Cloning,expression, and physicochemical characterization of a new diheme cytochrome <Emphasis Type="Italic">c</Emphasis> from <Emphasis Type="Italic">Shewanella baltica</Emphasis> OS155

The 16-kDa diheme cytochrome c from the bacterium Shewanella baltica OS155 (Sb-DHC) was cloned and expressed in Escherichia coli and investigated through UV–vis, magnetic circular dichroism, and ¹H NMR spectroscopies and protein voltammetry. The model structure was obtained by means of comparative modeling using the X-ray structure of Rhodobacter sphaeroides diheme cytochrome c (Rs-DHC) (with a 37% pairwise sequence identity) as a template. Sb-DHC folds into two distinct domains, each containing one heme center with a bis-His axial ligation. Both secondary and tertiary structures of the N-terminal domain resemble those of class I cytochrome c, displaying three α-helices and a compact overall folding. The C-terminal domain is less helical than the corresponding domain of Rs-DHC. The two heme groups are bridged by Tyr26 in correspondence with the shortest edge-to-edge distance, a feature which would facilitate fast internal electron transfer. The electronic properties of the two prosthetic centers are equivalent and sensitive to two acid–base equilibria with pK _a values of approximately 2.4 and 5, likely corresponding to protonation and detachment of the axial His ligands from the heme iron and a pH-linked conformational change of the protein, respectively. Reduction potentials of −0.144 and −0.257 V (vs. the standard hydrogen electrode), were determined for the C- and N-terminal heme groups, respectively. An approach based on the extended Debye–Hückel equation was applied for the first time to a two-centered metalloprotein and was found to reproduce successfully the ionic strength dependence of E°′.     

Cardiovascular and respiratory responses to apneas with and without face immersion in exercising humans.

The effect of the diving response on alveolar gas exchange was investigated in 15 subjects. During steady-state exercise (80 W) on a cycle ergometer, the subjects performed 40-s apneas in air and 40-s apneas with face immersion in cold (10 degrees C) water. Heart rate decreased and blood pressure increased during apneas, and the responses were augmented by face immersion. Oxygen uptake from the lungs decreased during apnea in air (-22% compared with eupneic control) and was further reduced during apnea with face immersion (-25% compared with eupneic control). The plasma lactate concentration increased from control (11%) after apnea in air and even more after apnea with face immersion (20%), suggesting an increased anaerobic metabolism during apneas. The lung oxygen store was depleted more slowly during apnea with face immersion because of the augmented diving response, probably including a decrease in cardiac output. Venous oxygen stores were probably reduced by the cardiovascular responses. The turnover times of these gas stores would have been prolonged, reducing their effect on the oxygen uptake in the lungs. Thus the human diving response has an oxygen-conserving effect.     

Testing an Ethnobiological Evolutionary Hypothesis on Plant-Based Remedies to Treat Malaria in Africa

The malaria hypothesis, which addresses a strong selective pressure on human genes resulting from a chain of processes that originated with the practice of agriculture, is an example of an evolutionary consequence of niche construction. This scenario has led us to formulate the following questions: Are the genetic adaptations of populations with a history of contact with malaria reflected in the local medical systems? Likewise, could environmental changes (deforestation) and the incidence of malaria result in an adaptive response in these local health care systems? We collected secondary data for the entire African continent from different databases and secondary sources and measured the response of health care systems as the variation in the richness of antimalarial medicinal plants. Our results did not indicate a cause-and-effect relationship between the tested variables and the medical systems, but a subsequent analysis of variance showed an increase in the mean of medicinal plants in regions with a higher incidence of malaria prior to disease control measures. We suggest that this response had a greater impact on local medical knowledge than other variables, such as genetic frequency and deforestation.     

