Production, crystallization and preliminary X-ray analysis of CTP: inositol-1-phosphate cytidylyltransferase from Archaeoglobus fulgidus

Brito, J. A.Archaeoglobus fulgidus, a hyperthermophilic archaeon, accumulates di-myo-inositol phosphate (DIP) in response to heat stress. Recently, the pathway for biosynthesis of DIP has been elucidated in this organism and involves a bifunctional enzyme that contains two domains: CTP:inositol-1-phosphate cytidylyltransferase (IPCT) as a soluble domain and di-myo-inositol-1,3'-phosphate-1-phosphate synthase (DIPPS) as a membrane domain. Here, the expression, purification, crystallization and preliminary X-ray diffraction analysis of the IPCT domain from A. fulgidus in the apo form are reported. The crystals diffracted to 2.4 A resolution using a synchrotron source and belonged to the orthorhombic space group P2(1)2(1)2, with unit-cell parameters a = 154.7, b = 83.9, c = 127.7 A.publishe

Croton argyrophyllus Kunth and Croton heliotropiifolius Kunth: phytochemical characterization and bioactive properties

Croton heliotropiifolius Kunth and Croton argyrophyllus Kunth are endemic plant species from northeastern Brazil widely used in folk medicine and scarcely studied. In this context, the essential oils (EO's) and methanolic extracts (leaves and stalk) of both species were chemically characterized, and their antioxidant and antimicrobial activities were assessed. The chemical characterization of the EO's identified sixty components,being the major ones in C. argyrophyllus bicyclogermacrene (14.0%), β-pinene (8.9%) and spathulenol (8.7%), and in C. heliotropiifolius limonene (16.9%), α-pinene (13.3%) and caryophyllene (12.1%). Essential oils and methanolic extracts from leaves of C. argyrophyllus possess greater antioxidant potential, which could be related to the high levels of total phenols and flavonols. The antimicrobial activity of C. argyrophyllus essential oil proven to be more efficient than chloramphenicol (30 μg mL−1), with a minimum inhibitory concentration (MIC) of 25 μL mL−1 against Bacillus subtilis, Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa and 10 μL mL−1 against B. cereus. Leaf extracts presented high activity against yeasts (MIC = 50 mg mL−1) being C. heliotropiifolius effective against Candida albicans and C. parapsilosis, while C. argyrophyllus was effective against C. glabrata. Overall results showed that these plant species are potential sources of phytochemicals with interest in the fields of both pharmacology (e.g., antimicrobial) and human health (e.g., antioxidant). Furthermore, in the socio-economic aspect, these results can improve and disseminate the cultivation of these species, inducing improvements in the rural populations.This work was financially supported by CNPQ/CsF and CAPES and UID/AGR/00690/2013 – CIMO funded by FEDER – Fundo Europeu de Desenvolvimento Regional through COMPETE2020 – Programa Operacional Competitividade e Internacionalização (POCI) – and by national funds through FCT – Fundação para a Ciência e a Tecnologia, Portugal. The authors are also grateful to UFRB Herbarium for the help with the plant species identification.info:eu-repo/semantics/publishedVersio

Tachyons on Dp-branes from Abelian Higgs sphalerons

We consider the Abelian Higgs model in a (p+2)-dimensional space time with topology M^{p+1} x S^1 as a field theoretical toy model for tachyon condensation on Dp-branes. The theory has periodic sphaleron solutions with the normal mode equations resembling Lame-type equations. These equations are quasi-exactly solvable (QES) for specific choices of the Higgs- to gauge boson mass ratio and hence a finite number of algebraic normal modes can be computed explicitely. We calculate the tachyon potential for two different values of the Higgs- to gauge boson mass ratio and show that in comparison to previously studied pure scalar field models an exact cancellation between the negative energy contribution at the minimum of the tachyon potential and the brane tension is possible for the simplest truncation in the expansion about the field around the sphaleron. This gives further evidence for the correctness of Sen's conjecture.Comment: 14 Latex pages including 3 eps-figure

Tachyon condensation on brane sphalerons

We consider a sphaleron solution in field theory that provides a toy model for unstable D-branes of string theory. We investigate the tachyon condensation on a Dp-brane. The localized modes, including a tachyon, arise in the spectrum of a sphaleron solution of a \phi^4 field theory on M^{p+1}\times S^1. We use these modes to find a multiscalar tachyon potential living on the sphaleron world-volume. A complete cancelation between brane tension and the minimum of the tachyon potential is found as the size of the circle becomes small.Comment: To appear in JHEP, 13 pages, 2 eps figures, minor changes and references adde

