ciência, Tecnologia, Inovação” (POCTI
Relationships between Brewer-Dobson circulation, double tropopauses, ozone and stratospheric water vapour
Statistical relationships between the variability of the area covered by double tropopause events (DTs), the strength of the tropical upwelling, the total column ozone and of the lower stratospheric water vapour are analyzed. The QBO and ENSO signals in the double tropopause and tropical upwelling as well as their influence on the statistical relationships are also presented. The analysis is based on both reanalysed data (ERA-Interim) and satellite data. Significant anticorrelations were found between the area covered by DTs and the total column ozone in the midlatitudes of the Northern Hemisphere. This relationship is confirmed by a large positive correlation between the areas covered by ozone laminae and double tropopause events as found in the HIRDLS satellite dataset. Significant anticorrelations were also found between the global area of double tropopause events and the near global (50◦S–50◦N) water vapour in the lower stratosphere. The correlations of DT variables with total column ozone and ozone laminae are both consistent with the poleward displacement of tropical air with lower ozone mixing ratio and with tropospheric intrusions of tropical tropospheric air into the lower extratropical stratosphere. The association of DTs with the poleward displacements of the tropical air is also consistent with a strong positive correlation between the area covered by DTs and the wave activity in the lower most stratosphere, between the first and second lapse rate tropopauses, as found in the ERA-Interim reanalysis. Finally, a significant anticorrelation was found between the tropical upwelling and the near global lower stratospheric water vapour. Moreover, the step like decrease in the lower stratospheric water vapour after 2001 is mirrored by a step like increase in the tropical upwelling.publishe
Development of pH-sensitive magnetoliposomes containing shape anisotropic magnetic nanoparticles for applications in dual cancer therapy
In this work, anisotropic magnetic nanoparticles of mixed calcium/magnesium ferrite were synthesized and characterized. These nanoparticles were encapsulated in pH-sensitive liposomes loaded with doxorubicin, and the resulting nanosystems were characterized by DLS. Fluorescence emission assays were performed to elucidate the structural characterization and study the release profile of doxorubicin at different pH values and promising results were obtained for application in combined cancer therapy.FCT under Strategic funding of CF-UM-UP (UIDB/04650/2020)
Expression of the functional carbohydrate-binding module (CBM) of human laforin
Laforin is a human protein associated with the glycogen metabolism, composed of two structurally and
functionally independent domains: a phosphatase catalytic domain and a substrate-binding module with
glycogen and starch affinity. The main goal of this work is the development of a methodology for the
expression of the so far poorly characterized carbohydrate-binding module (CBM) of laforin, allowing
its study and development of biomedical applications. The laforin’s CBM sequence was originally cloned
by PCR from a human muscle cDNA library. The recombinant protein, containing laforin’s CBM fused to an
Arg-Gly-Asp sequence (RGD), was cloned and expressed using vector pET29a and recovered as inclusion
bodies (IBs). Refolding of the IBs allowed the purification of soluble, dimeric and functional protein,
according to adsorption assays using starch and glycogen. Several other experimental approaches, using
both bacteria and yeast, were unsuccessfully tested, pointing towards the difficulties in producing the
heterologous protein. Indeed, this is the first work reporting the production of the functional CBM from
human laforin.Fundação para a Ciência e a Tecnologia (FCT, Portugal)
Biological activity of heterologous murine interleukin-10 and preliminary studies on the use of a dextrin nanogel as a delivery system
Analytical method for the determination of strychnine in tissues by gas chromatography/mass spectrometry: two case reports
This paper describes an analytical method for strychnine determination in biological samples by gas chromatography/mass spectrometry and their application in the investigation of two cases involving strychnine ingestion: A fatal case and a clinical one. The strychnine is isolated from biological samples using a liquid-liquid extraction procedure. The clean-up procedure is performed using an acid solution. Papaverine is used as internal standard in the quantification of strychnine. In the analysed specimens, the limits of quantification were 0.1 [mu]g/ml or 0.1 [mu]g/g. The recovery rate ranged from 75.0% to 98.7% and the coefficients of variation ranged from 4.8% to 10.5%.http://www.sciencedirect.com/science/article/B6T6W-408KCFB-8/1/f8bbeefad9e20909aef50467f67a2e8
Carbon footprint of apple and pear : orchards, storage and distribution
Apple and pear represent 51% of fresh fruit orchards in Portugal. This paper presents a life-cycle (LC) greenhouse gas (GHG) assessment (so-called carbon footprint) of 3 apple and 1 pear Portuguese production systems. An LC model and inventory were implemented, encompassing the farm stage (cultivation of fruit trees in orchards), storage and distribution (transport to retail). The functional unit considered in this study was 1 kg of distributed fruit (at retail). Four different LC inventories for orchards were implemented based on data collected from three farms. Inventory data from two storage companies were also gathered. The main results show that the GHG emissions of apple and pear ranged between 192 and 229 gCO2eq kgfruit-1. The GHG emissions (direct and indirect) from the cultivation phase ranged from 36% to 60% of total emissions. Fruit storage, which lasted for as much as 8-10 months, was also responsible for significant emissions due to high energy requirements
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