Backbone NMR assignments of tryparedoxin,the central protein in the hydroperoxide detoxification cascade of African trypanosomes,in the oxidized and reduced form

Tryparedoxin (Tpx) is a pivotal protein in the redox-metabolism of trypanosomatid parasites. Tpx has previously been identified as a potential target for drug development in the fight against human African sleeping sickness caused by Trypanosoma brucei. Tpx belongs to the thioredoxin superfamily and acts as an oxidoreductase in the parasite’s cytoplasm. It contains a WCPPC active site motif, which enables the protein to undergo thiol-disulfide exchange. To promote future protein-drug interaction analyses, we report the ¹H, ¹³C and ¹⁵N backbone chemical shift assignments for both the oxidized and reduced states of Tpx. The redox state of the protein has a significant impact on the chemical shifts of the residues at the active site of the protein, especially on the two redox active site cysteines. The NMR assignments presented here will be a prerequisite for investigating drug binding to Tpx in molecular detail and to drive further drug optimization.     

Characterization of <Emphasis Type="Italic">Arabidopsis thaliana</Emphasis> regrowth patterns suggests a trade-off between undamaged fitness and damage tolerance

Metacommunity ecology has rapidly become a dominant framework through which ecologists understand the natural world. Unfortunately, persistent misunderstandings regarding metacommunity theory and the methods for evaluating hypotheses based on the theory are common in the ecological literature. Since its beginnings, four major paradigms—species sorting, mass effects, neutrality, and patch dynamics—have been associated with metacommunity ecology. The Big 4 have been misconstrued to represent the complete set of metacommunity dynamics. As a result, many investigators attempt to evaluate community assembly processes as strictly belonging to one of the Big 4 types, rather than embracing the full scope of metacommunity theory. The Big 4 were never intended to represent the entire spectrum of metacommunity dynamics and were rather examples of historical paradigms that fit within the new framework. We argue that perpetuation of the Big 4 typology hurts community ecology and we encourage researchers to embrace the full inference space of metacommunity theory. A related, but distinct issue is that the technique of variation partitioning is often used to evaluate the dynamics of metacommunities. This methodology has produced its own set of misunderstandings, some of which are directly a product of the Big 4 typology and others which are simply the product of poor study design or statistical artefacts. However, variation partitioning is a potentially powerful technique when used appropriately and we identify several strategies for successful utilization of variation partitioning.     

Synthesis and antioxidant, anti-inflammatory and gastroprotector activities of anethole and related compounds

Some derivatives of trans-anethole [1-methoxy-4-(1-propenyl)-benzene] (1) were synthesized, by introducing hydroxyl groups in the double bond of the propenyl moiety. Two types of reactions were performed: (i) oxymercuration/demercuration that formed two products, the mono-hydroxyl derivative, 1-hydroxy-1-(4-methoxyphenyl)-propane (2) and in lesser extent the dihydroxyl derivative, 1,2-dihydroxy-1-(4-methoxyphenyl)-propane (3) and (ii) epoxidation with m-chloroperbenzoic acid that also led to the formation of two products, the dihydroxyl derivative (3) and the correspondent m-chloro-benzoic acid mono-ester, 1-hydroxy-1(4-methoxyphenyl)-2-m-chlorobenzoyl-propane (4). The structures of these compounds were confirmed mainly by mass, IR, 1H and 13C NMR spectral data. The activity of anethole and hydroxylated derivatives was evaluated using antioxidant, anti-inflammatory and gastroprotector tests. Compounds (2) and (3) were more active antioxidant agents than (1) and (4). In the anti-inflammatory assay, anethole showed lower activity than hydroxylated derivatives. Anethole and in lesser extent its derivatives 2 and 4 showed significant gastroprotector activity. All tested compounds do not alter significantly the total number of white blood cells.     

Enzymatic pre-hydrolysis applied to the anaerobic treatment of effluents from poultry slaughterhouses

A pool of hydrolases with 21.4 U g⁻¹ lipase activity was produced through solid-state fermentation of the fungus Penicillium restrictum in waste from the Orbignya oleifera (babassu) oil processing industry. Enzymatic hydrolysis and anaerobic biodegradability tests were conducted on poultry slaughterhouse effluents with varying oil and grease contents (150–1200 mg l⁻¹) and solid enzymatic pool concentrations (0.1–1.0% w/v). Enhanced anaerobic treatment efficiency relative to raw effluent was achieved when a 0.1% concentration of enzymatic pool was used in the pre-hydrolysis stage with 1200 mg oil and grease l⁻¹ (chemical oxygen demand (COD) removal efficiency of 85% vs. 53% and biogas production of 175 ml vs. 37 ml after 4 d).