Structural studies on the H3 influenza A virus haemagglutinin : Receptor binding and membrane fusion.

In this project, the receptor binding and membrane fusion activities of the membrane-anchored glycoprotein haemagglutinin (HA), H3 subtype, of the influenza A virus were studied. Influenza viruses from different hosts can distinguish between a.2-3 and a2-6 linkages that sialic acid (Sia) forms with the penultimate saccharide residue of the receptor. Human viruses prefer a2-6 linkages and avian viruses ct2-3 linkages. The side chain of residue 226 of the HA receptor binding site (RBS) is involved in the specific recognition of those linkages. The HA of the 1968 Hong Kong (HK) pandemic virus (H3 subtype), contained in the recombinant X-31 virus, has a 226-leucine and prefers binding to a2-6 linkages. The L226Q HA of the variant virus X-31/horse serum (X-31/HS), corresponding to a single-site mutant of the X-31 HA having 226-glutamine, prefers a2-3 linkages. To define the molecular interactions of the L226Q HA with the virus receptor, the crystal structures of L226Q HA in complex with the receptor analogues lactoseries tetrasaccharide a (LSTa), a2-3-terminated, and lactoseries tetrasaccharide c (LSTc), a2-6-terminated, were determined. The structures show the saccharide residues Sia and galactose (Gal) of LSTa and only the Sia of LSTc bound on the L226Q HA RBS, which correlates with the higher affinity of L226Q HA for the ct2-3 linkage. However, the L226Q HA binds both the trans and cis configurations of the Sia-Gal glycosidic bond of LSTa, which has never been observed before. These results are discussed in comparison with data from binding assays and the available crystal structures of the X-31 HA, the H3 avian HA of the influenza virus A/duck/Ukraine/63, a potential precursor of the 1968 HK pandemic virus, and other HAs, of different subtypes and hosts of origin, in complex with LSTa and LSTc. Upon endocytosis, at the low endosomal pH, the HA undergoes an irreversible conformational change associated with the fusion of the viral and endosomal membranes, a process by which the virus enters the target cell. To gain further insights into the membrane fusion mechanism catalysed by the influenza HA, the purification and crystallisation trials of three different X-31 HA forms representative of the neutral pH and fusion pH-induced conformations, containing the membrane-interacting segments fusion peptide and transmembrane anchor, were carried out with the future aim of their crystal structure determination. The procedures for the purification and crystallisation trials of the X-31 HA proteins in different conformations are discussed in the context of the general purification and crystallisation of membrane proteins. No promising hint has yet been obtained in the crystallisation trials

Random amplification of polymorphic DNA reveals clonal relationships among enteropathogenic Escherichia coli isolated from non-human primates and humans

Enteropathogenic Escherichia coli ( EPEC) strains are important agents of infantile diarrhea all over the world, gaining even greater importance in developing countries. EPEC have also been isolated from various animal species, but most isolates belong to serotypes that differ from those recovered from humans. However, it has been demonstrated that several isolates from non- human primates belong to the serogroups and/ or serotypes related to those implicated in human disease. The objective of this study was to evaluate the genetic differences between thirteen strains isolated from non- human primates and the same number of strains isolated from human infections. Human isolates belonged to the same serogroup/ serotype as the monkey strains and the evaluation was done by analysis of random amplified polymorphic DNA. Dendrogram analysis showed that there was no clustering between human and monkey strains. Human and non- human isolates of the EPEC serotypes O127:H40 and O128:H2 shared 90 and 87% of their bands, respectively, indicating strong genomic similarity between the strains, leading to the speculation that they may have arisen from the same pathogenic clone. To our knowledge, this study is the first one comparing genomic similarity between human and non- human primate strains and the results provide further evidence that monkey EPEC strains correlate with human EPEC, as suggested in a previous investigation

Improvement of antioxidant and antimicrobial activity of soy isoflavones extracts bioconverted with ?-glucosidase / Melhoria da atividade antioxidante e antimicrobiana de extratos de isoflavonas de soja bioconvertidos com ?-glucosidase

