1,002 research outputs found
On the Explanation of the Paramagnetic Meissner Effect in Superconductor/Ferromagnet Heterostructures
An increase of the magnetic moment in superconductor/ferromagnet (S/F)
bilayers V(40nm)/F [FFe(1,3nm), Co(3nm), Ni(3nm)] was observed using SQUID
magnetometry upon cooling below the superconducting transition temperature Tc
in magnetic fields of 10 Oe to 50 Oe applied parallel to the sample surface. A
similar increase, often called the paramagnetic Meissner effect (PME), was
observed before in various superconductors and superconductor/ferromagnet
systems. To explain the PME effect in the presented S/F bilayers a model based
on a row of vortices located at the S/F interface is proposed. According to the
model the magnetic moment induced below Tc consists of the paramagnetic
contribution of the vortex cores and the diamagnetic contribution of the
vortex-free region of the S layer. Since the thickness of the S layer is found
to be 3-4 times less than the magnetic field penetration depth, this latter
diamagnetic contribution is negligible. The model correctly accounts for the
sign, the approximate magnitude and the field dependence of the paramagnetic
and the Meissner contributions of the induced magnetic moment upon passing the
superconducting transition of a ferromagnet/superconductor bilayer
A new squat lobster of the genus Munidopsis (Crustacea, Decapoda, Munidopsidae) from the Mediterranean Sea
8 páginas, 4 figuras[EN]A new species of Munidopsis Whiteaves, 1874 is reported from the south of Crete, at 2046-2104 m, in the eastern Mediterranean Sea. The species (M. ariadne) is morphologically closely related to M. maunga Schnabel and Bruce, 2006, from New Zealand. The species is also close to M. polymorpha Koelbel, 1892, from Lanzarote, Canary Islands, and M. talismani A. Milne Edwards and Bouvier, 1894, from the NW Africa. The new species is described and illustrated and a diagnosis along with full illustration is provided for the latter 2 species.[ES]Una nueva especie de crustáceo del género Munidopsis (Crustacea: Decapoda: Munidopsidae) del mar Mediterráneo. – Se describe una especie nueva de Munidopsis Whiteaves, 1874 capturada al sur de Creta, a 2046-2104 m, en el Mediterráneo oriental. La especie (M. ariadne) es próxima morfológicamente a M. maunga Schnabel and Bruce, 2006, de Nueva Zelanda. La especie está también relacionada con M. polymorpha Koelbel, 1892, de Lanzarote, Islas Canarias, y M. talismani A. Milne Edwards and Bouvier, 1894, del NO de África.Peer reviewe
Comparative Adsorption of Saturated and Unsaturated Fatty Acids at the Iron Oxide/Oil Interface.
A detailed comparison of the adsorption behavior of long straight chain saturated and unsaturated fatty acids at the iron oxide/oil interface has been considered using a combination of surface study techniques. Both depletion isotherms and polarized neutron reflectometry (PNR) show that the extent of adsorption decreases as the number of double bonds in the alkyl chains increases. Sum frequency generation spectroscopic measurements demonstrate that there is also an increase in chain disorder within the adsorbed layer as the unsaturation increases. However, for the unsaturated analogues, a decrease in peak intensity is seen for the double bond peak upon heating, which is thought to arise from isomerization in the surface-bound layer. The PNR study of oleic acid adsorption indicates chemisorbed monolayer adsorption, with a further diffuse reversible adsorbed layer formed at higher concentrations.Mary Wood is grateful for funding from the Oppenheimer Trust. The PNR data were collected using the V6 instrument at the Helmholtz-Zentrum Berlin (experiment number MAT-04-2131).This is the author accepted manuscript. The final version is available from the American Chemical Society via http://dx.doi.org/10.1021/acs.langmuir.5b0443
Utilization of a deoxynucleoside diphosphate substrate by HIV reverse transcriptase
Background: Deoxynucleoside triphosphates (dNTPs) are the normal substrates for DNA sysnthesis is catalyzed by polymerases such as HIV-1 reverse transcriptase (RT). However, substantial amounts of deoxynucleoside diphosphates (dNDPs) are also present in the cell. Use of dNDPs in HIV-1 DNA sysnthesis could have significant implications for the efficacy of nucleoside RT inhibitors such as AZT which are first line therapeutics fro treatment of HIV infection. Our earlier work on HIV-1 reverse transcriptase (RT) suggested that the interaction between the γ phosphate of the incoming dNTP and RT residue K65 in the active site is not essential for dNTP insertion, implying that this polymerase may be able to insert dNPs in addition to dNTPs. Methodology/Principal Findings: We examined the ability of recombinant wild type (wt) and mutant RTs with substitutions at residue K65 to utilize a dNDP substrate in primer extension reactions. We found that wild type HIV-1 RT indeed catalyzes incorporation of dNDP substrates whereas RT with mutations of residue K645 were unable to catalyze this reaction. Wild type HIV-1 RT also catalyzed the reverse reaction, inorganic phosphate-dependent phosphorolysis. Nucleotide-mediated phosphorolytic removal of chain-terminating 3′-terminal nucleoside inhibitors such as AZT forms the basis of HIV-1 resistance to such drugs, and this removal is enhanced by thymidine analog mutations (TAMs). We found that both wt and TAM-containing RTs were able to catalyze Pi-mediated phosphorolysis of 3′-terminal AZT at physiological levels of Pi with an efficacy similar to that for ATP-dependent AZT-excision. Conclusion: We have identified two new catalytic function of HIV-1 RT, the use of dNDPs as substrates for DNA synthesis, and the use of Pi as substrate for phosphorolytic removal of primer 3′-terminal nucleotides. The ability to insert dNDPs has been documented for only one other DNA polymerase The RB69 DNA polymerase and the reverse reaction employing inorganic phosphate has not been documented for any DNA polymerase. Importantly, our results show that Pi-mediated phosphorolysis can contribute to AZT resistance and indicates that factors that influence HIV resistance to AZT are more complex than previously appreciated. © 2008 Garforth et al
