260 research outputs found
Plant cells synthesize glucose-containing lipid-linked oligosaccharides similar to those found in animals and yeast
Electron-Electron Interaction in Disordered Mesoscopic Systems: Weak Localization and Mesoscopic Fluctuations of Polarizability and Capacitance
The weak localization correction and the mesoscopic fluctuations of the
polarizability and the capacitance of a small disordered sample are studied
systematically in 2D and 3D geometries. While the grand canonical ensemble
calculation gives the positive magnetopolarizability, in the canonical ensemble
(appropriate for isolated samples) the sign of the effect is reversed. The
magnitude of mesoscopic fluctuations for a single sample exceeds considerably
the value of the weak localization correction.Comment: 13 pages Latex, 3 .eps figures included. To appear in Phys. Rev. B.
Minor corrections, in particular in formulae; new references adde
Free energy of colloidal particles at the surface of sessile drops
The influence of finite system size on the free energy of a spherical
particle floating at the surface of a sessile droplet is studied both
analytically and numerically. In the special case that the contact angle at the
substrate equals a capillary analogue of the method of images is
applied in order to calculate small deformations of the droplet shape if an
external force is applied to the particle. The type of boundary conditions for
the droplet shape at the substrate determines the sign of the capillary
monopole associated with the image particle. Therefore, the free energy of the
particle, which is proportional to the interaction energy of the original
particle with its image, can be of either sign, too. The analytic solutions,
given by the Green's function of the capillary equation, are constructed such
that the condition of the forces acting on the droplet being balanced and of
the volume constraint are fulfilled. Besides the known phenomena of attraction
of a particle to a free contact line and repulsion from a pinned one, we
observe a local free energy minimum for the particle being located at the drop
apex or at an intermediate angle, respectively. This peculiarity can be traced
back to a non-monotonic behavior of the Green's function, which reflects the
interplay between the deformations of the droplet shape and the volume
constraint.Comment: 24 pages, 19 figure
Evidence of Henipavirus Infection in West African Fruit Bats
Henipaviruses are emerging RNA viruses of fruit bat origin that can cause fatal encephalitis in man. Ghanaian fruit bats (megachiroptera) were tested for antibodies to henipaviruses. Using a Luminex multiplexed microsphere assay, antibodies were detected in sera of Eidolon helvum to both Nipah (39%, 95% confidence interval: 27–51%) and Hendra (22%, 95% CI: 11–33%) viruses. Virus neutralization tests further confirmed seropositivity for 30% (7/23) of Luminex positive serum samples. Our results indicate that henipavirus is present within West Africa
Flanker performance in female college students with ADHD: a diffusion model analysis
Attention-deficit hyperactivity disorder (ADHD) is characterized by poor adaptation to environmental demands, which leads to various everyday life problems. The present study had four aims: (1) to compare performance in a flanker task in female college students with and without ADHD (N = 39) in a classical analyses of reaction time and error rate and studying the underlying processes using a diffusion model, (2) to compare the amount of focused attention, (3) to explore the adaptation of focused attention, and (4) to relate adaptation to psychological functioning. The study followed a 2-between (group: ADHD vs. control) × 2-within (flanker conflict: incongruent vs. congruent) × 2-within (conflict frequency: 20 vs. 80 %) design. Compared to a control group, the ADHD group displayed prolonged response times accompanied by fewer errors in a flanker task. Results from the diffusion model analyses revealed that the members of the ADHD group showed deficits in non-decisional processes (i.e., higher non-decision time) and leaned more toward accuracy than participants without ADHD (i.e., setting higher boundaries). The ADHD group showed a more focused attention and less adaptation to the task conditions which is related to psychological functioning. Deficient non-decisional processes and poor adaptation are in line with theories of ADHD and presumably typical for the ADHD population, although this has not been shown using a diffusion model. However, we assume that the cautious strategy of trading speed of for accuracy is specific to the subgroup of female college students with ADHD and might be interpreted as a compensation mechanism
Production in Pichia pastoris of complementary protein-based polymers with heterodimer-forming WW and PPxY domains
Identification of O-mannosylated Virulence Factors in Ustilago maydis
The O-mannosyltransferase Pmt4 has emerged as crucial for fungal virulence in the animal pathogens Candida albicans or Cryptococcus neoformans as well as in the phytopathogenic fungus Ustilago maydis. Pmt4 O-mannosylates specific target proteins at the Endoplasmic Reticulum. Therefore a deficient O-mannosylation of these target proteins must be responsible for the loss of pathogenicity in pmt4 mutants. Taking advantage of the characteristics described for Pmt4 substrates in Saccharomyces cerevisiae, we performed a proteome-wide bioinformatic approach to identify putative Pmt4 targets in the corn smut fungus U. maydis and validated Pmt4-mediated glycosylation of candidate proteins by electrophoretic mobility shift assays. We found that the signalling mucin Msb2, which regulates appressorium differentiation upstream of the pathogenicity-related MAP kinase cascade, is O-mannosylated by Pmt4. The epistatic relationship of pmt4 and msb2 showed that both are likely to act in the same pathway. Furthermore, constitutive activation of the MAP kinase cascade restored appressorium development in pmt4 mutants, suggesting that during the initial phase of infection the failure to O-mannosylate Msb2 is responsible for the virulence defect of pmt4 mutants. On the other hand we demonstrate that during later stages of pathogenic development Pmt4 affects virulence independently of Msb2, probably by modifying secreted effector proteins. Pit1, a protein required for fungal spreading inside the infected leaf, was also identified as a Pmt4 target. Thus, O-mannosylation of different target proteins affects various stages of pathogenic development in U. maydis
Membrane-mediated interactions
Interactions mediated by the cell membrane between inclusions, such as
membrane proteins or antimicrobial peptides, play important roles in their
biological activity. They also constitute a fascinating challenge for
physicists, since they test the boundaries of our understanding of
self-assembled lipid membranes, which are remarkable examples of
two-dimensional complex fluids. Inclusions can couple to various degrees of
freedom of the membrane, resulting in different types of interactions. In this
chapter, we review the membrane-mediated interactions that arise from direct
constraints imposed by inclusions on the shape of the membrane. These effects
are generic and do not depend on specific chemical interactions. Hence, they
can be studied using coarse-grained soft matter descriptions. We deal with
long-range membrane-mediated interactions due to the constraints imposed by
inclusions on membrane curvature and on its fluctuations. We also discuss the
shorter-range interactions that arise from the constraints on membrane
thickness imposed by inclusions presenting a hydrophobic mismatch with the
membrane.Comment: 38 pages, 10 figures, pre-submission version. In: Bassereau P., Sens
P. (eds) Physics of Biological Membranes. Springer, Cha
Quantificação de sorgoleone em extratos e raízes de sorgo sob diferentes períodos de armazenamento
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