Properties of Confined Square-well Fluids using the Gibbs Ensemble Simulation Technique

In this work we have used the extension of the Gibbs ensemble simulation technique to inhomogeneous fluids [Panagiotopoulos, A.Z. (1987) "Adsorption and capillary condensation of fluid in cylindrical pores by Monte Carlo simulation in the Gibbs ensemble", Mol. Phys. , 62 (3), 701-719], which has been applied to adsorption phenomena of confined fluids. Fluid molecules are described by spherical particles interacting via a square-well potential. The fluid is confined in two types of walls: symmetrical (two hard walls) and non-symmetrical (one square-well wall and one hard wall). In order to analyze the behavior of the confined fluid by varying the potential parameters, we evaluated the bulk and confined densities, the internal energies and the density profiles for different supercritical temperatures. A variety of adsorption profiles can be obtained by using this model. The simulation data reported here complements the available simulation data for this system and can be useful in the development of inhomogeneous fluid theories. Since the square-well parameters can be related to real molecules this system can also be used to understand real adsorption systems.     

11 Findings and hurdles on the path leading from formamide to the spontaneous generation of RNA

Our laboratories analyze the synthetic reactions leading from formamide, NH₂COH to prebiotically relevant compounds in the presence of catalysts. We have described the formation of all the biological nucleic bases of carboxylic acids of two aminoacids, and of condensing agents in the presence of catalysts of terrestrial origin (Saladino et al., 2012) and of one meteorite. Heat-dependent synthetic reactions from NH₂COH lead to the synthesis of acyclonucleosides, not (yet?) to that of nucleosides [hurdle # 1]. Nucleosides are phosphorylated in the presence of NH₂COH and a phosphate source yielding cyclic nucleotides as well. (Costanzo et al., 2007). 3′,5′-cyclic GMP nonenzymatically polymerizes up to at least 25mers, as shown by PAGE, MALDI ToF, ³¹P-NMR, specific RNAse and inhibitors analyses (Costanzo et al., 2012).The reaction is stimulated by 1,8-diazabicycloundec-7-ene and dimethylformamide. 3′,5′-cUMP does not polymerize spontaneously [hurdle # 2], 3′,5′-cAMP polymerizes very poorly [hurdle # 3]. We will discuss data on the polymerization of 3′,5′-cCMP and on a ribozyme activity exerted by oligomers neosynthesized from cyclic nucleotides. This approach finds its larger perspective in the evolutionary scenario depicted by Trifonov (2009).     

Molecular characterization of PVAS3: An asparagine synthetase gene from common bean prevailing in developing organs

In common bean, asparagine synthetase (AS; EC 6.3.5.4) is encoded by three members of a multigene family called PVAS1, PVAS2 and PVAS3. Two of these genes, PVAS1 and PVAS2, have been extensively studied, but little is known about PVAS3, remaining unclear whether PVAS3 function is redundant to the other AS or if it plays a specific role in Phaseolus vulgaris metabolism. In this work, we used a molecular approach to characterize PVAS3 expression and to gain some knowledge about its physiological function. We showed that, in contrast to PVAS1 and PVAS2, PVAS3 was expressed in all organs analyzed. Interestingly, PVAS3 was the AS gene most highly expressed in nodules, leaves and pods at the earliest stages of development, and its expression decreased as these organs developed. Expression of PVAS3 parallels the accumulation of AS protein and the asparagine content during the earliest stages of nodule, leaf and pod development, suggesting an important role for PVAS3 in the synthesis of asparagine in that period. Furthermore, PVAS3 was not repressed by light, as most class-II AS genes. Surprisingly, fertilization of nodulated plants with nitrate or ammonium, conditions that induce PVAS1 and PVAS2 and the shift from ureides to amide synthesis, repressed the expression of PVAS3 in nodules and roots. The possible implications of this regulation are discussed.     

Pollen analysis of honeys from the Mamora forest region (NW Morocco)

The present work refers to the pollen analysis of 35 Moroccan honey samples from the Mamora forest region. The samples were directly provided by the beekeepers, all professionals. The quantitative analysis showed that nectar is the main honey source in the samples studied, and that most honeys have a medium-low presence of botanical elements (BEN). The qualitative analysis of the samples showed the presence of 54 taxa belonging to 29 families, and 31 of the samples were unifloral: 24 of eucalyptus, 3 of orange, 2 of Loeflingia, 1 of mint and 1 of Ridolfia segetum. The eucalyptus honeys of the studied region are characterized by their high content in pollen grains (NGP; x¯=180000) and their low honeydew indicator elements content (HDE; x¯=4000); Plantago f. (present in 70% of the samples), Quercus f. and Brassicaceae (50%) and Ceratonia siliqua (30%) could be mentioned among the characteristic accompanying species of this honey type.     

