130,463 research outputs found
Letter from Sandon, Maggie to Stilgebouer, Estella
No full textLetter from Sandon, Maggie (Maggie Esther Oblinger), 1877-1965 to Stilgebouer, Estella (Sabra Estella Oblinger), 1875-191
Higher plants light harvesting proteins. Structure and functions as revealed by mutational analysis of either protein or chromophore moietes.
No full textMutation analysis of higher plants light harvesting proteins has been prevented for a long time by the lack of a suitable expression system providing chromophores essential for the folding of these membrane-intrinsic pigment-protein complexes. Early work on in vitro reconstitution of the major light harvesting complex of photosystem II (LHCII) indicated an alternative way to mutation analysis of these proteins. A new procedure for in vitro refolding of the four light harvesting complexes of photosystem II, namely CP24, CP29, CP26 and LHCII yields recombinant pigment-proteins indistinguishable from the native proteins isolated from leaves. This method allows both the performing of single point mutations on protein sequence and the exchange of the chromophores bound to the protein scaffold. We review here recent results obtained by this method on the pigment-binding properties, on the chlorophyll-binding residues, on the identification of proton-binding sites and on the role of xanthophylls in the regulation of light harvesting function
Stimulation of P2 receptors causes release of IL-1beta-loaded microvescicles from human dendritic cells
No full textDendritic cells (DCs) are professional antigen-presenting cells that initiate the immune response by activating T lymphocytes. DCs express plasma membrane receptors for extracellular nucleotides named P2 receptors (P2Rs). Stimulation of P2Rs in these cells is known to cause chemotaxis, cytokine release, and cell death and to modulate LPS-dependent differentiation. Here we show that stimulation of the P2X(7) receptor subtype (P2X(7)R) causes fast microvesicle shedding from DC plasma membrane. Vesicle release occurs from both immature and mature DCs; however, only vesicles from mature DCs, due to their previous exposure to LPS, contain IL-1beta. Microvesicles, whether from immature or mature DCs, also contain caspase-1 and -3 and cathepsin D. They also express the P2X(7)R in addition to other P2Rs and known markers of immune cells such as major histocompatibility complex II (MHC II) and CD39. Activation of the P2X(7)R by extracellular ATP causes IL-1beta release from the vesicle lumen. Previous studies demonstrated that high extracellular K(+) inhibits IL-1beta processing and release; here we show that high ionic strength reduces microvesicle shedding when compared with a low ionic strength medium but strongly increases microvesicle IL-1beta loadin
Characterization of the ATP-hydrolysing activity of α-sarcoglycan
No full textα-Sarcoglycan is a glycoprotein associated with the dystrophin
complex at sarcolemma of skeletal and cardiac muscles. Gene defects
in α-sarcoglycan lead to a severe muscular dystrophy whose
molecular mechanisms are not yet clear. A first insight into the
function of α-sarcoglycan was obtained by finding that it is an
ATP-binding protein and that it probably confers ability to hydrolyse
ATP to the purified dystrophin complex [Betto, Senter,
Ceoldo, Tarricone, Biral and Salviati (1999) J. Biol. Chem. 274,
7907–7912]. In the present study, we present definitive evidence
showing that α-sarcoglycan is an ATP-hydrolysing enzyme.
The appearance of α-sarcoglycan protein expression was correlated
with the increase in ecto-nucleotidase activity during differentiation
of C2C12 cells. Approx. 25% of ecto-nucleotidase
activity displayed by the C2C12 myotubes was inhibited by
preincubating cells with an antibody specific for the ATP-binding
motif of α-sarcoglycan. This demonstrates that α-sarcoglycan
substantially contributes to total ecto-nucleotidase activity of
C2C12 myotubes. To characterize further this activity, human
embryonic kidney 293 cells were transfected with expression
plasmids containing α-sarcoglycan cDNA. Transfected cells exhibited
a significant increase in the ATP-hydrolysing activity that
was abolished by the anti-α-sarcoglycan antibody. The enzyme
had a substrate specificity for ATP and ADP, did not hydrolyse
other triphosphonucleosides, and the affinity for ATP was in
the low mM range. The ATPase activity strictly required the presence
of both Mg2+ and Ca2+ and was completely inhibited by
suramin and reactive blue-2. These results show that α-sarcoglycan
is aCa2+,Mg2+-ecto-ATPDase. The possible consequences
of the absence of α-sarcoglycan activity in the pathogenesis of
muscular dystrophy are discussed
MeSH term explosion and author rank improve expert recommendations
No full textInformation overload is an often-cited phenomenon that reduces the productivity, efficiency and efficacy of scientists. One challenge for scientists is to find appropriate collaborators in their research. The literature describes various solutions to the problem of expertise location, but most current approaches do not appear to be very suitable for expert recommendations in biomedical research. In this study, we present the development and initial evaluation of a vector space model-based algorithm to calculate researcher similarity using four inputs: 1) MeSH terms of publications; 2) MeSH terms and author rank; 3) exploded MeSH terms; and 4) exploded MeSH terms and author rank. We developed and evaluated the algorithm using a data set of 17,525 authors and their 22,542 papers. On average, our algorithms correctly predicted 2.5 of the top 5/10 coauthors of individual scientists. Exploded MeSH and author rank outperformed all other algorithms in accuracy, followed closely by MeSH and author rank. Our results show that the accuracy of MeSH term-based matching can be enhanced with other metadata such as author rank
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Heavy Metals Separation in Wastewater Comparing Different Types of Nanostructured Adsorbents
No full textIn the framework of sustainability, proposing new technologies to improve the current linear economy system is one of the most challenging aspects for both academics and industries. In this context, the optimization of wastewater recovery and re-use are among the most crucial aspects to improve; in fact, contaminated waters come from a wide range of industries: cooking, refineries, food, pharmaceuticals, textile and agriculture. Heavy metals are among the most critical pollutants, being widely spread (especially in the textile sector) and difficult to remove. In this work, two different sets of Magnetic Nanostructured Adsorbents (MNAs) to clean wastewaters containing Chromium (III), Nickel (II) and Copper (II) ions were studied and compared. The first type of MNA was a 2-D nanosheet structure generated using iron (II/III) salts and sodium (or ammonium) hydroxide solution to decorate a dispersion of graphene oxide (GO) in water. The second type of adsorbent was a 3-D structure composed of GO-MNAs embedded in cross-linked alginate beads. Performed experiments (in a wide range of metal ions concentrations) showed very promising results in terms of removal efficiencies (almost complete abatement could be achieved using a proper amount of MNAs) with respect to all tested contaminants, highlighting better performances of the beads with respect to the corresponding 2-D structure
"Closing the R&D Gap, Evaluating the Sources of R&D Spending"
No full textBoth spending and tax policies have been implemented in the United States with the goal of stimulating private sector research and development (R&D). Karier questions whether current R&D policy, especially the research and experimentation tax credit, can contribute to closing the gap between nondefense expenditures on R&D in the United States and such expenditures in other countries, such as Japan and Germany. He also explores possible changes to our current R&D policy to make it more effective.
Dispelling the Myths Behind First-author Citation Counts
No full textWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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