The storage of sewage sludge: influence of liming on the evolution of copper chemical fractions.

Sewage sludge re-used in agriculture has to be stabilized and is often stored for several months before land spreading. Stabilization treatment may affect the behaviour of heavy metals such as Cu, which is an element potentially toxic to the environment. In the present study, the chemical forms of copper have been investigated in heaps of limed and unlimed sludge coming from the wastewater treatment plant of Roselies (Belgium). These limed and unlimed aerobically digested sludges were stored during 4 mo in controlled conditions close to field ones. The sequential extraction procedure developed by Tessier was used to determine the copper chemical forms of representative samples taken in the outer shell and in the depth of the heaps. The physico-chemical properties (pH, organic matter, dry matter and temperature) of these samples were also monitored. This study shows that liming transforms part of organically-bound copper into both exchangeable and residual copper. These changes mainly occur during the first 2 wk of storage. After several months of storage, copper passes from the residual fraction to the exchangeable and oxide fractions. During the whole experiment, changes occur faster in the outer shell than in the depth of the heaps. Thus, we demonstrate that the distribution of the copper forms depends on the storage time and it is different in the outer shell from that in the depth of the heaps.

Hydrogen-deuterium exchange in membrane proteins monitored by IR spectroscopy: a new tool to resolve protein structure and dynamics.

As more and more high-resolution structures of proteins become available, the new challenge is the understanding of these small conformational changes that are responsible for protein activity. Specialized difference Fourier transform infrared (FTIR) techniques allow the recording of side-chain modifications or minute secondary structure changes. Yet, large domain movements remain usually unnoticed. FTIR spectroscopy provides a unique opportunity to record (1)H/(2)H exchange kinetics at the level of the amide proton. This approach is extremely sensitive to tertiary structure changes and yields quantitative data on domain/domain interactions. An experimental setup designed for attenuated total reflection and a specific approach for the analysis of the results is described. The study of one membrane protein, the gastric H(+),K(+)-ATPase, demonstrates the usefulness of (1)H/(2)H exchange kinetics for the understanding of the molecular movement related to the catalytic activity.

Screening procedure for beta-adrenergic drugs in sports drug testing by immunological methods.

A systematic study of the cross-reactivities of beta-adrenergic agonists and antagonists and their metabolites with an ELISA test designed to detect terbutaline and other beta 2-agonists has been performed in order to evaluate the applicability of this immunological test as screening method in routine human sports drug testing. Concentration response curves were calculated. IC50 values from 1.7 to 21.5 ng/mL were obtained for beta 2-agonists, and values from 3.1 to 520.8 ng/mL were obtained for most of the beta-blockers. The highest cross-reactivity was mainly depending on the amino substituent of the molecules although the structure of the aromatic ring was also important. Minor changes in the aromatic ring, such as 4-hydroxylation for propranolol, did not largely influence the IC50 value. Distribution of control activities (percentage of optical density as compared with a blank sample) of urines obtained in controlled excretion studies (70 samples) and urines collected after competition in sports in which beta-blockers are recommended to be tested (147 samples) showed a very small overlapping between the subpopulations of positive and negative samples. Cutoff values of 45 or 60% control activity were proposed for routine analysis. Sensitivity and specificity values of 92.8 and 98.8%, respectively (cutoff 45%), or 98.2 and 95.0%, respectively (cutoff 60%), were obtained. Because the known prevalence of positive results of beta-blockers and beta 2-agonists in the target population was very low, the predicted percentage of presumptive positive cases that would need further confirmation by gas chromatography-mass spectrometry was also low, accounting for a 1.48 and 5.28% (for the cutoffs of 45 and 60%, respectively) of the total number of samples to be screened by the presented ELISA test. Thus, in terms of time and cost savings, the ELISA test is a powerful tool for the purpose of screening for beta-adrenergic drugs in human urine.