An SOS-regulated operon involved in damage-inducible mutagenesis in Caulobacter crescentus

DNA polymerases of the Y-family, such as Escherichia coli UmuC and DinB, are specialized enzymes induced by the SOS response, which bypass lesions allowing the continuation of DNA replication. umuDC orthologs are absent in Caulobacter crescentus and other bacteria, raising the question about the existence of SOS mutagenesis in these organisms. Here, we report that the C.crescentus dinB ortholog is not involved in damage-induced mutagenesis. However, an operon composed of two hypothetical genes and dnaE2, encoding a second copy of the catalytic subunit of Pol III, is damage inducible in a recA-dependent manner, and is responsible for most ultraviolet (UV) and mitomycin C-induced mutations in C.crescentus. The results demonstrate that the three genes are required for the error-prone processing of DNA lesions. The two hypothetical genes were named imuA and imuB, after inducible mutagenesis. ImuB is similar to proteins of the Y-family of polymerases, and possibly cooperates with DnaE2 in lesion bypass. The mutations arising as a consequence of the activity of the imuAB dnaE2 operon are rather unusual for UV irradiation, including G:C to C:G transversions

Sistemas de Comunicacion Inalambrica MIMO - OFDM

En este articulo tutorial, se presenta la fundamentacion basica de la tecnica demodulation multiportadora OFDM (>Orthogonal Frequency Division Multiplexing). Y serealiza una introduction a los sistemas de transmision MIMO (Multi-Input and MultiOutput). Adicionalmente, se muestra un resumen de las estructuras espaciales de estossistemas. Finalmente se realiza una revision, de la estructura obtenida al combinar laestructura MIMO y la tecnica de modulation OFDM

Prediction of drug targets in human pathogens

The identification of new and druggable targets in bacteria is a critical endeavour in pharmaceutical research of novel antibiotics to fight infectious agents. The rapid emergence of resistant bacteria makes today's antibiotics more and more ineffective, consequently increasing the need for new pharmacological targets and novel classes of antibacterial drugs. A new model that combines the singular value decomposition technique with biological filters comprised of a set of protein properties associated with bacterial drug targets and similarity to protein-coding essential genes of E. coli has been developed to predict potential drug targets in the Enterobacteriaceae family [1]. This model identified 99 potential target proteins amongst the studied bacterial family, exhibiting eight different functions that suggest that the disruption of the activities of these proteins is critical for cells. Out of these candidates, one was selected for target confirmation. To find target modulators, receptor-based pharmacophore hypotheses were built and used in the screening of a virtual library of compounds. Postscreening filters were based on physicochemical and topological similarity to known Gram-negative antibiotics and applied to the retrieved compounds. Screening hits passing all filters were docked into the proteins catalytic groove and 15 of the most promising compounds were purchased from their chemical vendors to be experimentally tested in vitro. To the best of our knowledge, this is the first attempt to rationalize the search of compounds to probe the relevance of this candidate as a new pharmacological target

Di-ureasil ormolytes doped with Mg2+ ions : part 1: morphological, thermal and electrochemical properties

Poly(oxyethylene)(POE/siloxane-based materials incorporating magnesium triflate were prepared by the sol-gel process. The host Class II hybrid matrix (di-ureasil) employed was composed of a siliceous framework to which short POE chains were covalently bonded through urea linkages. Ormolytes with salt composition ranging from 500 to 1 were characterised. The nanohybrid with n = 20, thermally stable up to 360ºC, exhibited the highest ionic conductivity. The electrochemical stability of this material was found to span -3 to +2 volts.Fundação para a Ciência e Tecnologia - POCTI/P/CTM/33653/00; SFRH/BD/13559/03; POCTI/P/CTM/46780/03