Ucma/GRP inhibits phosphate-induced vascular smooth muscle cell calcification via SMAD-dependent BMP signalling
Vascular calcification (VC) is the process of deposition of calcium phosphate crystals in the blood vessel wall, with a central role for vascular smooth muscle cells (VSMCs). VC is highly prevalent in chronic kidney disease (CKD) patients and thought, in part, to be induced by phosphate imbalance. The molecular mechanisms that regulate VC are not fully known. Here we propose a novel role for the mineralisation regulator Ucma/GRP (Upper zone of growth plate and Cartilage Matrix Associated protein/Gla Rich Protein) in phosphate-induced VSMC calcification. We show that Ucma/GRP is present in calcified atherosclerotic plaques and highly expressed in calcifying VSMCs in vitro. VSMCs from Ucma/GRP(-/-) mice showed increased mineralisation and expression of osteo/chondrogenic markers (BMP-2, Runx2, beta-catenin, p-SMAD1/5/8, ALP, OCN), and decreased expression of mineralisation inhibitor MGP, suggesting that Ucma/GRP is an inhibitor of mineralisation. Using BMP signalling inhibitor noggin and SMAD1/5/8 signalling inhibitor dorsomorphin we showed that Ucma/GRP is involved in inhibiting the BMP-2-SMAD1/5/8 osteo/chondrogenic signalling pathway in VSMCs treated with elevated phosphate concentrations. Additionally, we showed for the first time evidence of a direct interaction between Ucma/GRP and BMP-2. These results demonstrate an important role of Ucma/GRP in regulating osteo/chondrogenic differentiation and phosphate-induced mineralisation of VSMCs.NWO ZonMw [MKMD 40-42600-98-13007]; FCT [SFRH/BPD/70277/2010]info:eu-repo/semantics/publishedVersio
Crystallization and preliminary X-ray crystallographic analysis of DNA polymerase from Thermus aquaticus
Surface Aggregate Structure of Nonionic Surfactants on Silica Nanoparticles
The self-assembly of two nonionic surfactants, pentaethylene glycol
monododecyl ether (C12E5) and n-dodecyl-{\ss}-maltoside ({\ss}-C12G2), in the
presence of a purpose-synthesized silica sol of uniform particle size (diameter
16 nm) has been studied by adsorption measurements, dynamic light scattering
and small-angle neutron scattering (SANS) using a H2O/D2O mixture matching the
silica, in order to highlight the structure of the surfactant aggregates. For
C12E5 strong aggregative adsorption onto the silica beads, with a high plateau
value of the adsorption isotherm above the CMC was found. SANS measurements
were made at a series of loadings, from zero surfactant up to maximum surface
coverage. It is found that the spherical core-shell model nicely reproduces the
SANS data up to and including the local maximum at q = 0.42 nm-1 but not in the
Porod region of high q, indicating that the surface area of the adsorbed
surfactant is underestimated by the model of a uniform adsorbed layer. A
satisfactory representation of the entire scattering profiles is obtained with
the model of micelle-decorated silica beads, indicating that C12E5 is adsorbed
as spherical micellar aggregates. This behaviour is attributed to the high
surface curvature of the silica which prevents an effective packing of the
hydrophobic chains of the amphiphile in a bilayer configuration. For the
maltoside surfactant {\ss}-C12G2 very weak adsorption on the silica beads was
found. The SANS profile indicates that this surfactant forms oblate ellipsoidal
micelles in the silica dispersion, as in the absence of the silica beads
Tumor Suppression by RNA from C/EBPβ 3′UTR through the Inhibition of Protein Kinase Cε Activity
BACKGROUND: Since the end of last century, RNAs from the 3'untranslated region (3'UTR) of several eukaryotic mRNAs have been found to exert tumor suppression activity when introduced into malignant cells independent of their whole mRNAs. In this study, we sought to determine the molecular mechanism of the tumor suppression activity of a short RNA from 3'UTR of C/EBPβ mRΝΑ (C/EBPβ 3'UTR RNA) in human hepatocarcinoma cells SMMC-7721. METHODOLOGY/PRINCIPAL FINDINGS: By using Western blotting, immunocytochemistry, molecular beacon, confocal microscopy, protein kinase inhibitors and in vitro kinase assays, we found that, in the C/EBPβ 3'UTR-transfectant cells of SMMC-7721, the overexpressed C/EBPβ 3'UTR RNA induced reorganization of keratin 18 by binding to this keratin; that the C/EBPβ 3'UTR RNA also reduced phosphorylation and expression of keratin 18; and that the enzyme responsible for phosphorylating keratin 18 is protein kinase Cε. We then found that the C/EBPβ 3'UTR RNA directly inhibited the phosphorylating activity of protein kinase Cε; and that C/EBPβ 3'UTR RNA specifically bound with the protein kinase Cε-keratin 18 conjugate. CONCLUSION/SIGNIFICANCE: Together, these facts suggest that the tumor suppression in SMMC-7721 by C/EBPβ 3'UTR RNA is due to the inhibition of protein kinase Cε activity through direct physical interaction between C/EBPβ 3'UTR RNA and protein kinase Cε. These facts indicate that the 3'UTR of some eukaryotic mRNAs may function as regulators for genes other than their own
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