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Self-assembly of Fmoc-tetrapeptides based on the RGDS cell adhesion motif
Self-assembly in aqueous solution has been investigated for two Fmoc [Fmoc ¼ N-(fluorenyl)-9-methoxycarbonyl] tetrapeptides comprising the RGDS cell adhesion motif from fibronectin or the scrambled sequence GRDS. The hydrophobic Fmoc unit confers amphiphilicity on the molecules, and
introduces aromatic stacking interactions. Circular dichroism and FTIR spectroscopy show that the self-assembly of both peptides at low concentration is dominated by interactions among Fmoc units, although Fmoc-GRDS shows b-sheet features, at lower concentration than Fmoc-RGDS. Fibre X-ray diffraction indicates b-sheet formation by both peptides at sufficiently high concentration. Strong
alignment effects are revealed by linear dichroism experiments for Fmoc-GRDS. Cryo-TEM and smallangle
X-ray scattering (SAXS) reveal that both samples form fibrils with a diameter of approximately 10 nm. Both Fmoc-tetrapeptides form self-supporting hydrogels at sufficiently high concentration. Dynamic shear rheometry enabled measurements of the moduli for the Fmoc-GRDS hydrogel, however syneresis was observed for the Fmoc-RGDS hydrogel which was significantly less stable to shear. Molecular dynamics computer simulations were carried out considering parallel and antiparallel b-sheet configurations of systems containing 7 and 21 molecules of Fmoc-RGDS or Fmoc-GRDS, the results being analyzed in terms of both intermolecular structural parameters and energy contributions
Robust signatures in the current-voltage characteristics of DNA molecules oriented between two graphene nanoribbon electrodes
In this work we numerically calculate the electric current through three
kinds of DNA sequences (telomeric, \lambda-DNA, and p53-DNA) described by
different heuristic models. A bias voltage is applied between two zig-zag edged
graphene contacts attached to the DNA segments, while a gate terminal modulates
the conductance of the molecule. The calculation of current is performed by
integrating the transmission function (calculated using the lattice Green's
function) over the range of energies allowed by the chemical potentials. We
show that a telomeric DNA sequence, when treated as a quantum wire in the fully
coherent low-temperature regime, works as an excellent semiconductor. Clear
steps are apparent in the current-voltage curves of telomeric sequences and are
present independent of lengths and sequence initialisation at the contacts. The
current-voltage curves suggest the existence of stepped structures independent
of length and sequencing initialisation at the contacts. We also find that the
molecule-electrode coupling can drastically influence the magnitude of the
current. The difference between telomeric DNA and other DNA, such as
\lambda-DNA and DNA for the tumour suppressor p53, is particularly visible in
the length dependence of the current
Retinoic-Acid-Induced Downregulation of the 67 KDa Laminin Receptor Correlates with Reduced Biological Aggressiveness of Human Neuroblastoma Cells
16 pages (217-232), 6 figuresThe authors are indebted to Dr. S. Menard (Milan, Italy) for the gift of the antibody against 37LRP. C. M. R. L. was supported by Programa de Personal Técnico de Apoyo (PTA-2003-02-00207; Ministry of Education and Science, Spain). This work was supported by grants from the Spanish former Ministry of Education and Science and Ministry of Science and Innovation (SAF2003-00311, SAF2006–00647 and SAF2007–60780) and Generalitat Valenciana (GRUPOS 03/15 and ACOMP 09/212) (to D. B.) , and Instituto de Salud Carlos III (RD20-102 to S. N.).Peer reviewe
Fast degenerate double proton transfer in the solid state between two indazolinone tautomers
The neutral dimer formed by 4,6-difluoro-1H,2H-indazolin-3-one and 3-hydroxy-4,6-difluoro-1H-indazole linked by two hydrogen bonds presents a very fast intermolecular double proton transfer in the solid state (ISSPT). The combined use of crystallography, solid state NMR and DFT [B3LYP/6-311++G(d,p)] calculations supports this interesting observation and allows us to estimate a barrier of about 20 kJ mol-1. © 2010 The Royal Society of Chemistry.Peer Reviewe
Assessing the responses of exploited marine populations in a context of rapid climate change: the case of blackspot seabream from Strait of Gibraltar.
Assessing the response of exploited marine populations in a context of rapid climate change: the case of
blackspot seabream from the Strait of Gibraltar.—
There is a growing concern over the decline of fisheries and
the possibility of the decline becoming worse due to climate change. Studies on
small–scale fisheries
could help
to improve our understanding of the effect of climate on the ecology of exploited stocks. The Strait of Gibraltar
is an important fishery ground for artisanal fleets.
In this area, b
lackspot seabream (
Pagellus bogaraveo
) is
the main species targeted by artisanal fisheries
in view of its relevance in landed weight.
