Multimodular biocatalysts for natural product assembly

Nonribosomal peptides and polyketides represent a large class of natural products that show an extreme structural diversity and broad pharmacological relevance. They are synthesized from simple building blocks such as amino or carboxy acids and malonate derivatives on multimodular enzymes called nonribosomal peptide synthetases (NRPSs) and polyketide synthases (PKSs), respectively. Although utilizing different substrates, NRPSs and PKSs show striking similarities in the modular architecture of their catalytic domains and product assembly-line mechanism. Among these compounds are well known antibiotics (penicillin, vancomycin and erythromycin) as well as potent immunosuppressive agents (cyclosporin, rapamycin and FK 506). This review focuses on the modular organization of NRPSs, PKSs and mixed NRPS/PKS systems and how modules and domains that build up the biosynthetic templates can be exploited for the rational design of recombinant enzymes capable of synthesizing novel compounds.     

Spatial and temporal distribution of cyanobacteria in Batticaloa Lagoon

The necessity to understand the relationship between cyanobacterial species abundance and water quality variations in coastal lagoons is crucial to develop strategies to prevent further cyanobacterial proliferation. This paper evaluates the relationship between water quality variations on the distribution of cyanobacteria during a 12-month period in Batticaloa Lagoon (Sri Lanka) using Redundancy analysis and Pearson correlations. Drastic variations in pH, temperature, salinity, dissolved oxygen (DO) and total phosphorus (TP) levels were reported, but not turbidity and NO₃⁻. This brackish waterbody is hypereutrophic (TP levels > 0.1 mg/L). The cyanobacterial community contained 13 genera and 22 species. NO₃⁻, TP and turbidity levels positively influenced cyanobacterial abundance during all seasons indicating that nutrient (largely phosphorus) and sediment entry control is highly crucial along with periodic monitoring of cyanobacterial growth.     

The effects of daily cover soils on shear strength of municipal solid waste in bioreactor landfills

Bioreactor landfills are operated to enhance refuse decomposition, gas production, and waste stabilization. The major aspect of bioreactor landfill operation is the recirculation of collected leachate back through the refuse mass. Due to the accelerated decomposition and settlement of solid waste, bioreactor landfills are gaining popularity as an alternative to the conventional landfill. The addition or recirculation of leachate to accelerate the waste decomposition changes the geotechnical characteristics of waste mass. The daily cover soils, usually up to 20–30% of total MSW volumes in the landfill, may also influence the decomposition and shear strength behavior of MSW. The objective of this paper is to study the effects of daily covers soils on the shear strength properties of municipal solid waste (MSW) in bioreactor landfills with time and decomposition. Two sets of laboratory-scale bioreactor landfills were simulated in a laboratory, and samples were prepared to represent different phases of decomposition. The state of decomposition was quantified by methane yield, pH, and volatile organic content (VOC). Due to decomposition, the matrix structure of the degradable solid waste component was broken down and contributed to a significant decrease in the reinforcing effect of MSW. However, the daily cover soil, a non-degradable constituent of MSW, remains constant. Therefore, the interaction between daily cover soil particles and MSW particles will affect shear strength behavior. A number of triaxial tests were performed to evaluate the shear strength of MSW. The test results indicated that the shear strength of MSW was affected by the presence of cover soils. The friction angle of MSW with the presence of cover soil is higher than the friction angle of MSW without any cover soils. The friction angle of MSW increased from 27° to 30° due to the presence of cover soils for Phase 1 samples. The increased strength was attributed to the friction nature of sandy soil that was used as daily covers soils. Therefore, the effects of cover soils on the shear strength properties of MSW should be evaluated and taken into consideration during stability analyses and design.     

Pedestrian crashes at priority-controlled junctions,roundabouts, and signalized junctions: The UK case study

Objectives: Over half of pedestrians killed and seriously injured in Great Britain in 2015 were involved in crashes at junctions. This study investigates the nature of these crashes.

