Characterization of two glutamate dehydrogenases from the symbiotic microalga Symbiodinium microadriaticum isolated from the coral Acropora formosa

In view of their possible involvement in ammonium assimilation in the coral/algal symbiosis, we have purified two distinct glutamate dehydrogenase isoenzymes from the symbiotic dinoflagellate Symbiodinium microadriaticum (Freudenthal) extracted from the staghorn coral Acropora formosa collected from Magnetic Island, North Queensland, Australia, in 1986–1987. An NADPH-specific glutamate dehydrogenase (GDH) displayed biphasic kinetics with respect to ammonium as the variable substrate; at low substrate concentrations the apparent K _m was below 1 mM, whereas at high substrate concentrations the corresponding value was approximately 200 mM. The NADPH-GDH displayed extremely low activity in the direction of glutamate oxidation; together with the kinetic data this suggests a probable role in ammonium assimilation. A second (NADH-specific) GDH was found to have both amination and deamination activities, and presumably functions in vivo in glutamate oxidation. Kinetic constants are reported for both GDH isoenzymes.     

Comparative study of 137Cs partitioning between solid and liquid phases in Lakes Constance, Lugano and Vorsee.

The methodology for estimating radiocaesium distribution between solid and liquid phases in lakes is applied for three prealpine lakes: Lake Constance (Germany), Lake Lugano (Switzerland) and Lake Vorsee (Germany). It is based on use of the exchangeable distribution coefficient and application of the exchangeable radiocaesium interception potential (RIPex). The methodology was tested against experimental data. Good agreement was found between estimated and measured 137Cs concentrations in Lake Constance and Lake Lugano, whereas for Lake Vorsee a discrepancy was found. Bottom sediments in Lake Vorsee are composed mainly of organic material and probably cannot be described in terms of the specific sorption characteristics attributed to illitic clay minerals.     

The prebiotic synthesis of pyrimidines in frozen solution

Most prebiotic syntheses depend on the reaction of concentrated precursor compounds to produce bio-organic molecules. It is now believed that the early Earth’s atmosphere was not reducing enough to have permitted copious synthesis of precursor molecules. Freezing allows reaction to occur even from dilute solution. This reaction has been demonstrated for the purines but not for the pyrimidines. It is shown here that dilute solutions of simple prebiotic molecules produce the biological pyrimidines cytosine and uracil upon freezing. Cold environments may have allowed synthesis of all of the RNA bases even from low organic yielding atmospheres, such as those of the early Earth, Mars, Titan and Europa.     

The risk assessment-policy gap: an example from the UK contaminated land regime

Risk-based regulation assumes that risk assessment can evaluate risks against policy objectives. However, policy goals are often ambiguous and require risk assessors to interpret them for use in risk assessment. This risk assessment-policy gap stems partly from normative and imprecise policy language but is rooted more fundamentally in society's uncertain expectations for the environment. Until this uncertainty is resolved, the democratic and regulatory effectiveness of risk regulation will be undermined by ad hoc policy decisions abdicated to risk assessors.     

Catalyst-free synthesis of α-acyloxycarboxamides in aqueous media

Environmental Chemistry Letters - Organic syntheses in aqueous solutions are being developed because water is an environmentally friendly, inexpensive, non-toxic and non-flammable solvent....     

Determination of bismuth in environmental samples by slurry sampling graphite furnace atomic absorption spectrometry using combined chemical modifiers

Persistence behavior of insecticides chlorpyriphos, profenofos, triazophos, cypermethrin, and deltamethrin following the use of three combination formulations Action 505 (chlorpyriphos?+?cypermethrin), Roket 44EC (profenofos?+?cypermethrin), and Anaconda Plus (triazophos?+?deltamethrin) was studied in cabbage following the spray application at the recommended and double doses. Bio-efficacy of these formulations was also evaluated against mustard aphids (Lipaphis erysimi Kaltenbach) and diamondback moth (Plutella xylostella L.). The residues of different insecticides persisted for 5–8 days at low dose and 8–12 days at high dose. The residues dissipated with time and 87–100 % dissipation was recorded on the 8th day. The half-life values varied from 0.4 to 1.6 days. Based on the acceptable daily intake (ADI) values, a safe waiting period of 1 day has been suggested for the formulations Action 505 and Roket 44EC and 3 days for Anaconda Plus at the recommended dose of application. Action (1.6 L/ha) treatment was found to be the best as it significantly reduced the diamondback moth (DBM) (~60 %) and aphid population (~70 %) besides giving the highest yield (170 % increase over control).     

Potential ecological risk assessment and predicting zinc accumulation in soils

Environmental Geochemistry and Health - The aims of this study were to investigate zinc content in the studied soils; evaluate the efficiency of geostatistics in presenting spatial variability of...