Comparative proteome profiling of host–pathogen interactions: insights into the adaptation mechanisms of Francisella tularensis in the host cell environment

The intracellular pathogens have the unique capacity to sense the host cell environment and to respond to it by alteration in gene expression and protein synthesis. Proteomic analysis of bacteria exposed directly to the host cell milieu might thus greatly contribute to the elucidation of processes leading to bacterial adaptation and proliferation inside the host cell. Here we have performed a global proteome analysis of a virulent Francisella tularensis subsp. holarctica strain during its intracellular cycle within the macrophage-like murine cell line J774.2 using the metabolic pulse-labeling of bacterial proteins with ³⁵S-methionine and ³⁵S-cysteine in various periods of infection. The two-dimensional gel analysis revealed macrophage-induced bacterial proteome changes in which 64 identified proteins were differentially expressed in comparison to controls grown in tissue culture medium. Nevertheless, activation of macrophages with interferon gamma before in vitro infection decreased the number of detected alterations in protein levels. Thus, these proteomic data indicate the F. tularensis ability to adapt to the intracellular hostile environment that is, however, diminished by prior interferon gamma treatment of host cells.     

Alternative Mating Tactics as Potential Prezygotic Barriers to Gene Flow Between Two Sister Species of Frugivorous Fruit Flies

Rhagoletis completa Cresson and Rhagoletis zoqui Bush, are two sister species in the suavis group that were thought to occupy non-overlapping geographical ranges. Recent discovery of a contact zone in North Eastern México where natural interspecific hybrids with intermediate morphotypes can be found has led to laboratory studies in small enclosures that failed to identify the existence of reproductive barriers capable of maintaining the genetic integrity of both species. Because the experimental approach used in such studies could have interfered with natural behavior of flies, a series of additional mating compatibility tests under much less restrictive conditions were performed. Our observations, confirmed the fact that males and females of both species engage in interspecific matings. However, R. completa females were more reluctant to engage in heterospecific matings than R. zoqui females, revealing asymmetries in sexual isolation. Also, careful scrutiny of male guarding behavior and species specific partitioning of mating location unveiled subtle differences that could result in reproductive isolation if reinforced during secondary contact.     

Wetting of Planar Surfaces by a Gay-Berne Liquid Crystal

Molecular simulation of the wetting of an unstructured attractive wall by Gay-Berne liquid crystals are reported. Simulations are performed in the grand canonical ensemble on a wide pore at constant temperatures of T *=0.53 and 0.56, corresponding to temperatures below and above the nematic-isotropic-vapor triple point. Close to the coexistence chemical potential, a thick liquid film wets the solid surface. The film is composed of stratified layers of molecules parallel to the solid surface, which follow to a nematic domain at the lower temperature and an isotropic one at the higher temperature. In both cases, the film is in equilibrium with the corresponding vapor phase. Close to the liquid-vapor interface there is a manifest tendency for the molecules to orient themselves parallel to the interface. The adsorption on the wall varies continuously with the thermodynamic parameters considered and no evidence of a first order prewetting transition is observed.     

Efficient protocol for backbone and side-chain assignments of large, intrinsically disordered proteins: transient secondary structure analysis of 49.2 kDa microtubule associated protein 2c

Microtubule-associated proteins (MAPs) are abundantly present in axons and dendrites, and have been shown to play crucial role during the neuronal morphogenesis. The period of main dendritic outgrowth and synaptogenesis coincides with high expression levels of one of MAPs, the MAP2c, in rats. The MAP2c is a 49.2 kDa intrinsically disordered protein. To achieve an atomic resolution characterization of such a large protein, we have developed a protocol based on the acquisition of two five-dimensional ¹³C-directly detected NMR experiments. Our previously published 5D CACONCACO experiment (Nová?ek et al. in J Biomol NMR 50(1):1–11, 2011) provides the sequential assignment of the backbone resonances, which is not interrupted by the presence of the proline residues in the amino acid sequence. A novel 5D HC(CC-TOCSY)CACON experiment facilitates the assignment of the aliphatic side chain resonances. To streamline the data analysis, we have developed a semi-automated procedure for signal assignments. The obtained data provides the first atomic resolution insight into the conformational state of MAP2c and constitutes a model for further functional studies of MAPs.     

Synthesis and characterization of a pH-sensitive conjugate of isoniazid with Fe3O4@SiO2 magnetic nanoparticles

The Letter describes the preparation and characterization of a conjugate of isoniazid (INH) with magnetic nanoparticles Fe₃O₄@SiO₂ 115 ± 60 nm in size. The INH molecules were attached to the surface of nanoparticles by a covalent pH-sensitive amidine bond. The conjugate was characterized by X-ray diffraction, SEM, dynamic light scattering, IR spectroscopy and microanalysis. The conjugate released isoniazid under in vitro conditions (pH = 4; 37 °C; t_1/2 ≈ 115 s). In addition, the cytotoxicity of the Fe₃O₄@SiO₂–INH conjugate was evaluated in SK-BR-3 cells using the xCELLigence system.     

Local Auxin Sources Orient the Apical-Basal Axis in Arabidopsis Embryos

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