Die Funktion des Arginins in den Enzymen

The Science of Nature - The average arginine content of proteins is 3.9%. Its frequency among the 20 amino acids of the proteins (13th position) is far lower than would be anticipated from the fact...     

Scanning tunneling microscopy (STM) of the Mo-Fe protein component ofAzotobacter vinelandii nitrogenase

The Science of Nature -     

PEPC-Aktivität

The criteria currently used to determine the extent of novel forest decline areleaf loss andyellowing of leaves. However, these criteria have only a limited value for indicating damage of woody trees, especially the early stages. Therefore, physiological-biochemical parameters will be useful to measure the extent of forest decline. Results from several natural spruce stands indicate that in needles with early signs of damage and needles with severe damage PEPC activity is significantly higher than in needles of healthy plants. Therefore, PEPC activity can reveal beginning damage and may be used as abiochemical indicator for damage assessments of spruce. The influence of air pollutants on PEPC activity in spruce needles was measured in fumigation chambers and open-top chambers; PEPC activity was shown to be affected by long-term exposition only.     

Desorption kinetics studies on PAH-contaminated soil under varying temperatures

The purpose of this study was to investigate the effect of temperature on the release of polycyclic aromatic hydrocarbons (PAHs) from aged contaminated soil. The release of fluorene, phenanthrene, anthracene, fluoranthene and pyrene at 7, 15, 18 and 23 degrees C was studied using a column leaching method with a hydraulic retention time of 0.5 h. As the temperature declined from 23 to 7 degrees C the concentrations decreased by a factor of 11-12 for all the studied compounds except for anthracene, which only decreased by a factor 7. Rate constants at maximum release rate at the four studied temperatures were assessed. From temperature dependence studies, apparent activation energies of desorption, E*(des), were calculated. E*(des)-values appeared to be in the range of 105-137 kJ mol(-1) for the studied PAHs and increased with the LeBas molar volume of the compounds. The increase of E*(des) with increased molecular size indicates stronger sorption with increased hydrophobicity of the compounds.     

Uptake of nitroaromatic compounds in plants

The uptake of nitroaromatic compounds by plants from the soil was studied at an ammunition site. After the development of analytical methods for 2,4,6-trinitrotoluene, aminodinitrotoluenes and dinitrotoluenes in plant material, we could show that these substances accumulated in the roots of plants and are found to a lesser extent inleaves and stems. We observed only moderate differences between various plant species. It is likely that a metabolic transformation in plants leads to the formation of dinitrotoluenes which are considered to be potent carcinogens. Results from soils with a wide range of explosive concentrations show a good correlation between the plant and soil concentrations. The relative accumulation in plant material is higher at lower soil concentrations. At low soil concentrations of about 1 mg trinitrotoluene/kg soil, an accumulation factor of about 0.5 can be derived. These data are an important input for the risk assessment of ammunition sites.