Study of sol-gel derived di-ureasils doped with zinc triflate

Prova tipográfica (In Press)A publicar em "Solid States Sciences".Zinc triflate (Zn(CF3SO3)2)-doped sol-gel derived di-urea cross-linked POE/siloxane ormolytes (designated as di-ureasils) with ∞ > n ≥ 1 (where the salt content is expressed as n, the molar ratio of oxyethylene moieties to Zn2+ ions) were investigated. The hybrids with n ≥ 5 are entirely amorphous; those with n > 10 are thermally stable up to approximately 305 ºC. The siliceous network of representative samples (n = 200 and 10) is essentially composed of (SiO)3Si(CH2)- environments and is thus highly branched. The distance between the structural units in samples with 200 ≥ n ≥ 10 and n ≤ 7 is 4.2 and 4.3 Å, respectively. The estimated interdomain distance is 11 and 13 Å for xerogels with 200 ≥ n ≥ 20 and n ≤ 10, respectively. At n = 1 a crystalline POE/Zn(CF3SO3)2 complex of unknown stoichiometry is formed. The conductivity maxima are located at n = 60 (3x10-6 S cm-1) and n = 20 (7x10-5 S cm-1) at 30 and 100 ºC, respectively.Fundação para a Ciência e a Tecnologia - POCTI/P/CTM/46780/03; SFRH/BD/13559/03

Di-urea cross-linked poly(oxyethylene)/siloxane ormolytes for lithium batteries

Poly(oxyethylene)( POE)/siloxane hybrids (di-ureasils) doped with a wide concentration range of lithium triflate were investigated. The host matrix of these materials (d-U(2000)) is a sol-gel derived siliceous network to which POE chains with about 40 repeat units are bonded through urea linkages. Xerogels with n between 500 and 5 (where n is the molar ration of OCH2CH2 repeat units to lithium íons) were obtained as amorphous monoliths thermally stable up to at least 340ºC. A crystalline POE/LiCF3SO3 complex was detected spectroscopically in samples with compositions of n less than 10. Below 90ºC the ormolyte with n = 20 exhibits the highest ionic conductivity of the series characterized. The redox stability of this material is about 4.1 volts

Sol-gel derived Li+-doped poly(ε-caprolactone)/siloxane biohybrid electrolytes

Electrolytes based on a poly(ε-caprolactone) (PCL)/siloxane organic/inorganic host framework doped with lithium triflate (LiCF3SO3) were synthesised through the sol-gel process. In this biohybrid matrix short PCL chains are covalently bonded via urethane linkages to the siliceous network. Samples with salt composition n (molar ratio of PCL repeat units per Li+ ion) ranging from ∞ to 0.5 were investigated. All the ormolyte materials analysed are amorphous. Xerogels with n > 0.5 are thermally stable up to about 300°C. The most conducting ormolyte of the series is that with n = 0.5 (1.6×10−7 and 3.2×10−5 Ω−1 cm−1 at 25 and 100°C, respectively). This sample is electrochemically stable between −1 and 6 V versus Li+.Fundação para a Ciência e Tecnologia - POCTI/P/CTM/33653/00, SFRH/BD/13559/03, POCTI/P/CTM/46780/03.Fundação para a Ciência e a Tecnologia (FCT

Variation in feeding ecology of five cnemidophorine lizard species along Brazilian eastern coast

