Design of europium(III) complexes with high quantum yield

This work describes a rational planning of a new light-conversion molecular device with high quantum yield. For this, we made modifications in the 3-amino-2-carboxypyridine and 3-amino-2-carboxypirazine acid ligands, generating eight different complexes. Theoretical methods have been used to calculate the quantum yield of each of the complexes. We first used the Sparkle model to calculate the ground-state geometries of the eight complexes. These data were used to perform theoretical predictions of the energy transitions using the INDO/S–CI method. After having obtained the geometry and the energy transitions, the energy transfer rates and quantum yield were calculated using a theoretical approach based on the application of the 4f–4f transition theory. The results show that the modifications in the 3-amino-2-carboxypyridine ligand had generated three complexes with high quantum yield (about 52.8, 51.6 and 52.8%). On the other hand, the modifications in the 3-amino-2-carboxypirazine led to only one complex with quantum yield larger than 50%, but it is the most efficient complex projected.     

Purification of a lectin from the marine red alga Gracilaria ornata and its effect on the development of the cowpea weevil Callosobruchus maculatus (Coleoptera: Bruchidae)

A lectin from the marine red alga Gracilaria ornata (Gracilariaceae, Rodophyta) was purified and characterized. The purification procedure consisted of extracting soluble proteins in 0.025 M Tris-HCl buffer, pH 7.5, followed by ammonium sulfate precipitation (70% saturation), ion exchange chromatography on DEAE-cellulose and affinity chromatography on mucin-Sepharose 4B. The purified G. ornata lectin (GOL) showed a single protein band with an apparent molecular mass of 17 kDa when submitted to SDS-polyacrylamide gel electrophoresis under reducing conditions. The native molecular mass of GOL determined by gel filtration on a Sephadex G-100 column was 17.4 kDa and its carbohydrate content was estimated to be 2.9%. Therefore, GOL is a monomeric glycoprotein. The purified lectin agglutinated trypsin-treated erythrocytes from rabbit and chicken but not from human. Its activity was not inhibited by any of the mono- and disaccharides tested but by the complex glycoproteins porcine stomach mucin, lactotransferrin, asialofetuin and bovine and porcine thyroglobulins. Isoelectric focusing showed that GOL is an acidic protein with a pI of 5.4 with analysis of its amino acid composition revealing high contents of Asx, Glx, Ser, Glu, Ala and Cys. When incorporated in artificial seeds, GOL significantly affected the development of Callosobruchus maculatus larvae, indicating the possibility of using this lectin in a biotechnological strategy for insect management of stored cowpea seeds.     

Isothermal titration calorimetry to determine association constants for high-affinity ligands

An important goal in drug development is to engineer inhibitors and ligands that have high binding affinities for their target molecules. In optimizing these interactions, the precise determination of the binding affinity becomes progressively difficult once it approaches and surpasses the nanomolar level. Isothermal titration calorimetry (ITC) can be used to determine the complete binding thermodynamics of a ligand down to the picomolar range by using an experimental mode called displacement titration. In a displacement titration, the association constant of a high-affinity ligand that cannot be measured directly is artificially lowered to a measurable level by premixing the protein with a weaker competitive ligand. To perform this protocol, two titrations must be carried out: a direct titration of the weak ligand to the target macromolecule and a displacement titration of the high-affinity ligand to the weak ligand-target macromolecule complex. This protocol takes approximately 5 h.     

Asymmetric alkene epoxidation by Mn(III)salen catalyst in ionic liquids

The enantioselective epoxidation of 6-cyano-2,2-dimethylchromene (Chrom) catalysed by the Jacobsen catalyst, using sodium hypochlorite (NaOCl) as oxygen source, at room temperature, was performed in a series of 1,3-dialkylimidazolium and tetra-alkyl-dimethylguanidium based ionic liquids. All the room temperature ionic liquids (RTILs) could be used as reaction media for the enantioselective epoxidation of the alkene giving, generally, moderate to good epoxide yields and enantiomeric excesses (ee%).For the series of ionic liquids derived from the 1,3-dialkylimidazolium cation, it was observed some relationship between the RTILs physical properties and the catalytic reaction parameters, exemplified by linear correlations between (i) the ee% and the α Kamlet-Taft parameter (hydrogen bond acidity of the solvent) for CH₂Cl₂ and [C₄m_nim][BF₄] ionic liquids (n = 1 or 2), and (ii) the ee% and the β Kamlet-Taft parameter (hydrogen bond basicity of the solvent) for CH₂Cl₂ and [C₄mim][X] ionic liquids (X = PF₆, NTf₂ or BF₄).All the RTILs could be reused in further catalytic cycles, with the exception of [C₈mim][PF₆]. The reutilisation of the Jacobsen catalyst for four times generally led to a decrease in the epoxide yield and to a slight decrease in the enantioselectivity. The recycling of the catalyst could be improved by imparting an ionic character to the complex through abstraction of the axially coordinated chloride anion (Cat 2). Other oxygen sources, such as iodosylbenzene, hydrogen peroxide and urea-hydrogen peroxide adduct, were also tested coupled with Jacobsen catalyst, but the best results were achieved with NaOCl.     

