Antimicrobial Peptide Mimetics Based on a Diphenylacetylene Scaffold: Synthesis,Conformational Analysis,and Activity

Mimics of natural antimicrobial peptides are promising compounds to fight the rising threat of multi-drug resistant bacteria. Here we report the design, synthesis and conformational analysis of a new class of antimicrobial peptide mimetics incorporating a diphenylacetylene scaffold. Within a small set of compounds, we observe a correlation between amphiphilicity, the efficiency of partitioning into negatively charged membranes and antibacterial activity. The most amphiphilic compound, which contains four isoleucine residues and four lysine residues, displays species-selective antibacterial activity (most active against Bacillus subtills) and low haemolytic activity. Solution-phase conformational analysis of this compound indicates that a defined structure is adopted in the presence of negatively charged phospholipid membranes and aqueous 2,2,2-trifluoroethanol but not in water. A conformation model indicates that the cationic and hydrophobic functional groups are segregated. These results may inform the development of highly selective antimicrobial peptide mimetics for therapeutic applications.     

The impact of floc size on respiration inhibition by soluble toxicants--a comparative investigation

Activated sludge facilities are susceptible to upset by shock loads of toxic compounds. We hypothesized that floc size plays an important role in determining the sensitivity of mixed liquor to shock by cadmium and 2,4-dinitrophenol (DNP). To test this hypothesis, heterotrophic respiration inhibition experiments were conducted using mixed liquor from a pilot-scale membrane bioreactor (MBR) and full-scale activated sludge (FSAS) facility with gravity settling secondary clarifiers that were operated under similar process conditions. MBR mixed liquor flocs were both 41% smaller and 2 and 1.25 times more sensitive to equivalent soluble cadmium and DNP concentrations, respectively, compared to FSAS mixed liquor flocs. Similarly, FSAS mixed liquor that had been sheared (resulting in a smaller average floc diameter) was 1.5 times more sensitive to soluble cadmium than non-sheared FSAS mixed liquor. These results suggest that activated sludge process conditions that create smaller floc particles, such as the use of membranes for liquid-solid separation, are more susceptible to upset events caused by shock loads of cadmium and DNP. The particle size distribution (PSD) and average floc diameter of a mixed liquor suspension should be measured and reported when stating the inhibition concentration of a specific toxicant.     

Mercury cycling between the water column and surface sediments in a contaminated area

Mercury cycling in the water column and upper sediments of a contaminated area, the Largo do Laranjo, Aveiro (Portugal), was evaluated after determination of reactive and non-reactive mercury concentrations in the water column and pore waters of sediments, collected in several places of this bay. In the water column, reactive mercury concentrations varied between 10 and 37 pmol dm(-3), the highest values being observed near the mercury anthropogenic source. However, reactive mercury was a narrowly constrained fraction of the total mercury, making up only 4-16% of the total, showing evidence of the importance of dissolved organic matter on mercury transport. In sediments, higher concentrations of mercury were also determined near industrial discharges. Results indicate the existence of an equilibrium between solid and liquid phases, determined by solid sediment/pore water distribution coefficients. Much of the mercury present in the solid fraction is associated with organic matter (r=0.837) and iron oxyhydroxides (r=0.919), but as oxides begin to dissolve in reduced sediments and organic matter decays, the adsorbed mercury is released. In fact, the mercury concentrations in pore waters of those contaminated sediments largely exceeded the values determined in the water column. As molecular diffusion may contribute to the dissolved mercury distribution in the overlying water column, this phenomenon was evaluated. However, the pore waters of Largo do Laranjo do not enrich the water column substantially in terms of reactive and non-reactive mercury. In fact, pore waters can contribute only to 0.2% and 0.5% of the reactive and non-reactive mercury present in the water column, respectively, showing that as long as mercury is being incorporated in sediments, it stays in stable forms.     

Deasphalting process using supercritical water

The authors aimed to study the deasphalting process on laboratory scale through the design and development of a supercritical extraction experimental unit. The experimental unity used in tests is composed by a pump, an extractor with useful volume of 3 L and one separator vessel. Extractions in supercritical condition were carried out using petroleum residue (vacuum residuum) as feedstock and water as solvent. Temperature and pressure were manipulated to maintain the solvent in the required conditions, thus facilitating the extraction process and avoiding sharp changes in the system. In both phases, the products in the deasphalted oil stream present adequate characteristics for the production of lubricant oils and those in the asphalt residue stream present an elevated concentration of asphalt molecules.     

Effect of Wind and Slope When Scaling the Forest Fires Rate of Spread of Laboratory Experiments

This paper uses the scaling laws obtained from a Froude Modeling perspective to analyze the variations experienced in the rate of spread of wind-aided and up-slope laboratory fires when changing the size of a scale model. The results have shown that the rate of spread scaling law is no longer verified when working at laboratory scale in steep slopes and high wind speed conditions. The paper also provides a framework for scaling and scale issues in forest fire research.