Feeding ecology of a particular species is associated to population dynamics and contributes for the understanding of natural history and trophic interactions in ecosystems. We investigated changes in the feeding habits of 16 populations belonging to five cnemidophorine lizard species (being four bisexual and one unisexual) along approximately 4000 km extension of the Brazilian eastern coast. Fieldwork was carried out in 15 areas of restinga habitats and for each cnemidophorine population, the composition of the diet was analyzed based on the number, volume (mm3) and frequency of each prey category or plant material.The arthropods were categorized in the taxonomic level of Order or Family (e.g.Formicidae). Cnemidophorine populations/species studied were mainly carnivorous and had, in general, a diet consisting predominantly of larvae and/or termites, with few instances of plant material consumption. The availability of termites locally at each restinga habitat was not a determinant factor in the increase of termite consumption by the local cnemodophorine population. However, differences in diet composition among populations partially resulted from differential consumption of termites, leading to the formation of two distinct groups depending on higher or lesser consumption of termites. Some populations had onthonegetic variation in diet, but males and females of different populations/species tended to have similar diet composition. The head width of lizards affected significantly the volume and the length of the largest prey ingested in 60% (3/5) of the species studied, indicating that adults tended to consume larger food items compared to coespecifics juveniles. The high level of importance of termites and larvae in almost all populations/species probably contributed to the low intra-and interspecific differences in food habit. The diet of cnemidophorine species studied in restinga habitats in general, tended to be similar to that found to other cnemidophorines, regardless its geographic distribution. Invertebrates were the dominant prey on cnemidophorines diet, but predation on vertebrates was also registered.A ecologia alimentar de uma determinada espécie está associada a dinâmica da população e contribui para a compreensão da história natural e das interações tróficas nos ecossistemas. No presente estudo, investigamos mudanças nos hábitos alimentares de 16 populações pertencentes a cinco espécies de lagartos cnemidophorines (quatro bissexuais e uma unissexual) ao longo de aproximadamente 4000 km da costa leste brasileira. O trabalho de campo foi realizado em 15 áreas de restinga. A composição da dieta de cada população foi baseada no número, volume (mm3) e frequência de cada categoria de presa e de material vegetal. Os artrópodes foram categorizados no nível taxonômico de Ordem ou Família (por exemplo, Formicidae). As populações/ espécies de cnemidophorines estudadas foram principalmente carnívoras com uma dieta constituída predominantemente por larvas e/ou cupins, com pouco consumo de material vegetal. A disponibilidade de cupins localmente em cada restinga não foi um fator determinante no aumento do consumo de cupins pela população do lagarto cnemidophorino local. No entanto, as diferenças na composição da dieta entre as populações resultaram do consumo diferencial de cupins, levando a formação de dois grupos distintos, dependendo do consumo maior ou menor de cupins. Algumas populações apresentaram variação ontogenética na dieta, mas machos e fêmeas tenderam a ter uma composição alimentar semelhante em cada população/espécie. A largura da cabeça afetou significativamente o volume e o comprimento da maior presa ingerida em 60% (3/5) das espécies estudadas, indicando que os adultos tendem a consumir itens alimentares maiores que os jovens coespecíficos. O elevado índice importância de cupins e larvas em quase todas as populações/espécies provavelmente contribuiu para as baixas diferenças intra e interespecíficas no hábito alimentar. A dieta das espécies estudadas, em geral, tendeu a ser semelhante a encontrada para outros cnemidophorinos, independentemente de sua distribuição geográfica. Os invertebrados foram as presas predominantes na dieta, mas a predação em vertebrados foi também registrada.Asociación Herpetológica Argentin

Structure and photoluminescent features of di-amide cross-linked alkylene-siloxane hybrids

Novel amide cross-linked alkylene/siloxane hybrid materials (di-amidosils) synthesized by the sol-gel process have been investigated. Two samples identified by the notation d-A(x) with x = 4 and 8 (where x is the number of methylene groups of the alkylene chain) have been produced as transparent, amorphous, rigid monoliths, thermally stable up to about 381 and 400 ºC, respectively. In the d-A(8) hybrid the siliceous framework is composed of [(SiO)3Si(CH2)-] and [(SiO)2(HO)Si(CH2)-] substructures. Structural unit distances of 4.1 and 4.2 Å and average interparticle distances of 12 and 17 Å have been determined for d-A(4) and d-A(8), respectively. In these compounds the alkyl chains are disordered and adopt gauche conformations. While a negligible proportion of the amide linkages remain non-bonded, the great majority of these groups belong to highly disordered strong hydrogen-bonded amide-amide associations. The hybrids introduced are room temperature white light emitters, presenting an emission large, broad band in the blue/purplish-blue spectral region. The origin of such band have been ascribed to the convolution of donor-acceptor pair (D-A) recombinations that occur in the NH groups of the urea linkages and in the siliceous nanodomains. The maximum quantum yield value of the d-A(8) di-amidosil is 5.4 %.Fundação para a Ciência e a Tecnologia (FCT) - POCTI/P/CTM/46780/03; SFRH/BD/13559/03