The temporal and spatial variation of arthropod associations inhabiting non-crop vegetation in a sisal crop, agave sisalana in the caatinga biome

Sisal, Agave sisalana Perrine, is cultivated for fiber production, with Brazil being its leading producer. Nowadays, given the increasing interest in organic products, the market for sisal could become an economical alternative for rural areas with low economic inputs. However, sisal is threatened by different pests and diseases. Conservation biological control could contribute to the limitation of these plant enemies, but this agroecosystem is poorly known. In this context, we aimed: (i) to identify the diversity of plants and arthropods and their potential relations, (ii) to study the spatial patterns of arthropods and plants in function of the proximity to the margin of the field, and (iii) to determine the minimum sampling effort needed to record the occurring biodiversity in a sisal crop. Arthropods were sampled using pit-fall traps located close to the border and in the inner plant of the sisal crop from June to September. Simultaneously, plant species and their abundance in quadrats next to each pitfall were recorded. Diversity indexes were calculated to describe the biodiversity, a redundancy analysis was performed to analyze relations among arthropods and plants and the spatial distribution was evaluated using the non-parametric Wilcoxon rank-sum test. The redundancy analysis and the Wilcoxon test revealed a temporal and spatial distribution of arthropods and plants during the period of study. Results indicated (i) similar temporal diversity patterns from June to July for both plants and arthropods, with a maximum in July, whereas in September the biodiversity increased for arthropods and decreased for plants; (ii) the importance of particular plant species for Collembola; and (iii) that arthropods seem to colonize the sisal crop from the fields beyond the crop during the rainy season. These results provide new information about arthropods and plant biodiversity from an agroecosystem in a semi-arid region and raise further queries about the management of sisal crops.This research was funded by Foundation for Science and Technology (FCT, Portugal) by national funds FCT/MCTES to CIMO (UIDB/00690/2020) and CsF/CNPq (Programa Ciência Sem Fronteiras/CNPq).info:eu-repo/semantics/publishedVersio

Collisional rates for the inelastic Maxwell model: application to the divergence of anisotropic high-order velocity moments in the homogeneous cooling state

The collisional rates associated with the isotropic velocity moments $$and the anisotropic moments$$ and $$ are exactly derived in the case of the inelastic Maxwell model as functions of the exponent $r$, the coefficient of restitution $\alpha$, and the dimensionality $d$. The results are applied to the evolution of the moments in the homogeneous free cooling state. It is found that, at a given value of $\alpha$, not only the isotropic moments of a degree higher than a certain value diverge but also the anisotropic moments do. This implies that, while the scaled distribution function has been proven in the literature to converge to the isotropic self-similar solution in well-defined mathematical terms, nonzero initial anisotropic moments do not decay with time. On the other hand, our results show that the ratio between an anisotropic moment and the isotropic moment of the same degree tends to zero.Comment: 7 pages, 2 figures; v2: clarification of some mathematical statements and addition of 7 new references; v3: Published in "Special Issue: Isaac Goldhirsch - A Pioneer of Granular Matter Theory

Metal and semimetal loadings in sediments and water from mangrove ecosystems: A preliminary assessment of anthropogenic enrichment in São Tomé island (central Africa)

Mangroves act as buffer areas for marine systems, providing a barrier to contamination from continental sources by retaining metal pollutants. This study evaluates metal and semimetal contamination in the water column and sediments of four mangroves located on the volcanic island of São Tomé. Several metals had a widespread distribution, with occasional high concentrations, linked to potential sources of contamination. However, the two smaller mangroves, located in the northern part of the island, tended to have high metal concentrations. Arsenic and chromium concentrations were notably concerning, particularly if we consider this is an isolated and non-industrialized island. This work highlights the need for further assessments and a better understanding of processes and implications of metal contamination in mangroves. This assumes a particular relevance in areas that have specific geochemical compositions (i.e., volcanic origin) and in developing countries, where people often rely directly and heavily on resources obtained from these ecosystems.info:eu-repo/semantics/publishedVersio