Protein-free models for the proton-coupled reduction of haemoproteins

Reduction of the bis-pilocarpate-haemin complex at pH greater than or equal to 10 involves the simultaneous uptake of an electron by the Fe(III) ion and a proton by the pendant alkoxide group of an axial ligand. This provides a protein-free model for reactions such as the proton-coupled reduction of cytochromes which involve cooperative Coulombic interaction between two non-bonded sites.     

Characterization of the yeast population in olive brines

Yeasts were isolated from spontaneous fermentations of olives in brines. Ascomycetous species dominated the yeast flora (>90%) and among them Pichia membranae-faciens and related species. Some components of the olives were tested as substrates for growth. Killer activity was observed in approximately half of the isolates, and the wider spectra were displayed by strains of Pichia anomala .     

Common and rare species respond to similar niche processes in macroinvertebrate metacommunities

Ecologists have long investigated why communities are composed of a few common species and many rare species. Most studies relate rarity to either niche differentiation among species or spatial processes. There is a parallel between these processes and the processes proposed to explain the structure of metacommunities. Based on a metacommunity perspective and on data on stream macroinvertebrates from different regions of Brazil, we answer two questions. 1) Are sets of common and rare species affected by similar niche and spatial processes? 2) How does the community composition of common and of rare species differ? The main hypothesis we test is that common species are mainly affected by environmental factors, whereas rare species are mostly influenced by dispersal limitation. We used variation partitioning to determine the proportion of variation explained by the environment and space in common and rare species matrices. Contrary to our expectations, evidence supported the idea that both common and rare species are affected mainly by environmental factors, even after controlling for the differing information content between common and rare species matrices. Moreover, the abundance of some common species is also a good predictor of variation in rare species matrices. Niche differences are unlikely to be the sole cause of patterns of rarity in these metacommunities. We suggest that sets of common and rare species react to similar major environmental gradients and that rare species also respond to processes that operate at a more fine‐grained spatial scale, particularly biotic interactions. We extend the view that species sorting is the dominant process structuring metacommunities and argue that future studies focusing on rarity would benefit from a metacommunity perspective.     

Iminodiacetyl-hydroxamate derivatives as metalloproteinase inhibitors: equilibrium complexation studies with Cu(II), Zn(II) and Ni(II)

Two new iminodiacetyl-hydroxamate derivatives, the N-benzyl-N-carboxymethyl-iminoacetohydroxamic acid (H(2)L(1)) and the N-benzyl-N'-hydroxypiperazine-2,6-dione (HL(2)), have been recently reported as very effective inhibitors against a set of zinc-containing matrix metalloproteinases (MMPs). Herein, aimed at understanding that inhibitory function, these compounds are studied in their complex formation equilibria with three biologically relevant first-row transition M(2+) metal ions (M=Cu, Zn, Ni) by using potentiometric and spectroscopic techniques. At physiological conditions, complexation of these metal ions by H(2)L(1) mostly occurs with formation of 1:1 species by tridentate co-ordination (O,N,N) (carboxylate-amino-hydroxamate), whereas complexation with HL(2) mainly involves the formation of 1:2 (M:L) species with normal (O,O) hydroxamate coordination. Moreover, at higher pH, H(2)L(1) is able to form a pentanuclear tetrameric copper complex with an interesting 12-metallacrown-4 structure.     

A DNA Vaccine against Yellow Fever Virus: Development and Evaluation

Attenuated yellow fever (YF) virus 17D/17DD vaccines are the only available protection from YF infection, which remains a significant source of morbidity and mortality in the tropical areas of the world. The attenuated YF virus vaccine, which is used worldwide, generates both long-lasting neutralizing antibodies and strong T-cell responses. However, on rare occasions, this vaccine has toxic side effects that can be fatal. This study presents the design of two non-viral DNA-based antigen formulations and the characterization of their expression and immunological properties. The two antigen formulations consist of DNA encoding the full-length envelope protein (p/YFE) or the full-length envelope protein fused to the lysosomal-associated membrane protein signal, LAMP-1 (pL/YFE), aimed at diverting antigen processing/presentation through the major histocompatibility complex II precursor compartments. The immune responses triggered by these formulations were evaluated in H2b and H2d backgrounds, corresponding to the C57Bl/6 and BALB/c mice strains, respectively. Both DNA constructs were able to induce very strong T-cell responses of similar magnitude against almost all epitopes that are also generated by the YF 17DD vaccine. The pL/YFE formulation performed best overall. In addition to the T-cell response, it was also able to stimulate high titers of anti-YF neutralizing antibodies comparable to the levels elicited by the 17DD vaccine. More importantly, the pL/YFE vaccine conferred 100% protection against the YF virus in intracerebrally challenged mice. These results indicate that pL/YFE DNA is an excellent vaccine candidate and should be considered for further developmental studies.     

Sex determination and optimal development in the Moorish gecko,Tarentola mauritanica

Under temperature sex determination (TSD), sex is determined by temperature during embryonic development. Depending on ecological and physiological traits and plasticity, TSD species may face demographic collapse due to climate change. In this context, asymmetry in bilateral organisms can be used as a proxy for developmental instability and, therefore, deviations from optimal incubation conditions. Using Tarentola mauritanica gecko as a model, this study aimed first to confirm TSD, its pattern and pivotal temperature, and second to assess the local adaptation of TSD and variation of asymmetry patterns across four populations under different thermal regimes. Eggs were incubated at different temperatures, and hatchlings were sexed and measured. The number of lamellae was counted in adults and hatchlings. Results were compatible with a TSD pattern with males generated at low and females at high incubation temperatures. Estimated pivotal temperature coincided with the temperature producing lower embryonic mortality, evidencing selection towards balanced sex ratios. The temperature of oviposition was conservatively selected by gravid females. Asymmetry patterns found were likely related to nest temperature fluctuations. Overall, the rigidity of TSD may compromise reproductive success, and demographic stability in this species in case thermal nest choice becomes constrained by climate change.