Dipeptide vinyl sultams: synthesis via the Wittig-Horner reaction and activity against papain, falcipain-2 and Plasmodium falciparum

The synthesis of phosphonate derivatives of N-phenyl- and N-benzyl-gamma- and delta-sultams, and their application in the Wittig-Horner reaction with N-Boc-L-phenylalanine aldehyde to afford E- and Z-isomers, are described. These compounds were further processed to provide five dipeptide vinyl sultams, which were found to be inactive against papain at concentrations up to 50 microM. In contrast, vinyl sultams demonstrated weak activity against recombinant falcipain-2 and Plasmodium falciparum W2.     

Optimization of the primary recovery of human interferon alpha2b from Escherichia coli inclusion bodies

The human interferon alpha2b (hu-IFNalpha2b) gene was cloned in Escherichia coli JM109(DE3) and the recombinant protein was expressed as cytoplasmic inclusion bodies (IB). The present work discusses the recovery of hu-IFNalpha2b IB from the E. coli cells. An optimized protocol is proposed based on the sequential evaluation of recovery steps and parameters: (i) cell disruption, (ii) IB recovery and separation from cell debris, (iii) IB washing, and (iv) IB solubilization. Parameters such as hu-IFNalpha2b purity and recovery yield were measured after each step. The optimized recovery protocol yielded 60% of hu-IFNalpha2b with a purity of up to 80%. The protein was renatured at high concentration after recovery and it was found to display biological activity.     

Synthesis and properties of polyaniline–cellulose acetate blends: The use of sugarcane bagasse waste and the effect of the substitution degree

Membranes of blends of polyaniline (PANi) and cellulose acetate (CA) produced from sugarcane bagasse with different degrees of substitution were produced and characterized using various techniques. Results showed that incorporation of PANi into the CA matrices leads to significant alterations of the blend morphologies, with phase separation, and that these differences are less significant for PANi/cellulose triacetate blends. The blends also showed a significant increase in electrical conductivity, with that of PANi/cellulose diacetate demonstrating an almost 200-fold increase.     

DIVERSIFICATION OF THE AFRICAN GENUS PROTEA (PROTEACEAE) IN THE CAPE BIODIVERSITY HOTSPOT AND BEYOND: EQUAL RATES IN DIFFERENT BIOMES

The Cape region of South Africa is a hotspot of flowering plant biodiversity. However, the reasons why levels of diversity and endemism are so high remain obscure. Here, we reconstructed phylogenetic relationships among species in the genus Protea, which has its center of species richness and endemism in the Cape, but also extends through tropical Africa as far as Eritrea and Angola. Contrary to previous views, the Cape is identified as the ancestral area for the radiation of the extant lineages: most species in subtropical and tropical Africa are derived from a single invasion of that region. Moreover, diversification rates have been similar within and outside the Cape region. Migration out of the Cape has opened up vast areas, but those lineages have not diversified as extensively at fine spatial scales as lineages in the Cape. Therefore, higher net rates of diversification do not explain the high diversity and endemism of Protea in the Cape. Instead, understanding why the Cape is so diverse requires an explanation for how Cape species are able to diverge and persist at such small spatial scales.     

Taxonomic boundaries,phylogenetic relationships and biogeography of the <Emphasis Type="Italic">Drosophila willistoni</Emphasis> subgroup (Diptera: Drosophilidae)

The Drosophila willistoni subgroup represents a complex with varying taxonomic levels. It encompasses D. willistoni and its five sibling species: D. equinoxialis, D. insularis, D. paulistorum, D. pavlovskiana and D. tropicalis. Of these, D. equinoxialis, D. tropicalis and D. willistoni present differentiation at subspecific level, whereas D. paulistorum represents a superspecies, formed by six semispecies. Despite this taxonomic and evolutionary complexity, many of these semi and subspecific taxa have not yet had their phylogenetic status tested in an explicitly molecular study. Aiming to contribute to the understanding of the evolution of this challenging group, we analyzed nucleotide sequences from two mitochondrial and four nuclear datasets, both individually and simultaneously, through different phylogenetic methods. High levels of incongruence were detected among partitions, especially concerning the mitochondrial sequences. As this incongruence was found to be statistically significant and robust to the use of different models and approaches, and basically restricted to mitochondrial loci, we suggest that it may stem mainly from hybridization-mediated asymmetrical introgression. Despite this, our nuclear data finally led to a phylogenetic hypothesis which further refines several aspects related to the willistoni subgroup phylogeny. In this respect, D. insularis, D. tropicalis, D. willistoni and D. equinoxialis successively branched off from the willistoni subgroup main stem, which recently subdivided to produce D. paulistorum and D. pavlovskiana. As regards the semispecies evolution, we found evidence of a recent diversification, which highly influenced the obtained results due to the associated small levels of genetic differentiation, further worsened by the possibly associated incompletely sorted ancestral polymorphisms and by the possibility of introgression. This study also raises the question of whether these semispecies are monophyletic at all. This reasoning is particularly interesting when one considers that similar levels of reproductive isolation could be attained through infection with different Wolbachia strains.     

Sex-specific methylation in <Emphasis Type="Italic">Drosophila</Emphasis>: an investigation of the <Emphasis Type="Italic">Sophophora</Emphasis> subgenus

Epigenetic phenomena have been widely characterized in the genomes of vertebrates and DNA methylation is a key mechanism of epigenetic regulation. The DNA methylation systems of invertebrates and vertebrates show several notable differences. However, the evolutionary implications of those differences only recently began to be revealed. Our study investigated the recurrence of sex-specific methylation, as previously described for the species Drosophila willistoni, in other species of the Sophophora subgenus that present close evolutionary relationship. The MSRE and Southern blot techniques were used to analyze rDNA of some species of the willistoni, melanogaster, saltans and obscura groups of Drosophila and the results suggested that differential DNA methylation between sexes only occurs in Drosophila tropicalis and D. insularis, two sibling species of the willistoni subgroup. However, only using the MSRE technique we could detect sex-specific patterns of DNA methylation in all species of willistoni subgroup. These results indicate that DNA methylation may present important differences, even between closely related species, shedding new light on this Neotropical species complex.     

Regulation of phagocyte NADPH oxidase by hydrogen peroxide through a Ca2+/c-Abl signaling pathway

The importance of H₂O₂ as a cellular signaling molecule has been demonstrated in a number of cell types and pathways. Here we explore a positive feedback mechanism of H₂O₂-mediated regulation of the phagocyte respiratory burst NADPH oxidase (NOX2). H₂O₂ induced a dose-dependent stimulation of superoxide production in human neutrophils, as well as in K562 leukemia cells overexpressing NOX2 system components. Stimulation was abrogated by the addition of catalase, the extracellular Ca²⁺ chelator BAPTA, the T-type Ca²⁺ channel inhibitor mibefradil, the PKCδ inhibitor rottlerin, or the c-Abl nonreceptor tyrosine kinase inhibitor imatinib mesylate or by overexpression of a dominant-negative form of c-Abl. H₂O₂ induced phosphorylation of tyrosine 311 on PKCδ and this activating phosphorylation was blocked by treatment with rottlerin, imatinib mesylate, or BAPTA. Rac GTPase activation in response to H₂O₂ was abrogated by BAPTA, imatinib mesylate, or rottlerin. In conclusion, H₂O₂ stimulates NOX2-mediated superoxide generation in neutrophils and K562/NOX2 cells via a signaling pathway involving Ca²⁺ influx and c-Abl tyrosine kinase acting upstream of PKCδ. This positive feedback regulatory pathway has important implications for amplifying the innate immune response and contributing to oxidative stress in inflammatory disorders.