Methods: A study was conducted into pedestrian casualty crashes at priority controlled junctions, roundabouts and signalised junctions in England between 2005 and 2015 using information from the UK STATS19 accident database, the UK National Travel Survey and the UK National Census. Consideration was given to coding frequencies of contributory factors, exposure (in terms of miles walked or driven) as well as age, gender and the resident deprivation index of the road users involved.

Results and Conclusions: In terms of indicative blame, the coding frequencies of subjectively determined pedestrian actions and behaviour factors which might have contributed to pedestrian casualty crashes were found to be between 1.6 and 2.8 times the frequencies of driver actions and behavioural factors. Substantial social gradients were found in pedestrian casualty rates per miles walked and in the driver involvement rates per mile driven with those from the most deprived quintile having higher rates. In addition, it was found that female pedestrians, aged 60 years and over, had higher pedestrian casualty rates, per billion miles walked, for all three junction types, when compared with males and females under the age of 60 years, apart from male pedestrians aged 16 years and younger at priority controlled junctions.     

Inhibition and recovery of serum,liver and brain acetylcholinesterase activities in rats exposed to new groups of O-ethyl phosphoramidates and benzo-1,3,2-dioxaphospholenes

Searching for new organophosphorus compounds with minimum effects on acetylcholinesterase of non-target organism especially mammals has gained an increased attention in the public concern. In this effort, the effects of some recently introduced O-ethyl phosphoramidates and benzo-1,3,2-dioxaphospholenes on rat acetylcholinesterase in different tissues have been evaluated in vivo and compared with the effects of fenitrothion, a commercial pesticide with reported moderate toxicity to mammals. The tested compounds were introduced orally in a single dose of 85?mg/kg body weight. Results indicated that the tested phosphoramidates lowered the enzyme activity to 54–69, 36–71 and 70–76% of its normal activity in serum, liver and brain, respectively. Meanwhile, the enzyme activity was depressed by fenitrothion to 11, 2 and 11% in the mentioned organs respectively. The lower anticholinesterase activity of the examined phosphoramidates than that of fenitrothion was attributed to their low hydrophobicity and low electrophilicity of their phosphorus atom, which reduces their interaction with the enzyme active site.     

Experimental investigation on the impact sensitivity of a match head composition influenced by the surface roughness of in-process contact materials

This study is aimed to investigate the influence of contact materials and their surface roughness on impact sensitivity of a match head composition. It was found that there were variations to the impact sensitivity, ranging from 2 to 14.7 J. The sensitivity response was quicker in case of steel–steel anvil combinations than with aluminium–aluminium anvil and brass–brass anvil combinations. The match head composition was found to be highly hazardous at the surface roughness values of 1.67, 1.80, and 1.60 μm for steel, aluminium and brass material surfaces, respectively. Such data are not available hitherto.     

Hazardous healthcare waste management in the Kingdom of Bahrain

Hazardous healthcare waste has become an environmental concern for many developing countries including the Kingdom of Bahrain. There have been several significant obstacles facing the Kingdom in dealing with this issue including; limited documentation regarding generation, handling, management, and disposal of waste. This in turn hinders efforts to plan better healthcare waste management. In this paper, hazardous waste management status in the Kingdom has been investigated through an extensive survey carried out on selected public and private healthcare premises. Hazardous waste management practices including: waste generation, segregation, storage, collection, transportation, treatment, and disposal were determined. The results of this study along with key findings are discussed and summarized. In addition; several effective recommendations and improvements of hazardous waste management are suggested.     

Tributyltin pollution in sediments from Alexandria's coastal areas

Presence of Tributyltin (TBT) in Alexandria's coastal water areas has been demonstrated by measuring concentrations of this compound. The TBT was measured in sediments from three docking areas namely: Western Harbour, Eastern Harbour and Abu Qir Bay. The sediment of those areas has been affected by marine traffic and other industrial activities. This is reflected by the distribution of TBT in the sediments nearby the shipyards in the three docking areas of the region where the average values of 258.6 ηg TBT/g for Western Harbour; 126.4 ηg TBT/g dw for Abu Qir Bay and 42.3 ηg TBT/g dw for the Eastern Harbour were recorded. This fact reflects the effect of industry and marine traffic on the marine environments of the Alexandria region.