Seasonal variation of pelagic invertebrate larvae in the shallow antarctic waters of Admiralty Bay (King George Island)

Recent studies have revealed increasing numbers of benthic invertebrate species producing pelagic larvae in Antarctic waters. This paper investigates temporal changes in larval abundance in shallow areas of Admiralty Bay. Plankton was collected from December to May of 2000/2001 and 2001/2002. Air and water temperature and solar radiation were significantly higher during the second year, characterising three seasonal periods early summer, late summer and early winter. Mean meroplankton abundance was 160 and 1,548 in d.100 m⁻³ for the first and second years, respectively. Mollusc veligers were dominant in both years. Analysis of variance showed that in 2001 veligers were present in the early winter and in 2002 they were synchronous with the late summer phytoplankton bloom; polychaetes and trochophors were concentrated in the early winter, while echinoderms and nemerteans were abundant in early summer. These results showed the importance of seasonality (i.e. a combination of air and water temperature, solar radiation and food supply) to the reproductive events of an Antarctic coastal nearshore environment.     

New Group-Specific 16S rDNA Primers for Monitoring Foaming Mycolata During Saline Waste-Water Treatment

Newly designed group-specific PCR primers for denaturing gradient gel electrophoresis (DGGE) were used to investigate foaming mycolata from a bioreactor treating an industrial saline waste-water. Genetic profiles on DGGE gels were different with NaCl at 1.65 and 8.24 g l⁻¹, demonstrating that mycolata community was affected by salinity. A semi-nested PCR strategy resulted in more bands in community genetic profiles than direct amplification. DNA sequencing of bands confirmed the efficacy of the novel primers with sequences recovered being most similar to foam producing mycolata. The new group-specific primers/DGGE approach is a new step toward a more complete understanding of functionally important groups of bacteria involved in biological treatment of waste-water. Revisions requested 1 December 2005; Revisions received 19 December 2005     

Pre- and post-hatching effects of corticosterone treatment on behavior of the domestic chick

We investigated the effect of 60 ìg of corticosterone administered to domestic chicks either before or after hatching on the behavioral response to isolation in a novel arena and performance in a task involving the simultaneous identification of food and detection of a predator (overhead silhouette of a hawk moving overhead). Following release into a novel arena, chicks treated with corticosterone at 18 days of incubation emitted more distress vocalizations. In contrast, no difference in the number of vocalizations was found between chicks treated with corticosterone at day 1 post-hatching and controls. Behavior in the home cages was generally similar across treatments, though chicks treated with corticosterone at 18 days of incubation slept more than control chicks. While searching for grain against a background of pebbles, chicks treated with corticosterone at embryonic day 18, but not chicks treated on day 1 post-hatching, took longer to detect the overhead image of a predator than did controls. Corticosterone treatment at both ages increased the rate of pecking at grains and pebbles. Our findings support work on other birds indicating that corticosterone treatment during incubation influences stress reactivity. The impairment in predator detection in chicks treated with corticosterone on day 18 of incubation appears to be caused by the known effects of corticosterone treatment at this age in preventing the development of lateralization of the thalamofugal visual projections. This further supports the hypothesis that brain lateralization provides an advantage in performing more than one task simultaneously.     

Serological Survey of Paracoccidioidomycosis in Sheep

The objective of this study was to evaluate the prevalence of antibodies against Paracoccidioides brasiliensis in sheep from Guarapuava, Paraná State, Brazil. The seroepidemiological study was carried out in 262 sheep. The samples were analyzed by ELISA and immunodiffusion test using P. brasiliensis gp43 and exoantigen as antigens, respectively. Initially, two sheep were immunized with P. brasiliensis to evaluate whether contact with the fungal cells could induce a humoral immune response against gp43 and exoantigen from P. brasiliensis. Both animals produced antibodies against gp43 and exoantigen, the main antigens used for diagnosis and seroepidemiology of paracoccidioidomycosis. A reactivity of 37% was observed to the P. brasiliensis gp43 antigen by ELISA although no reactivity had been observed by the immunodiffusion test. Sheep under extensive grazing system showed higher frequency of positivity to P. brasiliensis (P ≤ 0.05) than those under intensive and semi-intensive systems. These data suggest that sheep may be a useful epidemiological marker of P. brasiliensis presence in the environment and reinforce that contact with soil is an important risk factor for infection.     

Associations of polymorphisms of folate cycle enzymes and risk of breast cancer in a Brazilian population are age dependent

Polymorphisms in genes involved in folate metabolism have been shown to be implicated in breast cancer risk but with contradictory results. In this case–control study, we investigated the association between MTHFR C677T and A1298C, TYMS 5′-UTR, MTR A2756G and cSHMT C1420T and also the folate carrier (RFC1 G80A) and breast cancer risk in a northeastern Brazilian population. The study included 183 women diagnosed with breast cancer and 183 controls volunteers without any history of cancer. Also a significant number of healthy individuals were included for allelic frequency in the population studied. Risk of breast cancer was estimated by conditional logistic regression. An association with risk was found for women carrying the MTR A2756G polymorphic allele (AG, P = 0.0036; AG/GG, P = 0.0040), and a protective effect in carriers of the RFC1 G80A polymorphic allele (GA, P = 0.0015; AA, P = 0.0042). Stratifying the data by age (cutoff point of 50 years old), different distributions were observed for breast cancer risk. For women ≤50 years, the risk observed in the presence of the polymorphic allele MTR 2756 (AG/GG) in the general analysis was, restricted to this age group (P = 0.0118). Conversely, for women over 50, the risk of breast cancer development was statistically associated with the MTHFR 677CT genotype, but especially significant was risk associated with the presence of the polymorphic allele of cSHMT C1420T (P = 0.0120) and the protective effect associated with the RFC1 G80A polymorphism allele (P = 0.0021), was restrict to this age group. These data indicate that the cutoff age used (50 years old) was appropriate, since it was able to discriminate risk in each age group in the population studied and also to point to the importance of age in the analyses of cancer-associated polymorphisms.