Soybean is largely produced in Brazil being one of the main Brazilian Agricultural crop, achieving 223 million tons produced in 2017. The consumption of soy products increased in recent years due to the association with healthy benefits in oxidative stress and chronic diseases. The researches have been pointing that the isoflavones presenting in soy are the responsible compounds for alleviating these symptoms. The main purpose of this work were use of ?-glucosidase enzyme to convert glucoside isoflavones to aglycone form in isoflavone soy extract, and then evaluate the antioxidant and antimicrobial activity against some pathogens. The isoflavones were obtained according to Aguiar (2004) with modifications. The soy flour (65 mesh) was defatted with hexane (1:10 w/v) and the extraction of isoflavones was performed using 80% aqueous methanol solution under 100 rpm stirring for 1 hour at room temperature. The mixture was then filtrated, and the supernatant recovered. The extract was used for the bioconversion of glycosyl isoflavones from soy into aglycones isoflavones using ?-glucosidase enzyme. According to recent researches the aglycon form has greater absorption by organism and higher antioxidant activity than the glucoside form. According the results all antioxidant methods presented higher activity to bioconverted extract. The bioconverted extract (1060.73 mg Trolox equivalent) presented near 9 times superior antioxidant activity measured by DPPH method than raw extract (123.21 mg Trolox equivalent).  The Total phenolic content presented similar behavior being higher to bioconverted extract than in raw extract. The antimicrobial activity of the isoflavones extracts raw and bioconverted against S. aureus, C. albicans and E. coli were higher than 1600 ?g/mL in the range studied 0.78 to 1600 ?g/mL

Approximate solution of the Duffin-Kemmer-Petiau equation for a vector Yukawa potential with arbitrary total angular momenta

The usual approximation scheme is used to study the solution of the Duffin-Kemmer-Petiau (DKP) equation for a vector Yukawa potential in the framework of the parametric Nikiforov-Uvarov (NU) method. The approximate energy eigenvalue equation and the corresponding wave function spinor components are calculated for arbitrary total angular momentum in closed form. Further, the approximate energy equation and wave function spinor components are also given for case. A set of parameter values is used to obtain the numerical values for the energy states with various values of quantum levelsComment: 17 pages; Communications in Theoretical Physics (2012). arXiv admin note: substantial text overlap with arXiv:1205.0938, and with arXiv:quant-ph/0410159 by other author

Aspergillus fumigatus MADS-Box Transcription Factor rlmA Is Required for Regulation of the Cell Wall Integrity and Virulence

Microbial Biotechnolog

Twist Deformations of the Supersymmetric Quantum Mechanics

The N-extended Supersymmetric Quantum Mechanics is deformed via an abelian twist which preserves the super-Hopf algebra structure of its Universal Enveloping Superalgebra. Two constructions are possible. For even N one can identify the 1D N-extended superalgebra with the fermionic Heisenberg algebra. Alternatively, supersymmetry generators can be realized as operators belonging to the Universal Enveloping Superalgebra of one bosonic and several fermionic oscillators. The deformed system is described in terms of twisted operators satisfying twist-deformed (anti)commutators. The main differences between an abelian twist defined in terms of fermionic operators and an abelian twist defined in terms of bosonic operators are discussed.Comment: 18 pages; two references adde

Habitat specialization and phylogenetic structure of tree species in a coastal Brazilian white-sand forest

Aims The coastal Brazilian rainforest on white-sand (restinga) ranks among the most fragmented forest types in the tropics, owing to both the patchy distribution of sandy soils and widespread coastal development activities. Here we study the environmental and evolutionary determinants of a forest tree assemblage at a single restinga forest in Southeastern Brazil. We also explore the ability of competing hypotheses to explain the maintenance of species diversity in this forest type, which includes contrasting extremes of edaphic conditions associated with flooding stress. Methods The study was conducted in a white-sand forest permanent plot of 10.24 ha on the coastal plain of Southeastern Brazil. This plot was divided into 256 quadrats of 20×20 m, which were classified into two main edaphic habitats (flooded and drained). Trees with a diameter ≥1cm at breast height were identified. We assembled DNA sequence data for each of the 116 morphospecies recognized using two chloroplast markers (rbcL and matK). A phylogenetic tree was obtained using the maximum likelihood method, and a phylogenetic distance matrix was produced from an ultrametric tree. We analyzed similarity in floristic composition and structure between habitats and related them to cross-plot distances using permutation procedures. Null model torus shift simulations were performed to obtain a statistical significance level for habitat association for each species. The phylogenetic structure for the two habitats and for each 20×20 m quadrat was calculated using the mean phylogenetic distance weighted by species abundance and checked for significance using the standardized effect size generated by 5000 randomizations of phylogenetic tip labels. Important Findings Our results indicate that partitioning among edaphic habitats is important for explaining species distributions and coexistence in restinga forests. Species distributions within the plot were found to be non-random: there was greater floristic similarity within than between habitats, and >40% of the more abundant species were positively or negatively associated with at least one habitat. Patterns of habitat association were not independent of phylogenetic relatedness: the community was overdispersed with respect to space and habitat type. Closely related species tended to occur in different habitats, while neighboring trees tended to belong to more distantly related species. We conclude that habitat specialization is important for the coexistence of species in restinga forests and that habitat heterogeneity is therefore an essential factor in explaining the maintenance of diversity of this unique but fragile and threatened type of forest. © 2014 The Author