The aims of this
study were to explore the possible effects of two atmospheric oscillations, the North Atlantic Oscillation (NAO)
and the Arctic Oscillation (AO), on the capture of blackspot seabream in the Strait of Gibraltar, to determine
their association with oceanographic conditions, and to improve our knowledge about the possible effects of
climate change on fisheries ecology so that fishery management can be improved. We used two types of data
from different sources: (i) landings per unit of effort reported from a second working group between Morocco
and Spain on
Pagellus bogaraveo
in the Gibraltar Strait area,
for the period 1983–2011
, and (ii) the recorded
blackspot seabream landings obtained from the annual fisheries statistics published by the
Junta de Andalucía
(Andalusian Regional Government). Our results indicate that the long–term landing of blackspot seabream in
the Strait of Gibraltar is closely associated with atmospheric oscillations. Thus, prolonged periods of positive
trends in the NAO and AO could favour high fishery yields. In contrast, negative trends in NAO and AO could
drastically reduce yield.Postprint0,000
Analysis of the effect of atmospheric oscillations on physical condition of pre–reproductive bluefin tuna from the Strait of Gibraltar
Analysis of the effect of atmospheric oscillations on physical condition of pre–reproductive bluefin tuna from
the Strait of Gibraltar
.— The aim of this study was to explore the possible effects of atmospheric oscillations:
North Atlantic Oscillation (NAO) and Arctic Oscillation (AO), on the physical condition of bluefin tuna (
Thunnus
thynnus
). We estimated a fitness ratio from 3,501 pairs of length–weight data based on bluefin tuna caught in
bait–boat fisheries before the spawning season (January, February and March), for each length class and year.
In order to obtain a single fitness ratio (K–mean) per year we determined the average for all length classes.
We also evaluated
Le Cren’s condition index (K
LC
).
We observed significant positive correlations between the
atmospheric oscillations and both physical condition indexes. In the case of K–mean, the AO explained 75%
of the observed variability. Regarding K
LC
, the NAO explained approximately 73% of the observed variability,
while the AO explained 70% of the observed variability. The increase in physical conditions of bluefin tuna
in association with positive atmospheric oscillations could be mediated by the increase in the prevalence of
strong trade winds. We concluded that the increase in the prevalence of strong westerly winds, mediated by
a positive AO or NAO, favours the trip from the Atlantic to the Mediterranean by reducing energy costs due
to migration and by increasing the supply of nutrients at the surface by the mixing of deep water and surface
water in local areas such as the Strait of Gibraltar.Postprin
The Gondwana connections of northern Patagonia
A multidisciplinary study (U–Pb sensitive high-resolution ion microprobe geochronology, Hf and O isotopes in zircon, Sr and Nd isotopes in whole-rocks, as well as major and trace element geochemistry) has been carried out on granitoid samples from the area west of Valcheta, North Patagonian Massif, Argentina. These confirm the Cambrian age of the Tardugno Granodiorite (528 ± 4 Ma) and the Late Permian age of granites in the central part of the Yaminué complex (250 Ma). Together with petrological and structural information for the area, we consider a previously suggested idea that the Cambrian and Ordovician granites of northeastern Patagonia represent continuation of the Pampean and Famatinian orogenic belts of the Sierras Pampeanas, respectively. Our interpretation does not support the hypothesis that Patagonia was accreted in Late Palaeozoic times as a far-travelled terrane, originating in the Central Transantarctic Mountains, and the arguments for and against this idea are reviewed. A parautochthonous origin is preferred with no major ocean closure between the North Patagonian Massif and the Sierra de la Ventana fold belt.Centro de Investigaciones GeológicasConsejo Nacional de Investigaciones Científicas y Técnica
Development of an incipient Paleogene topography between the present-day Eastern Andean Plateau (Puna) and the Eastern Cordillera, southern Central Andes, NW Argentina
The structural and topographic evolution of orogenic plateaus is an important research topic because of its impact on atmospheric circulation patterns, the amount and distribution of rainfall, and resulting changes in surface processes. The Puna region in the north-western Argentina (between 13°S and 27°S) is part of the Andean Plateau, which is the world's second largest orogenic plateau. In order to investigate the deformational events responsible for the initial growth of this part of the Andean plateau, we carried out structural and stratigraphic investigations within the present-day transition zone between the northern Puna and the adjacent Eastern Cordillera to the east. This transition zone is characterized by ubiquitous exposures of continental middle Eocene redbeds of the Casa Grande Formation. Our structural mapping, together with a sedimentological analysis of these units and their relationships with the adjacent mountain ranges, has revealed growth structures and unconformities that are indicative of