Cocaine Inhibits Dopamine D2 Receptor Signaling via Sigma-1-D2 Receptor Heteromers

Under normal conditions the brain maintains a delicate balance between inputs of reward seeking controlled by neurons containing the D₁-like family of dopamine receptors and inputs of aversion coming from neurons containing the D₂-like family of dopamine receptors. Cocaine is able to subvert these balanced inputs by altering the cell signaling of these two pathways such that D₁ reward seeking pathway dominates. Here, we provide an explanation at the cellular and biochemical level how cocaine may achieve this. Exploring the effect of cocaine on dopamine D₂ receptors function, we present evidence of σ₁ receptor molecular and functional interaction with dopamine D₂ receptors. Using biophysical, biochemical, and cell biology approaches, we discovered that D₂ receptors (the long isoform of the D₂ receptor) can complex with σ₁ receptors, a result that is specific to D₂ receptors, as D₃ and D₄ receptors did not form heteromers. We demonstrate that the σ₁-D₂ receptor heteromers consist of higher order oligomers, are found in mouse striatum and that cocaine, by binding to σ₁ -D₂ receptor heteromers, inhibits downstream signaling in both cultured cells and in mouse striatum. In contrast, in striatum from σ₁ knockout animals these complexes are not found and this inhibition is not seen. Taken together, these data illuminate the mechanism by which the initial exposure to cocaine can inhibit signaling via D₂ receptor containing neurons, destabilizing the delicate signaling balance influencing drug seeking that emanates from the D₁ and D₂ receptor containing neurons in the brain.     

Enterobacteriaceae Isolated from the River Danube: Antibiotic Resistances,with a Focus on the Presence of ESBL and Carbapenemases

In a clinical setting it seems to be normal these days that a relevant proportion or even the majority of different bacterial species has already one or more acquired antibiotic resistances. Unfortunately, the overuse of antibiotics for livestock breeding and medicine has also altered the wild-type resistance profiles of many bacterial species in different environmental settings. As a matter of fact, getting in contact with resistant bacteria is no longer restricted to hospitals. Beside food and food production, the aquatic environment might also play an important role as reservoir and carrier. The aim of this study was the assessment of the resistance patterns of Escherichia coli and Klebsiella spp. out of surface water without prior enrichment and under non-selective culture conditions (for antibiotic resistance). In addition, the presence of clinically important extended spectrum beta lactamase (ESBL) and carbapenmase harboring Enterobacteriaceae should be investigated. During Joint Danube Survey 3 (2013), water samples were taken over the total course of the River Danube. Resistance testing was performed for 21 different antibiotics. Samples were additionally screened for ESBL or carbapenmase harboring Enterobacteriaceae. 39% of all isolated Escherichia coli and 15% of all Klebsiella spp. from the river Danube had at least one acquired resistance. Resistance was found against all tested antibiotics except tigecycline. Taking a look on the whole stretch of the River Danube the proportion of multiresistances did not differ significantly. In total, 35 ESBL harboring Enterobacteriaceae, 17 Escherichia coli, 13 Klebsiella pneumoniae and five Enterobacter spp. were isolated. One Klebsiella pneumoniae harboring NMD-1 carbapenmases and two Enterobacteriaceae with KPC-2 could be identified. Human generated antibiotic resistance is very common in E. coli and Klebsiella spp. in the River Danube. Even isolates with resistance patterns normally associated with intensive care units are present.     

Analysing freshwater fish biodiversity records and respective conservation areas in Spain

The number of threatened freshwater fish species in Spain is among the highest recorded in Europe and includes a high percentage of endemic taxa. Investigated were the distribution of Spanish freshwater fish to identify priority areas for conservation and assess the extent to which freshwater fish are included in the existing network of protected areas. Considered were those threatened species recorded in the Spanish National inventories. From these data, several biodiversity indices were calculated and analysed. The results reveal important discrepancies between the national and international assessments of conservation status, whereby the current Spanish national catalogue needs updating to reconcile these inconsistencies. Several important areas for the conservation of freshwater fish lie outside protected areas. The results encourage the establishment of protected areas specifically for freshwater environments. An extensive database of Spanish freshwater fish species is needed to redefine priority areas and to maintain freshwater biodiversity.     

Length–weight relationships of freshwater fishes of the Alto Madre de Dios River (Manu Biosphere Reserve,Peru)

The present work provides the estimates of morphometric relationships for 22 native freshwater fish species (11 Characidae, five Loricariidae, two Heptapteridae, one Astroblepidae, one Crenuchidae, one Curimatidae and one Erythrinidae) collected in the Alto Madre de Dios River (Cuzco and Madre de Dios, Peru) in June 2012 using a mobile backpack electrofishing unit. These are the first length–weight relationships reported for 24 species, mostly endemic to the Amazonian basin. Knowledge regarding these biometric relationships can be relevant in the management and conservation of the local fishes and fisheries.     

The histone-like protein HupB influences biofilm formation and virulence in Xanthomonas citri ssp. citri through the regulation of flagellar biosynthesis

Citrus canker is an important disease of citrus, whose causal agent is the bacterium Xanthomonas citri ssp. citri (Xcc). In previous studies, we found a group of Xcc mutants, generated by the insertion of the Tn5 transposon, which showed impaired ability to attach to an abiotic substrate. One of these mutants carries the Tn5 insertion in hupB, a gene encoding a bacterial histone-like protein, homologue to the β-subunit of the Heat-Unstable (HU) nucleoid protein of Escherichia coli. These types of protein are necessary to maintain the bacterial nucleoid organization and the global regulation of gene expression. Here, we characterized the influence of the mutation in hupB regarding Xcc biofilm formation and virulence. The mutant strain hupB was incapable of swimming in soft agar, whereas its complemented strain partially recovered this phenotype. Electron microscope imaging revealed that impaired motility of hupB was a consequence of the absence of the flagellum. Comparison of the expression of flagellar genes between the wild-type strain and hupB showed that the mutant exhibited decreased expression of fliC (encoding flagellin). The hupB mutant also displayed reduced virulence compared with the wild-type strain when they were used to infect Citrus lemon plants using different infection methods. Our results therefore show that the histone-like protein HupB plays an essential role in the pathogenesis of Xcc through the regulation of biofilm formation and biosynthesis of the flagellum.