Sub-femto-g free fall for space-based gravitational wave observatories: LISA pathfinder results

We report the first results of the LISA Pathfinder in-flight experiment. The results demonstrate that two free-falling reference test masses, such as those needed for a space-based gravitational wave observatory like LISA, can be put in free fall with a relative acceleration noise with a square root of the power spectral density of 5.2 ± 0.1 fm s−2/√Hz or (0.54 ± 0.01) × 10−15 g/√Hz, with g the standard gravity, for frequencies between 0.7 and 20 mHz. This value is lower than the LISA Pathfinder requirement by more than a factor 5 and within a factor 1.25 of the requirement for the LISA mission, and is compatible with Brownian noise from viscous damping due to the residual gas surrounding the test masses. Above 60 mHz the acceleration noise is dominated by interferometer displacement readout noise at a level of (34.8 ± 0.3) fm/√Hz, about 2 orders of magnitude better than requirements. At f ≤ 0.5 mHz we observe a low-frequency tail that stays below 12 fm s−2/√Hz down to 0.1 mHz. This performance would allow for a space-based gravitational wave observatory with a sensitivity close to what was originally foreseen for LISA

Sirtuin E deacetylase is required for full virulence of Aspergillus fumigatus

Aspergillus fumigatus represents a public health problem due to the high mortality rate in immunosuppressed patients and the emergence of antifungal-resistant isolates. Protein acetylation is a crucial post-translational modification that controls gene expression and biological processes. The strategic manipulation of enzymes involved in protein acetylation has emerged as a promising therapeutic approach for addressing fungal infections. Sirtuins, NAD+-dependent lysine deacetylases, regulate protein acetylation and gene expression in eukaryotes. However, their role in the human pathogenic fungus A. fumigatus remains unclear. This study constructs six single knockout strains of A. fumigatus and a strain lacking all predicted sirtuins (SIRTKO). The mutant strains are viable under laboratory conditions, indicating that sirtuins are not essential genes. Phenotypic assays suggest sirtuins’ involvement in cell wall integrity, secondary metabolite production, thermotolerance, and virulence. Deletion of sirE attenuates virulence in murine and Galleria mellonella infection models. The absence of SirE alters the acetylation status of proteins, including histones and non-histones, and triggers significant changes in the expression of genes associated with secondary metabolism, cell wall biosynthesis, and virulence factors. These findings encourage testing sirtuin inhibitors as potential therapeutic strategies to combat A. fumigatus infections or in combination therapy with available antifungals

The Fluorescence Detector of the Pierre Auger Observatory

The Pierre Auger Observatory is a hybrid detector for ultra-high energy cosmic rays. It combines a surface array to measure secondary particles at ground level together with a fluorescence detector to measure the development of air showers in the atmosphere above the array. The fluorescence detector comprises 24 large telescopes specialized for measuring the nitrogen fluorescence caused by charged particles of cosmic ray air showers. In this paper we describe the components of the fluorescence detector including its optical system, the design of the camera, the electronics, and the systems for relative and absolute calibration. We also discuss the operation and the monitoring of the detector. Finally, we evaluate the detector performance and precision of shower reconstructions.Comment: 53 pages. Submitted to Nuclear Instruments and Methods in Physics Research Section