syntectonic deposition. These findings support the notion that tectonic shortening in this part of the Central Andes was already active during the middle Paleogene, and that early Cenozoic deformation in the region that now constitutes the Puna occurred in a spatially irregular manner. The patterns of Paleogene deformation and uplift along the eastern margin of the present-day plateau correspond to an approximately north-south oriented swath of reactivated basement heterogeneities (i.e. zones of mechanical weakness) stemming from regional Paleozoic mountain building that may have led to local concentration of deformation belts.Fil: Montero López, Carolina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta. Instituto de Bio y Geociencias del NOA. Universidad Nacional de Salta. Facultad de Ciencias Naturales. Museo de Ciencias Naturales. Instituto de Bio y Geociencias del NOA; ArgentinaFil: Hongn, Fernando Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta. Instituto de Bio y Geociencias del NOA. Universidad Nacional de Salta. Facultad de Ciencias Naturales. Museo de Ciencias Naturales. Instituto de Bio y Geociencias del NOA; ArgentinaFil: López Steinmetz, Romina Lucrecia. Universidad Nacional de Jujuy. Instituto de Ecorregiones Andinas. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta. Instituto de Ecorregiones Andinas; ArgentinaFil: Aramayo, Alejandro José. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta. Instituto de Bio y Geociencias del NOA. Universidad Nacional de Salta. Facultad de Ciencias Naturales. Museo de Ciencias Naturales. Instituto de Bio y Geociencias del NOA; ArgentinaFil: Pingel, Heiko. Universitat Potsdam; AlemaniaFil: Strecker, Manfred R.. Universitat Potsdam; AlemaniaFil: Cottle, John M.. University of California; Estados UnidosFil: Bianchi, Carlos Luis. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta. Instituto de Bio y Geociencias del NOA. Universidad Nacional de Salta. Facultad de Ciencias Naturales. Museo de Ciencias Naturales. Instituto de Bio y Geociencias del NOA; Argentin
Palaeoenvironmental significance of middle Oxfordian deep marine deposits from La Manga Formation, Neuquén Basin, Argentina
The Callovian-Oxfordian of the Neuquén Basin (Argentina) is characterized by an extensive marine carbonate system (La Manga Formation) with a predominance of shallow and middle ramp deposits, although locally in tectonically controlled settings, deeper deposits also formed. These middle Oxfordian deeper deposits consist of mudstone-wackestone carbonates alternating with black shales and show marked centimetre-scale rhythmicity, probably controlled by the Earth’s orbit parameters, mainly precession and eccentricity. The present study was designed to examine these deposits in terms of their sedimentology, geochemistry, and small-scale stratigraphy in Arroyo Los Blancos, southern Mendoza Province, where they are exceptionally well exposed and preserved. Results indicate that the sediments were deposited in an anoxic to dysoxic, relatively deep, sea-floor environment as revealed by the presence of: a) organic-rich shales, b) undisrupted lamination in most facies, c) pyrite framboids, and d) absence or scarcity of trace fossils and benthic fauna. Thin beds of graded wackestone-packstone and accumulations of thin shells of Bositra bivalves indicate sporadic reworking of the sea floor by weak currents. Organic petrology, Rock-Eval pyrolysis and thermal maturity indicators were used to characterize TOC and different types of organic matter. Low pyrolysis S yields along with low hydrogen indices suggest poor kerogen convertibility. Vitrinite reflectance (%Ro) ranged from 2.39 to 2.97 with an average of 2.70. The thermal alteration index (TAI) was 4+(5), indicating overmaturity. A tectono-sedimentary model is proposed for these deposits. According to this model, the relatively deep, organic-matter rich facies of La Manga Formation would have been deposited in the deepest zones of topographic lows controlled by tilting and differential subsidence of tectonic blocks bounded by normal faults.These faults were probably inherited from previous extensional tectonics of Late Triassic - Early Jurassic age.Facultad de Ciencias Naturales y Muse
Ionic conductivity of nanocrystalline yttria-stabilized zirconia: grain boundary and size effects
We report on the effect of grain size on the ionic conductivity of yttria-stabilized zirconia samples synthesized by ball milling. Complex impedance measurements, as a function of temperature and frequency are performed on 10 mol % yttria-stabilized zirconia nanocrystalline samples with grain sizes ranging from 900 to 17 nm. Bulk ionic conductivity decreases dramatically for grain sizes below 100 nm, although its activation energy is essentially independent of grain size. The results are interpreted in terms of a space-charge layer resulting from segregation of mobile oxygen vacancies to the grain-boundary core. The thickness of this space-charge layer formed at the grain boundaries is on the order of 1 nm for large micron-sized grains but extends up to 7 nm when decreasing the grain size down to 17 nm. This gives rise to oxygen vacancies depletion over a large volume fraction of the grain and consequently to a significant decrease in oxide-ion conductivity
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